History

CHAPTER XVIII

Clinical Trials of Antimalarial Drugs

Harry Most, M.D.

Extensive military operations in various highly malariousregions during the Second World War stimulated intensive research in thechemotherapy of malaria. Interruption of the normal supplies of quinine from theFar East made it necessary, while conserving existing supplies, to reevaluatethe efficiency of Atabrine (quinacrine hydrochloride) and other agents withknown antimalarial properties and to widen the search for new drugs for thetreatment, suppression, and possible cure of malaria.

Numerous investigations were carried out by civilian,military, and public health research groups under contract of the Office ofScientific Research and Development, Committee on Medical Research of theNational Research Council, and integrated by the Board for the Coordination ofMalarial Studies.¹ Approximately 15,000 compounds were studied, and the more promising weregiven detailed pharmacological and toxicological examination prior to testing inhuman beings. Important contributions to the knowledge of chemotherapy ofmalaria resulted from this comprehensive program. Quinacrine proved as good asquinine in most, and superior in some, aspects of treatment. New agents werefound that proved superior both to quinacrine and quinine. In addition, otherdrugs which apparently produce definitive cure of malaria were later found.

The principal purpose of this chapter is to review briefly some of theclinical drug trials made during World War II in relation to their militaryapplication in the management of malaria. A note is added on some of thesestudies as continued, still under the auspices of the U.S. Army, and brought tosignificant conclusions in the immediate postwar period (p. 594).

PENICILLIN

The occurrence of acute attacks of malaria in military patients who weregiven large amounts of penicillin for surgical or other infections suggestedvery early in experience with this antibiotic that it would have no value in thetreatment of malaria. Failures to terminate acute attacks with penicillin inamounts of 460,000 toseveral million units were reported. The im-

¹A JointBody Composed of Representatives of the Office of Scientific Research andDevelopment, the Army, the Navy, the U.S. Public Health Service, and theNational Research Council, vols. I-VII. [Official record.]

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pression was further confirmed in the treatment ofneurosyphilis with penicillin and in the treatment of fever induced by malarialinfection (transmitted by Plasmodium vivax and Plasmodium malariae).²Of the patients who had remissions of fever, the larger percentage (31 percent of 147 patients) had had no penicillin duringtherapeutic malaria; the smaller percentage (13 percentof 46 patients) were given 30,000 units every 3 hoursfor 120 doses, beginning the dayafter a rise in temperature to 103^? F. Again, 15 patients were inoculated with the McCoystrain of P. vivax and studied under various schemes of treatment withpenicillin. Each patient received 3 millionunits.³ This therapy did not reduce the fever, after the cycle ofactivity, or affect the degree of parasitemia; it did not prevent, postpone, oralter the nature of the attack (chart 26). Penicillinhad evidently no place in the prevention, treatment, or suppression of malaria.

HEAVY METALS

Arsenicals-Arsenated benzine compounds (arsphenamine,neoarsphenamine, and oxophenarsine hydrochloride (Mapharsen)) commonly used inthe treatment of syphilis have for a long time been known to possessantimalarial properties in varying degrees. Studies made before and during WorldWar II⁴ showed that they wereineffective against infections caused by P. malariae and P. falciparum. Givenintravenously, intramuscularly, or orally, arsenicals were found to possessdefinite activity in terminating the paroxysms and parasitemia of malaria due toP. vivax, particularly in blood-induced infections; in naturally acquired malariaascribed to P. vivax, they proved inferior to quinacrine, quinine, and otherdrugs as regards control of fever, parasitemia, and the interval to relapse. Itwas found that their intensive use is not without danger, that they offer nopractical advantage over more effective drugs, and finally that arsenicalsadministered alone or in conjunction with quinacrine or bismuth do not affectthe natural relapse rate of this disease.

²Personal communication, Maj. Harry H. Gordon, MC,Chief of Communicable Diseases, Harmon General Hospital, Longview, Tex., to theauthor.
³Hindle, J. A., Rose, A. S., Trevett, L. D., and Prout,C.: The Effect of Penicillin on Inoculation Malaria; A Negative Report. NewEngland J. Med. 232: 133-136, 1 Feb. 1945.
⁴(1) Werner, H.: Das Ehrlich-Hata Mittel606 bei Malaria. Deutsche med. Wchnschr. 36 (Pt. 2): 1792-1794, 29 Sept. 1910. (2) Curd, F. H. S.: The Activity of Drugsin the Malaria of Man, Monkeys, and Birds. Ann. Trop. Med. 37: 115-143,September 1943. (3) Goldman, D.: The Use of Mapharsen in the Treatment ofMalaria. Am. J.M. Sc. 196: 502-509, October 1938. (4) Morrison, W. H., and Hill, E. R.: Use of Mapharsen inRelapsing Tertian Malaria. [Official record.] (5) Kay, C. F.: Failure ofMapharsen as an Adjuvant to Atabrine in the Treatment of Relapsing TertianMalaria. J.A.M.A. 127: 984, 14 Apr. 1945. (6) Spector, S., Haviland, J. W., andCoggleshall, L. T.: The Ineffectiveness of Intensive Mapharsen, Bismuth, andCarbarsone as Curative Drugs for Chronic Malaria. Am. J. Trop. Med. 25: 463-467,November 1945. (7) Bispham, William N.: Malaria: Its Diagnosis, Treatment andProphylaxis. Baltimore: Williams & Wilkins Co., 1944.

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CHART 26.-Penicillin studies in three patients¹ with vivax malaria

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Bismuth compounds.-In one study⁵ reported during World War II, it was shown that prolongedcourses of bismuth subsalicylate in conjunction with intensive Mapharsen therapydid not reduce the relapse rate in naturally acquired vivax malaria of Pacificorigin. Bismuth compounds have some limited value in therapeutic managementthrough their ability to establish tertian periodicity⁶ in patients with induced vivax malaria who have daily orirregular paroxysms, by interrupting, although not terminating, the infection.

Antimony compounds-These components have been shown tohave antimalarial properties⁷both in vivax⁸and falciparum⁹infections, but practical application was not found forthem in the treatment of vivax malaria of Pacific origin. They have beenprovocative in precipitating clinical attacks of falciparum or vivax malaria inpatients under treatment for kala-azar or schistosomiasis. It is of interest,too, that relapses of vivax malaria have occurred in nonendemic areas inpatients who had previously received one or more intensive courses of trivalentcompounds (stibophen (Fuadin) or tartar emetic) for schistosomiasis japonica, orpentavalent compounds (stibamine glucoside (Neostam) and/or ethylstibamine (Neostibosan))for kala-azar. The prolonged administration of tartar emetic (30 days or more)in therapeutic amounts (1.8 to 2.25 gm.) in many cases is moderately toxic.

SULFONAMIDES

Shortly after the introduction of the sulfonamides in thechemotherapy of infections, they were found to possess antimalarial activity ofvarying degree. Although data from many studies¹⁰ indicated their limitations, addi-

⁵See footnote 4 (6), p. 526.
⁶Young, M. D., McLendon, S. B., and Smarr, R. G.: TheSelective Action of Thiobismol on Induced Malaria. J.A.M.A. 122: 492-494, 19June 1943.
⁷Schmidt, Hans, and Peter, F. M.: Advances in theTherapeutics of Antimony. Leipzig: Georg Thieme, 1938, pp. 80-82.
⁸Cole, H. N., DeOreo, G. A., Driver, J.R., Johnson, H. H., and Schwartz, W. F.: Use of Bismuth Injections to ManageCourse of Therapeutic Malaria. J.A.M.A. 115: 422-427, 10 Aug. 1940.
⁹(1) De Nunno, R.: Azione del tartaro stibiato suigametociti del plasmodium vivax e del pl. falciparum. Ricerche sperimentali. Riforma med. 54: 1599-1601, 22 Oct. 1938.(2) De Nunno, R.: La stimolazione antimoniale del s.r.e. come mezzo terapeuticomella malaria estivo-autumnale chininoplasmochina-atebrin resistente. Notapreventiva. Riforma med. 51: 1087-1093, 20 July 1935.
¹⁰(1) Niven, J. C.: Sulphanilamide (Prontosil)in the Treatment of Malaria. Bull. Inst. M. Research, Federated Malay States(no. 4), pp. 1-27, 1938. (2) Niven, J. C.: Sulphanilamide in the Treatment ofMalaria. Tr. Roy. Soc. Trop. Med. & Hyg. 32: 413-418, November 1938. (3)Yamamato, K.: Sulfanilimide in Malaria. Japanese J. Dermat. & Urol. 46:78, 20 Oct. 1939. (4) Chopra, R. N., Das Gupta, B. M., Sen, B., and Hayter, R.T. M.: Prontosil in Indian Strains of Malaria. Indian M. Gaz. 74: 321-324, June1939. (5) De Leon, A. D.: El paludismo y su Tratamiento Intra-venoso por lasSulfanilimidas. Medicina, Mexico 20: 551, 10 Nov. 1940. (6) Chopra, R. N.,Hayter, R. T. M., and Sen, B.: M. & B. 693 in Indian Strains of Malaria.Indian M. Gaz. 74: 658-660, November 1939. (7) Coggeshall, L. T., Maier, J., andBest, C. A.: Effectiveness of 2 New Types of Chemotherapeutic Agents in Malaria.J.A.M.A. 117: 1077-1081, 27 Sept. 1941. (8) Johnson, C. E., Jr.: Status ofSulfonamide Therapy in Malaria. Am. J.M. Sc. 206: 327-336, September 1943. (9) Schwartz, L., Furst, W., and Flippin, H. F.:Sulfathiazole as an Antimalarial. Am. J. Hyg. Sect. C 34: 160-162, November1941.

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tional trials were undertaken to determine their suppressiveand clinical value in malaria of war origin. Observations showed quitedefinitely that sulfonamides do not affect the relapse rate of vivax malaria,and successful termination of acute attacks was achieved only with large doses,which not infrequently resulted in sulfonamide toxicity. Fever and parasitemiawere not controlled promptly, and relapses occurred early following treatment.In short, sulfonamides were inferior to quinine or quinacrine in terminatingacute attacks. They were found to be more effective in malaria caused by P. falciparum. In a study from West Africa, four out of six sulfonamide compoundsexerted a definite effect on fever and parasitemia, but all of them wereconsidered inferior to quinine and quinacrine in the treatment of falciparuminfections.

It was observed that sufonamides used in the treatment of bacterialinfections may suppress parasitemia due to P. falciparum or P. vivax and so delay the diagnosis ofmalaria in patients currently or recently under treatment for pneumonia or otherinfections.¹¹

Field studies were conducted in various theaters. It had previously beenshown that plasma levels of 4 mg. percent or higher maintained for 28 days afterthe inoculation of trophozoites of P. falciparum prevented the subsequent development of thisinfection but failed to suppress experimentally induced infections with P.vivax.In a series of brilliantly conceived and executed experiments by Australianresearch teams on the chemotherapeutic, suppressive, and prophylactic activityof various drugs, it was demonstrated that daily doses of 1 gm. of sulfamerazine,sulfadiazine, or sulfamethazine would effectively suppress falciparum malaria but would prove ineffective againstinfections with P. vivax.¹²

The practical application of sulfamerazine as a suppressive agent in variousfield studies is summarized in table 73. These observations show thatsulfamerazine in daily doses of 0.5 gm. was not a causal prophylactic, thatcyanosis and other manifestations of toxicity were not uncommon, that moreclinical attacks occurred during suppression with sulfamerazine than withquinacrine and that they occurred sooner after discontinuance of the drug, andthat sulfamerazine exhibited a high degree of suppressive activity but wasinferior to 0.6 gm. quinacrine weekly.

Thus, the sulfonamides at most have only limited if any valuein the practical treatment or suppression of malaria during war or in civilianlife if quinine, quinacrine, or equally effective agents are available.

¹¹Page, S. G., Jr., and McCall, J. V.,Jr.: Delay in Diagnosing Malaria After Sulfadiazine Therapy; Two Case Reports. South. M.J. 39 : 728-731, September 1946.
¹²Fairley, N. H.: ChemotherapeuticSuppression and Prophylaxis in Malaria; An Experimental Investigation Undertakenby Medical Research Teams in Australia. Tr. Roy. Soc. Trop. Med. & Hyg. 38:311-365, May 1945.

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TABLE 73.-Experimental field tests with sulfamerazine, Atabrine, and sulfapyrazine

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FIGURE 60.-Brig.Gen. James S. Simmons and Col. Arthur Fischer, GSC, inspect cinchona seedlings,November 1943. These are being grown in a cinchona seedling hothouse nearWashington, D.C., for shipment to South America to be used in production ofquinine for treatment of malaria.

CINCHONA ALKALOIDS

Quinine

With the loss, early in the war, of the main sources ofquinine, for centuries the drug of choice in the treatment of malaria, theproblem of supply was considered sufficiently critical to warrant restriction ofcinchona alkaloids to essential purposes in two War Production Board orders.¹³If quinine was to be allocated almost exclusively to theArmed Forces, some substitute would have to be made available for civilian use(fig. 60). It was desirable also to find out exactly how efficient the cinchonaalkaloids were in the treatment or suppression of malaria, and whether theywould be significantly practical for military use. Discussion in this sectionwill be limited to a few important observations in respect to the relativeefficiency of quinine or other cinchona alkaloids in the treatment andsuppression of malaria.

¹³War Production Board,Conservation Orders No. 131, 30 Apr. 1942 and No. M-131-a, 19 June 1942.

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Acute attacks

It had been shown that plasma concentrations of quinine of 4.5mg. per liter (dosage range 0.12 to1.8 gm. daily) were effective in suppressing and in terminating acute attacks ofvivax malaria. Plasma levels of 5.5 mg.per liter suppressed and terminated acute attacks of falciparum malaria.¹⁴Nevertheless, in a field-type experiment with New Guinea strains, daily doses of0.6 gm. failed to prevent attacks of falciparum malaria, and 0.3 gm.daily was incapable of preventing vivax attacks. When the latter dose wasincreased to 0.6 gm., completesuppression was achieved in some cases of infection with P. vivax but not inothers. By contrast, daily doses of 0.1 gm. of quinacrine were completelyeffective in suppressing infections with either agent.

In West Africa, daily suppressive doses of 0.3 gm. quinine were associated with a malaria rate of 651 per 1,000 in a group of 1,180men,with 4 cases of blackwater fever. Inanother group of 96 men given 0.3 gm. of quinine daily, 70 developedclinical malaria while on this regimen and 7 morewhile being transferred to quinacrine. On the other hand, in 752 men on relatively small doses of quinacrine(0.4 gm. weekly), the rate was 450 per1,000 with only 1 case of blackwater fever. This definite discrepancy in attackrate would doubtless have been larger if they had been given what wassubsequently found to be the optimum dosage of quinacrine (0.7 gm. weekly).

Relapses

Clinical studies in this country were undertaken¹⁵ todetermine the effectiveness of maximum doses of quinine in terminating acuteattacks of relapsing vivax malaria of Pacific origin. The following results werereported in a comparative study of a group of 100 patients treated with 28.35 gm. of quinine during14 daysand a control group of 150 patientstreated with 2.8 gm. of quinacrineduring 7 days: The mean level ofquinine in the plasma during treatment was 7.3 mg.per liter, well above the demonstrated effective range. Both groups hadblood-smear examinations twice weekly after completion of treatment and wereobserved for 120 days for clinicalor parasitemic relapse.

Special considerations

Control of parasitemia-As shown in chart 27, quinacrine proved significantly superior to quinine inrapidly clearing the blood of malarial parasites, in some patients within 12 hours of the first dose. At24 hours, 26

¹⁴Bi-Monthly Progress Report No. 12, Committee onMedical Research, Office of Scientific Research and Development, 1 Sept. 1943,subject: Malarial Chemotherapy, Contract No. OEMcmr-112.
¹⁵(1) Most, H., and Hayman, J. M., Jr.: Relative Efficiencyof Quinacrine (Atabrine) and Quinine in Treatment of Acute Attacks of VivaxMalaria. Am. J.M. Sc. 211: 320-324, March 1946. (2) Gordon, H. H.,Christianson, H. B., and Lippincott, S. W.: A Comparison of Quinine andQuinacrine in the Treatment of the Clinical Attacks of Vivax Malaria. South. M.J.39: 631-634, August 1946.

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percent of those treated with quinacrine and only 7 percentof those given quinine were free of parasites, as were 77 percent and 44 percent,respectively, at 48 hours. At 72 hours,only 4 percent of patients treated with quinacrine still showed parasites, andall were clear at 96 hours; almost one-fourth of the patients treated withquinine still had parasitemia at 72 hours,and in a few this persisted as long as 132 hours.

CHART 27.-Rate of disappearance ofparasites during treatment of 497 acute attacks of vivax malaria withquinacrine hydrochloride or quinine

Control of fever-The ideafrequently advanced that quinine should be used during the first few days of anacute attack because of its superiority in controlling fever quickly was notborne out in this study. Quinine was not significantly more effective in thisrespect in relapses and was in fact less effective in patients with delayedprimary attacks, of whom 32 percenthad fever on the second or third day after beginning treatment with quinine, ascompared to 16 percent with quinacrine.

Control of other symptoms-It is difficultto evaluate,in relation to therapy, data on such symptoms as headache, backache, nausea,malaise, and weakness, which usually occur in an attack of malaria.Statistically, there was little difference in the duration of these symptomsunder treatment with one or the other drug, although clinically one had theimpression that such symptoms, particularly weakness and anorexia, were morepromptly controlled with quinacrine.

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Toxicity.-Persistent vomiting associated with the malarial attack wascontrolled by withholding fluids and food by mouth and by giving intravenousglucose prior to the administration of quinacrine. Given several hours offreedom from vomiting, this symptom was not brought on again by the drug.

Gastrointestinal disturbances controlled as described were not aggravated byquinine. Patients with eczematoid or exfoliative dermatitis and malaria had noactivation of the skin process attributable to quinine. One patient, who provedto be hypersensitive to the drug, developed acute thrombopenic purpura andsevere angioneurotic edema of the face on the first day of treatment. Suchreactions, although not unknown, were admittedly rare. A fairly high proportionof patients treated with quinine, however, complained of severe and annoyingtinnitus and fullness in the ears or head. In many cases, this seemed to retardfull recovery from the symptoms of an acute attack.

No major toxic manifestations were seen during treatment with quinacrine.Patients who alleged previous intolerance to the drug displayed none when it wasgiven to them in colored capsules without their knowledge of the contents. Inthis series, signs and symptoms referable to the central nervous system were notencountered in relation to quinacrine therapy. Two patients with severeeczematoid dermatitis and acute malaria who were not having specificantimalarial treatment had flareups of the skin process, and many others withthe two conditions suffered no ill effects from treatment with quinacrine.

Relapse rate and interval to relapse-Approximately 80 percent of Pacificinfections relapsed within the observation period of 120 days, whether treatedwith quinacrine or quinine, but there was a striking difference in the length ofthe interval to relapse. In short, the mean interval following treatment withquinine was 22 days as compared with 53 days following treatment with quinacrine(chart 28). Quinacrine thus effected a longer interval to relapse by at least amonth, reducing to a minimum the number of relapses occurring within 30 days oftreatment and in 30 percent of cases prolonging the interval to more than 60days.

Falciparum infections

Single intravenous injections of as much as 1.2 gm. ofquinine failed to terminate acute attacks caused by P. falciparum in 5 out of 10patients, while intravenous injection of single doses of 0.4 to 1.0 gm. ofquinacrine terminated attacks due to P. falciparum in 49 out of 50 cases at the20th General Hospital, India-Burma theater. The relative merits of parenteralquinine and quinacrine in fulminating falciparum infections are discussed inthe section on quinacrine. Maximum doses of quinine have been shown to producemore minor and major toxic manifestations than therapeutic amounts of quinacrine.Aside from cinchonism, quinine used in 10,000 cases of ma-

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CHART 28.-Relapse rates and intervals to relapse following treatment, bydays, with quinacrine hydrochloride or quinine of 250 acute attacks of vivaxmalaria of Pacific origin

laria was associated with an incidence of purpura in 5percent, with 2 deaths, whereas no case of purpura occurred in 2,500 casestreated with quinacrine in Panama.¹⁶Fatal bullous erythemafollowing 1.95 gm. and severe dermatitis after 15 gm. of oral quinine werereported in two patients in India. In addition, gluteal abscesses fromintramuscular quinine and convulsions followed by death during or shortly afterintravenous quinine occurred in eight patients.¹⁷

Summary of comparative studies

There remained little question, therefore, afterconsideration of the data presented, that quinine is a relatively inferior drugin the treatment of acute attacks of vivax malaria or in the suppression ofinfections with P. vivax or P. falciparum in nonimmune military personnel. Itsearly use in the Pacific combat areas resulted in numerous"breakthroughs" of falciparum and vivax malaria during suppressionand in early and repeated relapses of the latter. Fortunately, quinacrine wasavailable in adequate amounts, and its establishment as the standard drugresulted in effective suppression and satisfactory control of clinical attacks.

¹⁶Shrager, J., and Kean, B. H.: Purpura as aComplication of Malaria. Am. J.M. Sc. 212: 54-59, July 1946.
¹⁷Essential Technical Medical Data, India-BurmaTheater, for June 1945.

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Totaquine

Totaquine (containing not less than 7 percent nor more than 12 percent ofanhydrous quinine and not less than 70 percent nor more than 80 percent of totalanhydrous crystallizable cinchona alkaloids) was studied at several generalhospitals in the Zone of Interior and overseas. Relatively large amounts wereavailable and more could be obtained for civilian or military use. Theantimalarial qualities of all the cinchona alkaloids it contained, if additive,could result in substantial saving in quinine and other alkaloids.

In a study carried out at Kennedy General Hospital, Memphis, Tenn., in July1944, totaquine proved as effective as quinine in terminating acute attacks ofmalaria due to P. vivax of Pacific origin, but it more frequently producedepigastric distress, blurred vision, dizziness, and severe vomiting. Similarfindings were reported in a study at Bushnell General Hospital, Brigham City,Utah. In addition to the patients treated for 5 days, 53 were maintained onsuppressive doses (0.6 gm. daily) for 55 days. Of these, 13 (about 25 percent)"broke through" with clinical malaria. Of the treated patients, 60percent relapsed; the average interval to relapse was 34 days after suppressivetreatment with totaquine.

At the 31st Station Hospital in New Caledonia, a study of patients in groupsof 80 treated with totaquine, quinine, or quinacrine, for relapsing malaria ofPacific origin, again showed not much difference as to control of parasitemia,fever, and other symptoms.¹⁸ Again nausea, vomiting, vertigo, andblurred vision were observed with totaquine and in some cases were severe.Relapses began within 1 week after completion of treatment with totaquine orquinine, reaching their peak in 2 weeks, whereas relapses after quinacrine didnot begin until 3 weeks after completion of treatment and reached their peak at6 weeks. Similar findings were reported from two Army hospitals in anothertheater.

In summary, these studies indicate that totaquine is as efficient as quininein terminating acute attacks of malaria, but is more toxic. Moreover, likequinine, totaquine is less effective than quinacrine in controlling fever andparasitemia and in shortening the intervals between relapses.

