Loperamide

Generic name

Loperamide

Active ingredient

Loperamide (variants: loperamide hydrochloride)

Product type

Small-molecule medicine

Drug class

Antimotility agents

Brand names

UK Imodium

Routes

Oral

Dosage forms

Capsule, Tablet

Also known as

Imodium

Onset and duration

The NHS says loperamide usually starts to make diarrhoea better within 1 hour.

Monitoring

The NHS says children aged 11 or under and adults with long-lasting diarrhoea need a prescription.

Availability by country

Legal status differs between countries and can change; each row cites the document it was taken from and applies only to the country named.

What it is used for

• Treating short-term diarrhoea.
• Helping with irritable bowel syndrome (IBS) in adults whose doctor has diagnosed it.
• Treating longer-lasting diarrhoea from conditions such as Crohn's disease and ulcerative colitis, on prescription.

How it works in the body

The NHS says loperamide works by slowing the activity of the bowel. Product information for UK loperamide medicines says it lengthens the time contents spend in the gut and increases absorption of water and electrolytes, so stools become firmer. UK and US product information describes loperamide as an opioid (mu) receptor agonist that acts on the gut wall to reduce propulsive movement of the bowel.

Cautions and interactions

• Over the counter, the NHS says loperamide is for anyone aged 12 or over with short-term diarrhoea, and for adults with IBS only if a doctor has diagnosed it.
• Children aged 11 or under and adults with long-lasting diarrhoea need a prescription, according to the NHS.
• The NHS lists severe diarrhoea after antibiotics, a flare-up of ulcerative colitis or another inflammatory bowel condition, constipation or a swollen stomach, and blood in the stool with a high temperature among the situations where it is not suitable.
• The NHS says loperamide is not usually recommended in pregnancy because there is not enough evidence about it, and that anyone pregnant should speak to a doctor first.
• The NHS says breastfeeding is considered acceptable because only tiny amounts pass into breast milk and no side effects are expected in the baby.
• The NHS says some medicines can affect how loperamide works, including clozapine, ritonavir, quinidine, itraconazole, gemfibrozil, desmopressin and other anti-diarrhoea or bowel medicines.
• The NHS says loperamide can be taken alongside paracetamol or ibuprofen and does not stop contraceptive pills working, although severe diarrhoea can make the pill less reliable.

Interactions

Interactions documented in the official sources cited on each card. The list covers the medicines represented on this site and is not exhaustive; how the interaction data is compiled.

No pair records for this medicine are in the sources currently represented by Anatomy Nexus. Absence from this list does not mean no interaction exists.

What is loperamide used for?

The NHS describes loperamide as a medicine to treat diarrhoea. It can help with short-term diarrhoea and with irritable bowel syndrome that a doctor has diagnosed in an adult. For longer-lasting diarrhoea, such as that from Crohn's disease or ulcerative colitis, it is available on prescription.

How does loperamide work?

Loperamide slows the activity of the bowel, so the contents move more slowly and stay in the intestine for longer. Product information for UK loperamide medicines says it lengthens the time contents spend in the gut and increases absorption of water and electrolytes, so stools become firmer. The NHS says it usually starts to improve diarrhoea within 1 hour.

Side effects and when to get help

The NHS lists constipation, headache and feeling sick as side effects of loperamide. Dizziness, tiredness and drowsiness are more likely with alcohol. A fast or irregular heartbeat after taking more than the recommended amount can be a sign of serious heart problems, and the NHS says to contact 111 straight away. Swelling of the lips, mouth, throat or tongue, or very fast or struggling breathing, may be a serious allergic reaction: call 999. Fainting, stomach pain with a high temperature, severe constipation or difficulty passing urine need medical advice straight away: contact NHS 111 or a doctor.

Who should not use loperamide, and other medicines

The NHS lists severe diarrhoea after antibiotics, a flare-up of ulcerative colitis or similar conditions, constipation or a swollen stomach, and blood in the stool with a high temperature as situations where it is not suitable. Pregnancy is a situation where the NHS says loperamide is not usually recommended and a doctor should be consulted first. Several medicines can change how loperamide works, including clozapine, ritonavir, quinidine, itraconazole, gemfibrozil and desmopressin.

Frequently asked questions