Fig. (2) Survival of Hartley guinea pigs treated with varying doses of ciprofloxacin 24 h after intranasal challenge with 5 LD50 of B. anthracis Ames spores. The horizontal bar indicates the period of treatment (6 days). The three highest doses were significant from days 3.5 through 11.5. The lower three doses were significant beginning at day 3.5, but ended at day 10 for the 15 mg/kg/day group, day 3.5 for the 7.5 mg/kg/day group, and day 3 for the 4 mg/kg/day group. Significance from the control was determined by the Fisher Exact Test (p<0.05).