These factors, in addition to its being inefficient as a suppressive,variable in alkaloid content, and difficult to standardize, would preclude theuse of totaquine on a wide scale for military purposes. It could, however, have a useful role in the treatment of malaria in highly immuneindividuals in whom small amounts of any antimalarial agent are effective interminating periods of clinical activity. A considerable advantage in the use oftotaquine in areas where it is locally available would be the relatively lowcost and ease of preparation, permitting the use of low grade barks of poorquinine content.

¹⁸Green, R. A.: Totaquine inthe Treatment of Malaria. Bull. U.S. Army M. Dept. No. 84, pp. 51-57, January1945.

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Other Cinchona Alkaloids

Dihydroquinine, more commonly known as hydroquinine, offeredan interesting possibility because it not only could be totally synthesized butcould be obtained in 95 to 100percent yield from the hydrogenation of quinine. If the higher therapeuticactivity of dihydroquinine claimed for it in studies of malaria in birds couldbe demonstrated in man, a useful substitute for quinine might be availablesynthetically, or the effective stores of quinine could be increased from 15 to 20percentby converting the latter to dihydroquinine. However, clinical tests in thePacific with total daily doses of 0.3 to 1.8 gm. for 6 days in relapsing vivaxmalaria failed to show any greater therapeutic activity of dihydroquinine overquinine. One patient complained of blurred vision after a total of 0.6 gm., andthree other men receiving 0.3 gm. three times daily complained of vertigo (twopatients) and weakness in the legs (one patient). Dihydroquinine thereforeoffered no advantage over quinine.

The antimalarial activity of quinidine, cinchonine, andcinchonidine have been known for a long time, and their ability in terminatingclinical attacks of malaria was demonstrated many years ago.¹⁹Quinidine as an antimalarial was not explored extensively because of itspotential cardiac toxicity, nor were cinchonine and cinchonidine, individuallyrepresenting small fractions of the total cinchona alkaloids. Development ofchemical methods²⁰ for estimatingplasma levels of these alkaloids made it possible to evaluate their relativeantimalarial activity in man. It was shown that plasma levels of 0.1 and 0.5 mg. per liter for cinchonine and2.5 and 3.0 mg.per liter for cinchonidine for clinical control of acute attacks of malaria wereeffective against vivax and falciparum infections, respectively, and that theselevels were attained with daily doses of 2.0 to 3.0 gm. of cinchonine and 1.0 to3.0 gm. of cinchonidine. The effective levels of quinine are4.0 mg. for vivax infections and 5.0 mg. for falciparum infections, althoughsome of the latter may not be controlled with levels as high as 10 mg. perliter. Total daily amounts of 1.5 gm. of quinine (0.65 every 8 hours) willprovide levels of 7.0 to 12.9 mg.per liter (average 10.3) , which are adequate to control most infections.Although it may appear that cinchonine and cinchonidine are more effective thanquinine by virtue of activity at lower plasma levels, it must be recognized thatsuch levels are obtained only with two to four times the amounts of these drugsin comparison with quinine. Consequently, no practical advantage could bederived from the individual use of cinchonine or cinchonidine in the routinetermination of attacks of malaria since they would ultimately have to be derivedfrom cinchona itself. No clinical studies with cinchonine or cinchonidine wereundertaken in the Army. However, it was concluded

¹⁹Nelson, E. E.: Cinchona and Its Alkaloids in theTreatment of Malaria. A Symposium on Human Malaria. (Pub. No. 15.) Washington:American Association for the Advancement of Science, 1941, pp. 255-260.
²⁰Bi-Monthly Progress Report No. 11, Committee onMedical Research, Office of Scientific Research and Development, 2 July 1943,subject: Malarial Chemotherapy, Contract No. OEMcmr-112.

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from civilian studies that they were less toxic than quinine,particularly with respect to symptoms attributable to the special senses, andthat these drugs singly or in combination, as in totaquine, should beapproximately equivalent to quinine in antimalarial activity.

Summary of Studies

Studies with cinchona alkaloids during the war were thereforeof definite practical value. It was demonstrated that totaquine and itscomponent alkaloids were as effective as quinine but more toxic, that thecinchona alkaloids were inferior to quinacrine in both suppression andtermination of acute attacks of malaria, and that the loss of quinine wasaccordingly not a serious military problem. A rational method of assay ofantimalarial properties of drugs was developed and the efficiency of the variouscinchona alkaloids reevaluated. No conclusive studies on the relative efficiencyof parenteral quinine and quinacrine in the treatment of cerebral malaria werereported, and this problem still requires investigation before a final estimatecan be made of the role quinine should play in the therapy of malaria.

QUINACRINE HYDROCHLORIDE (ATABRINE)²¹

The extensive prewar literature dealing with the antimalarialproperties and toxicity of quinacrine has been adequately reviewed.²² Followingthe introduction of this drug in 1931, it became apparent that the originallyadvocated dosage schedule of 0.1 gm. three times daily for 5 days was in manycases, particularly in severe falciparum infections, inadequate for prompt andeffective control of fever, symptoms, and parasitemia. There were numerousrevisions in treatment plans, but there was no rational pharmacological basisfor defining what dosage and treatment schedules were best for terminating acuteattacks or for suppression. The relative efficiency of quinacrine versus quininehad not been established, and it was questionable whether we would be able toproduce adequate amounts of effective antimalarial drugs. Numerous studies wereconducted in many laboratories and hospitals in the various theaters. It is thepurpose of this section to review briefly basic clinical and other observationsthat established quinacrine as a highly effective and satisfactory antimalarialduring the war.

In 1941, American chemists succeeded in completelysynthesizing quinacrine. Chemical, pharmacological, and clinical investigationssponsored by the National Research Council established the identity of theGerman and American drugs and found no appreciable difference between them asregards side reactions. Rumors that the American preparation was not identicalwith the German drug could be definitely dismissed. Finally, tremendouslyincreased production assured an adequate supply at least for military use atfirst and later for civilian and lend-lease purposes.

²¹Formula:3-Chloro-7-methoxy-9-(1-methyl-4-diethylamino-butylamino) acridinedihydrochloride.
²²Seefootnote 4 (7), p. 526.

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General Properties

Practical, highly sensitive, and accurate chemical methodsfor the estimation of quinacrine concentrations in the blood and tissues made itpossible to study its physiological disposition in the human body.²³It was shown that:

* * * Atabrine is almost completely absorbed in thegastrointestinal tract and renal excretion accounts for very little of the dailydose. It may be concluded from these facts and the fact that its plasmaconcentration becomes stabilized after several days of drug administration atconstant dosage, that it is disposed of by the body mainly by processes whichresult in its degradation. It follows, then, that the major factors which willrelate drug administration and plasma drug concentration are those whichcondition the processes of distribution and degradation in the body.

* * * It was found that the concentration of the drug in plasma,erythrocytes, and leukocytes is in the order of 1, to 1, to 100-200.

* * * Studies * * * in experimental animals indicated thatthe drug may achieve concentrations in the liver and spleen as high as10,000-20,000 times those currently observed in the plasma. Localization inother tissues was found to be less extensive, but highly significant. Anextension of these distribution studies to the human [subject] * * *demonstrated that a major portion of the administered Atabrine is localized inthe tissues of the body, leaving little in the plasma to exert achemotherapeutic effect. It is in consequence of this that unless large initialdoses of the drug are given the initial plasma drug concentrations areinvariably low. However, the extensive localization, together with the low ratesof degradation and renal excretion, lead to a low rate of decline of the plasmaAtabrine concentration, and consequently a low rate of loss of the protectionconferred by Atabrine, subsequent to the termination of drug administration.

It was apparent that a rational regimen of quinacrine therapywould have to be designed along the commonly accepted principles ofchemotherapy; namely, the administration of sufficient drug when the diagnosisof malaria is made, or when exposure to malaria is anticipated, to obtain thedesired plasma concentration, followed by the serial administration of smalldoses to maintain it.

The next step was to determine the plasma levels ofquinacrine that would be effective in the prompt control of symptoms, fever, andparasitemia associated with acute attacks of vivax and falciparum infections. Infections withvarious strains of P. vivax and P. falcparum, transmitted bymosquitoes or introduced by blood, were established in volunteers and paretics,and different amounts of quinacrine in different treatment schedules were usedto produce various plasma concentrations. It was found that if quinacrineconcentrations of 30 μg. per liter or more were maintained for 4 days in vivax infections there was complete termination of clinical activity and parasitemia.Levels between 10 and 30 μg. per liter produced temporary or partial effects,

²³(1) Brodie,B. B., and Udenfriend, S.: The Estimation of Atabrine in Biological Fluids andTissues. J. Biol. Chem. 151: 299-317, November 1943. (2) Mackie, Thomas T.,Hunter, George W., III, and Worth, C. Brooke: Manual of Tropical Medicine.Philadelphia: W. B. Saunders Co., 1945, pp. 675-677. (3) Shannon, J. A., Earle,D. P., Jr., Brodie, B. B., Taggart, J. V., and Berliner, R. W.: ThePharmacological Basis for the Rational Use of Atabrine in the Treatment ofMalaria. J. Parmacol. & Exper. Therap. 81: 307-330, August 1944.

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and levels below 10 μg. per liter produced little or noeffect when maintained for 4 days. Infections with P. falciparum requiredapproximately 50 μg. per liter maintained for 6 days for termination ofclinical activity and parasitemia.

With the treatment schedule for quinacrine commonly usedbefore 1943 (0.1 gm. three times daily for 5 days), very low concentrations inthe plasma were achieved during the first 2 or 3 days of therapy because of theextensive localization of the drug in tissues. If such dosage is continued for aperiod of days, the plasma levels will rise progressively, as more and more drugaccumulates in the tissues, until ultimately they reach sufficient height toterminate the attack. The delay in the initial effect of quinacrine in such adosage schedule had led to the belief that quinacrine therapy should be precededby a 2- to 3-day course of quinine. Actually, such a course is undesirablebecause 24 hours or less after the last dose the plasma level of quinine is nolonger effective. If parasitemia is still present, as it often is in cases sotreated, there will be a reactivation of the disease during the next few days(of treatment with 0.1 gm. quinacrine three times a day) until the plasmaquinacrine level in this schedule becomes effective.

If, on the other hand, total doses of 0.8 to 1.0 gm. ofquinacrine are given orally during the first 24 hours of therapy, or by acombination of parenteral and oral routes, high effective plasma concentrationsare quickly established and easily maintained by the serial administration of0.1 gm. three times daily for 6 days. These considerations led to the adoptionby the U.S. Army of a standard course of quinacrine therapy consisting of 2.8gm. during 7 days (1.0 gm. the first 24 hours and 0.3 g.m. daily for 6 moredays).²⁴

Clinical Use

In acute attacks-Clinical experiencein this country and overseas proved conclusively the efficiency of such aregimen in terminating acute attacks of malaria due to P. vivax and P. falciparum.It was found²⁵that 2.8 gm. of quinacrine administered asrecommended in Circular Letter No. 153, Office of the Surgeon General, 19 August1943, brought about cessation of fever within 24 hours in approximately 90percent of cases of vivax malaria and in the remainder within 48 to 72 hours;approximately 80 percent of patients had negative smears within 48 hours andalmost 100 percent at 96 hours. Relapses after treatment with quinacrineoccurred in an average of 53 days, in contrast to 24 days and the manyshort-term relapses following treatment with quinine. In the treatment of acuteattacks, there were no toxic manifestations similar to those induced byprolonged intensive treatment with quinine.

²⁴Circular Letter No. 153,Office of the Surgeon General, U.S. Army, 19 Aug. 1943, subject: The DrugTreatment of Malaria, Suppressive and Clinical.
²⁵See footnote 15, p. 532.

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In 291 patients, plasma levels were determined during andafter 412 attacksof vivax malaria acquired in the South Pacific.²⁶The average dailylevels from the second to the eighth days of treatment with quinacrine were 41 to52 μg.per liter. The average increase in level 2 to 4 hoursafter a dose of 0.1 gm. on the second to seventh day was 6.8 to 11.3 μg.per liter above the corresponding fasting level. The average level 4 weeks after completion of2.8 gm. of quinacrine therapy was 8 μg. per liter. It was foundthat this regimen produced plasma levels of 45 μg.per liter within 24 hoursafter treatment was begun and that all symptoms and parasitemia were abolishedwithin 72 hoursin almost 100 percent of the patients. No correlation was observed betweenplasma levels and the occurrence or spacing of relapses.

The question arose whether plasma levels would be affected bysuch factors as jungle climate, fatigue, combat, and diarrhea. It was shownoverseas that diarrhea or dysentery did not influence the pattern of thequinacrine plasma levels during therapy. In this country under simulated jungleconditions, and also overseas, it was shown that high temperatures, humidity,and fatigue did not adversely affect the absorption or stabilization ofquinacrine in the plasma.

Quinacrine was found to be effective also in the treatment ofdelayed primary vivax malaria appearing after discontinuance of quinacrinesuppression.²⁷ The continued use of this drug does not producestrains of parasites that are resistant to its action. It was noted that feverand sometimes parasitemia were not so promptly controlled in primary attacks asin relapses, although quinacrine was superior to quinine in both types ofattack, and the rate of disappearance of parasites from the blood in a relapsewas dependent on the degree of initial parasitemia rather than on the plasmalevel of quinacrine. This observation has no practical importance, however,since most patients are free of fever and symptoms before parasites havedisappeared completely from the blood, and regardless of initial parasitedensity almost all patients have negative smears within 96 hours after the initiation of anadequate schedule of quinacrine therapy.

Attempts to enhance the response to treatment by increasing the initial orthe total dose were made in several oversea installations. However, 2.8 gm. in 3 days, or 3.5to 4.8 gm. in a week, proved no moreeffective in controlling the acute attack or affecting subsequent relapse ratesthan the standard schedule of 2.8 gm. in 7 days. In the controlof relapses, short courses of treatment (1.2 gm. in 16 hours or 1.4 gm. in 12 to 16 hours)were effective in terminating acute attacks but, if not followed immediately bysuppressive doses, might be succeeded by early relapse or in a malarious area bynew infection because of the rapid fall of concentration in the plasma belowprotective levels. One-

²⁶Ellerbrook, L. D., Lippincott, S. W., Cateno, C. F.,Gordon, H. H., and Marble, A.: Plasma Quinacrine Concentration in Treatment ofPlasmodium Vivax Malaria Acquired in the South Pacific. Arch. Int. Med. 76:352-357, November-December 1945.
²⁷London, I. M., Kane, C. A., Schroeder, E. F., andMost, H.: The Delayed Primary Attack of Vivax Malaria. New England J. Med.235: 406-410, 19 Sept. 1946.

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day treatment courses or less have only a slight advantage ininsuring the administration of adequate amounts of drug in a short time, andlittle is gained in reduction of nursing care since patients with acute malariaare usually sick for several days. Moreover, unrecognized or severe falciparuminfections may not be controlled with this amount of medication. A false senseof security may cause carelessness in observation of patients.

A short course totaling 2.2 gm. in 3 days (1.0 gm. on thefirst day, then 0.6 gm. daily for 2 days) was found, in this country, aseffective as 2.8 gm. in 7 days in terminatingacute attacks of vivax malaria, with a similar spacing of the intervals torelapse. Many patients were symptom free in 3 days, and in some cases the periodof hospitalization could be reduced. Relapse of previously treated falciparuminfections, rarely seen in this country, would not constitute a hazard in 3-daytreatment of vivax relapses here. Total doses in excess of 2.8 gm. or inperiods of less than 7 days are not advocated except possibly in fulminating falciparum infections, since nothing is gained by excessive dosage and there ismore risk of toxic reactions.

In falciparum infections-The clinical studies discussed thus far havebeen concerned principally with vivax infections. It has been noted thatexperimentally induced falciparum infections were effectively controlled withquinacrine plasma levels in the range of 40 to 50 μg. per liter. Plasma levelsin that order are quite uniformly attained by initial doses of 1.0 gm. ofquinacrine administered during the first day of treatment by the oral orcombined oral and parenteral routes. It was to be expected, then, that standardquinacrine treatment would prove effective in the control of the majority ofinfections with P. falciparum.

In a report from India²⁸ summarizingthe treatment of over 5,000 cases of malaria of which more than two-thirds weredue to P. falciparum, it was stated that quinacrine was as effective as quininein terminating them. This is of particular significance since early in thattheater's experience the dosage of quinacrine was 0.1 gm. three times a day for5 to 7 days. Undoubtedly, higher doses on the first day would have produced evenmore satisfactory results. In fact, 50 patients so treated responded promptlyand were afebrile by the third day.

By contrast, patients treated with quinine for the first 2 days had areactivation of fever on the third day when quinine was discontinued. It wasstated that in this study the patients treated with quinacrine remained febrilea little longer than those treated initially with quinine, but the former hadconsiderably less nausea and vomiting and no tinnitus or deafness. Treatmentwith quinine was associated with the development of blackwater fever in twopatients. One patient developed a fatal diffuse bullous erythema after 1.95 gm.of quinine and another developed an extensive dermatitis after 15 gm.

Extensive experience in West Africa and in various Pacificislands where the majority of initial attacks of malaria were due to P.falciparum demonstrated the efficiency of standard quinacrine therapy interminating uncomplicated attacks. In general, its value in the more severeforms of malaria is attested by the remarkably low death rate from this diseaseduring the war in conjunction with the widespread use of quinacrine. Fulminatingcerebral malaria was fortunately not common in most theaters.

²⁸Ware, R. E., Brem, T. R., and Crane, N. F.:Experiences With Malaria in India. [Official record.]

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In India, of over 6,000 cases of malaria in native or foreigntroops there were 140 cases of the cerebral form, or an incidence of about 2percent of falciparum infections.²⁹The death rate in American troops with cerebral malaria was 5 percent and inChinese and other personnel, 33 percent. Quinacrine alone was said to have curedseveral cases. In another report,³⁰it was stated that 1 death occurred in 8 patients with cerebral malaria treatedwith quinacrine intramuscularly, and 31 deaths occurred in 61 patients treatedwith quinine parenterally. In the latter group, eight patients had convulsionsand died shortly after intravenous injection of quinine. Of five additionalpatients treated with a single infusion of quinacrine (0.8 to 1.0 gm.) forcerebral malaria, one died; this patient had also received more than 1.0 gm. ofquinine intravenously.³¹In the four patients who recovered, parasitemia was controlled within 48 hours.The serum quinacrine levels 24 hours after the infusion was given varied from100 to 320 μg. per liter. The mortality for cerebral malaria in a series of 146patients in the Southwest Pacific treated with quinine parenterally was 37percent and was 21 percent for 19 patients treated with quinacrine.

Parenteral quinacrine treatment thus gave definite evidence of effectivenessin some cases of cerebral malaria. No comparative studies in sufficient numberswere reported on which to base definite conclusions with regard to the relativeefficiency of quinacrine and quinine in severe cases with cerebral involvement.The surgeon in the India-Burma theater stated:

My conclusions as to the relative merits of parenteralquinine and Atabrine (in cerebral malaria) are that I am not certain that eitherpossesses a distinct advantage over the other. Atabrine may have a slightadvantage in that (1) it is probably less toxic, (2) its effect persists longer,and (3) it can be given intramuscularly. All data we possess indicate that whengiven in adequate amounts, it is at least as effective as quinine, and may bemore effective. Moreover, if a rapid and prolonged effect is desired 0.8 gm. in a slow intravenous drip (over 4 hours) clearsthe blood of parasites as rapidly as any other method and a parasiticidalconcentration remains in the blood for at least 5 days.³²

Intramuscular injections of quinacrine were found useful in vivax and falciparum infections with severe vomiting as a means of attaininghigh plasma levels promptly. For example, single doses of 0.4 gm. given intramuscularly result in levels of 168, 327, 297, 155, 89, 60,45, 37, and 20 μg. per liter at 5,15, 30, 60 minutes and 2,3, 5, 8, and 24 hours, respectively, afterinjection. Serial injections of 0.2 gm. at intervals of 4 to 8 hoursfor 24 hoursor more can be expected to maintain high effective levels until oral medicationcan be instituted.

Following a single intramuscular dose of 0.2 gm. of quinacrine, it was shown³³that the number of motile parasites with finely dispersed pigment wasreduced and the number of nonmotile parasites with clumped pigment wasincreased. Three hours after the injection when the plasma level of

²⁹Fitz-Hugh, T., Jr., Pepper, D. S., and Hopkins, H.U. : The Cerebral Form of Malaria. Bull. U.S. Army M. Dept. No. 83, pp. 39-48,December 1944.
³⁰See footnote 17, p. 535.
³¹Blumgart, Herrman L., and Pike, George M. : Historyof Internal Medicine in India-Burma Theater. [Official record.]
³²See footnote 17, p. 535.
³³Trager, W., Bang, F. B., andHairston, N. G.: Relation of Plasma Level of Atabrine to Morphology andMotility of Plasmodium Vivax. Proc. Soc. Exper. Biol. & Med. 60: 257-258,November 1945.

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quinacrine was falling rapidly the ratio of motile tononmotile parasites returned to normal, and since the total parasite count didnot change it was suggested the parasites had recovered after temporary damage.Similar changes during the first 3 hours after quinine at levels of 6 to 10 mg.per liter were noted. These observations emphasize the necessity for thecontinued serial administration of antimalarial agents in sufficient amounts andat properly spaced intervals so that adequate levels would be maintainedsufficiently long to terminate clinical activity and parasitemia.

The value of single intravenous infusions of quinacrine in falciparuminfections was studied at the 20th General Hospital.

Doses of 0.4 gm., 0.6 gm., and 0.8 gm. in 1,000 cc. of fluid were given intravenously togroups of 10 patients on each dosage schedule, and 1.0 gm. in a single infusion was given to each of 20patients. The acute attack was terminated in all but one patient (given 0.4 gm.)without further treatment. The duration of fever in the various groups was 8 to64 hours (average 27.2 hours) and smears became negative in from 1 to 3 days(average 2.2 days). Of the 30 patients treated with 0.8 or 1.0 gm., 19 wereobserved for a month or more after treatment and 4 relapsed within 3 to 5 weeks.Of the 20 patients who received 0.4 or 0.6 gm., 9 were followed for a month ormore and 8 of the 9 relapsed within 10 to 23 days after termination of theattack by intravenous quinacrine. Three patients had brief periods of vomitingshortly after the infusion; one patient had a generalized convulsion; a fifthpatient developed an acute state of exhilaration and excitement lasting 5 hours.Two patients with moderately severe cerebral malaria treated with 1.0 gm. or quinacrine intravenously responded well, being out ofstupor in 18 hours. Twenty control patients treated for acute attacks of falciparum malaria with quinacrine by mouth all responded well althoughparasitemia and fever persisted in them a little longer than in the groupstreated intravenously. In a comparison of the relative efficiency of singleintravenous doses of quinine and quinacrine, it was reported that of 10 patientstreated for acute falciparum malaria with 1.2 gm. of quinine in an infusion of1,000 cc., the attack was terminated in only 5. The remainder continued to havehigh fever for 60 to 132 hours after treatment and required additional therapy.Three relapses occurred in the successfully treated group 6, 9, and 13 days,respectively, after infusion. Three patients who received single doses of 2.0gm. of quinine in an infusion developed signs and symptoms of shock. It shouldbe pointed out that these doses of quinine (1.2 and 2.0 gm.) are in the toxicrange for this drug and are rarely if ever resorted to therapeutically. Further,a comparison of single doses of quinine and quinacrine does not take intoaccount the rapid excretion of quinine. A more practical estimation would havebeen the serial administration of nontoxic amounts of quinine intravenously.

