Loperamide

Prescription ·Exploratory record · not publication-reviewed ·Updated July 13, 2026

A synthetic opioid receptor agonist that acts peripherally on the gastrointestinal tract to reduce diarrhea. Loperamide does not cross the blood-brain barrier at therapeutic doses and therefore lacks central opioid effects. It is used for acute nonspecific diarrhea and chronic diarrhea associated with inflammatory bowel disease.

Exploratory record, not a reviewed medical publication.

See the editorial and medical-review policies for the publication gate.

This generated database record has not completed a claim-level review by a qualified human medical reviewer. Bibliography links and evidence labels are not approval. The page remains available for reference and is excluded from search indexing.

In short

What the research says.

A quick, data-only summary. The full evidence, dosing, and sources are below.

A synthetic opioid receptor agonist that acts peripherally on the gastrointestinal tract to reduce diarrhea. NutriStack rates the supporting evidence as strong. Common adult dosing is Initial: 4 mg, then 2 mg after each unformed stool; maximum 16 mg/day for OTC use (as prescribed by your physician), though a prescriber sets the actual dose. This profile indexes 10 sources.

What it's good for

Rapid control of acute diarrhea^2,3
Reduction of stool frequency and volume
Management of chronic diarrhea^2,9
Control of ileostomy output

What to watch for

Constipation
Abdominal cramping
Nausea
Acute dysentery (bloody diarrhea with high fever)^2,3
Bacterial enterocolitis caused by invasive organisms (Salmonella, Shigella, Campylobacter)

The bottom line

Evidence rating strong. Most-documented uses: rapid control of acute diarrhea, reduction of stool frequency and volume, management of chronic diarrhea. 10 sources indexed (2007–2024), with 0 interaction records on file.

The science

How it works, mechanistically.

Core mechanism

Acts on mu-opioid receptors in the myenteric plexus of the intestinal wall, slowing intestinal motility and increasing transit time. It also reduces fecal volume, increases viscosity and bulk density, and diminishes fluid and electrolyte loss by enhancing absorption of water and electrolytes. Loperamide increases anal sphincter tone, reducing fecal incontinence.

Class

Anti-Diarrheal

Dosing

Dosing & protocol.

Common range

Initial: 4 mg, then 2 mg after each unformed stool; maximum 16 mg/day for OTC use (as prescribed by your physician)

Recommended form

Capsule, tablet, or oral solution

Can be taken with or without food; maintain adequate hydration during use

Safety

Full safety detail.

Side effects

Constipation
Abdominal cramping
Nausea
Dizziness
Dry mouth
Cardiac arrhythmias at supratherapeutic doses (QT prolongation, Torsades de Pointes)

Contraindications

Acute dysentery (bloody diarrhea with high fever)^2,3
Bacterial enterocolitis caused by invasive organisms (Salmonella, Shigella, Campylobacter)
Pseudomembranous colitis (C. difficile)⁹
Abdominal distension or ileus
Children under 2 years of age²

Sources

Sources, by evidence tier.

Numbered references. Citations throughout the page link here.

Meta-analyses & systematic reviews

1Cardiac Dysrhythmias Associated With Substitutive Use of Loperamide: A Systematic ReviewPMIDRiaz IB, Khan MS, Kamal MU et al. · American journal of therapeutics · 2019
Riaz IB, Khan MS, Kamal MU et al.. Cardiac Dysrhythmias Associated With Substitutive Use of Loperamide: A Systematic Review. American journal of therapeutics. 2019
2Loperamide therapy for acute diarrhea in children: systematic review and meta-analysisPMIDLi ST, Grossman DC, Cummings P · PLoS medicine · 2007
Li ST, Grossman DC, Cummings P. Loperamide therapy for acute diarrhea in children: systematic review and meta-analysis. PLoS medicine. 2007

Randomized controlled trials

3Racecadotril Versus Loperamide in Acute Radiation Enteritis: A Randomized, Double-Masked, Phase 3, Noninferiority TrialPMIDP B A, Sudha SP, Mohan P et al. · International journal of radiation oncology, biology, physics · 2024
P B A, Sudha SP, Mohan P et al.. Racecadotril Versus Loperamide in Acute Radiation Enteritis: A Randomized, Double-Masked, Phase 3, Noninferiority Trial. International journal of radiation oncology, biology, physics. 2024

Reviews & position papers

4Electrocardiographic changes in loperamide toxicity: Case report and review of literaturePMIDTeigeler T, Stahura H, Alimohammad R et al. · Journal of cardiovascular electrophysiology · 2019
Teigeler T, Stahura H, Alimohammad R et al.. Electrocardiographic changes in loperamide toxicity: Case report and review of literature. Journal of cardiovascular electrophysiology. 2019
5Loperamide cardiotoxicity: "A Brief Review"PMIDAkel T, Bekheit S · Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc · 2018
Akel T, Bekheit S. Loperamide cardiotoxicity: "A Brief Review". Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc. 2018
6Clinical Review: Loperamide ToxicityPMIDWu PE, Juurlink DN · Annals of emergency medicine · 2017
Wu PE, Juurlink DN. Clinical Review: Loperamide Toxicity. Annals of emergency medicine. 2017

Reference material

7Baker DE. Loperamide: a pharmacological review. Rev Gastroenterol Disord. 2007.Source linkedPMID
8Hanauer SB. The role of loperamide in gastrointestinal disorders. Rev Gastroenterol Disord. 2008.Source linkedPMID
9Rehde A et al. Effectiveness of Non-Budesonide Therapies in Management of Microscopic Colitis: A Systematic Review and Meta-analysis. Drugs. 2023.Source linkedPMID
10Sahi N, Nguyen R, Patel P et al.. Loperamide. 2026Source linkedPMID

FAQ

Common questions.

Quick answers about Loperamide, drawn from the data on this page.

What is Loperamide?

What is Loperamide used for?

Commonly cited benefits of Loperamide include: Rapid control of acute diarrhea; Reduction of stool frequency and volume; Management of chronic diarrhea; Control of ileostomy output. NutriStack rates the overall evidence as strong.

What is a typical dose of Loperamide?

A typical adult dose of Loperamide is Initial: 4 mg, then 2 mg after each unformed stool; maximum 16 mg/day for OTC use (as prescribed by your physician). The commonly recommended form is Capsule, tablet, or oral solution. These are general ranges, not personalized advice; confirm the right dose with a clinician.

What are the side effects of Loperamide?

Reported side effects include constipation, abdominal cramping, nausea, dizziness, dry mouth, cardiac arrhythmias at supratherapeutic doses (qt prolongation, torsades de pointes). This is educational information; check with a healthcare professional before use.

How strong is the evidence for Loperamide?

NutriStack rates this as Strong, meaning multiple high-quality meta-analyses or systematic reviews converge on the same finding. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.

Use this with your stack

Loperamide in NutriStack.

Add it to your stack, see how it interacts with everything else you take, and get a Stack Score that updates the moment it does.

Download on the App Store → Read the methodology