Local and systemic actions of loperamide on fluid transport and transmural potential difference across rat small intestine.

The ability of loperamide to influence intestinal fluid transport was assessed using a dual loop preparation. Loperamide was applied to the lumen of the oral, but not the aboral loop, yet basal and prostaglandin-stimulated fluid transport was affected in both, indicating that the drug can act systemically in addition to any local actions. Loperamide had both pro-absorptive and anti-absorptive effects, the latter only occurring when basal fluid absorption was high. The effects of loperamide were greater in the aboral loop to which it was available only via the systemic route. This difference may reflect the absence of counteracting local influences in the aboral loop or a variation in the sensitivity of different regions of the gut to loperamide.