The primary objective of this study is to assess the safety and tolerability of rifaximin 600 mg (3 x 200-mg tablets) once daily compared with placebo when taken for 14 days by healthy subjects to prevent travelers' diarrhea (TD) from all causes.

Travelers' diarrhea (TD) is the most common illness in travelers to the developing world, occurring in 60% or more of international travelers to high-risk areas. It can be quite debilitating for the usual 2 to 4 days of the illness and may lead to disruption of travel plans. Findings from recent studies have indicated that the chronic post-travel illness may prove to be of greater clinical and public health significance than the acute illness. Specifically, persistent diarrhea has been reported in 2% to 10% of travelers developing diarrhea. Moreover, bacterial enterocolitis, including that associated with TD, leads to post-infectious irritable bowel syndrome in 4% to 31% of patients.

Inclusion Criteria:

1. Subject is in good health (as determined by medical history)
2. Subject is planning on traveling anywhere outside the US (except Canada) for at least 5 and no more than 14 days
3. Subject is scheduled to depart on their planned trip no later than 14 days and no earlier than 4 days after having blood drawn for clinical laboratory assessments and urine collected for a pregnancy test (females of childbearing potential only)

Exclusion Criteria:

1. Subject has hypersensitivity or allergy to rifaximin or rifampin
2. Subject has known or suspected alcohol abuse or illicit drug use within 1 year of enrollment
3. Subject participated in an investigational drug or device study within the 30 days prior to enrollment
4. Subject received rifaximin in a previous clinical study
5. Subject received any systemic or gastrointestinal-specific antibiotic within 7 days of the first dose of study drug
6. Subject received antidiarrheal medication (eg, loperamide, lactobacillus, BSS, Kaopectate®) within 24 hours of the first dose of study drug