Abstract
BACKGROUND: Drug-combination therapies are needed to combat treatment refractory giardiasis. However, data describing the activity of combinations of currently used drugs against Giardia duodenalis are unavailable. METHODS: The in vitro activity of combinations of currently used antigiardial drugs were investigated against G. duodenalis. RESULTS: Combinations of metronidazole with albendazole or quinacrine, and quinacrine with nitazoxanide, behaved additively, whereas combinations of metronidazole with nitazoxanide, albendazole or quinacrine behaved synergistically. Combinations of albendazole with nitazoxanide behaved antagonistically. CONCLUSIONS: While combinations of metronidazole with nitazoxanide, or albendazole with quinacrine, may be effective treatments of giardiasis, combinations of albendazole with nitazoxanide are likely to result in negative pharmacodynamic interactions.