From these observations, it is apparent that although quinacrine givenintravenously effectively terminates attacks of falciparum malaria such aprocedure is not without danger and has little advantage over oral treatment inmost cases. In cerebral malaria, comparably high effective plasma levels may bereached as quickly by serial intramuscular injections without the dangersinherent in intravenous therapy. Relapses, which occurred at short intervalsafter single doses of 0.8 or 1.0 gm. of quinacrine injected intravenously, arevery common in falciparum infections after 2.8 gm. given in 7 days by mouth.Finally, the prompt response from intravenous quinacrine reported in Chinesepatients with a high degree of immunity may not be

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duplicated in nonimmune white American troops. The question of parenteralquinacrine versus quinine therapy remained unsettled.

In suppression-The dosage of quinacrine for suppressivepurposes recommended before World War II was based on evidence derived frommalaria rates in various parts of the world, populated, for the most part, byimmune natives. Daily doses of 0.05 gm. of quinacrine were considered inferiorto a daily dose of quinine, but 0.4 gm. of quinacrine weekly in two divideddoses was considered more effective than daily doses of quinine in suppressingclinical malaria.³⁴Althoughnumerous reports indicated varying success in the suppression of malaria withthis divided dose of quinacrine, it was not known when we entered the war howeffective such a schedule would be in nonimmune troops in highly malariouszones and under combat conditions.

Studies of the course of plasma levels resulting from 0.4 gm.and 0.6 gm. of quinacrine weekly as well as from larger amounts were conductedin England on volunteers, and in the United States on medical students³⁵ and at a military installation. Of 230 white soldiersobserved in active training at Fort Knox, Ky., 100 men received 0.4 gm. ofquinacrine weekly and another 100 received 0.6 gm. weekly. Thirty volunteerssubjected to conditions simulating jungle climate were given 1.2 gm. during thefirst week and 0.6 gm. weekly for the next 11 weeks. It was shown that, withconstant regimens, the plasma concentrations differed widely in individuals butthat the group plasma level at any time was a function of the daily dose, thepreexisting level, and the interval since the last dose. The group mean levelrose progressively for 4 to 8 weeks to reach an equilibrium, which thenremained substantially constant. The equilibrium level for the group given 0.4gm. weekly was 1.2 μg. per liter, and was 17 for the group on 0.6 gm. weekly.It was shown that a hot, humid environment did not influence the groupequilibrium level and that suppressive therapy under such environmentalconditions did not affect the rate of acclimatization and performance of themen. The time for reaching equilibrium levels could be reduced from 5 to 6 weeksto 1 week by administering high initial doses for a short period (0.2 gm. dailyfor 5 to 6 successive days). Similar results and conclusions were reported fromstudies in England and civilian installations in the United States.

It was obvious that such plasma levels would give little orno protection during the first 4 to 6 weeks, or until maximum equilibrium wasattained with these doses. Furthermore, marked variations in individual levelsmeant that the smaller weekly dosage (0.4 mg.) would frequently fail to protectsignificant numbers of men, especially if occasional doses were omitted. It wasclearly necessary to give a large initial or priming dose before or when troopsentered malarious zones in order to give immediate protection and

³⁴The Treatment of Malaria; Study ofSynthetic Drugs, as Compared With Quinine, in the Therapeutics and Prophylaxisof Malaria. Fourth General Report of the Malaria Commission, League of Nations,Bull. Health Organ. 6: 895, December 1937.
³⁵Minutes, Subcommittee on the Coordination ofMalarial Studies, 3 June 1943, National Research Council. Bulletin on Malaria Research, pp. 99-105.

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prevent clinical "breakthroughs." These data werecollected during the early months of 1943. Shortlythereafter, these conclusions were translated in terms of the specificrecommendations for suppression of malaria contained in Circular Letter No. 153(p. 540).

In the meantime, numerous reports from overseas had beenreceived which documented the development of the clinical disease in largenumbers of troops shortly after their arrival in malarious areas and clearlydemonstrated the value of priming doses and the superiority of from 0.6 to 0.7gm. quinacrine weekly over 0.4 gm.for suppression. Valuable information was obtained on "breakthroughs"during suppression with 0.4 and0.6 gm. weekly and the relation of such failures to plasma levels and quinacrinediscipline. Brief reference to a few field experiences to elucidate some of thefactors associated with poor and successful suppression follows.

The Americal Division, which was on New Caledonia from Marchto October 1942, was moved to Guadalcanal during October, November, andDecember, where it remained until March 1943.³⁶ The men were forced tolive and fight in hypermalarious areas with little to no field control and nomosquito repellent. Quinacrine, 0.4 gm. weekly, was prescribed but the extent ofits use was not known. The malaria rates on Guadalcanal were as high as 2,500per 1,000 per annum. The ratio of falciparum to vivax infections was 3 to 1.Following removal of these troops to the Fiji Islands and mass treatment endingon 10 June 1943, the rates in August and October were still 4,220 and 2,948 per1,000 per annum, respectively. In September, 613 men were placed on suppressivedoses of quinacrine of 0.4 to 0.6 gm. per week. The malaria rate in this groupfell from 219 per 1,000 per month to 23. In November, the Division was placed on0.4 gm. weekly and this dosage was increased to 0.6 gm. on 12 December. Themalaria rate fell from 2,948 per 1,000 per annum to 80 and after 2 months'combat in Bougainville the rate in March 1944 was only 97.1. The experience inthis division showed that early suppressive doses of 0.4 gm. weekly wereinadequate to control malaria in combat although a moderate degree ofsatisfactory suppression was obtained in a nonmalarious area under fairly gooddisciplinary conditions. On the other hand, 0.6 gm. of quinacrine proved highlyeffective both in malarious areas and in regions free from malaria (chart 29).Another example was the 43d Division, which had also been on 0.4 gm. weekly witha high incidence of malaria. Half the division was taken off suppression and hada malaria rate of 2,000 per 1,000 per annum. The other half was placed on 0.6gm. weekly and their rate fell to 236 per 1,000 per annum. Again, a navalconstruction battalion of 840 men, on a suppressive regimen of 0.4 gm. weekly,arrived on Guadalcanal on 12 December 1942.³⁷ During the first 5weeks, 123 men were down with malaria, about 95 percent of which was due to P.falciparum. In the same report it was stated that two combat infantry outfits on0.4 gm. weekly entered a highly malarious area and within 2 weeks malaria wasoccurring at the rate of 40 to 60 cases a day, most of them caused by P.falciparum.

Although the great majority of initial infections in the Pacific islands werecaused by P. falciparum, subsequent relapses were principally caused by P. vivax.When adequate amounts of quinacrine were used in termination of the attack of falciparum malaria and when suppressive medication of 0.1

³⁶Essential Technical Medical Data, South PacificArea, for April 1944.
³⁷Lewis,R. A.: The Suppression of Malaria. [Official record.]

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CHART 29.-Malaria rates in aninfantry regiment under various schedules of suppression with quinacrinehydrochloride, by week

gm. daily was continued, falciparum malaria rarely occurred ondiscontinuance of suppression.

In the Australian studies that have been referred to,³⁸it was conclusively shown in volunteers infected with P.falciparum (New Guineastrain) transmitted by mosquitoes that, if 0.1 gm. of quinacrine wereadministered during the period of infection and for 23 days after the lastinfective bite, clinical malaria did not occur during suppression or after itstermination. Actual cure was demonstrated by subinoculation of 200 cc. of bloodinto other volunteers. If subinoculation was done on the 9th to 11th days afterinfection, malaria developed in the recipients, indicating that quinacrine wasnot a causal prophylactic but effected a cure by permanently destroying theerythrocytic parasites after their appearance in the blood. Similar studies inEngland and in this country with other strains of P. falciparum also demonstrated thecurative action of quinacrine suppression in such infections. In the Australianexperiments along the same lines with P. vivax, therewas shown complete clinical suppression during therapy but no curative effect,for all the volunteers developed vivax malariaat varying intervals after quinacrine was discontinued.

The practical inferences from these observations were that effective plasmaequilibrium having been established, quinacrine administered in doses

³⁸See footnote 12, p. 529.

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of 0.1 gm. daily without interruption would effectively suppress both falciparum and vivax malaria and that, if suppression were continued for about 3weeks in troops leaving the malarious area, falciparum malaria would notdevelop. Vivax relapses would occur later and could be effectively terminatedwith quinacrine or delayed indefinitely if necessary by continued suppression.These results were seen in many studies overseas and in this country.

In one experiment, for example, 107 volunteers were taken toa highly malarious area in New Guinea where they were exposed to infection for44 days. Initial priming doses were followed by 0.1 gm. of quinacrine dailyadministered 6 days a week during the period of exposure and for 10 daysthereafter. No case of malaria developed during the period of suppression,whereas of 44 men who acted as controls and received no medication, 32 developedmalaria (in 9 caused by P. falciparum). Subsequent to the discontinuance ofsuppressive therapy 25 cases of malaria due to P. vivax developed. No case ofmalaria caused by P. falciparum developed in the group receiving quinacrineeither during or after suppressive treatment. This field study showed definitelythe value of quinacrine in absolutely preventing clinical malaria due to P.vivax and P. falciparum during adequate suppression and the curative as well assuppressive action of quinacrine in falciparum infections.

In general, the plan of suppression with doses of 0.1 gm. daily was widelyused with excellent results. In one oversea area, it was suggested that troopson patrol or in combat may fail to take occasional doses. Studies with singledoses of 0.4 or 0.5 gm. twice a week carried out in the field showed that such aschedule would provide adequate protection and insure affective levels all thetime.³⁹ This modified plan was not generally adopted but could beused under circumstances precluding regular daily suppressive medication.

By continuing quinacrine therapy for suppression followingtermination of acute attacks of vivax infections, it was possible to maintaineffective fighting strength in combat units highly seeded with malaria. In thiscountry, continued suppression for 3 months or more reduced the number ofhospital admissions for relapses without interrupting training or rehabilitationprograms. At one hospital in the United States, for example, 79 men treated with2.8 gm. of quinacrine in 7 days for acute attacks of vivax malaria of Pacificorigin were maintained on 0.1 gm. daily for 150 days after termination of theacute attack. No parasitemia or clinical attack occurred during the 5 months ofsuppression. In a similar sized group, also treated for acute attacks but notsubsequently placed on suppressive therapy, 80 percent relapsed during the first120 days' observation after treatment. The group given effective protectionduring 5 months by continued therapy was not thereby protected againstsubsequent relapse, for 82 percent relapsed during the 120-day period ofobservation after discontinuance of suppression (chart 30).

³⁹Duncan, G. G.: Quinacrine Hydrochloride as aMalaria-Suppressive Agent for Combat Troops. War Med. 8: 305-318,November-December 1945.

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CHART 30.-Distributionof relapses in two groups of patients after treatment for acute attacks of vivaxmalaria of Pacific origin

The subject of "breakthroughs" or clinical attacksduring suppression received attention at many oversea installations. In India,six patients supposedly taking 0.1 gm. of quinacrine a day were admitted to the20th General Hospital and found to have plasma levels of 6, 7, 8, 12, 12, and 14μg. per liter, respectively. In every case, it was possible to show that theindividual was able to absorb quinacrine normally, the reason for the low levelsbeing failure to take the prescribed dose daily. In the Southwest Pacific, 80percent of 116 men who had attacks while on suppression were found to havelevels of less than 10, whereas only 25 percent of another group of 853 men hadsimilarly low levels. Seventy-five officers having attacks while supposedlytaking 0.1 gm. quinacrine daily were found to have low plasma levels andadmitted not taking the drug regularly. On the other hand, four men with acuteattacks were found to have levels of from 16 to 30 μg. per liter whenadmitted. It is possible that self-administered medication for beginningsymptoms may account for apparently adequate levels in some"breakthroughs." In a division in the Southwest Pacific, the averagelevel for 1,021 men on suppression for a year or more was 13 μg. per liter andvaried from an average of 5 in men who "broke through" to an averageof over 20 in companies with good discipline.⁴⁰

⁴⁰Schaffer, A. J., and Lewis, R. A.:Atabrine Studies in the Field. I. Relation of Serum Atabrine Level toBreakthrough of Previously Contracted Vivax Malaria. Bull. Johns Hopkins Hosp.78: 265-281, May 1946.

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Toxicity

Effects of prolonged administration

Toxic reactions, principally related to the gastrointestinaltract and nervous system, associated with the ingestion of quinacrine or itsparenteral use had been reported before World War II. In an analysis of toxicreactions observed in 49,681 patientsto whom quinacrine had been administered before 1941, it was concluded that neurogenic symptoms (headache,mental depression, delirium, psychoses, convulsions) occurred rarely (less than1 per 1,000) and that gastrointestinal symptoms (nausea, vomiting, diarrhea)were uncommon and of little significance and were frequently related to theconcomitant administration of other drugs. More serious reactions were poorlydocumented and could not be unequivocably related to quinacrine.

Following our entry into the war and the extensive use of quinacrine overprolonged periods for suppression and frequently for termination of acuteattacks with larger amounts of drug than were previously used for eitherpurpose, great interest was stimulated in the potential acute or chronic toxiceffects of such medication. No attempt will be made in this section to reviewthe voluminous studies made with various experimental animals. Brief referencewill be made to observations on the effects of quinacrine not previouslyreported or to findings that were of significance during World War II.

Liver and kidneys-Studies of hippuric acid synthesis, serum phosphatase,urea clearance, and liver biopsies (10 cases) performed on 101 men who had beenon suppression from 8 to 36 monthsrevealed no abnormalities. Similar negative findings resulted from detailedexaminations of liver and kidney function of 43 Oxford University undergraduates who took 0.1gm. of quinacrine daily over a period of 9 to 12 months.

Studies to discover subclinical hepatic damage in white and Negro Americantroops who had been taking 0.6 gm.quinacrine weekly for 18 to 24 monthswere done on various groups of 50 men. The icteric index, urinary urobilinogen,sulfobromophthalein excretion, fibrinogen, galactose tolerance, and cephalin-cholesterolflocculation tests failed to detect any evidence of subclinical hepaticdysfunction.⁴¹On the other hand, there were a few reports ofvarying degrees of liver disease believed related to quinacrine ingestion.

Four cases of hepatic dysfunction (two subclinical and twosevere hepatitis, one of which ended fatally) believed related to quinacrinewere reported from an oversea theater. An interesting feature in these cases wasthe association of corneal edema, manifested by blurred vision. In three of thepatients corneal edema became less marked after discontinuance of quinacrine andwas aggravated by its readministration. Impaired liver function did not becomeapparent until 3 to 6 months after the initial episode of visual disturbance.The observers of these patients felt that corneal edema and

⁴¹Gottfried, S. P., and Levine, A. C.: Liver FunctionStudies on Soldiers Under Prolonged Atabrine Administration. J. Lab. & Clin.Med. 30: 853-855, October 1945.

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punctate erosions of the surface epithelium were due toquinacrine, that this was a rare manifestation of quinacrine toxicity, and thatits occurrence may be followed by liver disease.

In a large series of Chinese patients receiving quinacrinefor suppression or treatment of malaria there were 5 with severe hepatitis andexfoliative dermatitis, 3 of whom died of this complication (incidence 1 in2,000-3,000 Chinese).⁴² Therash present in each case appeared as early as the 2d day and as late as the10th day of medication and consisted of a scarlatiniform, maculopapular, dry,scaling eruption beginning on the face and involving the entire body.Conjunctivitis and exfoliation of the tongue were observed. Jaundice, whichappeared several days after the rash, was accompanied by a high("septic") fever, leukocytosis, proteinuria, and bilirubinuria. Theliver was large and tender at first but shrank rapidly. Mental clouding wasprominent and death followed in coma in the third to fifth week of the disease.At autopsy there was gross and microscopic evidence of severe hepatitis ornecrosis of the liver. It was concluded that quinacrine in previously sensitizedindividuals was responsible for both the hepatitis and the severe dermatitis.

Aplastic anemia-A small number ofcases of aplastic anemia with and without atypical lichen planus had beenreported from the Pacific area, and this was thought to be possibly ascribableto quinacrine. In an attempt to determine whether prolonged use of quinacrinewas responsible for the production of pathological changes in the body, the ArmyInstitute of Pathology (now the Armed Forces Institute of Pathology),Washington, D.C., instructed laboratory officers to furnish data of quinacrineingestion with all autopsy protocols, regardless of the cause of death. For sometime, nothing of significance was observed. Later, it became apparent thataplastic anemia was the cause of death in a disproportionately large number ofcases represented by autopsy material sent from the South and Southwest PacificAreas where an extensive regimen of quinacrine suppression was in force.Fifty-seven cases of aplastic anemia were the basis of a report⁴³onthe possible relation of this disease and quinacrine. The incidence of aplasticanemia per 100,000 men varied little (0.1 to 0.3) from 1942 to 1945 inthe continental United States and all foreign theaters, exclusive of the Southand Southwest Pacific Areas and the China-Burma-India theater, where it rosefrom zero in 1942 to a peak of 2.84 per 100,000 during the last 6 months of 1944.Quinacrine was the common drug in at least 47 cases, 9 others being excluded because of the possiblerole of arsenic, irradiation, or sulfonamides in the production of the aplasticstate. In the group treated principally with quinacrine, the drug had been takenfor a period of from 1 to 34 months;in the majority, from 4 to 9 months. Large doses were specifically reported in sixcases. Four patients had increased the daily dose to 0.2 gm.for a period of from 3 weeks to 8 months; one patient took 20 to 30 tablets during4 days before onset of symptoms and another was said to haveingested "massive doses" for 3 weeksbefore he became sick. Hepatitis was present in 10 cases

⁴²Agress, C. M.: Atabrine as a Cause of FatalExfoliative Dermatitis and Hepatitis. J.A.M.A. 131: 14-21, 4 May 1946.
⁴³Custer, R. P.: Aplastic Anemia in Soldiers TreatedWith Atabrine (Quinacrine). Am. J.M. Sc. 212: 211-224, August 1946.

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and the "quinacrine dermatitis complex" in 25. Theliver lesions in five cases were indistinguishable from epidemic hepatitis.Cerebral hemorrhage was the immediate cause of death in 10 cases. The bonemarrow in all cases was badly depleted of normal hematopoietic elements, oftenalmost totally so without evidence of extramedullary hematopoiesis.Occasionally, the influx of lymphocytes, plasmocytes, and histiocytes attainedsuch proportions that at first glance the fundamental hypoplastic state was notapparent. One man who received 65 transfusions and lived 10 months had extensivesecondary fibrosis of the marrow cavity. Clinically, the onset was gradual inmost cases, and purpuric manifestations were commonly seen early. In many cases,the red blood cell count could be maintained at fairly good levels by repeatedtransfusions, but the white cells and platelets remained uniformly depressed.In 20 cases, the "quinacrine dermatitis complex" preceded the anemia.Although this form of possible quinacrine toxicity has proved fatal in the greatmajority of cases, recovery has been reported.⁴⁴

Asymptomatic changes in the skin-Changes in the skinand mucous membranes resulting from the prolonged administration of quinacrine werethe subject of numerous reports. They varied from asymptomatic pigmentarychanges to severe and disabling forms of dermatitis.

The yellow discoloration of the skin associated withquinacrine ingestion was a common finding in the majority of men on prolongedsuppression. The intensity of the discoloration, which is not a toxicmanifestation of drug ingestion but rather an expression of its deposition inthe skin, varied with duration and dosage of suppression, exposure to sunlight,and complexion, being most marked in subjects with dark skin and hair.

Attempts were made to correlate the degree of fluorescenceproduced by quinacrine in the skin and plasma levels with the use of adermofluorometer. A high degree of correlation of induced palmar skinfluorescence with mean plasma levels was found in 33 volunteers on 0.2 gm. dailyfor 1 week and 0.1 gm. daily for 3 weeks. The peak of fluorescence in the skinwas reached in 4 to 5 weeks after initial dosage and decreased slowly over a12-week period after the drug was discontinued. It was believed that thisinstrument might be useful in the field in determining whether quinacrinesuppression discipline was effective.

Quinacrine discoloration of the sclera, as observed in asmall number of individuals, was described⁴⁵as consisting ofyellowish pigmentation, most marked around the limbus in the part of the scleraexposed in the palpebral fissure, and fading toward the fornices. On the otherhand, in jaundice, the pigmentation is most marked in the fornices toward theequator of the globe and fading toward the limbus.

Ochronosis-like pigmentation of mucous membranes, skin, and cartilage wasdescribed in many individuals on quinacrine suppression. In a dental

⁴⁴Most, H., and Hayman, J.M., Jr.: Recovery From Severe Hypoplastic Anemia Associated With Atypical Lichen Planus. Bull. U.S. Army M. Dept.5: 339-342, March 1946.
⁴⁵Hayman, J. M., Jr.:Atabrine Pigmentation of the Sclera. Bull. U.S. Army M. Dept. No. 82, pp.120-121, November 1944.

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survey of 1,000 men in the Philippine Islands, 300 showedbluish-purple pigmentation of the hard palate. The color varied from a lightblue purple to intense blue black involving from 1 cm. to the entire palate.⁴⁶In another report,⁴⁷ the incidence in 500 men in the SouthwestPacific Area was 31 percent. The majority of the men with pigmentation of thepalate had been on quinacrine suppression for at least 7 months. The nature ofthe pigment based on staining reactions of biopsy sections was considered to behemosiderin. A detailed study of a small number of patients showed theochronosislike pigment to be distributed in the skin, hard palate, nail beds,the cartilages of the nose, ears, epiglottis, and trachea, the conjunctivae andcorneoscleral limbus. Phenol and alkaptonuria were excluded as causativefactors. Surveys at Harmon General Hospital, Longview, Tex., and Moore GeneralHospital, Swannanoa, N.C., likewise demonstrated an incidence of 15 to 30percent of asymptomatic pigmentation as described above in patients who had beenon prolonged quinacrine suppression overseas.

