What is loperamide (Imodium)? How does it work (mechanism of action)?
Loperamide is a medication that is used for the relief of acute diarrhea and the management of chronic diarrhea in patients with inflammatory bowel disease (Crohn's disease and ulcerative colitis). The effectiveness of loperamide is comparable to another anti-diarrheal, diphenoxylate (Lomotil). Loperamide reduces diarrhea by slowing the forward propulsion of intestinal contents by the intestinal muscles. Although loperamide is related chemically to narcotics such as morphine, it does not have any of narcotics' pain– relieving effects even at high doses.
Loperamide was approved by the FDA in 1976.
What are the uses for loperamide?
Loperamide is used for the relief of acute or chronic diarrhea and traveler's diarrhea.
What are the side effects of loperamide?
Loperamide is generally well- tolerated. The side effects that have been reported during loperamide treatment include:
- Abdominal pain
- Constipation
- Drowsiness
- Dizziness
- Dry mouth
- Fatigue
- Nausea
- Vomiting
Loperamide is generally safe at approved doses, but when large doses are taken, or if it is taken in conjunction with other drugs of abuse it can lead to severe heart rhythm problems (arrhythmia, slow or fast rhythms), fainting (syncope), low blood pressure, and death.
What is the dosage for loperamide?
Adult dosage
- In adults and children 12 years of age and older, the usual dose is 4 mg initially, followed by 2 mg after each loose stool. The maximum dose is 16 mg/day (8 mg if self medicating).
- Chronic diarrhea: 4-8 mg per day may be administered after control is achieved.
Dosage for children
- Acute diarrhea in children: The dose for acute diarrhea in children is: age 8 to 12 years, 2 mg three times the first day; age 6 to 8 years, 2 mg twice the first day; age 2 to 5 years, 1 mg three times the first day. After the first day, children less than 12 years of age usually receive a dose of 0.1 mg/kg after a loose stool.
- Chronic diarrhea in children: 0.08-0.24 mg/kg/d divided into two doses, one dose given every 12 hours.
- Traveler's diarrhea in children 6-12 years old receive 2 mg after the first lose stool then 1 mg after each subsequent stool. Children older than 12 receive 4 mg initially then 1 mg after each loose stool. The maximum daily dose for traveler’s diarrhea is 4 mg (6-8 years old), 6 mg (6-12 years old), and 8 mg (>12 years old).
According to guidelines from the U.S. Food and Drug Administration (FDA), if you are using OTC loperamide and your diarrhea lasts more than 2 days, stop taking the drug and contact your doctor.
Which drugs or supplements interact with loperamide?
Cholestyramine (Questran) binds to loperamide in the intestines and prevents its absorption, thereby reducing the effect of loperamide. Therefore, there should be at least a two-hour interval between doses of loperamide and cholestyramine.
Theoretically, some drugs that are used to increase propulsion of intestinal contents could counteract loperamide. Such drugs include bethanechol (Urecholine), cisapride (Propulsid), metoclopramide (Reglan), and erythromycin.
Is loperamide safe to take if I’m pregnant or breastfeeding?
There are no adequate studies of loperamide in pregnant women. However, studies in animals receiving very high doses of loperamide suggest no important, detrimental effects on the fetus. Doctors may prescribe loperamide during pregnancy if its benefits outweigh the potential but unknown risks.
What else should I know about loperamide?
Loperamide:
- Is available as capsules or tablets: 1 or 2 mg; liquid: 1 mg per teaspoonful (5 ml)
- Should be stored at room temperature, 15 C – 30 C (59 F – 86 F).
- Is available in generic form, over the counter (OTC), and by prescription.
Brand names available for loperamide in the US include Imodium, Kaopectate II, Imodium A-D, Maalox Anti-Diarrheal Caplets, Pepto Diarrhea Control.
The FDA released a drug safety communication regarding loperamide in 2018. The FDA received reports of serious heart problems and deaths associated with taking much higher than the recommended doses of loperamide, primarily among people who are intentionally misusing or abusing the product. The FDA is attempting to work with manufacturers to limit the number of doses available in a package to promote its safe use. Loperamide is a safe drug when used as directed.