Chemotherapy of Trypanosoma venezuelense (T. evansi), I

Abstract

The clearing and curative Sb_III doses of the antimonials available for clinical use were compared in Trypanosoma venezuelense (T. evansi) infections of mice, using inocula of different magnitude. Repeated injections were required in order to reach cure in tolerated doses. The single clearing dose (5–6 mg Sb/kg) of the more effective antimonials (sodium-emetic (AST), its dimethylcysteine chelate (NAP) and Anthiomaline) is 1/4–1/7 of the total curative dose. This relationship corresponds to that found also for T. equiperdum cleared by lower (1·8–2·7 mg) Sb doses, and is attributed to the ratio between trypanostatic and trypanocidal Sb_III effects in mice. In the infection studied, Stibophen, Triostam and Astiban are considerably less effective in terms of Sb content than is AST, in clearing and curing T. venezuelense infections of two different intensities. However, the relative activity ratios among antimonials varied somewhat considering the four activity estimates. Whatever parasite (T. equiperdum, S. mansoni or T. venezuelense) is used for the test in mice, the relative order of drug activity remains the same and gives the measure of the antimonial effect, which is a resultant of its bio-activity and availability. These activity differences can be shown in a test as simple as the follow-up of parasitaemia immediately after drug injections.