Oxybutynin

How it works

It antagonises muscarinic (M3) receptors on detrusor smooth muscle and also has a direct antispasmodic action, reducing involuntary detrusor contractions and increasing bladder capacity.

Prescribing in practice

• Use cautiously in frail older people because of antimuscarinic cognitive impairment and confusion, and avoid where there is untreated angle-closure glaucoma, significant bladder outflow obstruction, urinary retention or gastrointestinal obstruction.
• Anticholinergic side effects (dry mouth, constipation, blurred vision) are common, and modified-release or transdermal forms may improve tolerability.
• Cumulative anticholinergic burden should be considered when it is combined with other antimuscarinic medicines.

Monitoring

Review symptom benefit and antimuscarinic adverse effects after an adequate trial, with particular attention to cognition in older patients.

Counselling the patient

• Dry mouth and constipation are common; sips of water and adequate fibre and fluids can help.
• Report eye pain or visual disturbance, or new difficulty passing urine.

Evidence & guidelines

Oxybutynin is a long-established antimuscarinic for overactive bladder; NICE recommends against immediate-release oxybutynin as first choice in frail older women due to anticholinergic risks.