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Background Rifaximin (Xifaxan), a semisynthetic, virtually unabsorbed rifamycin, received FDA approval in May 2004 for treatment of traveler's diarrhea caused by noninvasive (enterotoxigenic and enteroaggregative) strains of Escherichia coli in patients ≥12 years old. It is currently approved in 17 countries.
Spectrum of Action: A structural analogue of rifampin, rifaximin inhibits bacterial RNA synthesis by binding to the β subunit of bacterial DNA-dependent RNA polymerase. It has broad activity against gram-positive and gram-negative bacteria and against aerobes and anaerobes.
Pharmacology and Dosing: Approximately 97% of the drug can be recovered unchanged in feces; <0.4% is found in the urine. Fecal concentrations reach levels of 4000-80…