The duration of protection from blood-stage malarial challenge following single injections of pyrimethamine pamoate was assessed in mice and monkeys. This duration was dose-related and ranged from several weeks in mice to over 4 months in the monkeys. Comparisons with the previously reported repository drugs, cycloguanil pamoate and acedapsone (diacetyldiaminodiphenyl sulfone), in mice demonstrated that pyrimethamine pamoate provides an equal or greater duration of protection. Studies with mixtures containing acedapsone gave good protection against a pyrimethamine-resistant strain of Plasmodium berghei.
Present address: Department of Veterinary Microbiology, Connaway Hall, University of Missouri, Columbia, Missouri 65211.