One of the long-acting synthetic antidiarrheals; it is not significantly absorbed from the gut, and has no effect on the adrenergic system or central nervous system, but may antagonize histamine and interfere with acetylcholine release locally. [PubChem]
Indication
For the control and symptomatic relief of acute nonspecific diarrhea and of chronic diarrhea associated with inflammatory bowel disease or gastroenteritis. Also used for reducing the volume of discharge from ileostomies.
Pharmacology
Loperamide is a synthetic anti-diarrheal indicated for the control and symptomatic relief of acute nonspecific diarrhea and of chronic diarrhea associated with inflammatory bowel disease. Loperamide is also indicated for reducing the volume of discharge from ileostomies. In man, Loperamide prolongs the transit time of the intestinal contents. It reduces the daily fecal volume, increases the viscosity and bulk density, and diminishes the loss of fluid and electrolytes. Tolerance to the antidiarrheal effect has not been observed. Loperamide is an opioid receptor agonist and acts on the mu opioid receptors in the myenteric plexus large intestines; it does not affect the central nervous system like other opioids. It works specifically by decreasing the activity of the myenteric plexus which decreases the motility of the circular and longitudinal smooth muscles of the intestinal wall. This increases the amount of time substances stay in the intestine, allowing for more water to be absorbed out of the fecal matter. Loperamide also decreases colonic mass movements and suppresses the gastrocolic reflex.
Toxicity
Oral, mouse: LD50 = 105 mg/kg. Symptoms of overdose include constipation, drowsiness, lethargy, and nausea.
Affected Organisms
Humans and other mammals
Biotransformation
Hepatic
Absorption
Not significantly absorbed from the gut
Half Life
9.1 to 14.4 hours (average 10.8 hours)
Protein Binding
97%
Elimination
Excretion of the unchanged loperamide and its metabolites mainly occurs through the feces.
