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.
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 1 interaction record 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)
Loperamide and psyllium husk can both reduce loose stool or fecal incontinence, but they work differently and may overcorrect stool consistency when combined. In a randomized crossover trial, both improved fecal incontinence, while constipation occurred more often with loperamide than psyllium. The combination may be useful for selected patients, but constipation, bloating, impaction risk, or masking infectious diarrhea are the main concerns.
Recommendation: Start with one therapy at a time unless your clinician gives you a combined plan. If both are used, begin psyllium at a low dose with plenty of fluid and use the lowest effective loperamide dose. Avoid loperamide for bloody diarrhea, high fever, suspected C. difficile, or severe abdominal swelling, and stop or reduce therapy if constipation develops.
Riaz IB, Khan MS, Kamal MU et al.. Cardiac Dysrhythmias Associated With Substitutive Use of Loperamide: A Systematic Review. American journal of therapeutics. 2019
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
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"Needs reviewPMIDAkel 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
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
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.
NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.
NutriStack