Loperamide slows the bowel to reduce diarrhoea. Used briefly at the label dose for ordinary short-lived diarrhoea, it is generally well tolerated. Two things make it worth reading about rather than simply taking: there are situations where it should not be used at all, and there is a serious risk at high doses.
Common side effects of this pharmacy medicine or category
- Constipation, sometimes lasting a few days after stopping
- Abdominal cramping or bloating
- Nausea
- Dizziness or drowsiness
- Dry mouth
See diarrhoea medicine causing constipation.
The most important treatment for diarrhoea is fluid, not a tablet. Stopping the diarrhoea addresses the symptom; replacing lost fluid and salts addresses what actually causes harm, especially in children and older adults. Oral rehydration solution does that better than water alone.
Interactions and duplicate-ingredient risks
Do not use it, and see a doctor instead, if you have:
- Blood or mucus in the stool
- A fever alongside the diarrhoea
- Severe abdominal pain or swelling
- Diarrhoea that began during or after a course of antibiotics
- A known inflammatory bowel condition, unless your specialist has advised it
The reason matters. These features suggest an infection or inflammation where slowing the bowel can keep harmful organisms or toxins in place rather than clearing them, and can make things worse. See antibiotics causing diarrhoea.
Mention it if you take medicines affecting heart rhythm, since combining them with loperamide adds to the cardiac risk described below. Some antifungals, antibiotics and HIV medicines can also raise loperamide levels.
Children, pregnancy, older adults and chronic medicine cautions
- Children. Loperamide is not suitable for young children, and dehydration is the greater danger in that age group. Use oral rehydration and seek advice instead.
- Older adults. More vulnerable to dehydration and to constipation afterwards.
- Pregnancy and breastfeeding. Ask a pharmacist first.
- Liver disease, where loperamide can accumulate.
- Heart rhythm conditions, which raise the risk at higher doses.
Warning signs and overdose concerns
Taking substantially more than the label dose can cause dangerous heart rhythm problems, including cardiac arrest. This is not a theoretical concern: it has occurred where very large amounts were taken, sometimes deliberately in an attempt to produce an opioid-like effect or to manage withdrawal. Loperamide is safe at label doses and is genuinely dangerous well above them, and there is no benefit to exceeding the recommended amount.
Get emergency help for fainting, a fast or irregular heartbeat, or chest pain, and for any suspected overdose even if the person seems well.
Also seek help for severe abdominal pain or swelling, no bowel movement with ongoing pain, or signs of dehydration such as passing little urine, dizziness on standing, or a dry mouth with drowsiness.
See a doctor if diarrhoea lasts longer than the label allows, keeps returning, or comes with weight loss or blood.
Questions to ask a pharmacist before using it
- Given my symptoms, should I be using this at all?
- What is the maximum I should take in a day?
- Should I be using rehydration solution as well?
- Is it safe with my other medicines?
- How long before I should see a doctor?
Related OTC and medicine-safety guides
- Diarrhoea medicine side effects
- Stomach medicine side effects
- OTC medicine side effects
- When to see a doctor about an OTC medicine
- Report an OTC medicine side effect
See also Imodium.
Medical Disclaimer: This content is for informational and educational purposes only and does not constitute medical diagnosis, prescription, or professional advice. Always read the patient information leaflet and consult a qualified doctor or pharmacist regarding any medicine or health concern.