Antiplasmodial interactions between artemisinin and triclosan or ketoconazole combinations against blood stages of Plasmodium falciparum in vitro.

Emergence of drug-resistant Plasmodium falciparum strains to conventional first-line antimalarial drugs has compelled many countries to reorient their drug policies to adopt artemisinin-based combination therapies (ACTs) for treatment of uncomplicated malaria. This has increased the demand of artemisinin, already a scarce commodity. Synthesis of artemisinin is not yet commercially viable. Extensive use of available ACTs will invariably lead to emergence of resistance to these combinations. Thus, there is need to search for new artemisinin-based synthetic, inexpensive, synergistic combinations to reduce dependence on artemisinin. In vitro cultures of P. falciparum provide an appropriate system for identification of such new combinations. We evaluated interactions of artemisinin with triclosan or ketoconazole against blood stages of P. falciparum by a fixed-ratio isobologram method. Artemisinin shows mild synergistic interaction with triclosan and slight to marked antagonism with ketoconazole in vitro. These antiplasmodial interactions, however, require confirmation using in vivo model systems.