<P> Loperamide is a substrate of P - glycoprotein; therefore, the concentration of loperamide will increase when given with a P - glycoprotein inhibitor . Common P - glycoprotein inhibitors include quinidine, ritonavir, and ketoconazole, among others . Loperamide is capable of decreasing the absorption of some other drugs . As an example, saquinavir concentrations can decrease by half when given with loperamide . </P> <P> Loperamide is an anti-diarrheal agent which decreases intestinal movement . As such, when combined with other antimotility drugs, there is an increased risk of constipation . These drugs include other opioids, antihistamines, antipsychotics, and anticholinergics . </P> <P> Loperamide is an opioid - receptor agonist and acts on the μ - opioid receptors in the myenteric plexus of the large intestine . Loperamide works like morphine, decreasing the activity of the myenteric plexus, which decreases the tone of the longitudinal and circular smooth muscles of the intestinal wall . This increases the time material stays in the intestine, allowing more water to be absorbed from the fecal matter . Loperamide also decreases colonic mass movements and suppresses the gastrocolic reflex . </P> <P> Loperamide's circulation in the bloodstream is limited in two ways . Efflux by P - glycoprotein in the intestinal wall reduces passage of loperamide, and the fraction of drug crossing is then further reduced through first pass metabolism by the liver . Loperamide metabolizes into an MPTP - like compound, but is unlikely to exert neurotoxicity . </P>

What is the mechanism of action for loperamide (imodium)
find me the text answering this question