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Antispasmodic (Natural — Calcium Channel Blocker in Intestinal Smooth Muscle) Pregnancy: Insufficient data — avoid in pregnancy; topical menthol use generally considered safe but oral peppermint oil capsules have insufficient evidence.

Peppermint Oil

Brand names: Colpermin, Mintec

Adult dose

Dose: 1–2 capsules (0.2mL each; Colpermin = 0.2mL per capsule) three times daily, 30–60 minutes before meals. Swallow whole — do not chew or crush (prevents oesophageal release and heartburn).
Route: Oral (enteric-coated capsules)
Frequency: Three times daily before meals
Max: 6 capsules/day (1.2mL/day peppermint oil)
NICE CG61: recommended for IBS-associated abdominal pain and cramping when mebeverine or hyoscine insufficient. Enteric coating essential — releases in small intestine/colon, not stomach. Swallow with water 30–60 minutes before food.

Paediatric dose

Route: N/A
Frequency: N/A
Max: Not recommended in children <15 years
Not recommended in children under 15 years — risk of heartburn and respiratory depression (menthol component). Seek specialist opinion.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required.

Clinical pearls

  • Mechanism: menthol (main active component) blocks calcium channels in intestinal smooth muscle — direct antispasmodic effect without anticholinergic side effects.
  • Enteric coating critical: do not crush or chew. If patient reports heartburn — ensure they are swallowing whole. Heartburn occurs when peppermint oil released in oesophagus/stomach (relaxes LOS).
  • Perianal burning on defecation: menthol excreted unchanged — warn patients. Not harmful.
  • NICE CG61: second-line antispasmodic option after mebeverine or hyoscine butylbromide for IBS abdominal pain.

Contraindications

  • Achlorhydria (reduced gastric acid — capsule may release in stomach, causing heartburn)
  • Known hypersensitivity to peppermint or menthol
  • Children under 15 years

Side effects

  • Heartburn / oesophageal burning (if capsule chewed or broken — menthol relaxes lower oesophageal sphincter)
  • Perianal burning (menthol excreted in stool)
  • Nausea
  • Allergic reactions (rare — menthol hypersensitivity)

Interactions

  • No clinically significant drug interactions documented

Monitoring

  • Symptom response at 4 weeks
  • Heartburn symptoms

Reference: BNFc; BNF 90; NICE CG61 Irritable Bowel Syndrome; SPC Colpermin. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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