The effect of loperamide oxide on prostaglandin-stimulated fluid transport in rat small intestine.

The effects of loperamide and loperamide oxide on basal and prostaglandin E2-stimulated fluid transport by rat small intestine have been investigated. In contrast to loperamide, loperamide oxide, when applied intraperitoneally, failed to inhibit either basal or prostaglandin E2-stimulated fluid transport. However, intraperitoneal administration of loperamide oxide following its incubation with the contents of the intestinal lumen under aerobic conditions resulted in an effective inhibition of fluid secretion. The activating material was present in the essentially non-particulate 3000 g supernatant fraction of the luminal contents and was heat-stable.