The Effect of Pyrimethamine (Daraprim) against Plasmodium gallinaceum Infections in Chicks

Abstract
Summary The effect of single and multiple doses of pyrimethamine (Daraprim) against blood- and sporozoite-induced Plasmodium gallinaceum infections in chicks was examined. When administered twice daily for 4 days, the maximum tolerated dose for the chick was 0.016 mg./gm.; the minimum effective dose, 0.00002 mg./gm.; the drug was completely prophylactic at 0.00025 mg./gm. and partially prophylactic at 0.00003 mg./gm. When administered as a single dose, the minimum effective dose was 0.00025 mg./gm.; the completely prophylactic dose, 0.004 mg./gm.; and the partially prophylactic dose, 0.0005 mg./gm. When chicks were pretreated with single doses of pyrimethamine, about 50 per cent of the antimalarial activity disappeared per day. Single doses of 0.005 mg./gm. given to chicks with well established sporozoite-induced infections prevented deaths from tissue forms, but doses as high as 0.016 mg./gm. did not cure the infection.

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