Atabrine dermatitis complex-More significant changes inthe skin were reported from overseas as causing disability and frequentlyserious prolonged illness. For security reasons and in order to maintain themorale of quinacrine suppression, the data accumulated were not made generallyavailable at first. It was necessary in the beginning to collect information onthe incidence of these reactions and to evaluate fully the relation ofquinacrine to them. The possibility of substituting another suppressive agentfor quinacrine had to be considered if this cutaneous complex proved to bewidespread or if unfounded rumors as to its incidence and severity threatened abreakdown in discipline. Fortunately, this did not occur nor was it found thatthe incidence of the Atabrine dermatitis complex was very great. The followingparagraphs from a report entitled "Evaluation of the Untoward ReactionsAttributable to Atabrine" prepared by the Medical Consultants Division ofthe Surgeon General's Office⁴⁸ summarize the vast amount of clinical and otherdata collected overseas and in this country:

Medical officers in the Southwest Pacific Area calledattention, in the latter part of 1943, to a characteristic cutaneous syndromewhich was occurring in soldiers who had been evacuated from New Guinea andadjacent islands. Lt. Col. Charles L. Schmitt, MC, and Maj. (later Lt. Col.)Thomas W. Nisbet, MC, dermatologists stationed with general hospitals in thatarea, were the first to submit to The Surgeon General official reports in whichthey described the disease and its probable etiology. Later, similar cases werereported from all other theaters where suppressive atabrine medication was ingeneral use as a control measure for malaria. This syndrome has been observedmost frequently in New Guinea and adjacent islands and in Assam and northernBurma; in other areas only small numbers of cases have occurred.

⁴⁶Summer, S.: An OralManifestation of the Use of Atabrine. [Official record.]
⁴⁷Lippard, V. W., and Kauer, G. L., Jr.: Pigmentation of the Palate and Subungual TissuesAssociated With Suppressive Quinacrine Hydrochloride Therapy. Am. J. Trop. Med.25: 469-471, November 1945.
⁴⁸Evaluation of the UntowardReactions Attributable to Atabrine. Bull. U.S. Army M. Dept. 4: 653-659,December 1945.

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This skin disease which has acquired the name atypical lichenplanus is characterized by various * * * types of lesions. * * * Almost allpatients have both violaceous, hypertrophic lichenoid plaques and some form ofcutaneous eczematoid reaction. During the course of the disease, a considerablenumber of these patients have acute, "explosive" generalizedexacerbations, manifested by oozing eczematoid dermatitis having a predilectionfor the flexors, groins, axillae, extremities, and neck. Such exacerbationsresemble exfoliative dermatitis * * * which is as severe as the cases of primaryexfoliative dermatitis described below. The seriousness of such a state and theneed for expert management of these patients cannot be overemphasized.

Usually the disease is characterized by the onset of localized violaceous orerythematous eczematoid plaques * * * followed by generalization of the lesionswith subsequent appearance of the lichenoid plaques and mucous membrane lesions.* * * Any part of the cutaneous surface may be involved, but there is apredilection for the lower legs, forearms, dorsal surface of hands and feet,face, buttocks, lower anterior surface of the neck, genitalia, mucous membranesof the mouth, eyes, and eyelids. Residual effects and lesions which developlater in the course of the disease include: atrophy; hyperpigmentation (melanin)and depigmentation; diffuse follicular accentuation over the upper back,shoulders, and extremities; changes in the nails; moth-eaten, patchy alopecia;and marked disturbance in sweating function.

* * * A characteristic type of eczematoid dermatitis which also has occurredin individuals taking suppressive Atabrine * * * is characterized by bilateral,symmetrical, violaceous-tinged, vesicular, eczematoid and oozing plaquesinvolving the hands, arms, feet, legs, and sometimes other parts of the body.Secondary pyogenic infection is common. The nail bed and skin of the nail foldsare usually involved, frequently resulting in exfoliation of the nails withouttrue suppurative paronychia. With experience, on clinical grounds, one can inmost cases distinguish between this eruption and other forms of eczematoiddermatitis. Tentatively the term "symmetrical eczematoid dermatitis"has been used * * *.

It does not seem advisable to make a sharp distinction between the so-calledatypical lichen planus and the symmetrical eczematoid dermatitis syndrome. Froma broad point of view, it seems that all of these patients have either alichenoid cutaneous reaction or an eczematoid cutaneous reaction or acombination * * *. A small percentage of the total group have lichenoid lesionsalone; a larger group have a combination of lichenoid and eczematoid lesions;and a still larger group have eczematoid lesions that are not accompanied bylichenoid lesions.

* * * reports of general Army experience * * * indicate thatAtabrine is the essential etiological factor. The mechanisms resulting in thelichenoid reaction and the eczematoid reaction are probably different. Forexample, it was observed in a carefully controlled series of cases at MooreGeneral Hospital that the time interval preceding exacerbations of eczematoidlesions is much shorter than with the lichenoid lesions. The fact that theincidence has been so very much higher in New Guinea and adjacent islands and inAssam and northern Burma suggests that climatic or geographic factors may play acontributory role in the etiology. There is evidence that various forms ofcutaneous trauma may contribute to the onset and localization of the lesions,particularly the eczematoid phase of the eruption. The sequence of events inmany cases suggests that individuals taking suppressive Atabrine have a tendencyto acquire chronic eczematoid dermatitis on contact with external allergens(such as certain jungle plants and trees) rather than self-limited contactdermatitis which is the usual course * * *. It appears that cutaneous reactionsare more frequent in individuals who have been taking Atabrine in dosages abovethe recommended suppressive amount (0.7 gm. per week). It should be emphasizedthat the incidence of these cutaneous diseases has been relatively low, even inNew Guinea, and, from the military point of view, has not been an importanthandicap.

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Since available evidence indicates that we are dealing with one complex, itis suggested that it would be best to group these cutaneous reactions attributedto Atabrine under one heading "Atabrine dermatitis complex" andclassify the various manifestations as follows: (1) lichenoid dermatitis; (2)lichenoid and eczematoid dermatitis (both including cases heretofore referred toas "atypical lichen planus"); (3) eczematoid dermatitis (including cases heretofore referred to as"symmetrical eczematoiddermatitis"); (4) exfoliative dermatitis secondary to (1), (2), or(3).

The treatment of these conditions depends for the most part on earlyrecognition of the trouble and discontinuation of Atabrine. In many instances,it is difficult to decide whether or not a given case of eczematoid dermatitisis due to Atabrine. It is necessary to study such cases carefully, with carefulobservation after withdrawal of Atabrine and possibly cautious trialreadministration of the drug (do not attempt readministration of Atabrine to apatient who has had exfoliative dermatitis or a severe generalized eczematoidexacerbation). * * * When possible, such patients should be seen by a competentdermatologist, and every effort should be made to rule out other etiologicalfactors. Parenteral administration of penicillin is indicated in patients withsecondary pyogenic infection. Local treatment should be bland and nonirritating,and should consist of preparations such as 1: 9,000 potassium permanganatesoaks, Burow's solution soaks, 5 percent aqueous solution of tannic acid sprayfor oozing intertriginous sites, and application of borated cold cream if agrease is indicated. Preparations such as salicylic acid ointment, tincture ofiodine, and sulfonamide ointments should not be used. Arsenicals and bismuthhave been tried in some cases without affecting the course significantly; theyshould not be used. Superficial X-ray therapy, if indicated, should be used onlyunder the direction of a competent dermatologist and in small doses (not morethan 75 r and not to exceed a total of more than 375 r to 450 r). At least someof these patients have some degree of light sensitivity. Therefore, exposure tosunlight should be avoided and ultraviolet light therapy should not be used. Allpatients should be studied from the general medical standpoint, includingstudies of blood, serum proteins, and liver function. Therapeutic agents such asplasma, liver extract, multiple vitamins, and intravenous glucose should be usedwhen indicated.

The prognosis varies from individual to individual. In general it isexcellent, especially if the patient is hospitalized early in the course of thedisease * * *. The lichenoid lesions involute slowly, but they do not tend torecur; the eczematoid phase of the eruption may involute rapidly, but it tendsto recur and is responsible for the prolonged disability which occurs in somecases. In general, recovery is a matter of weeks and months. Residualhyperpigmentation, depigmentation, and atrophy at the sites of lesions becomeless pronounced as time goes on and the hypohidrosis which occurs in manypatients also improves spontaneously. The course is usually prolonged in allcases of exfoliative dermatitis because of frequent exacerbations. It should benoted that these patients have not been followed for a sufficient length of timeto make final statements in regard to the prognosis of these cutaneousreactions.

Another major type of cutaneous reaction which has been attributed toAtabrine is primary exfoliative dermatitis, not secondary to thelichenoid-eczematoid syndrome. This is characterized by acute fulminatingexfoliative dermatitis, demonstrably associated with true hypersensitivity toAtabrine. It is in every respect similar to exfoliative dermatitis due to otheragents such as arsenicals. This type of cutaneous reaction * * * is believed to beassociated with Atabrine, much less commonly with quinine. Hypersensitivity ofthis degree may constitute a dangerous state in either instance.

Acute reactions to short-term administration

The principal toxic rnanifestations from therapeutic amounts of quinacrineusually employed in terminating acute attacks of malaria or from small

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initial doses early in suppression are related mainly to the skin,gastrointestinal tract, and central nervous system.

Skin.-Acute reactions in the skin related to hypersensitivityor reactivation of eczematoid dermatitis following small amounts of quinacrinehave been discussed. In addition, urticaria and pruritus have been described asan uncommon toxic manifestation of quinacrine ingestion. In a report⁴⁹ from India, 12 cases of pruritusand urticaria, particularly of the palms, were described in the course ofquinacrine suppression. In 2 patients, symptoms began within 3 days after suppressive medicationwas started and, in the other 10 patients, within 2 to 3 weeks. The symptoms subsided inthree patients while they were still on the drug and in nine within 4 days afterthe drug was discontinued. Six patients had no recurrence when quinacrine wasreadministered, and, in the three who had a recurrence, symptoms disappearedwith continued medication.

Gastrointestinal tract-Gastrointestinal symptoms (nauseaand vomiting) are rarely encountered with quinacrine during therapeutictermination of acute attacks of malaria. Frequently, these symptoms when presentare due to malaria rather than to ingestion of the drug. The administration ofquinacrine in colored capsules to patients who stated they could not take itbecause of gastrointestinal symptoms completely forestalled the development ofsuch symptoms.⁵⁰ Likewise, giving the drug after meals or withsweetened fluids during an attack of malaria reduced the incidence of nausea.Nausea, vomiting, and diarrhea were reported in large numbers of men on initialsuppressive doses of 0.2 gm. twice weekly in some series and not at all inothers. Symptoms usually disappeared after three or four doses and occurred onlyinfrequently in the 0.1 gm. daily schedule. Psychological factors, fieldsanitary conditions, and other reasons were held mainly responsible forgastrointestinal symptoms. The consensus was that these reactions were neversevere and almost invariably disappeared if the drug was continued.⁵¹

Central nervous system-Before World War II, mental disturbances werereported as occurring in approximately 1 to 2 of every 1,000 cases of malariatreated with quinacrine orally or intramuscularly, and various aberrations ofthe central nervous system attributed to quinacrine were reported in a number ofcases during the war.

In 7,604 patientstreated with quinacrine in a period of 7 monthsat an oversea general hospital, 35 casesof toxic psychosis were observed.⁵² Totaldoses of 2.1 gm. quinacrine in a week were routine. The greatest number ofreactions occurred within 6 daysof completion of therapy, although one was observed after only 0.9 gm. had beengiven and one developed as late as 12 days after therapy. There were two maintypes of onset. The most frequent

⁴⁹Essential Technical Medical Data, India-Burma Theater, for August 1945,inclosure 3 thereto.
⁵⁰See footnote 15 (1), p. 532.
⁵¹The Drug Suppressive Treatment of Malaria. Bull. U.S. Army M. Dept.No. 73, pp. 29-34, February 1944.
⁵²Gaskill, H. S., and Fitz-Hugh, T.,Jr.: Toxic Psychoses Following Atabrine. Bull. U.S. Army M. Dept. No. 86, pp. 63-69, March 1945.

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(65 percent) was marked by excitation, hallucinations, and delusions. Theother (35 percent) began with retardation, disorientation, and amnesia forrecent events together with confabulation. No constant physical or laboratoryfindings were obtained. The course of the psychosis was benign in mostinstances. Sixteen patients were subsequently (after 16 to 210 days) retested with quinacrine and only one showed anyuntoward reaction, consisting of mild excitement which cleared within 24 hours. There was no evidence that the men who developedtoxic quinacrine psychoses were unstable psychologically. Two patients who didnot recover developed typical schizophrenic reactions. There was no evidence oflatent psychosis in the previous behavior of these two patients. Treatmentconsisted of restraint, sedation, supervision, and nursing care. The authorsbelieved that the psychoses represented a quinacrine sensitivity reactionfollowing which there was an unreactive period.

In another report from overseas,⁵³ 28 cases of quinacrine psychosiswere observed in the Americal Division. The degree of malarial infection and thegreat number of relapses treated in this division would indicate the incidenceof this reaction to be extremely low. Two patients gave a history of previouspsychotic reactions to quinacrine, and in two additional patients it wasbelieved that schizophrenia was induced by the drug. Only one case was notedduring the standard course of 2.8 gm.of quinacrine in 7 days. Theremainder developed during or after larger total doses, 18 patients receiving more than 3 gm. Confusion was theprominent clinical feature of the psychosis in 27 patients.Hallucinations occurred in eight cases. Recovery was complete within 10 days in16 patients. By the use of the Koh's block test, these authors showed that therewas evidence of confusion in 7 of 31patients treated with 4.5 gm. quinacrine during 9 days, while no such changescould be demonstrated in 27 patientstreated with 2.1 gm. in 7 days.Additional cases of quinacrine psychosis were reported from variousinstallations overseas and in the United States, but their incidence was aninsignificant fraction of the total number of psychoses that occurred in theU.S. Army.

Convulsions were reported in six patients treated with"massive" amounts of quinacrine orally⁵⁴ and in two who were treated intravenously. The convulsionsoccurred during treatment or on the following day, with unconsciousness for 5to 15 minutes followed by confusion. Within 24 hours,these patients were all mentally clear. Plasma levels determined in three caseswere from 180 to 280 μg. per liter. Studies were stimulated by observation ofhigh plasma levels with parenteral quinacrine therapy and by reports in theliterature before World War II⁵⁵ ofmental changes associated with parenteral medication. A group of 13 volunteerswere given 0.9 gm. of quinacrine

⁵³Newell, H. W., and Lidz, T.: TheToxicity of Atabrine to the Central Nervous System. I. ToxicPsychoses. Am. J. Psychiat. 102: 805-818, May 1946.
⁵⁴Newell, H. W., and Lidz, T.: TheToxicity of Atabrine to the Central Nervous System. II. Convulsions. Am. J.Psychiat. 102: 805-818, May 1946.
⁵⁵See footnote 34, p. 545.

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daily for 7 days. Peak plasma levels were from 156 to 420with a mean of 286 μg. per liter. No symptoms or signs related to the nervoussystem were observed. Electroencephalographic studies revealed only small andinconsistent changes not characteristic of those observed in convulsivedisorders of the brain. In another study, five normal subjects were givensufficient quinacrine by mouth during 7 to 10 days to produce plasma levels inexcess of 100 μg. per liter. In all cases, there was evidence of markedpsychologic stimulation (motor acceleration, restlessness, sleeplessness, andincreased capacity for work), and the electroencephalogram showed a significantshift toward faster frequencies. These manifestations appeared by the third dayand persisted for 6 to 8 days after the drug was discontinued. The authorsconsidered the data convincing evidence that quinacrine acted as a corticalstimulant.

Summary of Studies

An experimental approach to the chemotherapy of malaria ledto a rational use of quinacrine for effective treatment of attacks and forsuppression. The development of chemical methods for estimating quinacrine inbiological fluids and tissues resulted in a better understanding of thelimitations of treatment and suppressive schedules in use before and early inWorld War II. Clinical and field studies carried out on a large scaledemonstrated that quinacrine if properly used was superior to totaquine or itscomponent alkaloids for treatment or suppression of malaria due to P. vivax or P. falciparum. Quinacrine produced more promptcontrol of fever, symptoms, and parasitemia; was less toxic; and provided alonger interval to relapse than quinine, sulfonamides, or heavy metals.Quinacrine was shown to induce definitive cure in falciparum infections and to provide effectivesuppression of relapsing malaria when priming initial doses were followed bydaily doses of 0.1 gm. Failures in suppression (breakthroughs) were shown mainlydue to poor discipline and failure to take the drug. Parenteral use ofquinacrine was found effective in severe falciparum infections, but no conclusive comparativestudy was reported between quinine and quinacrine given parenterally. Toxicreactions known before the war were encountered, these consisting of minorgastrointestinal symptoms and toxic psychoses. In addition, prolonged quinacrineingestion produced edema of the cornea in some cases, and in a large number ofcases, the following reactions were described: (1) Ochronosis-like pigmentation of skin, mucous membranes,and cartilage (possibly with hepatitis), (2) urticaria and, more significantly,a dermatitis complex (atypical lichen planus and/or eczematoid dermatitis), and(3) aplastic anemia. It was only shown that long-continued suppression producedthese reactions in only a small proportion of men taking the drug and that onthe whole no significant disturbances in organ function resulted. The proper useof quinacrine made possible effective military operations in highly malariousareas.

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4-AMINOQUINOLINE COMPOUNDS

The background for the elaboration and study of this group ofcompounds is reviewed in a report on investigations of potentially antimalarialdrugs in the laboratories of the I. G. Farben Werke in Elberfeld, Germany.Following the discovery, in 1924, of Plasmochin (a trade name for pamaquinenaphthoate, an 8-aminoquinoline) interest was centered on the possibilities ofquinoline derivatives. A total of 314 acridine derivatives were prepared, butnone was found to be more active than quinacrine. In 1929, work with the4-aminoquinoline compounds was begun, and in 1934 a compound as effective asquinacrine was discovered and furnished the impetus for the preparation ofnumerous derivatives during the years following. Although this information wasnot available to us during World War II, it is of interest that two reportsappeared in the French literature which discussed very generally theantimalarial properties of Sontochin (SN 6,911), one of the 4-aminoquinolinedrugs prepared in Germany.

This drug became available in North Africa during the SecondWorld War, and its chemical identity was established. It was subsequentlysynthesized and made available to the U.S. Army for experimental and clinicaltesting. A brief discussion of the antimalarial properties of Sontochin ispresented, to be followed in turn by brief discussions of several otherderivatives prepared in this country, particularly SN 7,618 or ChloroquineDiphosphate, which proved to be the most effective. The proper uses ofPlasmochin, rediscovered during the war, will be discussed in due course.

Sontochin (SN 6,911)⁵⁶

General properties

Absorption of the bisulfate of SN 6,911 is essentially complete whereas onlyabout 80 percent of the binaphthoate is absorbed. Following its absorption, thedrug is extensively localized in the tissues. About 25 percent of the daily doseis excreted; about 75 percent is degraded. The plasma level falls approximately25 percent per day. Daily doses of 0.3 gm. of base result in mean plasma levelsof 160 μg. per liter (range 66 to 292). Therapeutic effects in vivaxinfections, that is, control of fever and parasitemia without recurrence within14 days, are obtained with mean plasma levels above 80 μg. per liter for 4 daysand, in falciparum infections,with levels of 110 to 200 μg. per liter for 6 days. A therapeutic scheduleconsisting of 0.9 gm. on the first day and 0.3 gm. daily for 3 additional daysproduces plasma levels of from 125 to 193 μg. per liter for 4 days and iseffective in terminating induced vivax and falciparum infections.

⁵⁶Formula:3-Methyl-7-chloro-4-(4-diethylamino-1-methylbutylamino) quinoline bisulfate orbinaphthoate.

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Clinical testing

Acute attacks-The relativeefficiency of SN 6,911 and quinacrine in the treatment of acute attacks of vivaxmalaria of Pacific and Mediterranean origin was studied at Harmon GeneralHospital. A total of 99 patients were treated with 3.2 gm. of SN 6,911 baseduring 7 days. There was prompt control of fever and symptoms (86 to 100 percentfever free on the second day), but not significantly more so than withquinacrine, and parasites disappeared from the blood at approximately the samerate with either drug. Of 75 patients followed for at least 60 days aftercompletion of treatment, 49 (about 65 percent) relapsed; the interval to relapsewas shorter, 27 percent occurring in the first 5 weeks after treatment with SN6,911, compared with only 7 percent in the same interval after treatment withquinacrine. In this study, no advantage of SN 6,911 over quinacrine was found.

From similar observations in studies carried out at various U.S. navalinstallations, similar conclusions were drawn. Single doses of 1.0 gm. SN 6,911were found effective in terminating acute attacks of vivax malaria of Pacificorigin in 45 patients. Parasitemia was controlled within 36 hours, and usuallyno further paroxysms occurred. Relapses were observed in as little as 24 daysafter therapy. Toxic symptoms or signs were not encountered.

No extensive studies on treatment with SN 6,911 for malaria caused by P. falciparum were carried out in the field. In India, it was shown that a singleinfusion of 0.64 gm. of SN 6,911 in 1,000 cc. of saline given intravenouslyduring 2 to 3 hours was effective in terminating acute attacks of falciparummalaria. Twenty Chinese soldiers were so treated, and within 1 to 4 days(average 2.5 days) blood smears became negative. Fever was controlled in 12 to80 hours (average 41 hours). The response was comparable to that observed in 20patients who were given 0.6 gm. of quinacrine intravenously although the latterbecame fever free on the average of 12 hours sooner than those treated with SN6,911. In the United States, it was shown that 0.9 gm. of SN 6,911 administeredfor 1 day followed by 0.3 gm. daily for 6 days effected definitive cure ininduced falciparuminfections.

Suppression-Studies with SN 6,911 were carried out inAustralia on volunteers infected by mosquitoes with the New Guinea strains of P.vivax and P. falciparum, the method of approach being the same as previously described. Volunteers who received "build-up" doses of SN 6,911 of 0.2gm. twice daily for 4 days before exposure to infection and then had 0.1 or 0.2gm. daily during the period of exposure and for 23 days after the last infectivebite had smears completely parasite free (except one patient who had oneparasite on 1 day only), and they had no attacks of malaria. Followingdiscontinuance of suppressive medication, all volunteers infected with P. vivaxdeveloped acute attacks (average 27 days), but none of those infected with P.falciparum developed malaria within 92 days after discontinuance of the drug. Inthe latter group, cure was demonstrated by failure to

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produce malaria in recipients who were given 200 cc. of blood from the test subjects. No immunity wasdemonstrated since subsequently it was possible to induce malaria in the samesubjects with the same strain of falciparum parasites. Subinoculation of bloodfrom subjects treated with SN 6,911, onthe eighth and ninth days after reinfection with P. falciparum produced malariain the recipients. These studies therefore showed that SN 6,911 was curative in falciparuminfections through its effect on the parasites after they reached the peripheralblood.

In an experiment of simulated field type, volunteers wereheavily exposed to infection for 58 dayswhile suppressive doses of 0.1 gm. SN 6,911 weregiven daily; this dosage was continued for 28 daysafter the last infective bite. In addition, the men were subjected to extremeexercise, cold, and adrenalin injections. During the period of exposure andcontinued suppression, no parasitemia or clinical malaria occurred. After thedrug was stopped, malaria developed in all volunteers infected with P. vivax andin none of those infected with P. falciparum. Control studies with similardoses of quinacrine gave identical results.

