Small molecule · Gastrointestinal

Loperamide

Imodium
Small moleculePeripheral mu-opioid receptor agonist

PubChem CID 3955 · 3D model

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Binds to opioid in the gut wall to slow down intestinal movement, without reaching the brain, so it calms diarrhea without producing typical opioid effects elsewhere in the body.

How it works

Loperamide attaches to opioid receptors in the nerve network lining the gut wall, which controls how the intestines squeeze and move. This slows the wave-like contractions that push stool through the bowel, giving the body more time to reabsorb water and firm things up. It also tightens the muscle at the base of the rectum, cutting down on urgency and accidents. Because the drug is kept out of the bloodstream and brain by the body's own defenses, it calms the gut without causing the drowsiness or dependence risk typical of other opioid medicines.

What it’s used for

Used to relieve short-term diarrhea, including travelers' diarrhea, as well as ongoing diarrhea linked to inflammatory bowel disease. Also used by people with an ileostomy to reduce the amount of fluid output from the stoma.

Mechanism
Peripheral mu-opioid receptor
Drug class
Therapeutic area
Gastrointestinal

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