In vitro activity and fecal concentration of rifaximin after oral administration.

Rifaximin showed moderately high MICs (the MIC at which 90% of the isolates tested were inhibited = 50 microg/ml) for 145 bacterial enteropathogens from patients with traveler's diarrhea acquired in Mexico during the summers of 1997 and 1998. Rifaximin concentrations in stool the day after oral administration (800 mg daily for 3 days) were high (average, 7,961 microg/g), proving the value of the drug.