Toxicity

No toxic manifestations related to SN 6,911 were reported from these studies in which more than200 patients were given 3.2 gm.of drug during 7 days' treatment for acute attacks of vivax malaria. There wereno toxic signs or symptoms in subjects who received 0.1 or 0.2 gm. daily for suppression for several weeks or months norwere any noted in subjects who received 0.4 gm. daily for 20 or more days. No skin discoloration was observed.

Convulsions occurred during the administration of SN 6,911 in three patients with general paresis and malaria. Acuteconfusional psychosis was observed in two additional patients with plasmaconcentrations over 400 μg. per liter. One patient who had 1.5 gm. of SN6,911 intravenouslyafter a preliminary full therapeutic course of quinacrine developed aconvulsion. The drug was given in a 2.5 percentsaline solution, injected at the rate of 1 cc. per minute. Plasma levels in theorder of 1,000 μg. per liter at the end of the injection and levels above 200μg.24 hourslater were observed in other patients who received similar amounts of SN 6,911 intravenously.

Experience with SN 6,911 was notsufficiently prolonged or extensive to permit the accumulation of data withregard to more chronic toxic manifestations of the nature reported fromprolonged quinacrine administration. However, it is of interest that stimulationof the central nervous system was demonstrated in subjects with high plasmalevels of SN 6,911.

Summary

SN 6,911 was found to be aseffective as quinacrine, except for the briefer interval between relapses aftercessation of treatment, but was in no way superior to quinacrine, except that itdid not discolor the skin. It might have proved a useful substitute had therebeen a serious breakdown in the

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use of quinacrine because of alleged or proved toxicity.These studies stimulated further syntheses and alterations of various 4-aminoacid compounds which ultimately resulted in a drug that was, in fact, superiorto quinacrine. This was SN 7,618, or Chloroquine Diphosphate.

Chloroquine Diphosphate (SN 7,618)⁵⁷

An intensive 2-year study was made of this drug in man and inexperimental animals. Its pharmacology was studied in fairly extensiveexperiments with mice, rats, dogs, monkeys, and man. Extensive studies were madeon its prophylactic activity against domestic strains and Southwest Pacificstrains of vivax malaria, on its curative activity against sporozoite-inducedinfections when administered alone and in combination with other compounds, andon its suppressive activity. Large-scale investigations of its use interminating the acute attack and for suppression were carried out in militaryinstallations. Most of these studies were made in comparison with quinine.

General properties

Absorption of SN 7,618 from the gastrointestinal tract iscomplete or nearly complete, and somewhat more rapid than absorption ofquinacrine. Like quinacrine, SN 7,618 is metabolized in the body. Only 10 to 20percent is excreted unchanged in the urine; this fraction can be increased byacidification of the urine, decreased by alkalinization. On any given dosageschedule there are substantially higher concentrations of SN 7,618 in theplasma, since there is less localization in the tissues than there is withquinacrine. The pattern of distribution is in general similar. SN 7,618 isconcentrated in nucleated cells (also in leukocytes); the liver, spleen,kidneys, and lungs contain from 200 to 500 times the amount in the plasma, whilethe brain and spinal cord contain no more than 10 to 25 times the plasmaconcentration.

The marked localization of this drug in the organs, togetherwith the slow rate of excretion and degradation, necessitate a priming dose ifthe desired concentration in the plasma is to be rapidly reached and maintained.As with quinacrine, these factors result in slow disappearance of the drug fromthe body when it is discontinued; its concentration in the body fluids generallyfalls about 60 percent per week when administration stops.

Antimalarial activity

SN 7,618 proved more active than quinacrine in all of theavian malarias in which it was tested. In Plasmodium cathemerium both inthe canary and in the duck it is 3.5 times as active as quinacrine, 5 to 13times as active against Plasmodium gallinaceum and 2.5 times as activein Plasmodium lophurae in the duck. Like quinacrine, it does not producepermanent cures in any of these infections, nor is either drug prophylactic insporozoite-

⁵⁷Formula:7-Chloro-4-(4-diethylamino-1-methylbutylamino) quinoline diphosphate.

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induced cathemerium malaria in the canary or gallinaceum malaria in thechick.

SN 7,618 is highly active against the erythrocytic forms of P. vivax and P. falciparum. It does not prevent relapses in vivax malaria even in doses manytimes those required to terminate an acute attack, nor will it prevent theestablishment of a vivax infection when administered as a prophylactic. It ishighly effective as a suppressive agent and in the termination of the acuteattack, significantly lengthening the interval between treatment and relapsebeyond that observed with quinacrine or quinine. In falciparum malaria it has been shown tosuppress the acute attack and to effect complete cure of the infection. Studiesof the antimalarial activity of SN 7,618 against well-standardized strains of P.vivax and P. falciparum have shown it to be approximately three times that ofquinacrine. In well-tolerated therapeutic doses a great majority of patientswill be afebrile within 24 hours and the remainder within 48 hours. Thick smearsfor parasites will generally be negative at 48 to 72 hours.

Mean plasma levels in the range of 10 μg. per liter have been shown to beeffective in treating attacks of induced vivax malaria. Initial oral doses of aslittle as 100 mg. followed by daily doses of 85 mg. for 4 days produce plasmalevels above the therapeutic range and result in termination of the attack. Thetherapeutic level for terminating attacks due to P. falciparum are in the range of 20μg.per liter and such levels and clinical effects have been produced with initialdoses of as little as 150 to 300 mg. followed by daily doses of approximatelythe same amount for 4 to 6 days. It is evident from these observations that theantimalarial activity of SN 7,618 is significantly greater than quinacrine bothon the basis of oral dosage and plasma drug concentration.

Clinical testing

SN 7,618 has been given to more than 1,000 patients withacute attacks of vivax malaria of domestic, Pacific, and Mediterranean origin.The clinical testing of this drug in vivax malaria of war origin was carried outprincipally at Harmon and Moore General Hospitals, designated as specializedtreatment centers in the United States for the study of tropical diseases. Otherstudies in the U.S. Army with SN 7,618 were carried out overseas. In addition,clinical and toxicologic investigations were conducted at various naval,Federal, and civilian installations in this country and abroad as well as byinvestigators of Allied Nations.

The observations on the use of SN 7,618 in the treatment of vivax malaria reported from Moore General Hospital,⁵⁸summarized in the following paragraphs, are representative of other reportedstudies.

⁵⁸Most, H., London, I. M., Kane, C.A., Lavietes, P. H., Schroeder, E. F., and Hayman, J. M., Jr.:Chloroquine for Treatment of Acute Attacks of Vivax Malaria. J.A.M.A. 131: 963-967, 20July 1946.

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STUDY AT A SPECIALTY CENTER

Material and methods-The patients were military personnel who hadacquired vivax infections in the Pacific area or Mediterranean theater.Allphases of the disease, first attacks as well as early and late relapses, wererepresented by significant numbers of men. Approximately 50 to 75 patients wereincluded in each of the five treatment plans.

All patients with an acute clinical attack were admitted totwo special-study wards for observation and therapy with SN 7,618. No patient wastreated unless his blood smear was positive for malaria parasites and histemperature over 100? F. Cases were selected only with respect to thegeographic origin and age of the disease, to ensure adequate representation on each treatment schedule.

All treatment was begun on the morning following the onset ofthe current attack. Parasite counts were done twice daily and continued untilnegative for 3 consecutive days. The plasma levels of SN 7,618 were ascertainedfrequently during and after treatment to determine the pattern of accumulation,stabilization, and disappearance of the drug from the plasma. Temperatures weretaken every 4 hours during treatment and every 15 minutes during a paroxysm. Theclinical response was followed during daily rounds. All signs and symptomspossibly related to malaria or to treatment with SN 7,618 were recorded. Inaddition, clinical and laboratory observations were directed specifically torecognizing possible toxic manifestations. All drugs were administered by amedical officer.

Following completion of treatment and study on the wards, thepatients were transferred to a convalescent area on the hospital grounds forobservation until relapse or for 120 days from the last day oftreatment.

During this interval smears were examined twice weekly. Inthe event of parasitemia the temperature was recorded three times daily andsmears made every day. A temperature rise of over 100? F. by mouth associatedwith a positive smear was considered a relapse, and the patient was readmittedto a ward for further observation and treatment. Approximately 80 percent of therelapsed cases were direct admissions from the convalescent area followingparoxysms with temperatures of from 103? to 105? F. The other 20 percent wereadmitted as a result of temperature observations made during intervalparasitemia. Of the latter group at least one-half developed paroxysms shortlyafter admission to the ward. No patient was treated without coincident fever andparasitemia.

Treatment plans-Protocols fortreatment schedules were furnished by the Office of the Surgeon General.Representative treatment schedules which have been found most satisfactory arepresented in table 74. (Tablets of 0.1 gm. and 0.3 gm. of SN 7,618⁵⁹ were available and were usedsingly or in combination to supply the proper individual dose.)

Other treatment plans consisting of the administration of a total of 0.8 gm.during 7 days and 1.5 gm. during 3 days were also studied.

⁵⁹The dosage, wherever it appearsin this chapter, is in terms of base. This drug was not commercially availableat the time these studies were made, and the tablets were specially prepared.-H.M.

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TABLE 74.-Representativetreatment schedules for chloroquine

Schedule	Hour	Dosage (grams)
Plan A:
1st day	8 a.m.	0.4
	12 m	0.3
	5 p.m.	0.3
Total	---	1.0
Plan B:¹
1st day	8 a.m.	0.3
	12 m	0.3
2d day	8 a.m.	0.3
3d day	8 a.m.	0.3
4th day	8 a.m.	0.3
Total	---	1.5
Plan C:
1st day	8 a.m.	0.4
	12 m	0.2
	5 p.m.	0.2
2d day	8 a.m.	0.2
3d day	8 a.m.	0.2
4th day	8 a.m.	0.2
5th day	8 a.m.	0.2
6th day	8 a.m.	0.2
7th day	8 a.m.	0.2
Total	---	2.0

¹This schedule advocated for routine use.

Results.-These results are as follows:

1. Control of parasitemia.-The rate of disappearanceof parasites from the peripheral blood during the administration of SN 7,618 in comparison with quinine and quinacrine are shown inchart 31. It may be seen that the peripheral blood becomes free of parasitesmore rapidly with SN 7,618 (plansA, B, and C) than with either of the other drugs, the difference being moremarked between SN 7,618 andquinine than between SN 7,618 andquinacrine. The superiority of SN 7,618 was manifest in vivax malaria of Mediterranean orPacific origin in first attacks as well as in relapses occurring at any stage ofthe disease.

2. Control of fever.-In a total of 244 attacks treated with SN7,618 according to plans A, B, and C, only 5 patients or 2.1 percent had fever (temperature of 100^?F. or more) the day after treatment was begun or subsequently. By contrast,treatment with quinine in 184 attacksand with quinacrine in 391 attacks was associated with fever on the second dayor later in

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CHART 31.-Comparative rate ofdisappearance of parasites from peripheral blood during treatment of vivax malaria with quinine (172 attacks), quinacrine hydrochloride (397 attacks), andchloroquine (293 attacks)

8.7 and 8.0 percent, respectively, of patients treated. Thesuperiority of SN 7,618 inthis respect is manifest in infections of both Mediterranean and Pacific origin,regardless of the initial parasite density, and in Pacific infections regardlessof whether the attack is the very first or a relapse at any stage of thedisease. In delayed primary attacks the proportion of patients who have fever onthe second day after treatment with SN 7,618 is begun is higher than in patients treated in relapse.This is also true even to a greater extent for delayed primary attacks treatedwith quinine or quinacrine, shown in chart 32.

3. Control of symptoms.-It isdifficult to evaluate comparative effects of quinine,quinacrine, and SN 7,618 incontrolling symptoms which are usually present for a few days in a treatedattack of malaria. However, clinical impressions based on treatment of more than1,000 acute attacks of vivax malaria and supported by a more detailedstatistical analysis, indicate that SN 7,618 is at least as good as quinine or quinacrine in thecontrol of all symptoms, and is superior to one or the other in the control ofsome symptoms.

Headache and backache are relieved more rapidly with SN 7,618or quinine than with quinacrine. Quinine is more effectivethan quinacrine in the control of generalized aching, but is not significantlybetter than SN 7,618. Weakness,dizziness, and lightheadedness disappear more rapidly with SN 7,618 or quinacrine than with quinine. Nausea persists longer inpatients treated with quinine than in those treated with SN 7,618 or Atabrine. The effect of each of these drugs on theduration of vomiting, abdominal pain, and abdominal tenderness is essentiallythe same.

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CHART 32.-Comparative efficiency of quinine, quinacrinehydrochloride, and chloroquine in controlling fever during treatment of delayedprimary attacks of relapses of vivax malaria

4. Effect on interval to relapse.-Quinine, quinacrine,and SN 7,618 do not materially influence the ultimate relapse rate followingtreatment of the acute attack. Apparently the ultimate relapse rate in largegroups is not affected by the age of the disease, the number of previousattacks, total amount of drug, or duration of treatment. More than 500 patientstreated for acute attacks of vivax malaria of Pacific and Mediterranean originwere followed to relapse, or for a minimum of 120 days. The relapse ratesfollowing treatment with quinine, quinacrine, or SN 7,618 were from 75 to 85percent for Pacific infections and approximately 35 percent for Mediterraneaninfections. The cumulative relapse rates following treatment of acute attacks ofvivax malaria of Pacific origin are shown in chart 33. At 120 days, 85, 80, and70 percent of patients treated with quinine, quinacrine, and SN 7,618,respectively, had relapses.

The interval to relapse, however, and the distribution of the relapses thatoccurred during the first 2 months after treatment are strikingly different forthe three drugs. These differences are presented in chart 34.

During the first month after treatment, 54 percent of the patients treatedwith quinine relapsed, 9 percent relapsed after quinacrine, and none relapsedafter SN 7,618. At 40 days, relapses following SN 7,618 begin to occur, butthese represent less than 1 percent of treated patients, whereas 67 and 28percent relapsed at 40 days after treatment with quinine and quinacrine,respectively. At 50 days, 72, 40, and 11 percent of the patients relapsed afterquinine, quinacrine, and SN 7,618, respectively.

In terms of the total number of relapses that occur within 120 days, thepercentages of patients who relapsed within 50 days were 85, 50, and 16 percent,respectively, for quinine, quinacrine, and SN 7,618. Thus, of the total relapsesthat occur within 120 days, more than three-fourths of them will take place inthe first 50 days after quinine,

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while during the same time after quinacrine only one-half,and after SN 7,618 only one-sixth will occur. The median interval to relapsefollowing treatment with quinine is 24 days, with quinacrine, 50 days, and withSN 7,618, 61 days.

CHART 33.-Cumulativerates of relapses during a minimum of 120 days following treatment of acuteattacks of vivax malaria with quinine (76 patients),quinacrine hydrochloride(118 patients), and chloroquine (156 patients)

Since none of these drugs produces a complete cure ofmalaria, the drug of choice on the basis of interval to relapse is the one thatgives the longest mean interval, the greatest median interval for a large groupof patients, and the smallest number of short-term relapses. The data presentedshow that the interval to relapse after treatment with SN 7,618 will be on theaverage at least 5 weeks longer than after quinine and about 2 weeks longer thanafter quinacrine. Only a negligible number of patients treated with SN 7,618will relapse during the first 50 days after treatment. Accordingly, SN 7,618 notonly controls symptoms, fever, and parasitemia promptly but, in addition,confers freedom from another attack for a period of approximately 2 months.

Plasma levels-Blood was drawn at such times as to determine the rate ofaccumulation, stabilization, and disappearance of SN 7,618 from the plasmaduring and after treatment with various dosage regimens. The values obtainedduring and after treatment on schedules A, B, and C are presented in chart 35.

The minimal plasma concentration of SN 7,618 that iseffective in terminating an acute attack has been shown to be in the range of 10μg. per liter. The levels observed during and after treatment on plans A, B, orC are well above this range.

No correlation has been found between variations observed inlevels obtained in single individuals receiving the same amount of drug andtheir interval to relapse or to the first parasitemia after completion oftreatment.

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CHART 34.-Comparison of distribution of relapses occurringduring the first 60 days after treatment of acute attacks of vivax malaria of Pacific origin with quinine, quinacrine hydrochloride, andchloroquine

Summary.-The data presented in the study on the relativeefficiency of quinine, quinacrine, and SN 7,618 are summarized and presented forreference in table 75.

TABLE 75.-Relative efficiency of quinine,quinacrine hydrochloride, and chloroquine in treatment of acute attacks of vivaxmalaria

Efficiency factors	Quinine	Quinacrine hydrochloride	Chloroquine (SN 7,618)
Total amount of drug.....grams...	28.35	2.8	¹1.0, 1.5, 2.0
Duration of treatment.....days...	14	⁷	¹1, 4, 7
Rate of parasite clearance	⁺	⁺⁺⁺	++++
^{Control of fever:}
Delayed primary attacks²	+	++	+++
Relapses³	++	++	++++
Interval to relapse:
Median.....days...	24	50	61
Relapses:
First 50 days.....percent...	85	50	16
Total, 120 days...do...	90	82	75
Control of symptoms	++	+++	++++
Toxicity	⁴+++	⁵+	⁶+

¹Plans A, B, and C. See table 74.
²Infectionsof Pacific origin.
³Infections of Mediterraneanor of Pacific origin.
⁴Cinchonism.
⁵Eczematoid reactions in patients sensitive to quinacrine hydrochloride.
⁶Slight, transitory pruritus; rareerythema or urticaria.

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From this study it was concluded that SN 7,618 is a highlyeffective, safe antimalarial drug which is superior to quinine and quinacrine inthe treatment of acute attacks of vivax malaria. Routine treatment wasrecommended as follows:

One tablet (0.3 gm.) of SN 7,618 is administered when the diagnosis of vivaxmalaria is established by a positive blood smear. This amount of drug (0.3 gm.)is repeated 4 hours after the first dose. One tablet (0.3 gm.) is then given oneach of the following three mornings. The total dose is 5 tablets, totaling 1.5gm. of SN 7,618 administered during 4 days.

CHART 35.-Averageplasma levels of chloroquine (176 patients) during and after treatment underplans A, B, and C

OTHER STUDIES OF VIVAX INFECTIONS

Treatment plans with SN 7,618 in which total doses of 1.0 gm.in 1 day, 0.8 gm. in 6 days, 2.0 gm. in 6 days, and 1.2 gm. in 3 days were studied atHarmon General Hospital. The results reported from a total of 235 attackstreated on the above schedules were essentially the same as those reported fromthe Moore General Hospital. Treatment of primary attacks of Pacific origin orrelapses of Pacific or Mediterranean vivax malaria with SN 7,618 resulted inprompt control of symptoms. Parasitemia and fever disappeared more promptly thanwith quinacrine, and the interval to relapse was greater

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than with the latter except in the patients who had a totalof only 0.8 gm. of SN 7,618 during 6 days.It was felt that SN 7,618 wassuperior to other antimalarial agents previously studied at that installation(quinine, quinacrine, and SN 6,911).

A single dose of 1.0 gm. SN 7,618 wasadministered to each of 50 patientswith acute attacks of vivax malaria at a U.S. naval installation. There wasprompt subsidence of fever, and parasites disappeared in all cases within 36 hours. The interval to relapse from this single-doseschedule was longer than that following the standard quinacrine course. Atanother naval installation, more than 100 patients were treated with SN 7,618 for acute attacks of vivax malaria of Pacific origin. Themajority received 1.0 gm. within a period of 16 to 24 hours. Control of symptoms andfever was more prompt than was observed in patients treated with quinacrine, andparasites disappeared from the blood in most cases within 48 hours. Short-term relapses, that is, less than40 days, did not occur after treatment with SN 7,618, in contrast to a significant number of relapses in lessthan 40 days after treatment withquinacrine.

SN 7,618 was used clinically toterminate acute attacks of vivax malaria in various oversea areas. In India, 26 American military patients with acute vivax infectionswere treated with 0.9 gm. during thefirst 24 hours followed by a singledose of 0.3 gm. on each of the 2 successive days (total 1.5 gm. in 3 days).The average duration of fever was 24.1 hoursand parasitemia 1.5 days. In Peru,more than 300 natives were treated for acute attacks of vivax, falciparum, andmixed malaria with relatively small doses of SN 7,618(0.75 gm. on the first day and 0.25 gm. on the second day; total 1.0 gm. in 2 days).In 70 cases carefully studied, bloodsmears were positive in only 17 and 5 at 24 and 48 hours,respectively, after the initiation of therapy. The clinical response totreatment was considered good in the majority of patients. It was noted the falciparum infections responded more slowly than those due to P. vivax.

STUDIES OF FALCIPARUM INFECTIONS

SN 7,618 did not have any extensiveclinical trial in the treatment of falciparum infections, particularly thefulminating variety with cerebral involvement. Preliminary studies in thiscountry with injections of domestic strains of P. falciparum indicated thatplasma concentrations of 20μg. ofdrug per liter maintained for 4 to 6 days resulted in the control of fever and parasitemiawithout recurrence of symptoms or signs of infection for 14 days or more. Such relatively low plasma levels are easilyobtained with initial doses of 200 mg. and maintained with daily doses of 100mg. In actual practice, the oral dosage schedules of 0.6 to1.0 gm. during the first 24 hoursfollowed by daily doses of 0.2 to0.3 gm. result in plasma levels of 5 to 10 timesthat required to terminate falciparum activity. It is probable therefore that SN7,618 would prove effective in terminating most infectionswith P. falciparum.

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At the 20th General Hospital in the India-Burma theater, 10 Chinese soldierswith acute falciparum malaria were treated with 1.5 gm. of SN 7,618 during 3days. Clinical response was satisfactory in all patients. The average durationof fever (102? to 105? F. at onset) was 34 hours after the first dose (range 8to 64 hours), and blood smears became negative within 3 days. In another reportfrom the same hospital, similar results were recorded in eight American soldierswith acute falciparum malaria treated with SN 7,618 (total 1.5 gm. during 3 days). The averageduration of fever (102.4^? to 104.8^? F. at onset) was28.4 hours after the first dose, and blood smears were free of parasites within1 to 3 days.

In the Peru study of more than 300 acute attacks of malaria (many P. falciparum or mixedvivax-falciparum)treated with a total of 1.0 gm. of SN 7,618 during 2 days, 17 infections with P.falciparum and 7 mixed cases were closely followed; the response to treatmentwas considered rapid or good. There were no treatment failures. Fever andparasitemia were quickly controlled. In general, the rapidity of disappearanceof parasites and the clinical response to treatment varied with the severity ofthe infection. It should be borne in mind that the total duration of treatmentand total doses of drug employed were no optimum and that the satisfactoryresponse was observed in highly immune natives who are not comparable withnonimmune American troops.

Unfortunately, no parenteral SN 7,618 was available, and no opportunity wasafforded for comparing the relative efficiency of SN 7,618 and parenteralquinine or quinacrine in the treatment of fulminating falciparum infectionscomplicated by severe vomiting or involvement of the central nervous system.

