Comparative effects of enoxacin and norfloxacin on human colonic microflora.

Ten healthy volunteers received 400 mg of enoxacin and another ten healthy volunteers received 200 mg of norfloxacin orally twice a day for 7 days. Fecal specimens were collected before, during, and after drug administration to study the impact of enoxacin and norfloxacin on the normal colonic microflora. On day 7, the mean concentrations of enoxacin and norfloxacin were 350 and 950 mg/kg of feces, respectively. Enoxacin and norfloxacin affected the colonic microflora in similar ways. The number of strains of the family Enterobacteriaceae was markedly suppressed during drug administration, whereas the gram-positive and anaerobic microfloras were not significantly altered. Two weeks after withdrawal of the drugs, the colonic microflora had returned to normal.