The oral antibacterial rifamycin has been approved to treat travelers' diarrhea driven by noninvasive strains of E. coli. The drug, an RNA-polymerase inhibitor, is indicated for adults whose condition is not complicated by blood in the stool or fever.
In a study of 250 adults, rifamycin significantly reduced travelers' diarrhea symptoms compared with placebo. Drug safety was tested in two clinical trials of some 620 patients. Constipation and headache were the most common side effects.