STUDIES OF SUPPRESSION

The suppressive efficacy of SN 7,618 and the mode of its action against vivaxand falciparuminfections were investigated in Australia in the manner of similar studies ofquinine, quinacrine, and SN 6,911.⁶⁰ New Guinea strains of P. vivax and P. falciparum were employed. The "build-up" doses of SN 7,618were 0.2 gm. twice daily for 4 days. Subsequently, the daily dosage was 0.1 gm.continued for 23 days after the last exposure to infective mosquitoes. None ofthe volunteers infected with P. vivax or P. falciparum developed clinicalmalaria or microscopically detectable parasitemia during the period ofsuppression. However, subinoculation of 200 cc. of blood to other volunteers 9or 10 days after infection produced malaria in the recipients. This proved thatthe test subjects were infected and demonstrated that the action of SN 7,618 wasnot prophylactic and that its suppressive action against the parasites wasexerted after their appearance in the blood. Following discontinuance ofmedication, all volunteers infected with P. vivax developed malaria within 40 to60 days, but no falciparum malaria developed during a

60 See footnote 12, p. 529.

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period of 81 days in the men infected with P. falciparum.SN 7,618 was thus shown to be equally as effective as quinacrine or SN 6,911 insuppressing both vivax and falciparum infections and in curing the latter.

Anticipating the practical application of SN 7,618 as a suppressive agent,one must consider the persistence of this drug in the body and the fact thatrelatively low plasma levels (10μg. per liter) have pronounced antimalarialactivity. It was shown that the administration of 0.3 gm. of SN 7,618 in singledoses once a week resulted in the maintenance of mean levels above 10μg. perliter in the majority of more than 50 subjects who remained on this suppressiveschedule for 4 to 8 weeks.

Suppressive schedules of single weekly doses of SN 7,618 were studied, inthis country, in patients with recurrent vivax malaria of Pacific origin.Ninety-four men who previously were having frequent relapses were placed on 0.3gm. weekly for approximately 3 months. During the period of suppression, onlyone man had a positive blood smear on one occasion. During the last 10 days ofsuppression, 75 men were placed on an extremely rugged test of physicalendurance, consisting of daily hikes of 5 to 15 miles over very rough terrain,forced marches, and rifle drill. In this period. six men developed transientparasitemia. No clinical attacks occurred during suppression, including theperiod of exercise. It was calculated on the basis of the number of attacksthese men had had in 3 months prior to suppression that at least 75 relapsesshould have occurred if no suppressive therapy had been taken. It was thusshown that SN 7,618 given once a week was completely effective in suppressingclinical malaria in a group with a high index of relapse and parasitemia(positive smears in 84 percent in the 5-week period prior to suppression).

At Moore General Hospital, more than 100 patients who had had an attack of vivax malaria within the previous 3 months were placed on 0.3 gm. SN 7,618 oncea week for 8 to 16 weeks. More than half of these patients had tuberculosis.During the period of suppression, no parasitemia and no clinical malariaoccurred. The patients, especially those with tuberculosis, were reluctant todiscontinue their weekly dose of SN 7,618 because they felt reassured that theywould not have malaria while they were taking the drug.

In a series of more than 200 mentreated with 1.0 gm. of SN 7,618 in 1 day for acute attacks of vivax malaria ofPacific origin, the shortest interval to relapse was 33 days. It was thereforebelieved that successful suppression could be accomplished by the administrationof 1.0 gm. in 1 day at monthlyintervals. Accordingly, 35 men recently treated for an acute attack with 1.0 gm.of SN 7,618 in 1 day were advised to take 1.0 gm. within 1 day every 4 to 6 weeks. They were observed from60 to 162 dayswhile on this schedule of self-medication. In this period, the expected numberof relapses was calculated to be 24, butonly 8 occurred. It is possible that, if medication had been supervised andadministered regularly once a month rather than at irreg-

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ular intervals up to 6 weeks, more effective or completesuppression might have been produced. Thus, SN 7,618 is not only effective as asuppressive with weekly doses of 0.3 gm. but it is possible that satisfactorysuppression may result from larger doses at greater intervals.

Studies on suppression with SN 7,618 were made in various areas overseas: InPeru, in more than 1,200 adults and children (natives); in India, in schoolchildren, in coolies, and in colored troops; and in the Philippines, in Americansoldiers during, unfortunately, a time when there was practically notransmission of malaria. Military deactivation of units prevented completion ofthe last investigation as previously planned. In all these studies, the resultswere good, but such observations in natives, or in American troops duringperiods of nontransmission, offered no conclusive evidence that completesuppression under combat conditions in highly malarious areas would result fromthe administration to troops of a weekly dose of 0.3 gm. of SN 7,618.

The experiments in Australia, the observations on the control of parasitemiaoverseas, and the suppression of relapses in this country indicate, however,that SN 7,618 in weekly suppressive doses should prove effective under combatconditions. The apparent advantage of SN 7,618 as a suppressive agent lies inthe ease of administering it in the form of one tablet once a week, the absenceof the yellowish discoloration of the skin resulting from the prolonged use ofquinacrine, and its tolerability.

Toxicity

Extensive studies of the acute and chronic toxicity of SN7,618 were conducted in animals prior to its clinical application in man.Observations were made on the tolerability and toxicity of varying amounts ofdrug administered to human volunteers, often for prolonged periods. Finally,data collected on possible toxic signs or symptoms during the administration oftherapeutic or suppressive amounts of SN 7,618 in several thousand individualsfurnished the background for the following statement approved by the Board ofCoordination of Malarial Studies:

There is little difference in the toxicity of SN 7,618 and that of quinacrinein experimental animals. The acute toxicity of both drugs given orally is aboutthe same in the rat and monkey. The acute toxicity of intravenous SN7,618 is greater than that of quinacrine in the dog. Short-term chronictoxicity tests in the mouse show the two drugs are about equally toxic. In suchtests carried out in the rat and the monkey for periods not exceeding 30 days,SN 7,618 is slightly more toxic than quinacrine. In longer term studies with therat and monkey extending up to 120 days, the drugs are about equally toxic or,if anything, SN 7,618 is slightly less toxic than quinacrine.

In man, the symptoms that have been observed following doses of SN 7,618adequate for treatment of the acute attack include mild and transient headache,visual disturbances, pruritus, and gastrointestinal complaints. In chronictoxicity studies in man using a dose (0.5 gm. weekly) in excess of thatnecessary for adequate suppression, no serious symptoms and no impairment ofhealth have been observed in 31 subjects over a period of 11 months ofconsecutive drug administration. In studying the record

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of 2,655 individuals who have received SN 7,618, everysymptom that has been observed has been recorded in an effort to bring out even minimal toxic manifestations.In a small number of instances, usually with dosages higher than necessary foreither treatment or suppression, individual subjects have refused to continuedrug administration because of unpleasant symptoms; none of these manifestationshas been constitutionally serious and all have been readily reversible. Unlikequinacrine, SN 7,618 does not discolor the skin.

Statements on toxicity in various reports concerned with the therapeutic orsuppressive use of SN 7,618 will be briefly cited.

In a treatment study⁶¹ inwhich 365 patients with acute attacks of vivax malaria were given total doses of0.8 to 2.0 gm. of SN 7,618 during a period of 1 to 7 days, no major toxicmanifestations were encountered clinically or in numerous laboratory investigations. It was not necessary to interrupt or discontinue treatment in asingle case. Occasionally, there was mild nausea if the drug was taken in thefasting state. No visual disturbances were noted. Particular effort was made todetect cutaneous symptoms or signs that might be attributed to SN 7,618, andspecial questioning elicited information that would rarely have beenvolunteered. Of the 284 patients treated with SN 7,618, 56 complained ofpruritus during the course of drug administration. The pruritus was occasionallygeneralized but more often localized, particularly to the palms and soles, andin the great majority it was transitory and very mild. Of the 56 patients whodeveloped pruritus, 50 had no coincident skin eruptions. Seven patients, or only2.4 percent of the total number treated, developed erythema, urticaria, or amild papular eruption. No similar emphasis was placed on skin symptoms inpatients treated with quinine or quinacrine and it is likely that the reportedincidence in association with SN 7,618 therapy is disproportionately high. Inthis study, the administration of SN 7,618 to patients with eczematoiddermatitis or the eczematoid-lichen-planus complex due to quinacrine did notresult in exacerbation of the underlying skin condition in any case.

In another series of 236 patients treated with similar totaldoses of SN 7,618 the incidence of pruritus was 7 percent but urticaria or rashoccurred only in 3 cases. Visual disturbances were not encountered.Gastrointestinal symptoms were negligible.

Visual disturbances, that is, blurred vision and difficulty in shiftingfixation from near to distant objects, have been described in volunteers ondaily doses of 0.5 gm. SN 7,618 and in patients treated for acute attacks of vivax malaria with 3.2 gm. These symptoms are undoubtedly of importance inevaluating the toxicity of SN 7,618 since they originate in the central nervoussystem. It must be pointed out, however, that symptoms or signs have notoccurred in almost 1,000 patients treated with total doses of less than 2.0 gm.or with suppressive doses of not more than 0.3 to 0.5 gm. per week. The amountsof SN 7,618 reported to have produced visual disturbances are in the order of 10times that required for adequate suppression and 2 to 4 times the required dosefor termination of an acute attack.

In the field studies of suppression that have been cited, based on severalthousand subjects, no striking toxicity is noted, and the incidence ofgastrointestinal or other symptoms requiring the discontinuance of the drug isremarkably low. Detailed investigations of the effects of SN 7,618 suppressionon various organ functions were carried out at Randolph Field, San Antonio, Tex.Doses of 0.5 gm. weekly and twice weekly

⁶¹See footnote 58, p. 563.

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were given for 4 weeks. No significant effects on physicalfitness, on psychological performance at ground level and at 18,000 feet, onvision (as indicated by scotopic vision, visual fields, or near-pointaccommodation), on auditory acuity, on heart (as indicated byelectrocardiograms), or on ability to retain balance while blindfolded, wereobserved.

Observations on the prolonged administration of SN 7,618 were made inconscientious objectors. Forty men given 0.3 gm. daily for 77 days and then 0.5gm. weekly for 12 weeks showed no serious toxic reactions. Headache anddifficulty in quickly fixing on distant objects occurred in this group on verylarge doses. Visual symptoms persisted in only 2 men of 31 who remained on thedrug for 9 months. Bleaching of the hair at the roots was observed in fiveblonde subjects while they were receiving 0.3 gm. of SN 7,618 daily. The colorof the hair returned to normal when the drug was discontinued. One patient givenSN 7,618, 0.5 gm. weekly, for 8 months developed an eruption resembling lichenplanus which persisted during the subsequent administration of the drug andbegan to subside 2 weeks after its discontinuance.

The last observation is of extreme importance in that itsuggests the possibility that the prolonged administration of SN 7,618 in largedoses may result in the dermatitis complex (eczematoid dermatitis and/or lichenplanus) described with quinacrine suppression. In this connection it is ofinterest that of 30 patients with atypical lichen planus who were placed onsuppression doses of SN 7,618 in the India-Burma theater (0.3 gm. weekly), onesuffered an actual flareup of the dermatitis described as a mild acuteeczematoid reaction which came on after one dose and disappeared within 2 days.It must be remembered that patients with eczematoid dermatitis may react tomany drugs. At Moore General Hospital more than 50 patients with atypical lichenplanus and a like number with eczematoid skin conditions were given SN 7,618 fortermination of acute attacks of malaria. There was no exacerbation in the skindisease in these cases, and in a group of patients with lichen planus whocontinued on suppressive therapy of 0.3 gm. weekly up to 3 months, no changewas noted in the lichenoid lesions other than continued regression.

The toxic manifestations of SN 7,618 may be summarized briefly. Little to notoxicity was encountered with therapeutic (1.0 to 2.0 gm.) or suppressive (0.3gm. weekly) doses of SN 7,618. Minor toxic symptoms consisted of occasionalgastrointestinal complaints and pruritus in a small number of subjects.Following large doses for therapy or suppression, visual disturbancesoccurred, and in one case atypical lichen planus developed after suppressivemedication for 8 months (0.5 gm. weekly). In general, it was felt by mostobservers that SN 7,618 in recommended doses was a safe drug.

Summary

Clinical experience with SN 7,618 proved this drug to be ahighly effective antimalarial agent, superior to quinacrine, quinine, and SN6,911. It excels quinacrine and quinine in more prompt control of fever,symptoms, and parasitemia, in a shorter course of treatment, in a longerinterval to relapse, in the abolition of short-term relapses, and in freedomfrom major toxic reactions. Given in single weekly doses, SN 7,618 is able toprovide effective suppression against vivax and falciparum infections and tocure the latter. SN 7,618 does not discolor the skin. Unfortunately, no assay ofits value in fulminating falciparum infections was possible. Experience hasshown SN 7,618 to be a safe drug.

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Oxychloroquine (SN 8,137)⁶²

General properties and antimalarial activity

The absorption, degradation, distribution, and antimalarialproperties of SN 8,137 are essentially similar to SN 7,618 although it appearsto have less antimalarial activity in oral dosage. The greater persistence of SN7,618 in the body is reflected in the smaller weekly dose required of this drugthan of SN 8,137 for comparable suppressive effects. The latter appears to beless toxic, but this advantage may be offset by the larger doses necessary forequivalent suppressive action.

The estimated "critical" plasma levels of SN 8,137necessary for terminating clinical activity and parasitemia due to P. vivax andP. falciparum have been shown to be approximately 17 and 19 μg. per liter,respectively. In induced experimental malaria, total doses of 0.3 gm. for vivaxinfections and 0.6 gm. for falciparum infections have given the mean plasmalevels in the order of 25 to 50 μg. per liter in the falciparum infections and17 to 31 μg. per liter in the vivax infections. It is apparent therefore thatrelatively greater doses and higher plasma levels are required for equivalentantimalarial activity than with SN 7,618. Single weekly doses of 0.25 gm. of SN8,137 for 4 weeks were found effective in suppressing vivax (domestic strain)infections transmitted by mosquitoes, whereas weekly doses of 0.125 gm. wereineffective.

No toxicity was reported in 16 volunteers who were given SN8,137 daily for 6 weeks. The dosage in the sixth week was 600 mg. daily and thetotal dosage per man during the entire period was 12.2 gm. or an average of 0.3gm. daily for 42 days. Headache, anorexia, and visual disturbances occurred withmoderate frequency in subjects receiving similar amounts of SN 7,618,particularly if the plasma levels were above 275 μg. per liter.

Clinical testing

SN 8,137 had only limited clinical application in thetreatment of malaria in the U.S. Army. At Harmon General Hospital, 63 patientswith acute attacks of vivax malaria were treated with total doses of2.0 gm. in 3 days (1.0 gm. on the first day and 0.5 gm. oneach of the next 2 days). A greater number of patients treated with SN 8,137 hadfever on the second day of treatment than had groups treated with SN 6,911, SN7,618, or quinacrine. Parasite clearance was not as rapid during the first 24hours of treatment as with quinacrine or SN 7,618, although more rapid than withquinine or SN 6,911. In the next 48 hours, the parasite clearance rate was aboutthe same for SN 8,137 as for the other 4-aminoquinolines as well as quinacrine.Toxic symptoms with SN 8,137 in this study appeared more frequently than withthe other synthetic drugs used. There was nausea, vomiting, anorexia,

⁶²Formula:7-Chloro-4-(3-diethylamino-2-hydroxypropylamine) quinoline diphosphate.

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and abdominal cramps in a total of four patients, diarrhea infive patients, pruritus in four patients, urticaria and a rash in two patients,and dizziness in four patients.

Although the patients were not retained for determination of the interval torelapse, six patients did relapse within 31 to 39 days after completion oftreatment. It appears from this small amount of data that SN 8,137 is inferiorto SN 7,618 in its poorer control of fever, slower parasite clearance, shorterinterval to relapse, and greater toxicity.

Summary

SN 8,137 has not been studied as extensively as other4-aminoquinoline compounds. Despite the fact that it appears to haveconsiderable antimalarial activity, although less than SN 7,618, it is doubtfulif it offers any advantage over the latter. In the treatment of acute attacks,SN 8,137 proved to be inferior and more toxic than SN 7,618. As a suppressiveagent, SN 8,137 may possibly have some value because of its apparenttolerability in relatively large doses. On the other hand, its rapiddisappearance from the body compared to SN 7,618 may require doses of an orderto offset its alleged tolerability.

Summary of Studies

As a result of extensive clinical and pharmacological studieswith these drugs, compounds were found that could be substituted, if necessary,for quinacrine without sacrificing any of the advantages of the latter in thetreatment or suppression of malaria. In addition, one of the derivatives of thisgroup of drugs (SN 7,618 or chloroquine) proved superior to quinacrine and otherdrugs both for treatment and suppression. The 4-aminoquinolines were found tocure falciparum infectionsand to be effective as suppressive agents in single weekly doses. They do notdiscolor the skin and may be taken for prolonged periods without apparent severetoxicity. The relapse rate in vivax infections is not materially influenced bytreatment with these drugs, although with SN 7,618 there is a significantprolongation of the interval to relapse and a reduction in the number ofshort-interval relapses after treatment. Treatment schedules of 1 to 4 days arepractical in acute attacks of vivax malaria. Extensive field studies of falciparum infections were not carried out, and thisphase of the treatment of malaria requires further investigation. The occurrenceof atypical lichen planus during the prolonged administration of SN 7,618suggests the possibility of the significant development of this syndrome ifchloroquine were to be used as widely as quinacrine. The careful and completeclinical and pharmacological studies carried out with these drugs have addedmuch to knowledge of the chemotherapy of malaria.

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8-AMINOQUINOLINE COMPOUNDS

Pamaquine (Plasmochin Naphthoate)⁶³

Historical review

The first promising synthetic antimalarial drug wasintroduced in Germany in 1924, by Schulemann and his coworkers at Leverkusen.The schizonticidal and gametocidal properties of Plasmochin in experimentalhosts and in man were such as to represent a major advance in the chemotherapyof malaria. It was hoped that as a result of continued chemical andpharmacological investigations a less toxic and more curative compound would befound. Actually, as will be demonstrated in this section, Plasmochin if properlyused produces definitive cure in infections with strains of P. vivax that have ahigh index of repeated relapse after all other forms of treatment. Thedrug-testing program in Germany continued during World War II and resulted inthe synthesis and testing of more than 200 of these 8-aminoquinoline compounds.In the United States, similar activity was directed in a search for an8-aminoquinoline drug that would be superior to Plasmochin, be less toxic, andmight be a true causal prophylactic or curative agent in the prevention,suppression, and treatment of malaria. As a result of these studies, areevaluation of Plasmochin led to its rational and successful use in curingrelapsing vivax infections and to the discovery of several compounds that areconsidered less toxic and in other respects superior to Plasmochin. Certainprewar studies on the clinical application of Plasmochin, reviewed at MooreGeneral Hospital,⁶⁴ will be described briefly. In addition, clinicalstudies made during the war that led to the successful use of Plasmochin as acurative agent will be discussed.

Acute attacks of malaria are more effectively and safelyterminated by the use of quinine, quinacrine, or the more recently introduced4-aminoquinoline compounds than by Plasmochin alone. In recent years, Plasmochinhas been used almost entirely as an adjunct to other antimalarial therapybecause of its ability to eradicate gametocytes of P. falciparum with smallamounts of the drug in a matter of a few days. This practice is of questionablevalue as a control measure in areas where malaria is endemic. There is evidence,however, that simultaneous administration of Plasmochin and quinine daily for 2weeks or more is highly effective in reducing relapse rates in vivax malariaduring an observation period of 2 to 6 months. This is in sharp contrast tocurative failure or high relapse rates in malaria caused by Pacific strains of P. vivax after treatment with quinine, quinacrine, or 4-aminoquinolinecompounds.

⁶³Formula (pamaquine naphthoate): methylene-bis-β-hydroxynaphthoate of6-methoxy-8- (1-methyl-4-diethylamino)butylaminoquinoline.
⁶⁴Most, H., Kane, C. A., Lavietes, P.H., London, I. M., Schroeder, E. F., and Hayman, J. M., Jr.: Combined Quinine-PlasmochinTreatment of Vivax Malaria; Effect on Relapse Rate. Am. J.M. Sc. 212: 550-560,November 1946.

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Prewar studies.-Sinton andBird,⁶⁵ in 1928, reported from India on 86 patients given Plasmochinalone or Plasmochin and quinine together for an attack of vivax malaria andobserved for 2 to 4 months after treatment. Occasionally, patients failed tocomplete treatment because of toxic reactions or disappearance from observation.The percentage of relapses was calculated on this basis. Twenty-nine patientswere given 0.08 gm. of Plasmochin (probably Plasmochin naphthoate) on 17treatment days during a period of 39 days as suggested by the Germanmanufacturers of the drug. The relapse rate during the period of observation was36 percent. Twenty-two patients were given 0.08 gm. on as many consecutive daysas possible for 28 treatment days with interruptions only for toxicmanifestations, the average treatment period being 36 days with a range from 28to 53 days. The relapse rate in this group was 23 percent. Fifteen patients weregiven 0.10 gm. Plasmochin plus 1.25 gm. quinine sulfate on 17 treatment daysduring a 39-day course of treatment. The relapse rate during 2 to 4 months was20 percent. Finally, a group of 20 patients received these same daily amounts ofboth drugs for 28 days as continuously as possible during an average treatmentperiod of 37 days. None relapsed during the period of observation. The relapserate for the 51 patients who received Plasmochin alone was 30 percent and forthe 35 patients who received Plasmochin and quinine together, 8.5 percent. Thus,of the total number of 86 patients who received Plasmochin for 17 to 28 days,the relapse rate as given by the authors was 21 percent. This percentageincludes 6 patients who were lost to followup studies or who did not completethe full course of treatment and were counted as failures; the failure rateactually observed in 80 men during a period of 2 to 4 months after treatment was16 percent. In contrast to this finding, the relapse rate for 111 men treatedwith quinine alone and similarly observed was 77 percent. There is littlequestion that in this study combined quinine-Plasmochin treatment verysubstantially reduced the incidence of relapse during 2 to 4 months aftertreatment.

In 1930, Sinton and his coworkers⁶⁶reported two additionalgroups of patients on combined quinine-Plasmochin treatment for acute attacks ofvivax malaria. Seventeen were given, daily, Plasmochin, 0.06 gm., and quininesulfate, 1.25 gm., from 4 to 21 days. None of them had a clinical or parasitemicrelapse during 2 months after treatment, when the experiment was terminated. Anadditional 44 patients received Plasmochin, 0.04 gm., and quinine, 1.25 gm.,daily for 21 days. Three patients relapsed, making a total failure rate of 6percent for 54 men who had Plasmochin for 14 or more days in contrast to arelapse rate of 42 percent for 38 patients who were treated with quinine alone.

