Results of a double-blind placebo-controlled study using ciprofloxacin for prevention of travelers' diarrhea.

To determine the efficacy, safety and effect on fecal flora of ciprofloxacin in the prevention of travelers' diarrhea, 54 volunteers traveling to Tunisia were randomized in a double-blind manner to receive either 500 mg ciprofloxacin or a placebo once daily for one week. Results of 53 volunteers were available for evaluation of efficacy. One of 25 subjects (4%) receiving ciprofloxacin versus 18 of 28 subjects (64%) in the placebo group experienced travelers' diarrhea (p less than 0.0001). The protection offered by ciprofloxacin was 94%. In one volunteer taking ciprofloxacin, prophylaxis was terminated due to sunburn with blistering. Among 41 subjects reporting sunburn, no statistical difference was observed between the two treatment groups in the percentage of body surface area of sunburn. Quantitative feces cultures revealed a marked decrease in the number of gram-negative organisms in volunteers receiving ciprofloxacin and a significant increase in the number of Escherichia coli in the placebo group. Five weeks after return, the aerobic bacterial flora of both treatment groups showed the pre-travel pattern.