The effect of pyrimethamine (daraprim) on the gametocytes and oocysts of Plasmodium falciparum and Plasmodium vivax

Plasmodium vivax. When only 5 mg. or less of pyrimethamine was given, most of the oocysts developed normally and the resulting sporozoites were infective.Some, however, were drug-affected and failed to develop. When 50 mg. of pyrimethamine was given, none of the oocysts reached maturity even when the mosquitoes were fed 2 hours after the drug was given. Plasmodium falciparum. When 25 mg. of pyrimethamine was given, none of the oocysts reached maturity.The gametocytes were affected by the drug as early as 3 hours after treatment and as late as 144 hours. These results suggest that pyrimethamine could play an important part in severing the parasite cycle between man and mosquito.