Glucantime resistant Leishmania promastigotes are sensitive to pentostam.

Growth inhibition in vitro tests were used to study the susceptibility to pentostam of different Leishmania strains involved in cutaneous and mucocutaneous leishmaniasis--one glucantime sensitive strain, three naturally glucantime resistant strains and one glucantime resistant line developed by in vitro drug exposure. Contrasting with the high degree of glucantime resistance, all strains were sensitive to pentostam. These differences suggest that there is some relationship between chemical structure and in vitro activity for these antimonial compounds. These data justify a clinical re-evaluation to compare therapeutic efficacy of glucantime and pentostam in the treatment of leishmaniasis.