LOPERAMIDE (IMODIUM)
Worldwide, loperamide is one of the most widely used drugs for treating acute diarrhea in adults. Approved for use in the U.S. in 1976, it is primarily marketed as Imodium. It relieves sudden diarrhea by slowing the movement of the gut. (Not for children under six.)
CHEMICAL NAME
loperamide hydrochloride (4-(p-chlorophenyl)4-hydroxy-n, N-dimethyl-a, a-diphenyl-1-piperidinebutyramide monohydrochloride)
MEDICINES
Loperamide was approved in the United States in 1976 for treatment of acute diarrhea. Since 1988 it has been available as the OTC brand Imodium or as generic loperamide hydrochloride.
HOW IT WORKS
Loperamide is a synthetic opioid that docks with μ opiate receptors in the myenteric plexus of the intestines, which normally receives input from the vagus nerve to make muscles contract in peristaltic waves that push food through the digestive tract. With loperamide, muscle activity is reduced, relieving the symptoms of diarrhea.
SIDE EFFECTS
Clinical studies have shown loperamide not only eases gastrointestinal problems but can also cause them. The side effects include bloating, constipation, and stomach pain with nausea and vomiting. Other possible side effects are skin rash and itching as well as dizziness and drowsiness. The FDA has issued a warning that taking higher-than-recommended doses of the medication “may cause serious heart problems that can lead to death.” Those who suffer from heart disease shouldn’t take loperamide without first consulting a physician.
INTERACTIONS
Taking loperamide with certain medicines can result in unsafe drug interactions: Loperamide taken with quinidine (for treating irregular heartbeat and also malaria) can result in a much higher concentration of loperamide in the blood. That greatly increases the risk of such side effects as dizziness, headache, acute abdominal pain, constipation, and dry mouth. Other medications that should not be combined with loperamide: the antimalarial drug quinine, ritonavir (for treating HIV), itraconazole and ketoconazole (antifungal drugs), gemfibrozil (cholesterol-lowering drug), and the antibiotics erythromycin and clarithromycin.
PROPER USE
Initial dose for adults: 4 mg, then 2 mg after each loose stool. (Maximum daily dose: 16 mg.) Improvement is usually seen within 48 hours. Children ages 8 to 12: 2 mg three times a day. Ages 6 to 8: 2 mg twice a day. Under 6 years old: No loperamide unless called for by a physician.