⁶⁵Sinton, J. A., and Bird,W.: Studies in Malaria, With Special Reference to Treatment. Part IX.Plasmoquine in the Treatment of Malaria. Indian J.M. Res. 16: 159-177, July1928.
⁶⁶Sinton,J. A., Smith, S., and Pottinger, D.: Studies in Malaria, With Special Referenceto Treatment. Part XII. Further Researches into the Treatment of Chronic BenignTertian Malaria With Plasmoquine and Quinine. Indian J.M. Res. 17: 793-814,January 1930.

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In 1932, Jarvis⁶⁷reported 8.0 percentrelapses during a 2 to 4 months' period of observation of 75 patientswho received Plasmochin, 0.03 gm.,and quinine, 1.3 gm., daily for 21 days. Manifold⁶⁸ reporteda study of some 3,000 Indian andBritish troops treated for acute attacks of vivax malaria with Plasmochin, 0.04gm., and quinine, 1.3 gm., daily for 21 consecutive days. Of these, 98 percent were able to complete the full course oftreatment. Analysis of readmission records for 5 monthsafter treatment showed the relapse rate for the whole group was 5.2 percent in contrast to a wideexperience of rates from42 to 77 percentafter treatment with quinine alone.

Wartime studies-In 1945, Kelleherand Thompson⁶⁹ reportedobservations made during the war on the effects of combined quinine-Plasmochintreatment of vivax malaria of Mediterranean origin. Of 100 patients with delayedprimary attacks treated with 4.6 gm.of quinacrine during 12 days, 29 percent relapsed during an observation period of5 months. Of 76 patientswith delayed primary attacks treated for 10 days with Plasmochin base, 0.03 gm., and quinine2.0 gm.,daily, only 14, or 18 percent, relapsed. The relapse rate for 650 men treated with quinacrine as above for later relapsesand followed for 5 months was 34 percent, whereas the relapse rate for 584 men treated for later attacks with combined quinine-Plasmochinwas 10 percent. In American experience, the relapse rate in 120 days for Mediterranean vivax malaria(150 patients) treated with quinacrine or quinine was 32 percent. There can be no question about the significanceof the reduced relapse rate in this British report.

Thus far, references have been cited which indicated thatcombined quinine-Plasmochin given for at least 10 days, the amounts ofPlasmochin base being at least 0.03 gm.a day, is highly effective in reducing the relapse incidence of vivax malariaduring an observation period of 2 to 5 months. Small amounts ofPlasmochin or short-term schedules are definitely of no value in vivax malariaof Pacific origin, and experiences with such schedules are generallyunconvincing. Dieuaide,⁷⁰in reviewing relapses following various schedules of treatment in the Pacificarea, cites 83 percent within 16 weeks for 185 menwho had had two courses of quinacrine hydrochloride for acute attacks of vivaxmalaria and 78 percent for 136 patientswho had had two consecutive courses of treatment consisting of quinacrine (0.1gm. three times daily for 7 days), followed by Plasmochin naphthoate (0.02 gm. three times daily for5 days),after which both were repeated. Thus, Plasmochin for 5 daysand repeated a week later was not effective in reducing the relapse rate ascompared with quinine or various schedules of quinacrine mentioned

⁶⁷Jarvis, O. D.: Further Researches into the Treatment of Chronic BenignTertian Malaria With Plasmoquine and Quinine. Indian J.M. Res. 20: 627-631,October 1932.
⁶⁸Manifold, J. A.: Report on a Trial of Plasmoquine and Quinine in theTreatment of Benign Tertian Malaria. J. Roy. Army M. Corps 56: 321, May; 410,June 1931.
⁶⁹Kelleher, M. F. H., and Thompson, K.: Treatment ofMalaria. Lancet 2: 217, 18 Aug. 1945.
⁷⁰Dieuaide, R.: Clinical Malaria in Wartime. War Med. 7: 7-11, January 1945.

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by Dieuaide. In the Bulletin of the U.S. Army MedicalDepartment,⁷¹ relapse rates are compared for variousgroups of patients treated in this country for acute attacks of vivax malaria ofPacific origin and followed for at least 90 days afterward. Of these, 176patients were given quinacrine or totaquine alone, and 57 percent relapsed; 299patients received 0.01 gm. Plasmochin base three times daily for 3 days afterquinacrine or totaquine and quinacrine, and the combined relapse rate in allthese Plasmochin groups was 56 percent. Here, again, is good evidence thatPlasmochin for 3 days after other antimalarial therapy is not effective ininfluencing the relapse rate of Pacific vivax malaria. On the other hand,Gentzkow and Callender,⁷² in 1938, reported from Panama that thisamount of Plasmochin (0.01 gm. three times a day for 3 days) in addition to 2.4gm. of quinacrine, during 4 days, given to 128 patients resulted in a relapserate of 9.4 percent in 6 months compared to 45.6 percent in 215 patients whoreceived quinacrine alone. This report is based on analysis of patient malariaregisters. From India, Bird⁷³ reported30.9 percent relapses in 152 patients treated with Plasmochin, 0.01 gm. threetimes a day for 5 days, following 5 to 7 days of quinacrine, and a relapse rateof 46.3 percent for 201 patients who received the same amount of Plasmochinafter 7 days of quinine.

Summary-The evidence that has been cited indicates quitedefinitely that simultaneous quinine-Plasmochin treatment for 14 days or moreof vivax malaria of Indian or Mediterranean origin resulted in a verysignificant reduction in relapse rates during periods of observation of from 2to 6 months and that Plasmochin for 3 to 5 days after quinine, totaquine, orAtabrine is of no benefit in reducing relapses in vivax malaria of Pacificorigin. In this connection, it should be borne in mind that the majority ofrelapses occur within a month after quinine or totaquine treatment and within 3months after quinacrine or the 4-aminoquinoline drugs. Short-term courses ofPlasmochin (3 to 5 days) are of doubtful value in reducing relapse rates in vivax malaria of Indian origin, and the reported beneficial effect of 3 days ofPlasmochin after quinacrine in reducing relapses in vivax malaria of Panamanianorigin remains unconfirmed.

Study at a specialty center

The following report from Moore General Hospital, a specialtycenter for tropical diseases, deals with the effect on subsequent relapse ofsimultaneous combined quinine-Plasmochin treatment for 14 days in vivax malariaof Pacific origin, which had not previously been studied.

⁷¹Treatment of Relapses of Vivax Malaria. Bull. U.S. Army M. Dept. No. 89, pp. 21-22, June1945.
⁷²Gentzkow, C. J., and Callender, G. R.: Malaria in the Panama Canal Department, UnitedStates Army.II. Results of Treatment With Quinine, Atabrine, and Plasmochin. Am. J. Hyg. 28:174-189,September 1938. ⁷³Bird, W.: Atebrin and Plasmoquine in Treatment of Benign Tertian Malaria.J. Mal. Inst. India 5: 395, 1944.

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Material and methods.-The protocol described here was furnished by theOffice of the Surgeon General. Seventy-two white patients with acute attacks of vivax malaria of Pacific origin having fever and positive smears were admittedto a special treatment and study ward. No attempt at selection of patients wasmade. All drugs were administered by a medical officer. On the first day,quinine sulfate, 1.0 gm., and Plasmochin naphthoate, 0.02 gm. (0.01 gm. base),were given together at 8-hour intervals. On days 2 to 14 inclusive, quininesulfate, 0.65 gm., and Plasmochin naphthoate, 0.02 gm., were given together at8-hour intervals. The total amount administered during the treatment period of14 days was 28.35 gm. of quinine sulfate and 0.84 gm. of Plasmochinnaphthoate. A control group of 75 patients with acute attacks of vivax malariaof Pacific origin were treated with a total of 28.35 gm. of quinine alone on thesame schedule. Temperatures were recorded every 4 hours. Parasite counts weredone twice daily until negative for 3 consecutive days. Hemoglobin,methemoglobin, and total white blood count determinations were made daily.(Hemoglobin and methemoglobin were determined colorimetrically ascyamethemoglobin.) Each patient was examined at least once daily by a medicalofficer, and special attention was paid to possible manifestations of Plasmochintoxicity. On the day after completion of treatment on the ward, the patientswere transferred to a convalescent area for further observation. The duration ofobservation was until relapse or for a minimum of 120 days. During thisinterval, smears were examined twice weekly. In the event of parasitemia,temperature observations were made every 4 hours and parasite counts were donedaily. A temperature of 100^? F. or more by mouth in association witha positive smear was considered a clinical relapse.

Results-The cumulative clinical relapse rates during 120 days'observation after treatment of acute attacks with quinine, quinacrine, andcombined quinine-Plasmochin are shown in chart 36. The total failures aftertreatment are summarized in table 76.

1. Quinine.-Seventy-five patients with acute attacks of vivax malaria ofPacific origin were treated with 28.35 gm. of quinine sulfate during 14 days.Sixty-two patients or 82.6 percent had a clinical relapse within 120 days. Fivepatients who did not relapse had, at one time or another during their period ofobservation, a positive smear without fever or symptoms. Thus, quinine failed toeradicate the infection in 67 or 89.3 percent of patients treated and observedfor 120 days.

2. Quinacrine hydrochloride (Atabrine).-Sixty-ninepatients with acute attacks of vivax malaria of Pacific origin were treated with2.8 gm. of quinacrine during 7 days. Fifty-six patients or 81.2 percent hadclinical relapses within 120 days after completion of treatment. An additionaltwo patients who did not relapse had, at one time or another during their periodof observation, positive smears without fever or symptoms. Thus, within

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CHART 36.-Relapse rates and intervals to relapse aftertreatment of acute attacks of vivax malaria of Pacific origin with various drugs

120 days following quinacrine, 84.1 percent of treated patients exhibitedevidence that they were not cured of the infection.

3. Chloroquine diphosphate (SN 7,618).-Eighty-two patients with acuteattacks of Pacific vivax malaria were treated with 1.5 to 2.0 gm. of SN 7,618from 4 to 7 days. Sixty-two or 75.6 percent had a clinical relapse within 120days after completion of treatment. Four additional patients developedasymptomatic parasitemia without clinical relapse during the 120-

TABLE 76.-Results of treatment in four groups of patientsadministered antimalarial drugs for acute attacks of vivax malaria of Pacificorigin

¹Clinicalrecurrence with fever, symptoms, and positive blood smear, observed within 120days after treatment.
²Positive smear only, withoutfever or symptoms and not followed by clinical relapse during 120 days'observation after treatment.
³Clinical relapses plusparasitemic relapses during 120 days after treatment.

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day period of observation. In other words, a total of 66 patientsor 80.5 percent of the whole number treated represent treatment failuresin that they suffered clinical or parasitemic relapses while under observationafter treatment with SN 7,618.

4. Combined quinine-Plasmochin.-Seventy-two whitepatients with acute attacks of vivax malaria of Pacific origin were treated withPlasmochin and quinine as described under "Material and Methods."Three clinical relapses occurred within 120 days after completion oftreatment, a clinical relapse rate of 4.2 percent. Five additionalpatients showed parasitemia but had neither fever nor symptoms during theobservation period. Thus, of 72 Pacific infections treated, there werealtogether only 8 failures, making a total failure rate of 11.1 percentfor the 120 days.

Toxicity

Clinical experience-Numerous references can be found inthe literature dealing with toxic manifestations of Plasmochin of varying typeand severity. Most frequently reported are gastrointestinal complaints, that is,mild to severe epigastric pain or soreness, anorexia, abdominal cramps, nausea,vomiting, and diarrhea; cyanosis; dyspnea and changes in pulse, in bloodpressure and in electrocardiograms; changes in the blood varying from mildanemia to severe or fatal hemolytic crisis or agranulocytosis; vague muscularaches and pains and weakness; and symptoms referable to the central nervoussystem, principally headache, dizziness, "nervousness," psychosis, andcoma. The incidence of severe toxic reactions varies from 1 to 10 percent indifferent series reported. The hemolytic reaction is the most seriousmanifestation of Plasmochin intoxication and may vary from mild progressiveanemia to a sudden fatal hemolytic crisis associated with shock, severe anemia,jaundice, hemoglobinuria, and azotemia. This reaction may come on early afterrelatively small amounts of drug but also may occur at any time during theadministration of Plasmochin. Weakness and dark urine are the most commonsymptoms at onset. During the acute episode the erythrocyte sedimentation rateaccelerates; the white blood cell count and hemoglobin diminish. Race, diet,climate, and the prior administration of other drugs have all been suggested asfactors that may be responsible for initiating a hemolytic reaction. Evidencewill be reviewed regarding the possible relation of race to predisposition. Thedegree of methemoglobinemia in many individuals is probably related to the doseof drug. Gastrointestinal symptoms are most common during the fourth and fifthdays of therapy and X-ray studies during this time have revealed gastrichyperperistalsis and intestinal spasm. There follows a brief summary of theincidence of toxic experiences reported in relatively large groups.

Manifold, in a 1931 report⁷⁴dealingwith the results of treatment of vivax malaria in India with quinine, 1.25 gm.,and Plasmochin, 0.04 gm.,

⁷⁴See footnote 68, p. 581.

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given together daily for 21 days,noted toxic symptoms or signs occurring in 21 percentof 1,298 British soldiers and in 10percent of 1,915 Indians treated.Epigastric pain or other gastrointestinal symptoms were complaints in15 percent of the British and in 8 percentof the Indian patients. Cyanosis was observed in 4 percentof the British cases but was not accurately determined in the Indians because ofthe color of their skin. Jaundice was observed in only three patients, and inone of these, an Indian, death followed as a result of a severe hemolyticreaction. In Manifold's opinion, the majority of the symptoms were mild. He alsoemphasized that, of 480 Britishpatients personally treated, the full course of 21 daysof Plasmochin was completed without interruption by all but 2 patients. He further stated that98 to 99 percent of the patients in theentire series of more than 3,000 cases completed a full course of treatment.

West and Henderson,⁷⁵ in 1944, reported an incidence of2.85 percentPlasmochin toxicity in 846 patientstreated for falciparum infections in Africa with quinine, 2.0 gm. daily for 3 days, quinacrine, 0.3 gm. daily for5 days, no treatment for 2 days,then Plasmochin base, 0.03 gm. daily for 5 days.Twenty-two of the twenty-four patients with toxic signs had primary falciparuminfections, and the other two had had malaria and had been treated withPlasmochin previously. Four patients were hospitalized after being given 0.66gm. of Plasmochin base, and the mean total toxic dose was0.119 gm. Jaundice was the most common finding and was observed in 20 patients, the mean icteric index being27.6. Twenty patients had abdominal pain. Headache, weakness,and dizziness occurred in 16, 14, and11 patients, respectively. Two patients were psychotic and one in coma. Therewas anemia in 19 patients, and in 1the red cell count was 1.4 millionper cubic millimeter, the average being 2.88 millionper cubic millimeter. The white cell counts varied from 4.5 to 20.8 andaveraged 10.2 thousand per cubicmillimeter. All patients except one were ambulatory during the period ofPlasmochin therapy. Unfortunately, the race of the patients or the ratio ofblack to white in the population sample reported is not stated in this paper.

The color of the skin is of particular interest, as Swantzand Bayliss⁷⁶ in 1945 reportedmoderately severe hemolytic toxic reactions in nine Negroes who had receivedPlasmochin in the course of treatment for malaria. These reactions wereencountered during a period in which approximately 3,000 cases of malaria weretreated. The amount or duration of Plasmochin treatment is not stated. As torace, the authors say only that the majority of their malarial patients werewhite. The absence of a single hemolytic reaction in the whites treated and theoccurrence of nine cases of severe intoxication in the Negroes suggest somepredisposition to Plasmochin hemolytic reactions in Negroes. In studiessummarized by Shannon, 6 hemolyticreactions

⁷⁵West, J. B., and Henderson, A. B.: PlasmochinIntoxication. Bull. U.S. Army M. Dept. No. 82, pp. 87-99, November 1944.
⁷⁶Swantz, H. E., and Bayliss, M.: Hemoglobinuria;Report of Ten Cases of Its Occurrence in Negroes During Convalescence FromMalaria. War Med. 7: 104-107, February 1945.

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(5 Negroes and 1 Chinese) were observed among 71 pigmentedpatients, an incidence of 8.4 percent, but none in 35 white patients whoreceived 0.03 gm. Plasmochin base for from 2 to 14 days. All reactions occurredduring the third to fifth days of Plasmochin therapy and were characterized byweakness, dark urine, and icterus at onset.

Hardgrove and Applebaum,⁷⁷ in 1945, reported fromPanama an incidence of 10.13 percent hemolytic reactions in 4,361 laborers whowere given a routine mass treatment for suppression of malaria, the treatmentconsisting of quinacrine, 0.1 gm. three times daily for 5 consecutive days, nomedication for the next 2 days, and then Plasmochin base, 0.01 gm. three timesdaily, for 5 consecutive days. In 8.12 percent of the whole treated group, thereactions were sufficiently severe to require hospitalization. Three-fourths ofthese patients were admitted during a 48-hour period corresponding to the lastday of Plasmochin treatment and the day following; only 21 toxic reactionsoccurred following less than 0.10 gm. of Plasmochin base. The principalcomplaints and findings were abdominal pain, dark urine, anorexia, jaundice,headache, nausea, and vomiting; abdominal tenderness, enlarged liver, pallor,cyanosis, low grade fever, hemoglobinuria, bilirubinemia, anemia, andleukocytosis. Treatment was essentially blood transfusion, intravenous glucosesolution, and sodium bicarbonate by mouth. There were no deaths. It should benoted that in this series of patients a large proportion (not precisely stated)were not of the white race; also that the Plasmochin was administered to the menwhile they were working.

Kelleher and Thompson⁷⁸ in theirstudy of 660 British soldiers who were treated for acute attacks of vivaxmalaria with quinine, 2.0 gm., and Plasmochin base, 0.03 gm., daily for 10consecutive days encountered practically no severe toxic manifestations. Of 295patients personally treated by the authors, in only 3 was therapy interruptedbecause of toxicity. Other medical officers participating in the study, havingless experience with Plasmochin, interrupted therapy in 2 to 4 percent of 365subjects. No serious reactions were encountered.

It is evident from this brief survey of the literature thattoxic experiences with Plasmochin vary considerably in their incidence andseverity. Large groups of patients have been given 0.03 gm. of Plasmochin basefor 10 to 21 days with practically no toxicity. On the other hand, serioushemolytic reactions have been reported when the drug was given for only 3 to 5days. There is evidence that hemolytic reactions occur more frequently inpatients who are not of the white race. Some investigators believe that toxicmanifestations are more common in patients who have recently receivedquinacrine. Although it is true that the levels of Plasmochin in the plasmaare very much higher in patients who have recently had quinacrine than inpatients who have not, it has not been established that high plasma levels and

⁷⁷Hardgrove, M., and Applebaum, I. L.: PlasmochinToxicity; Analysis of 258 Cases. Ann. Int. Med. 25: 103-112,July 1946.
⁷⁸See footnotes 69, p. 581.

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toxicity are related. It seems probable that taking Plasmochin while workingmay be a factor in producing serious reactions.

The writer (H.M.) and his coworkers administered Plasmochinnaphthoate in doses of 0.02 gm. three times daily at 8-hour intervals for 14 days to 100 white patients. Nomajor toxic manifestations were observed, and all patients were able to completethe full course of therapy.

Forty percent of the patients had some form of complaint referred to thegastrointestinal tract and probably related to Plasmochin. These symptomsusually began from the third to the fifth day and lasted from 1 to 7 days; theyconsisted principally of abdominal cramps or abdominal soreness which wererarely severe.

Cyanosis was observed on the 11th day of treatment in one patient who had amethemoglobin value of 12 percent. Ninety percent of the patients showedmethemoglobinemia above normal values at some time during treatment withamounts ranging from 1.0 to 12 percent(average 2.3 percent)of total hemoglobin.

In 16 percent of the patients who were given Plasmochin for 14days, there was a fall in totalhemoglobin of from 11 to 20 percentduring the second week of treatment which we considered related to the drug. Anequal number of patients had an average fall in hemoglobin of 15.3 percentduring the first 5 days. In the latter group, this fall in hemoglobin wasapparently due to active malaria rather than to Plasmochin therapy since itoccurred in the first few days of the acute attack and reversed itself withcontinued treatment. Severe anemia did not occur, and no hemolytic crisis wasobserved.

The effect of Plasmochin on the white blood cell count was toproduce leukocytosis in a significant number of men (15 percent with countsabove 10,000 per cubic millimeter) during the second week of treatment and leukopenia (24 percentwith counts below 5,000 per cubic millimeter) during the first week afterdiscontinuance of the drug. Subsequent counts 2 weeks after treatment were allnormal.

In our experience, the toxic manifestations related to theadministration of Plasmochin were not severe or serious and should not detractfrom the value of the drug if proper care is taken in recognizing potentiallyserious signs of toxicity.

Recommendations for therapeutic use-It is suggested thatpatients given Plasmochin as described in this chapter be hospitalized duringtreatment and observed frequently to recognize early severe hemolysis, should itoccur. Treatment with Plasmochin should be limited to white patients. Hemoglobindeterminations should be done daily and complete blood counts at least twice aweek. Cyanosis alone is not an indication for discontinuance of therapy. A fallin total hemoglobin of more than 20 percentin any one day should be regarded with suspicion; if followed by a furtherdecline in the amount of total hemoglobin on the next day, Plasmochin treatmentshould stop. One cannot anticipate sudden hemolysis by any laboratory method,

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but symptoms of severe weakness and dark urine during thefirst 5 days of therapy should be investigated with this possibility in mind.Fluids, blood, and alkalies by vein are indicated if a severe reaction shouldoccur. Abdominal cramps occur most frequently during the first week of treatmentand if severe may be controlled with atropine. The usual symptoms of cinchonism,namely, tinnitus, fullness in the head and ears, and headache, were encounteredin varying severity in the first week of treatment in the majority of patients.These symptoms gradually subsided in the second week and caused no interruptionof therapy. During the first 2 to 5 days of the acute attack ofmalaria, most patients should remain in bed. For the remainder of the 2-weekperiod of treatment in the hospital, the patients may be ambulant on the wardbut should not be permitted vigorous exercise nor be given overnight passes.Each dose of drug must be personally administered by a nurse or physician, andeach patient should be seen at least twice daily. Patients with anemia, severelymalnourished, or in poor physical condition should not be treated withPlasmochin.

Discussion

The clinical relapse rate of only 4 percent and a totalfailure of 11.1 percent following combined treatment with quinine and Plasmochinis very striking. In our experience, the clinical relapse in 10 groups of atleast 50 patientseach has varied from 65 to 85 percent,with total failure rates after treatment of from 75 to 90 percent for all groupsexcept the group treated with quinine-Plasmochin as here reported.

