Ciprofloxacin decreases the rate of ethanol elimination in humans

Background-Extrahepatic ethanol metabolism is postulated to take place via microbial oxidation in the colon, mediated by aerobic and facultative anaer obic bacteria. Aims-To evaluate the role of microbial ethanol oxidation in the total elimi nation rate of ethanol in humans by reducing gut flora with ciprofloxacin. Methods-Ethanol was administered intravenously at the beginning and end of a one week period to eight male volunteers. Between ethanol doses volunteer s received 750 mg ciprofloxacin twice daily. Results-A highly significant (p = 0.001) reduction in the ethanol eliminati on rate (EER) was detected after ciprofloxacin medication. Mean (SEM) EER w as 107.0 (5.3) and 96.9 (4.8) mg/kg/h before and after ciprofloxacin, respe ctively. Faecal Enterobacteriaceae and Enterococcus sp. were totally absent after medication, and faecal acetaldehyde production capacity was signific antly (p < 0.05) decreased from 0.91 (0.15) to 0.39 (0.08) nmol/min/mg prot ein. Mean faecal alcohol dehydrogenase (ADH) activity was significantly (p < 0.05) decreased after medication, but ciprofloxacin did not inhibit human hepatic ADH activity in vitro. Conclusions-Ciprofloxacin treatment decreased the ethanol elimination rate by 9.4%, with a concomitant decrease in intestinal aerobic and facultative anaerobic bacteria, faecal ADH activity, and acetaldehyde production. As ci profloxacin has no effect on liver blood flow, hepatic ADH activity, or cyt ochrome CYP2E1 activity, these effects are probably caused by the reduction in intestinal flora.