In vitro activity: Nitazoxanide reduces parasite growth in cell culture by more than 90% with little evidence of drug-associated cytotoxicity. Nitazoxanide is a new thiazolide antiparasitic agent that shows excellent in vitro activity against a wide variety of protozoa and helminths. Nitazoxanide and its metabolite tizoxanide are more active in vitro than metronidazole against G. intestinalis, E. histolytica and T. vaginalis. Nitazoxanide exhibits potent inhibition of both HBV and HCV replication. Nitazoxanide potentiates the effect of subsequent treatment with Nitazoxanide plus IFN, but not Nitazoxanide plus 2'CmeC, in HCV replicon-containing cells. Nitazoxanide induces reductions in several HBV proteins (HBsAg, HBeAg, HBcAg) produced by 2.2.15 cells, but does not affect HBV RNA transcription. Nitazoxanide exhibits IC50, and IC90 values of 0.017 and 0.776 mg/mL respectively, against E. histolytica, 0.004 and 0.067 mg/mL against G. intestinalis, and 0.034 and 2.046 mg/mL against T. vaginalis. Nitazoxanide is more toxic than metronidazole and albendazole against E. histolytica.

Antimicrob Agents Chemother. 1998 Aug;42(8):1959-65; Clin Infect Dis. 2005 Apr 15;40(8):1173-80; J Antimicrob Chemother. 2002 Jan;49(1):103-11.