Ciprofloxacin administration decreases enhanced ethanol elimination in ethanol-fed rats

Many colonic aerobic bacteria possess alcohol dehydrogenase (ADH) activity and are capable of oxidizing ethanol to acetaldehyde. Accordingly, some ing ested ethanol can be metabolized in the colon in vivo via the bacteriocolon ic pathway for ethanol oxidation. By diminishing the amount of aerobic colo nic bacteria with ciprofloxacin treatment, we recently showed that the bact eriocolonic pathway may contribute up to 9% of total ethanol elimination in naive rats. In the current study we evaluated the role of the bacteriocolo nic pathway in enhanced ethanol metabolism following chronic alcohol admini stration by diminishing the amount of gut aerobic flora by ciprofloxacin tr eatment. We found that ciprofloxacin treatment totally abolished the enhanc ement in ethanol elimination rate (EER) caused by chronic alcohol administr ation and significantly diminished the amount of colonic aerobic bacteria a nd faecal ADH activity. However, ciprofloxacin treatment had no significant effects on the hepatic microsomal ethanol-oxidizing system, hepatic ADH ac tivity or plasma endotoxin level. Our data suggest that the decrease in the amount of the aerobic colonic bacteria and in faecal ADH activity by cipro floxacin is primarily responsible for the decrease in the enhanced EER in r ats fed alcohol chronically. Extrahepatic ethanol metabolism by gastrointes tinal bacteria may therefore contribute significantly to enhanced EER.