Antidiarrhoeal (Opioid Receptor Agonist — Peripheral) Pregnancy: Not advisable to administer in pregnancy, especially during the first trimester; pregnant or breast-feeding women should be advised to consult their doctor for appropriate treatment. Small amounts may appear in human breast milk, so loperamide is not recommended during breast-feeding. The effect on human fertility has not been evaluated.

Loperamide Hydrochloride

Brand names: Imodium, Arret

Loperamide is an antimotility agent used for the symptomatic relief of acute diarrhoea and chronic diarrhoea (for example in adults with irritable bowel syndrome), and to reduce stool frequency in ileostomy.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Acute diarrhoea (adults and children 12 years of age and over): 4 mg (2 capsules) initially, then 2 mg (1 capsule) after every subsequent loose stool. Usual dose 6-8 mg a day.

Route: Oral (capsules taken with liquid)

Frequency: Initial dose, then one 2 mg dose after each subsequent loose stool

Max: 12 mg (6 capsules) in 24 hours

Second indication, same dosing: symptomatic treatment of acute episodes of diarrhoea associated with irritable bowel syndrome in adults aged 18 years and over, following initial diagnosis by a doctor - 4 mg initially, then 2 mg after every loose stool (or as previously advised by the doctor), maximum daily dose 12 mg; the patient should consult their doctor if new symptoms develop, symptoms worsen, or symptoms have not improved over two weeks. In acute diarrhoea, if symptoms persist for more than 24 hours the patient should consult a doctor, and if clinical improvement is not observed within 48 hours loperamide should be discontinued (SPC 4.4). Elderly: no dose adjustment required. Renal impairment: no dose adjustment required. Hepatic impairment: use with caution because of reduced first-pass metabolism, which may result in a relative overdose leading to CNS toxicity. PAEDIATRIC: loperamide capsules should not be used in children under 12 years of age (also a contraindication) - no paediatric dose is stated in this SPC; verify any paediatric use against a children's formulary. Cardiac events including QT interval and QRS complex prolongation and torsade de pointes have been reported in association with overdose, some with a fatal outcome, and overdose can unmask existing Brugada syndrome - patients should not exceed the recommended dose or duration of treatment. Caution is needed in patients with a history of drug abuse (abuse and misuse of loperamide have been described). SOURCE SCOPE: UK SPC for 'Boots Diarrhoea Relief 2 mg Capsules (P and GSL)', a 2 mg capsule pharmacy/general-sale presentation - chronic-diarrhoea or other prescription regimens are NOT covered by this label. SPC 4.4 was truncated at the source-fetch limit and no 4.5 interactions section was retrieved, so no interactions list is given here.

Dose adjustments

Renal

No dose adjustment is required for patients with renal impairment.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DIRECTIONS • drink plenty of clear fluids to help prevent dehydration caused by diarrhea • take only on an empty stomach (1 hour before or 2 hours after a meal) • take with a full (8 oz.) glass of water • find right dose on chart below. If possible, use weight to dose; otherwise, use age. adults and children 12 years and over 2 tablets after the first loose stool; 1 tablet after each subsequent loose stool; but no more than 4 tablets in 24 hours children 9-11 years (60-95 lbs) 1 tablet after the first loose stool; 1/2 tablet after each subsequent loose stool; but no more than 3 tablets in 24 hours children 6-8 years (48-59 lbs) 1 tablet after the first loose stool; 1/2 tablet after each …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-04-05. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Known hypersensitivity to loperamide hydrochloride or to any of the excipients
Children under 12 years of age
Acute dysentery, characterised by blood in stools and high fever
Acute ulcerative colitis
Bacterial enterocolitis caused by invasive organisms including Salmonella, Shigella and Campylobacter
Pseudomembranous colitis associated with the use of broad-spectrum antibiotics
Should not be used when inhibition of peristalsis is to be avoided, because of the possible risk of significant sequelae including ileus, megacolon and toxic megacolon; must be discontinued promptly if constipation, abdominal distension or ileus develop

Side effects

Constipation (2.7%)
Flatulence (1.7%)
Headache (1.2%)
Nausea (1.1%)
Dizziness, abdominal pain, abdominal discomfort, dry mouth, vomiting
Serious/post-marketing: ileus (including paralytic ileus), megacolon (including toxic megacolon), anaphylactic reaction, bullous eruption (including Stevens-Johnson syndrome and toxic epidermal necrolysis), angioedema, urinary retention

Clinical monograph

How it works

It is a peripheral opioid-receptor agonist acting on the gut wall; it slows intestinal motility and increases transit time without normally crossing into the central nervous system at therapeutic doses.

Prescribing in practice

Do not use in acute ulcerative colitis, bloody or inflammatory diarrhoea, or suspected infective (e.g. invasive bacterial) diarrhoea, because inhibiting motility risks toxic megacolon.
Serious cardiac effects, including QT prolongation and arrhythmia, have been reported with abuse or overdose at very high doses (MHRA warning).
Not suitable for young children; check the licensed lower age limit before recommending.

Monitoring

Mainly a clinical assessment: review response, hydration and stool frequency, and reassess if diarrhoea persists, worsens, or is accompanied by fever or blood.

Counselling the patient

Stop and seek medical advice if you develop a fever, see blood in your stools, or your symptoms do not settle within a couple of days.
Keep drinking fluids to replace what you lose.
Never take more than the recommended amount — very high doses can cause dangerous heart rhythm problems.

Evidence & guidelines

Established symptomatic therapy; MHRA Drug Safety Update highlights cardiac risks with high-dose misuse.

Reference: MHRA Drug Safety Update 2018 (Loperamide); SPC Imodium; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways