Antidiarrhoeal activity of loperamide: studies of its influence on ion transport across rabbit ileal mucosa in vitro.

Loperamide is a well-established antidiarrhoeal agent with effects on gastrointestinal motility. We have now shown that the drug influences ion transport. In isolated rabbit ileal mucosa loperamide caused a dose-related fall in potential difference and short-circuit current and reduced the serosa to mucosa flux of chloride. The electrical effects were inhibited by naloxone (10(-6)M) suggesting that they were mediated by opiate receptors. Loperamide (10(-6)M) inhibited secretion provoked by heat stable and heat labile E. coli toxins and by prostaglandin E2. We conclude that loperamide is able to inhibit secretion mediated by cAMP or cGNP, and that this may be relevant to its antidiarrhoeal properties.