How Loperamide Works: How Fast Imodium Starts Working

Last Updated: June 10, 2020

Authored by Olivier George, Ph.D.

Imodium (loperamide) is a medication meant to treat diarrhea; however, thanks to its mechanism of action, loperamide is used for other purposes as well. While many have used it, few know how Imodium works. It is important that users understand the medication’s mechanism of action.

How Does Imodium Work?

What Imodium does is treat the symptoms of diarrhea, specifically sudden (acute) diarrhea, including traveler’s diarrhea. It is not designed to be taken for long periods, though in some cases patients will, of time and it does not treat the underlying causes of sudden bowel disturbances.
How Imodium works is it slows down the movement of the intestines. The result is the person taking the Imodium AD has fewer bowel movements, and less water enters the stool. It is vital that patients stick to the recommended doses unless directed to do otherwise by a doctor. These are 4mg for the first dose, then loperamide hydrochloride 2 mg for each subsequent dose until stopping the medication.
Of course, this does not offer a complete understanding of how loperamide works. For that, the loperamide mechanism of action must be understood.

What Is Imodium Mechanism Of Action?

how does imodium workFor most patients, understanding how Imodium works to stop diarrhea ends with a general explanation. However, the more informed patients are, the better. To truly understand loperamide, people must understand the Imodium mechanism of action – or the specific biochemical interaction between the medication and the body. This can be broken down into five aspects of loperamide MOA: pharmacodynamics, absorption, metabolism, protein binding, route of elimination.

Loperamide Pharmacodynamics

Much of what Imodium does comes down to pharmacodynamics. Loperamide, the active ingredient in Imodium, binds to opiate receptors within the gut wall. Through this binding, the release of acetylcholine and prostaglandins is inhibited. This results in reduced propulsive peristalsis, which means it takes longer for the intestines to move waste, increasing the time between bowel movements and allowing the body to absorb more water, creating firmer stool.

Loperamide Absorption

Absorption determines how fast Imodium works. Imodium for diarrhea is primarily absorbed through the stomach, though the intestines can absorb some of the medication. Once it is absorbed, it does not have a significant impact on plasma. Concentrations are the highest between 2.5 hours and 5 hours after taking the medication. The Imodium half-life is approximately 10 hours.

Loperamide Metabolism

Loperamide is metabolized primarily by cytochrome P450 (CYP450) isozymes, CYP2C8 and CYP3A4. These then form N-desmethyl-loperamide, which is the compound that allows Imodium to work. This must be formed for the medication to act on the body. Such metabolism is considered quite safe. In fact, people can take Imodium while breastfeeding, if taken in small amounts.

Loperamide Protein Binding

Loperamide protein binding occurs primarily in the gut wall. The medication almost exclusively binds to the receptors in the longitudinal muscle layer. The plasma protein binding of the medication comes in at 95%, making this the primary site where Imodium does work on the body.

Loperamide Route Of Elimination

Loperamide is primarily excreted through the feces. While some of the medication and its metabolites can be excreted in other manners, the amount is so small as to be considered statistically insignificant.

Does Imodium Pass The Blood-Brain Barrier?

Because loperamide binds to opioid receptors, it theoretically could act as an opioid in the body and produce a high. However, there is a problem with this theory: loperamide does not easily cross the blood-brain barrier (BBB).

People desperate to get high or access affordable pain medication have looked into how to make loperamide cross the BBB. The only way to do this is to take it in incredibly high doses. Loperamide amount for recreational purposes varies from person to person, with some reporting to need as many as 100 pills to achieve any effect.

How Long Does It Take For Imodium To Work?

how long does imodium take to workHow long it takes for Imodium to work will depend on what the user is taking it for. While the only on-label use of loperamide is in the treatment of diarrhea, some will use Imodium AD for opiate withdrawal or recreational purposes.

How long it takes for Imodium to stop diarrhea is usually somewhere in the range of 24 to 48 hours. However, the medication will start working well before then; the user just will not see the results. For those using it for other purposes, it can range from a few hours to never working at all.

Getting Help

Imodium is a medication that binds to opioid receptors and can cross the blood-brain barrier if taken in excessively large amounts. Anyone who is abusing loperamide or considering it should seek treatment programs provided by professional addiction facilities. Rehabilitation centers can help addicts manage their addiction, craving, and withdrawal symptoms and get clean.

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Published on: May 6th, 2019

Updated on: June 10th, 2020

About Author

Olivier George, Ph.D.

Olivier George is a medical writer and head manager of the rehab center in California. He spends a lot of time in collecting and analyzing the traditional approaches for substance abuse treatment and assessing their efficiency.


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