page_title: Loperamide
section_title: Mechanism of action
hierarchical_section_title: Loperamide / Mechanism of action
caption_attribution_description: English: Ball-and-stick model of loperamide molecule. The structure is taken from ChemSpider. ID 3818
context_page_description: Loperamide, sold under the brand name Imodium, among others, is a medication used to decrease the frequency of diarrhea. It is often used for this purpose in, inflammatory bowel disease, and short bowel syndrome. It is not recommended for those with blood in the stool, mucus in the stool or fevers. The medication is taken by mouth.
  Common side effects include abdominal pain, constipation, sleepiness, vomiting, and a dry mouth. It may increase the risk of toxic megacolon. Loperamide's safety in pregnancy is unclear, but no evidence of harm has been found. It appears to be safe in breastfeeding. It is an opioid with no significant absorption from the gut and does not cross the blood–brain barrier when used at normal doses. It works by slowing the contractions of the intestines.
  Loperamide was first made in 1969 and used medically in 1976. It is on the World Health Organization's List of Essential Medicines. Loperamide is available as a generic medication. In 2017, it was the 351st most commonly prescribed medication in the United States, with more than 700 thousand prescriptions.
context_section_description: Loperamide 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.
  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.
caption: Ball-and-stick model of loperamide molecule
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