Five mice per group infected with A/PR/8/34 (100 TCID50) were treated orally with BXM (1.5, 15 or 50 mg/kg), OSP (5 or 50 mg/kg), or vehicle bid for 5 days from 120 hours p.i.. The mice were monitored daily for body weight up to day 10 p.i. and their lungs were harvested on days 5, 6, 7, 8, 9 and 10 p.i. to determine virus titers. Treatment periods are indicated by the gray zones. (A) A significant reduction in virus titer from days 5 to 10 p.i. was observed in all groups administered BXM in comparison with the group administered the vehicle or OSP at doses of 5 and 50 mg/kg bid (*, P < 0.0001 vs vehicle; †, P < 0.0001 vs OSP 5 mg/kg bid; ‡, P < 0.0001 vs OSP 50 mg/kg bid). (B) All groups treated with BXM showed significantly less reduction of body weight compared with the vehicle-treated group or OSP-treated groups (*, P < 0.0001 vs vehicle; †, P < 0.0005; ††, P < 0.0001 vs OSP 5 mg/kg bid; ‡, P < 0.005, ‡‡, P < 0.0001 vs OSP 50 mg/kg bid).