Mebeverine

Mebeverine is a musculotropic antispasmodic that acts directly on gut smooth muscle without systemic anticholinergic effects. It is used for abdominal pain and cramp in irritable bowel syndrome and related disorders. Study evidence of benefit is weak, but it is well tolerated.

Classification. Antispasmodic (musculotropic); not an anticholinergic.

Mechanism. Reduces ion channel permeability in gut smooth muscle, blocking sodium and calcium influx and relieving spasm. It does not appear to cause generalised hypomotility.

Pharmacodynamics. Effect begins within 1 to 2 hours. Symptom improvement builds over days to weeks.

Pharmacokinetics. Rapidly and completely hydrolysed by esterases to mebeverine alcohol and veratric acid, so the parent drug is barely detectable in plasma. The modified-release capsule gives sustained levels over 12 hours.

Metabolism. Hydrolysis then conjugation; excreted mainly in urine as metabolites.

Adult oral doses unless stated.

Irritable bowel syndrome and gastrointestinal spasm.

• Mebeverine hydrochloride tablets 135 mg three times daily, 20 minutes before meals.

• Modified-release capsules 200 mg twice daily, before breakfast and evening meal.

• Review at 4 weeks; stop if there is no benefit.

Children.

• Age 10 to 17 years: 135 mg three times daily before meals (tablets) in most labels.

• Under 10 years: not advised in most labels; specialist advice only.

Kidney and liver adjustment. No adjustment is established; use with caution in severe impairment.

Contraindications. Hypersensitivity; paralytic ileus in some labels.

Common adverse effects. Usually well tolerated; occasional indigestion, constipation, headache, dizziness and insomnia.

Serious adverse effects.

• Hypersensitivity: urticaria, rash, angioedema, facial oedema and exanthema (rare).

• Anaphylaxis (very rare).

Major interactions. No clinically significant interactions are established. Anticholinergic drugs may add to the antispasmodic effect.

Special groups.

• Pregnancy: limited data; avoid unless necessary.

• Breastfeeding: limited data; avoid unless necessary.

• Children: restricted; over 10 years only in most labels.

• Older adults: no adjustment.

• Kidney impairment: caution.

• Liver impairment: caution.

• Regional: widely available and often sold without a diagnosis; exclude organic disease first.

Formulations. Tablets 135 mg; modified-release capsules 200 mg; oral suspension 50 mg in 5 mL in some markets.

Administration. Take tablets 20 minutes before meals with water. Swallow modified-release capsules whole; do not crush or chew.

Baseline. Symptom pattern; red flags excluded; coeliac serology and faecal calprotectin where indicated.

Monitoring.

• Pain and stool pattern at 4 weeks.

• Rash or swelling.

Therapeutic drug monitoring. Not applicable.

Stopping. No taper is needed. Stop if there is no benefit after 4 weeks or if a hypersensitivity reaction occurs.

Referral and escalation. Investigate red flags: weight loss, rectal bleeding, anaemia, nocturnal symptoms, family history of bowel cancer or onset over age 50.