Loperamide hydrochloride

How it works

It is a peripherally acting opioid receptor agonist in the gut wall that slows intestinal motility and increases transit time, allowing greater absorption of fluid and electrolytes, with negligible central effects at normal doses.

Prescribing in practice

• Avoid in acute diarrhoea where reducing motility is hazardous, including suspected bacterial colitis, dysentery with blood and fever, and active ulcerative colitis flares where it can precipitate toxic megacolon.
• Serious cardiac events including QT prolongation and arrhythmia have been reported with overdose, so it must not be exceeded and is liable to misuse.
• It should not be used as the sole treatment in young children and is not a substitute for rehydration in infective diarrhoea.

Monitoring

No routine monitoring is required for short-term use; review if diarrhoea persists, worsens, or is accompanied by blood, fever or abdominal distension.

Counselling the patient

• Take plenty of fluids to replace what is lost; this medicine treats the symptom but not the cause.
• Stop and seek advice if you develop a high fever, blood in the stool, or marked abdominal swelling, and never exceed the stated dose.

Evidence & guidelines

Loperamide is a widely established first-line antimotility treatment for symptomatic relief of uncomplicated diarrhoea.