Analysis of more than 1,000 attacks of vivax malaria treatedand observed at Moore General Hospital for 120 days indicated that within thisperiod of observation the relapse rate for any given attack is not significantlyinfluenced by the number of previous attacks, by the age of the disease (table 76),or by the amount or durationof treatment with quinine or quinacrine. It is unlikely that these factors canaccount for the wide discrepancy in the observed results. One must also considerwhat the probability may be of late relapses occurring in the quinine-Plasmochingroup after the 120 days' period of observation. The median interval to clinicalrelapse following treatment with quinine or totaquine is 24 days and following quinacrineor 4-aminoquinoline drugs, 50 to 65 days. Within 120 days, 80 to90 percent of all patients treated for an acute attack of vivax malaria ofPacific origin with currently used antimalarial drugs will have intervalparasitemia without fever or symptoms or will actually relapse clinically. Weknow that a relatively small percentage of failures do occur after 120 days. It is unlikely thatabsolutely no definitive cures follow treatment with quinine or quinacrine, buteven if this were so, the maximum number of failures that could possibly occurafter 120 days'observation would be only 10 to 20 percentof treated patients. The median interval to failure (parasitemic and clinical)in the relapses that actually were observed in the quinine-Plasmochin group was 34 days compared to 36 days for the quininecontrols. In other words, when

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quinine-Plasmochin failed it did so in the same intervalafter treatment as did quinine alone. Subsequently, we observed 20 percent ofthe Plasmochin group for at least 180 days after treatment and no failures after120 days had occurred. Unless Plasmochin alters the biology of vivax malaria inman so that very late failures will occur in the majority of treated patients,it is our opinion that the freedom from parasitemia or clinical relapse for 120days in 90 percent of our treated patients represents definitive cure for atleast 80 percent of men so treated.

Analysis of our Plasmochin relapses gives us no clue to a possibleexplanation for failure. The average mean plasma levels of quinine andPlasmochin are in the same order and range in the failures as in the whole grouptreated as well as for the patients in whom 120-day cures were observed. Therewas one failure in nine delayed primary attacks treated. As regards the averageage of the disease and the average number of previous attacks, the other sevenfailures were comparable to the patients in whom treatment was successful.

Clinical use-Four-month cures in 90 percent of patients treated withcombined quinine-Plasmochin raised the question of the general application ofthis form of treatment for vivax malaria. In infections of Mediterranean origin,the relatively low clinical relapse rate of 30 percent within 120 days for vivaxmalaria following treatment with quinacrine or quinine makes it questionablewhether routine Plasmochin treatment is indicated in such infections, especiallyin the second year of the disease. Certain individuals, however, with vivaxmalaria of Mediterranean origin relapse frequently and at short intervals aftertreatment during the first year of the disease particularly if quinine is usedto terminate the acute attack. In these cases, combined quinine-Plasmochintreatment should be considered.

Since 120-day failure rates after treatment of attacks ofPacific vivax malaria may be as high as 90 percent, more serious considerationshould be given to the use of combined quinine-Plasmochin in this type ofinfection. Even though there is only a 10 to 20 percent chance that a patienttreated with quinine or quinacrine for his first attack will have no subsequentattack in 120 days, it seems worthwhile to take this chance for that attack andpossibly for the next one or two relapses. However, the occurrence of repeatedattacks, at short intervals, for example, 3 to 6 attacks during the first 6months of the disease or repeated attacks later in the disease, is in ouropinion an indication for the use of combined quinine-Plasmochin therapy. Theco-existence of other diseases precluding the use of quinacrine therapeuticallyor for suppression (quinacrine sensitivity and/or exfoliative or eczematoiddermatitis or atypical lichen planus) is another indication for the use ofcombined quinine-Plasmochin. Likewise, patients who relapse frequently atintervals of a month or less after quinine and who cannot take quinacrine can betreated with Plasmochin, as outlined. Finally, patients whose convalescence fromother diseases is interrupted or delayed by repeated attacks

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of malaria should be considered candidates for combinedquinine-Plasmochin therapy. Each case must be considered individually and theprobability of cure weighed against potential toxicity and a 2 weeks' course ofhospital treatment with Plasmochin, compared with a short, safe course oftreatment with other antimalarial drugs and the high possibility of failure.

Appreciating the potential dangers of Plasmochin, one is neverthelessimpressed by the complete absence of severe or serious toxicity in a series of100 consecutive white patients who were given 0.06 gm. Plasmochin naphthoatedaily for 14 days. The fact that the patients were all white, closely observedin the hospital, and in good physical condition may be factors in the absence oftoxicity.

Further study-Following completion of the study just described, 30additional white patients with acute attacks of vivax malaria of Pacific originhad, in addition to quinine, quinacrine, or SN 7,618, received Plasmochin for 14days. Information was now available on relapse rates during 120 to 180 days'observation after treatment for more than 100 cases of vivax malaria. Theobserved relapse rate for the group was 4 percent and the total failure rateless than 10 percent. There can be little question about the curative value ofPlasmochin.

It is interesting that, in a group of 10 men who received Plasmochin for 14days after 2.2 gm. of quinacrine had been given to terminate the attack, onlyone relapse occurred during 120 to 180 days' subsequent observation. No relapseoccurred in a similar period of observation in another 10 men who received,during the first 4 days of treatment with Plasmochin, a total of 1.4 gm. of SN7,618 in addition to the Plasmochin, which was given for a total of 14 days. Itseems that successful treatment with Plasmochin may be accomplished after theacute attack is terminated with quinacrine or SN 7,618, or by giving either ofthese drugs simultaneously with Plasmochin for a few days until the acute attackhas been terminated and then continuing Plasmochin until it has been given for14 consecutive days.

It is noteworthy that of the 100 cases successfully treatedwith Plasmochin there were 20 patients with primary attacks and 19 with onlyone prior attack. There were only 2 failures in this group of 39 men, or afailure rate of 5 percent. The severity of infection acquired naturally may varyconsiderably, but all evidence suggests that the age of the disease or severityof infection is of secondary importance in determining the end results ofPlasmochin therapy. Likewise, no correlation has been found between Plasmochinplasma levels and success or failure of treatment. On the other hand, total doseand duration of treatment appear to be crucial factors. For example, in a groupof 10 men who received combined quinine-Plasmochin treatment for only 10 insteadof 14 days, 6 relapses occurred.⁷⁹ Similar failures were reported intreatment of primary attacks or relapses if the total dose of Plasmochin was0.42 instead of 0.84 gm. during 14 days.

⁷⁹Most, H.: Unpublished data.

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Summary

The clinical studies on the effect of Plasmochin indefinitively terminating vivax infections are of the utmost importance in thechemotherapy of malaria. As a result of these carefully controlled experiments,Plasmochin or similar drugs were established with a definite place in themanagement of relapsing vivax malaria. The original observation by James⁸⁰thatPlasmochin given in adequate amounts before, during, and after sporozoiteinfections resulted in cure of vivax malaria has been clinically applied.Similar results with domestic and foreign strains of P. vivax in protective andtherapeutic tests have been reported in the United States. Treatment of primaryattacks or relapses resulted in cures in the great majority of cases in whichtotal doses of Plasmochin of 0.84 gm. were given with quinine or other drugs for14 days.⁸¹

Extension of these studies has been made with other8-aminoquinoline compounds. At least one of these, SN 13,276 or pentaquine, has great promise. No clinical studies withthis drug were made in the U.S. Army during World War II. However, it has beenshown by civilian and Federal research agencies that it will produce a greaternumber of cures than Plasmochin in primary attacks and relapses of vivax infections transmitted by mosquitoes as well as in protective tests. It has alsobeen shown that it may be less toxic.

Summary of Studies

Protective tests and clinical trials conclusivelydemonstrated the curative properties of this class of compounds. A reevaluationof Plasmochin resulted in the demonstration that if this drug is administeredwith quinine or other drugs for 14 days vivax malaria will be cured in 80 to 90 percent of naturally acquired clinical disease. Incontrast, relapse will be forestalled in only 10 to 20 percentof vivax infections after treatment with quinine, quinacrine, or the4-aminoquinolines. The feasibility and safety of administering 0.84 gm. ofPlasmochin to white patients was shown, with only minor toxicity occurring.Plasmochin, which has had its "ups and downs" in the story of thetreatment of malaria, was shown to have a definite and important position in themanagement of relapsing vivax malaria. As a result of detailed studies of the8-aminoquinoline compounds, new members of this group have been found which maybe so superior to Plasmochin as to end the search for a curative antimalarialdrug.

SUMMARY

The magnitude of the malaria problem during World War II canbe appreciated only if it is realized that the war was fought in areas where thedisease is endemic and that about a half million cases developed in the U.S.

⁸⁰James, S. P., Nichol, W. D., and Shute, P. G.: On the Prevention ofMalaria With Plasmoquine. Lancet 2: 341-342, 15 Aug. 1931.
⁸¹See footnote 64, p. 579.

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Army. At the beginning of the war, there was great anxietywith regard to the loss of our sources of quinine, and there was some questionconcerning the efficacy of quinacrine as a suppressive and therapeutic agent.Our scientific resources were beautifully organized in a search for betterantimalarial drugs. Fundamental studies and a rational approach to the problemled to a clear understanding of the optimum methods of using quinine andquinacrine. Newly developed methods made it possible to compare the relativeefficiency of various drugs. It was shown that certain sulfonamides could besubstituted in extreme emergencies as suppressive agents. Heavy metals on thewhole offered little promise. Antibiotics were of no value.

Quinacrine was shown to be superior to quinine for all purposes exceptpossibly for the treatment of fulminant infections with P. falciparum. Thetoxicity of quinacrine was extensively studied; hitherto undescribed reactions,in particular the eczematoid-lichen-planus-dermatitis complex, and aplasticanemia were encountered in a small percentage of cases. In proper dosage,quinacrine was more effective than quinine in terminating acute attacks and incuring those caused by P. falciparum, while the proper use of quinacrine forsuppression made possible successful military campaigns in highly malariousareas. Mortality from malaria during World War II was negligible principallybecause of effective treatment and suppression of clinical malaria.

In the search for new drugs, the 4- and 8-aminoquinolines were widelystudied. Several (SN 6,911 and SN 8,137) were as effective as quinacrine and ifnecessary might have been substituted for it. In addition, one was found (SN7,618 or chloroquine) that was superior to quinacrine. It does not discolor theskin; it could apparently be given with safety over a long time and wouldproduce satisfactory suppression by single weekly doses. These drugs also curefalciparum infections. No studies were available on their value in fulminating falciparum infections in comparison with quinine or quinacrine.

Finally, the curative properties of the 8-aminoquinoline compounds weredemonstrated. Plasmochin was reestablished as a drug of great value in thetreatment of relapsing vivax malaria in conjunction with quinine, and newcompounds were found (SN 13,276 or pentaquine) which may have fulfilled thesearch for a generally curative antimalarial agent. The final step in progressto the ideal therapeutic will be an agent that is truly chemoprophylactic. Sucha drug may be found, which will be safe when taken over long periods and willcompletely prevent the development of infection.

This is how the matter stood when World War II ended. The momentum of thesestudies carried over into investigations continued during the postwar years1946-54. These investigations were for the most part under the auspices of theU.S. Army. A note is appended on this work, as it ties together the whole and brings it to more sharply defined conclusions.This addendum

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on postwar research is drawn from a review prepared by Dr. L. H. Schmidt andDr. G. Robert Coatney.⁸²

Postwar Research

At the close of hostilities, it was evident that much workremained to be done with intent (1) to evaluate known but inadequately assessedsuppressive and therapeutic agents and (2) to develop new curative drugs. Manyinvestigators who during the war had taken part in the research programs of theOffice of Scientific Research and Development (OSRD) retained their interest inthe chemotherapy of malaria. It seemed to them that this unfinished businesscould best be completed within a similar pattern of cooperative effort.

Accordingly, the fruitful period from 1946 to 1954,inclusive, saw investigations in large part conducted with the activeparticipation and support of the armed services. A Malaria Study Section, underthe U.S. Public Health Service, recommended grants-in-aid to interestedscientific workers at various institutions. They, together with parasitologistsand clinical investigators in the Section on Chemotherapy, Laboratory ofTropical Diseases, National Institutes of Health, agreed to coordinate theiractivities to achieve specified objectives. A joint group known as Investigatorsin Malaria Chemotherapy met frequently from October 1946 through 1948 to assessprogress and plan new activities.

Investigations under OSRD had established the value ofquinacrine. Of the compounds that gave promise in preliminary tests or of havingeven superior qualities, only one, chloroquine, had been tested sufficiently tobe recommended for general use. Two other compounds, amodiaquin andoxychloroquine, belonging to the same chemical group, the 4-aminoquinolines,seemed to merit further trial, as did the 4-quinoline-methanols and a smallnumber of naphthoquinones. In addition, there were the biguanides, particularlychlorguanide, made available to OSRD investigators through the scientificliaison between Great Britain and the United States.

It had been recognized also, during the latter years of thewartime studies, that certain prewar work by the British had shown that the oldGerman drug pamaquine (Plasmochin) possessed a property not common to otherantimalarial drugs; namely, its ability to cure naturally acquired vivax malaria. This recognition led to confirmatory observations and subsequently to alarge program involving synthesis, pharmacological study, and clinicalevaluation of the 8-aminoquinolines, a program which dominated the last year ofOSRD activities in this field. At the end of the war, this effort had led to thedevelopment of at least one compound, pentaquine (SN 13,276), believed to besuperior to pamaquine.

⁸²Schmidt, L. H., and Coatney, G. R.: Review of Investigations in MalariaChemotherapy (U.S.A.) 1946 to 1954. Am. J. Trop. Med. 4: 208-216, March 1955.

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In the first of the cooperative postwar studies, the naphthoquinones werefound to have only a low level of therapeutic effectiveness and gave noevidence, in man or monkey, of prophylactic or curative properties. Of the4-quinoline-methanols, three compounds were shown to possess no significantadvantages over quinine in the treatment of vivax malaria. The fourth producedphenomenal lengthening of the relapse interval, but this was associated with thedevelopment of photosensitivity. Accordingly, work on all of these compounds wasabandoned. In the 4-aminoquinoline group, continued investigation on thelong-term suppressive activity of chloroquine, and on the short-term suppressiveand therapeutic properties of amodiaquin, showed that these drugs possesssimilarly high therapeutic and suppressive activity. The effectiveness andtolerability of chloroquine given intramuscularly, and its effectiveness insingle doses given orally, were amply demonstrated.

Chlorguanide, the biguanide that had shown considerable promise inpreliminary clinical evaluation by British, Australian, and OSRD investigators,was now thoroughly studied in man and experimental animals. Long-termadministration was found to be safe. In the body, the drug was degradedextensively to products that, like the parent drug, exhibited activity againstsimian malaria. Although, as shown by British investigators, one compound wasformed that was more active than the parent compound against avian malaria,subsequent work by other British investigators showed that this metabolicproduct was no more active than the parent drug against infections with P. falciparum. In therapeutic and suppressive studies, chlorguanide exhibited a highdegree of activity against infections with P. vivax, but it was definitelyslower than chloroquine in reducing fever and parasitemia. It was further shownthat each of the species of avian, simian, and human plasmodia studied acquireda high order of resistance to the drug when exposed to suboptimal doses and thatthe resistant characteristic of the simian plasmodium could be transmittedunaltered through the mosquito. When produced in sporozite-induced infections,resistance was a property of the erythrocytic parasites only. Infections withchlorguanide-resistant strains responded normally to drugs such as quinine,quinacrine, and the 4-aminoquinolines. Field study in Guatemala confirmed thesuperiority of chloroquine for suppression in a systematic comparison withchlorguanide.

These various studies had thus established the therapeutic potentialities ofboth chloroquine and amodiaquin and demonstrated that either drug was superiorto chlorguanide in the general management of malaria in man. The work ofconsolidation was in general complete.

The major new effort of the Investigators in MalariaChemotherapy was directed toward development of a generally useful drug thatwould not merely suppress but would cure the relapsing malaria caused by P.vivax. This attempt, centered about work on the 8-aminoquinolines, during 1946and 1947 followed the pattern of the last year of the OSRD program. Thisinvolved synthesis of various congeners of pamaquine (Plasmochin), testing fortox-

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icity in monkeys, and finally testing of compounds free ofneuronal toxicity against vivax infections in human volunteers. In addition,efforts were made to define more precisely the activity of pentaquine and themore effective ways of using it.

In 1948, this pattern of work was changed as the result of a demonstration bySchmidt and his colleagues at the Christ Hospital Institute of Medical Research,Cincinnati, Ohio. They showed that infections with Plasmodium cynomolgi in therhesus monkey were the biological and chemotherapeutic counterparts ofinfections in man with Southwest Pacific strains of P. vivax, with essentiallycomplete parallelism in response both to qualitative and to quantitative aspectsof drug activity. For the first time, it was possible to carry out toxicologicaland, particularly, therapeutic studies in an experimental animal with reasonableexpectation that the results could be translated in terms of malaria in man.

Collaborating groups of chemists at Columbia University, New York, N.Y.,University of Maryland, College Park, Md., and University of Notre Dame, NotreDame, Ind., synthesized 42 new 8-aminoquinoline derivatives and remade olderanalogs in quantities sufficient for simian and human studies. Toxicological andcurative therapeutic studies were carried out on all of these compounds inmonkeys at the Christ Hospital Institute, and 18 of the compounds were selectedfor human trial at the University of Chicago, Chicago, Ill. Both in man and inmonkey, four compounds emerged with properties superior to pamaquine. These werepentaquine and isopentaquine, which had been developed in 1946 and 1947,respectively, primaquine (SN 13,272), and SN 3,883. The last two compounds, withterminal primary amino groups on the side chain, had been prepared during theOSRD program but were subjected to study in man only after investigations at theChrist Hospital Institute had focused attention upon the high tolerability ofthis class of compounds and their unusual activity against the early and lateexo-erythrocytic stages of P. cynomolgi.

Between 1948 and 1950, considerable study was also given tothe mechanisms for enhancing the effectiveness of known agents. Two observationsthat proved of practical significance were made at the Christ Hospital Instituteand later confirmed in principle in the human subject at the University ofChicago. These observations were (1) quinine had no specific enhancing effect onthe curative activities of 8-aminoquinolines such as pentaquine, isopentaquine,and primaquine, and (2) that these drugs could cure and in some cases preventmalaria infections when given alone. It followed that the sole contribution ofquinine was the control of erythrocytic infection. This contribution explainsthe therapeutic effectiveness of Plasmochin combined with quinine; it could bemade as well by chloroquine or any other schizonticidal drug, or could bedispensed with if the 8-aminoquinoline were administered, in establishedinfections, in the interval between relapses. This finding formed the basis forthe "interim primaquine" regimens which allegedly have

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been responsible for the reduced incidence of malaria among troops returningfrom Korea in 1952 and 1953.

Late in 1950, it was decided to concentrate the cooperative studies upon therelative merits and best use of the four compounds that seemed most promising,pentaquine, isopentaquine, primaquine, and SN 3,883. Evaluation of these drugsin curing established infections with P. vivax in volunteers was in part madethe responsibility of a group of investigators headed by Dr. Alf S. Alving atthe University of Chicago. A second clinical testing facility was established atthe U.S. Penitentiary, Atlanta, Ga., under the direction of Dr. Coatney.

In the meantime, the appearance of numerous cases of acute malaria amongmilitary personnel returning from Korea demanded more immediate solutions. At ameeting called by The Surgeon General, Department of the Army, on 3 July 1951,it was decided to focus attention upon primaquine and particularly toinvestigate (1) its effectiveness in eradicating established infections inreturnees from Korea and (2) the feasibility of administering 15 mg. daily for14 days to all servicemen returning from Korea by ship.

The overall safety of this dosage schedule for military men on full duty wasdemonstrated in a preliminary investigation, involving 1,000 U.S. Armypersonnel, carried out at Fort Benning, Ga., and Fort Knox, Ky. Beginning on 18September 1951 with a group of servicemen returning by ship from Korea, theadministration of 15 mg. of primaquine daily for 14 days was adopted as ageneral procedure pending more precise data from the controlled studies underwayin the United States. Collateral studies at the University of Chicago showedthat daily doses of 30 mg. of primaquine were tolerated by Caucasians; inNegroes, such doses evoked intravascular hemolysis in 5 percent.

Data from the controlled studies on prisoner volunteers,available in January 1952, showed the superiority of primaquine over pentaquine,isopentaquine, and SN 3,833 as a curative drug. The results obtained in activeinfections with P. vivax in returnees from Korea showed the high order ofcurative effectiveness of primaquine and its superiority over pamaquine (Plasmochin).The effectiveness of interim treatment with primaquine was demonstrated inselected returnees. This composite information, together with toxicological dataobtained by study of prisoner volunteers, provided a solid basis for theadoption of interim treatment with primaquine for the cure of vivax malaria ofKorean origin. This procedure was eventually applied to all military personnelreturning by ship from Korea and has been associated with the virtualelimination of malaria among them.

Late in 1950, interest was aroused in a new type of antimalarial drug whichhad been produced in the Wellcome Research Laboratories, New York, as aby-product of investigations on purines and pyrimidines as carcinolytic agents.Attention centered on pyrimethamine (2, 4-diamino-5-p-chlorophenyl-6-ethylpyrimidine,Daraprim). Extensive studieswere carried out on its

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pharmacology in man and lower animals, on its activity against avian andsimian malarias, and against infections with P. vivax and P. falciparum. Therapeutic studies in both lower animalsand man showed that the compound had higher activity against erythrocyticparasites than any known antimalarial drug. It was slower, however, thanchloroquine in controlling active simian and human infections. It was activeagainst the exo-erythrocytic stages of all species of malarial parasitesstudied. It was able to effect suppressive cure in a high proportion ofinfections with P. vivax. Resistance to pyrimethamine developed rapidly duringinadequate treatment of erythrocytic infections with avian, simian, and humanplasmodia. In cynomolgi and vivax malarias, the resistance characteristic couldbe transferred unchanged through the mosquito. Pharmacological studies in themonkey demonstrated that repeated administration of pyrimethamine producedsignificant deleterious changes in the bone marrow, kidney, and adrenal cortex.Tolerability studies in man attested to the safety of the currently recommendeddoses of pyrimethamine but showed that, at a sevenfold increase in dosage,changes occurred in the bone marrow similar to those exhibited by the monkey.

The capacity of pyrimethamine to function as a suppressive cure stronglyrecommended its use by U.S. armed services. On the other hand, its potential forinducing resistant strains and its slowness of action in treatment of acuteattacks were disadvantages not possessed by chloroquine.

In conclusion, one sees that during the period from 1946 to 1954, inclusive,there were marked developments in the chemotherapy of malaria. The position ofchloroquine and amodiaquin in the suppression and treatment of vivax and falciparum malarias and in the cure of the latter wasestablished firmly. The usefulness and limitations of chlorguanide were definedwith reasonable certainty. A generally useful drug for the cure of relapsinginfections with P. vivax was developed in primaquine, and the value of thisagent was proved in both laboratory and field investigations. Finally, a newcompound, pyrimethamine, possessing interesting possibilities as a suppressiveantimalarial drug, was introduced. The ultimate significance of thesedevelopments for worldwide control of malaria remains to be appraised. It seemslikely, however, that satisfactory measures are now at hand for suppression,treatment, and cure of all human malarias. This remarkably favorable position ofmalaria therapy is in marked contrast to the uncertainty of the pre-World War IIperiod. It is a tribute to all who took part in the OSRD and postwarmalaria researches.

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