Ball-and-stick model of<unk>  molecule<unk>  is an opioid-receptor agonist and acts on the μ-opioid receptors in the myenteric plexus of the large intestine. It 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. It also decreases colonic mass movements and suppresses the gastrocolic reflex.<unk> 's circulation in the bloodstream is limited in two ways. Efflux by P-glycoprotein in the intestinal wall reduces passage of<unk> , and the fraction of drug crossing is then further reduced through first-pass metabolism by the liver.<unk>  metabolizes into an MPTP-like compound, but is unlikely to exert neurotoxicity. Blood–brain barrier Efflux by P-glycoprotein also prevents circulating<unk>  from effectively crossing the blood–brain barrier, so it can generally only antagonize muscarinic receptors in the peripheral nervous system, and currently has a score of one on the anticholinergic cognitive burden scale. Concurrent administration of P-glycoprotein inhibitors such as quinidine potentially allows<unk>  to cross the blood–brain barrier and produce central morphine-like effects.<unk>  taken with quinidine was found to produce respiratory depression, indicative of central opioid action.<unk>  has been shown to cause a mild physical dependence during preclinical studies, specifically in mice, rats, and rhesus monkeys. Symptoms of mild opiate withdrawal were observed following abrupt discontinuation of long-term treatment of animals with<unk> . When originally approved for medical use in the United States,<unk>  was considered a narcotic and was put into Schedule II of the Controlled Substances Act 1970. It was transferred to Schedule V on 17 July 1977, and then decontrolled on 3 November 1982.
Loperamide
Sucralfate
Cimetidine
Lansoprazole
Dexlansoprazole
Trifluoperazine
Sodium hydroxide
Ethacizine