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Anticholinergic — Antispasmodic (Muscarinic Antagonist) Pregnancy: Use with caution — limited data; smooth muscle relaxation may affect labour.

Oxybutynin (OAB — Anticholinergic Caution in Elderly)

Brand names: Ditropan, Kentera (patch), Lyrinel XL

Adult dose

Dose: Immediate-release: 2.5–5 mg 2–3 times daily; XL formulation: 5–10 mg once daily; Patch: 3.9 mg/24h applied twice weekly
Route: Oral (tablet or MR) / Transdermal patch
Frequency: 2–3 times daily (IR); once daily (XL); twice weekly (patch)
Max: 5 mg three times daily (IR); 20 mg/day (XL)
BEERS CRITERIA 2023 and STOPP v3: oxybutynin should be AVOIDED in elderly — particularly IR formulation; highly anticholinergic, crosses blood-brain barrier. Associated with cognitive impairment, delirium, falls, dry mouth, constipation, and urinary retention. If OAB treatment required in elderly, prefer mirabegron or XL/patch formulations over IR oxybutynin.

Paediatric dose

Dose: 0.2 mg/kg
Route: Oral
Frequency: 2–3 times daily
Max: 5 mg three times daily
Children ≥5 years for neurogenic detrusor overactivity: 2.5 mg BD increasing to 5 mg TDS. BNFc guidance.

Dose adjustments

Renal

Use with caution — retention risk; no specific dose adjustment for mild-moderate impairment.

Hepatic

Use with caution in hepatic impairment.

Paediatric weight-based calculator

Children ≥5 years for neurogenic detrusor overactivity: 2.5 mg BD increasing to 5 mg TDS. BNFc guidance.

Clinical pearls

  • Anticholinergic Cognitive Burden (ACB) Score: oxybutynin IR has one of the HIGHEST ACB scores of all drugs (score 3 — definite cognitive effect). Cumulative anticholinergic exposure is strongly associated with dementia risk — MHRA 2021 warning. Prescribing oxybutynin IR in elderly with any cognitive impairment is generally inappropriate
  • Transdermal patch reduces CNS effects: patch bypasses first-pass hepatic conversion to the CNS-active N-desethyl metabolite — lower peak CNS levels vs oral; preferred if oxybutynin must be used in elderly (though mirabegron still preferred overall)
  • Deprescribing oxybutynin: taper dose gradually to avoid symptom recurrence; transition to mirabegron as part of medication review; OAB symptoms often respond to bladder training and pelvic floor exercises — trial before starting any drug in elderly

Contraindications

  • Urinary retention (absolute)
  • Gastric retention
  • Uncontrolled narrow-angle glaucoma
  • Myasthenia gravis
  • Dementia (relative — significant anticholinergic CNS effects)

Side effects

  • Dry mouth (very common — up to 60%)
  • Constipation
  • Urinary retention
  • Blurred vision
  • Cognitive impairment and confusion (significant in elderly)
  • Delirium (particularly IR formulation)
  • Tachycardia
  • Increased intraocular pressure (glaucoma risk)
  • Falls (anticholinergic CNS effects)

Interactions

  • Other anticholinergics (additive anticholinergic burden — tricyclics, antihistamines, antipsychotics)
  • CYP3A4 inhibitors (ketoconazole, erythromycin — increase oxybutynin levels significantly)
  • Amantadine, memantine (additive anticholinergic CNS effects)

Monitoring

  • Cognitive function (MMSE, 4AT for delirium) — anticholinergic CNS effects
  • Urinary retention (post-void residual in men with BPH)
  • Dry mouth and constipation (quality of life impact)
  • Intraocular pressure (if history of or risk of glaucoma)
  • ACB score (total anticholinergic burden of all medications)

Reference: BNFc; BNF 90; AGS Beers Criteria 2023; STOPP/START v3 2023; MHRA Drug Safety Update 2021 (anticholinergic drugs and dementia risk); NICE CG171 (Urinary Incontinence). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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