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Antispasmodic (Anticholinergic) Pregnancy: Epidemiological studies (doses up to 40 mg/day) have not shown an increased risk of foetal abnormality in the first trimester, and animal studies revealed no impaired fertility or foetal harm; however teratogenicity cannot be excluded with absolute certainty, so use in pregnancy only if the benefit outweighs the risk. Breast-feeding: excretion in human milk is unknown - exercise caution.

Dicycloverine Hydrochloride (Dicyclomine)

Brand names: Merbentyl

Dicycloverine hydrochloride is an antimuscarinic antispasmodic used for the symptomatic relief of smooth muscle spasm in irritable bowel syndrome and other functional gastrointestinal disorders.

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: 10-20 mg
Route: Oral
Frequency: Three times daily, before or after meals
SPC §4.2 states this dose for adults and children over 12 years. Children 2-12 years: 10 mg three times daily (a dicycloverine hydrochloride syrup is available for this age group) - flat dose, not weight-based; verify paediatric use against a children's formulary. Source is the Dicycloverine hydrochloride 10 mg Tablets SPC (oral use). Use with caution in patients with or suspected of having glaucoma or prostatic hypertrophy, and in hiatus hernia with reflux oesophagitis (§4.4). Tablets contain lactose monohydrate.

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.

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients
  • Known idiosyncrasy to dicycloverine hydrochloride

Side effects

  • Dry mouth and thirst
  • Dizziness
  • Fatigue, sedation, blurred vision (rare)
  • Constipation, anorexia, nausea and vomiting (rare)
  • Rash, headache, dysuria (rare)

Interactions

  • No interaction studies have been performed (SPC §4.5)

Clinical monograph

How it works

It relaxes gastrointestinal smooth muscle through both a direct (non-specific) relaxant action and antimuscarinic blockade of acetylcholine at muscarinic receptors.

Prescribing in practice

  • Avoid in conditions worsened by antimuscarinic effects, including angle-closure glaucoma, significant gastrointestinal obstruction or atony, and prostatic enlargement with urinary retention.
  • It is not recommended for infants and should be used with caution in the elderly, who are more susceptible to antimuscarinic adverse effects.
  • Expect typical antimuscarinic effects such as dry mouth, blurred vision and constipation, and use cautiously in cardiovascular disease.

Monitoring

No specific routine monitoring is required; review symptom response and watch for troublesome antimuscarinic adverse effects.

Counselling the patient

  • It may cause a dry mouth, blurred vision or drowsiness.
  • Take care if driving until you know how it affects you.
  • Report difficulty passing urine or eye pain.

Evidence & guidelines

Its antispasmodic use in functional bowel disorders is long established and reflected in current prescribing references and the SPC.

Reference: NICE CG61 Irritable Bowel Syndrome; SPC Merbentyl; 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).

Related

Curated clinical cross-links plus same-class fallbacks.

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