A previously sensitive Chesson strain of Plasmodium vivax was made resistant to chlorguanide by the stepwise use of increasing subcurative dosages.
Two volunteers medicated with CI-501 (5 mg/kg body weight) two days before challenge, and an untreated control, were exposed to the bites of Anopheles quadrimaculatus infected with this resistant Chesson strain of P. vivax. The two medicated volunteers as well as the control developed infections with no significant differences in the prepatent period or the clinical course.
The results indicate that CI-501 has no demonstrable effect on the Chesson strain of P. vivax once resistance to the parent compound, chlorguanide, has been induced.
Present address: Department of Medicine, University Hospital, Syracuse, New York.