Efficacy of antiamebic drugs in vivo: regimen 1. (A) Drugs were administered by oral gavage or intraperitoneal injection before and after intracecal injection of E. histolytica trophozoites (days −1, +1, +3, and +5 relative to challenge). Mice were then killed for evaluation of infection by culture (B), cecal parasite antigen (C), and histology (D). Antigen data represent average OD value ± standard error of the mean (SEM). *P ≤ 0.05 between drug and PBS. **P ≤ 0.05 between metronidazole and PBS.