Loperamide has structural properties of an opioid and therefore binds to certain opioid receptors in the nerves of the intestine. This reduces the activity of the small intestinal muscles and the intestinal contents take longer to pass through. This gives more time for the intestinal contents to extract water. Loperamide, unlike conventional opioids, has no effect on the central nervous system.
Plasma protein binding is 97% and plasma half-life is 9-14 hours. Loperamide is metabolized mainly in the liver and subsequently excreted almost entirely in the stool.
When taken with quinidine, verapamil or ketoconazole, respiratory depression may occur.