Darifenacin

How it works

It antagonises M3 muscarinic receptors on detrusor smooth muscle, reducing involuntary bladder contractions and increasing functional bladder capacity.

Prescribing in practice

• Contraindicated in untreated narrow-angle glaucoma, urinary retention, and significant gastrointestinal obstruction because antimuscarinic action can precipitate these.
• Use cautiously alongside other antimuscarinics and sedating drugs given the additive anticholinergic burden, especially in older patients.
• Exposure is increased by potent CYP enzyme inhibitors and dose limits apply in hepatic impairment per the SPC.

Monitoring

Review symptom response after several weeks and monitor for anticholinergic side effects and signs of urinary retention.

Counselling the patient

• Dry mouth and constipation are common; increasing fluids and fibre may help.
• Report inability to pass urine or significant visual disturbance promptly.
• Swallow the modified-release tablet whole without crushing.

Evidence & guidelines

Licensed for overactive bladder on the basis of randomised trials showing reduced urgency incontinence episodes versus placebo.