A Randomized, Double-Blind, Single Center, Comparative Dose Ranging Study of Rifaximin Vs. Placebo in the Prevention of Travelers' Diarrhea Due to Enteropathogenic Bacteria

This is an investigator-initiated proposal wherein 220 male and female subjects >17 years of age from industrialized regions were randomized to receive a poorly absorbed antibiotic, rifaximin, in one of three doses at mealtime (when they are exposed to diarrhea-causing bacteria), 200 mg once a day, 200 mg twice a day or 200 mg three times a day versus a placebo starting on arrival (within the first 72 hours) to Mexico and continuing for two weeks with diaries of symptoms recorded for three weeks. Adverse events in the subjects were followed for five weeks. If mild diarrhea (1 or 2 unformed stools/24 hours plus an enteric symptom) or diarrheal illness (>2 unformed stools/24 hours plus an enteric symptom) developed, subjects provided a stool sample to determine cause of illness. Forty subjects provided stool samples after 7 days and 14 days treatment to see if their intestinal bacterial flora had developed resistance to rifaximin and to see the level of drug achieved. Stool samples from these forty subjects were studied for enteric pathogens to look for asymptomatic infection during the period of prophylaxis. The stool samples collected were initially processed in our enteric laboratories in Guadalajara, Mexico. Specialized tests such as studies of toxigenicity for enterotoxigenic E. coli and enteroadherence for enteroaggregative E. coli were done in Houston.