Loperamide, opioid receptor agonist

Pharmacological studies with selective agonists have shown that opioid control of intestinal electrolyte transport is predominantly mediated by delta opioid receptors [58], while the gastrointestinal propulsion is under the control of mu receptors [59,60]. The antidiarrheal effects of NEP inhibitors, such as acetorphan, the prodrug of thiorphan, have been compared to those of an opiate agonist, loperamide, in a model of castor oil-induced diarrhea in rats. When administered peripherally, they produced a delayed onset of diarrhea with no reduction in the gastrointestinal transit [61,62], as is commonly observed with loperamide [63],... 

Loperamide is a narcotic agonist acting on opioid JL receptors. Loperamide has mild antisecretory effects but its primary effects are to increase segmental intestinal contractions and slow the propulsion of intestinal contents (Ruppin 1987). Loperamide has been associated with reduction in diarrhea in many clinical studies in humans but has minimal impact on the patient s fluid and electrolyte balance because the secreted fluid remains in the bowel lumen. Loperamide can have dose-dependent CNS depressant effects. Loperamide also has been shown to promote intestinal bacterial overgrowth because of promoting the retention of fluid within bowel segments (Duval-Iflah et al 1999), which may favor the proliferation of enteropathogenic bacteria. 

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