How Long Does It take Imodium to Work?

Loperamide, the active ingredient in Imodium, relieves diarrhea symptoms by slowing the digestive system back down to its normal rhythm.

Imodium may start to relieve diarrhea within one hour, reaching its peak therapeutic effect within two and a half hours of taking liquid Imodium, and five hours of taking an Imodium capsule.

This article explains how long it takes for Imodium to work, how soon it starts to work, and what exactly Imodium does in your body.

How Imodium Works

Loperamide, the active ingredient in Imodium, acts on your digestive system by binding to the opiate receptors (which regulate gut motility) in the wall of your gut.

In doing so, loperamide reduces the speed and frequency of colon contractions, slowing the movement of food through the digestive system. This gives your bowel more time to absorb water, electrolytes, and other nutrients from your intestines, adding bulk and firmness to the stool.

By binding to the opioid receptor, loperamide also prevents soiling accidents by increasing muscle tone in the anal sphincter—the ring of muscles around the anus that controls the release of stool.

When Will Imodium Start Working?

Imodium doesn't stop diarrhea immediately, but you may experience symptom relief within an hour of taking the medication.

Loperamide levels in your bloodstream are at their highest two and a half hours after ingesting liquid Imodium, and five hours after ingesting an Imodium capsule. Imodium reaches its peak effectiveness around these times.

How Long Will Imodium Last?

A single dose of loperamide has a half-life of approximately 11 hours with a range of nine to 14 hours. This means that it takes about 11 hours for your body to eliminate 50% of one loperamide dose from your system.

It takes five half-lives for 97% of a drug to be eliminated from your system. Thus, a single dose of loperamide should stay active in your body for up to 55 hours, relieving diarrhea for up to three days.

Is it OK to Use Immodium Every Day?

No. Imodium is intended as a short-term medication to treat diarrhea. You should not use it for more than two days in a row. If your diarrhea continues beyond that, stop taking Imodium and contact your healthcare provider.

Summary

Imodium may start to relieve diarrhea in as little as one hour. The antidiarrheal medication works by slowing the movement of food through the digestive system and restoring bulk to the stool. Imodium should relieve diarrhea within 48 hours. If it doesn't, contact your healthcare provider.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Imodium brand website. Who can use Imodium?

  3. Imodium brand website. How Imodium products work.

  4. Clarke W, Marzinke M. Basic pharmacokinetics. Contemp Pract Clin Chem. 2020 Jun;4(1):895-904. doi:10.1016/B978-0-12-815499-1.00050-8

  5. U.S. Food & Drug Administration. FDA drug safety communication: FDA warns about serious heart problems with high doses of the antidiarrheal medicine loperamide (Imodium), including from abuse and misuse. Published January 2018.

Barbara Bolen, PhD

By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.