Rifaximin Versus Placebo in the Prevention of Travelers' Diarrhea

Inclusion Criteria: * An Investigational Review Board approved, written informed consent is appropriately witnessed, signed and dated prior to any study-related activities * Male or female subjects 18 years of age or older * Able to read and understand English * Enrolled and started on prophylaxis within 72 hours of arrival in Mexico * If the subject is female, only women with non-childbearing potential or those who are not pregnant will be eligible. Urine pregnancy tests will be performed on those women who question their pregnancy status. Women on the study are required to employ a reliable method of contraception while taking medication. Forms of acceptable contraception include: * Double barrier method of contraception. * Oral birth control pills for at least two cycles before enrollment and continuing during therapy - subjects will be told they should use a barrier contraception method during the study as well. * Norplant inserted at least one month before enrollment. * An intrauterine device inserted by a qualified clinician. * Medroxyprogesterone acetate for a minimum of one month before study and administered for one month following study completion. * An approved birth control patch for at least two cycles before enrollment and continuing during therapy. OR * Complete abstinence from intercourse for the two weeks of medication. Exclusion Criteria: * Acute diarrhea (criteria for travelers' diarrhea above) within the past week * Diarrhea developing wi…