The Antimalarial Activity of CI-501 (Camolar®) against Falciparum Malaria

Abstract

Summary A repository preparation of the dihydrotriazine metabolite of chlorguanide, known as CI-501 (Camolar®), given as a single intramuscular injection at a dose of 5 mg (base) per kg body weight, was tested for its antimalarial activity against Plasmodium falciparum in 14 prisoner volunteers. The medicated volunteers were exposed to infection with a Southern Rhodesian strain of P. falciparum, either by the intravenous inoculation of parasitized homologous blood and/or by the bites of heavily infected Anopheles freeborni mosquitoes. The number of challenges (i.e., exposures to infection) ranged from 1 to 6. The intervals of time between exposures were variable. Twelve volunteers served as controls to prove the infectivity of the challenges. Whereas CI-501 did not protect against infection with this strain when the challenge was by trophozoites (parasitized blood), it did protect through a minimum of 383 days against infection when challenges were by the bites of heavily infected mosquitoes. One volunteer, after his sixth exposure at 446 days after medication, developed patent parasitemia on day 458. These results indicate that CI-501 has the capacity to exert long-term protection against falciparum malaria, as it was previously demonstrated to have for vivax malaria, provided the parasites are sensitive to chlorguanide. Moreover, in the case of falciparum malaria, which is nonrelapsing, complete eradication could be effected by single injections of this preparation provided certain qualifications were fulfilled.