Trypanostatic drug action: its relation to relapse following chemotherapy.

Analogies with dose-dependent transient prophylaxis and with delayed take of reinfection in drug-cleared Trypanosoma evansi (T. venezuelense) infected animals indicate that relapse following chemotherapy is induced by the same underlying mechanism, i.e., termination of the trypanostatic effect of residual drug concentrations. Correspondingly, both the complete ('true') prophylaxis and the radical cure without relapse require trypanocidal drug concentrations.