M3-Selective Antimuscarinic — Overactive Bladder Pregnancy: eMC §4.6: there are limited data from use in pregnant women and studies in animals have shown toxicity to parturition; 'Darifenacin Aristo is not recommended during pregnancy.' Breast-feeding: darifenacin is excreted in the milk of rats and it is not known whether it is excreted in human milk; a risk to the nursing child cannot be excluded, so a decision whether to avoid breast-feeding or to abstain from therapy should be based on a benefit-risk comparison. Fertility: no human data; women of child-bearing potential should be made aware of the lack of fertility data and treatment should only be given after consideration of individual risks and benefits.

Darifenacin

Brand names: Emselex

Darifenacin is an oral antimuscarinic used for overactive bladder with symptoms of urgency, frequency, and urge incontinence. It is relatively selective for the M3 muscarinic receptor subtype.

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: 7.5 mg once daily as the recommended starting dose; after 2 weeks of therapy patients should be reassessed and, for those requiring greater symptom relief, the dose may be increased to 15 mg once daily based on individual response

Route: Oral — 'The tablets should be taken once daily with liquid. They can be taken with or without food, and must be swallowed whole and not chewed, divided or crushed' (prolonged-release tablets)

Frequency: Once daily

Max: 15 mg daily. Restricted to 7.5 mg daily in moderate hepatic impairment (Child Pugh B); the US label additionally caps the daily dose at 7.5 mg when co-administered with potent CYP3A4 inhibitors

SOURCE: eMC UK SPC 'Darifenacin 15 mg prolonged-release tablets' §4.2, quoted verbatim. ELDERLY (≥65 years): same starting dose of 7.5 mg daily; reassess for efficacy and safety after 2 weeks and, in those with acceptable tolerability who require greater symptom relief, the dose may be increased to 15 mg daily. HEPATIC IMPAIRMENT: no dose adjustment in mild impairment (Child Pugh A), though exposure may be increased; in moderate impairment (Child Pugh B) treat only if the benefit outweighs the risk and restrict the dose to 7.5 mg daily; contraindicated in severe impairment (Child Pugh C). CYP INTERACTION DOSING: with potent CYP2D6 inhibitors (paroxetine, terbinafine, quinidine, cimetidine) start at 7.5 mg — the dose may be titrated to 15 mg daily for improved clinical response if well tolerated, with caution; with moderate CYP3A4 inhibitors (fluconazole, grapefruit juice, erythromycin) the recommended starting dose is 7.5 mg daily, titratable to 15 mg daily if well tolerated, with caution; potent CYP3A4 inhibitors are contraindicated. PAEDIATRIC: 'not recommended for use in children below 18 years of age due to a lack of data on safety and efficacy' — verify any under-18 use against a children's formulary. US CROSS-CHECK: starting dose 7.5 mg once daily, may increase to 15 mg once daily as early as two weeks after starting; the daily dose should not exceed 7.5 mg in moderate hepatic impairment (Child-Pugh B) or with potent CYP3A4 inhibitors; not recommended in severe hepatic impairment (Child-Pugh C). §4.5 of the SPC was truncated at the source-fetch limit.

Dose adjustments

Renal

eMC §4.2: 'No dose adjustment is required in patients with impaired renal function. However, caution should be exercised when treating this population.'

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — 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
Urinary retention
Gastric retention
Uncontrolled narrow-angle glaucoma
Myasthenia gravis
Severe hepatic impairment (Child Pugh C)
Severe ulcerative colitis
Toxic megacolon
Concomitant treatment with potent CYP3A4 inhibitors

Side effects

Dry mouth — very common; 20.2% and 35% at the 7.5 mg and 15 mg doses respectively (18.7% after flexible dose titration) versus 8-9% for placebo
Constipation — very common; 14.8% and 21% at the 7.5 mg and 15 mg doses respectively (20.9% after flexible dose titration) versus 5.4-7.9% for placebo
Headache and dry eye (common); nasal dryness (common); abdominal pain, nausea and dyspepsia (common)
Dizziness, dysgeusia, somnolence, visual disturbance including blurred vision, hypertension, dyspnoea, cough, rhinitis, flatulence, diarrhoea, mouth ulceration, rash, dry skin, pruritus and hyperhidrosis (uncommon)
Urinary retention, urinary tract disorder, bladder pain, urinary tract infection, erectile dysfunction, vaginitis, peripheral oedema, asthenia, insomnia, abnormal thinking and raised AST/ALT (uncommon); confusional state, depressed mood/mood altered, hallucination, generalised hypersensitivity reactions including angioedema and muscle spasms (frequency not known, post-marketing)

Interactions

Potent CYP3A4 inhibitors (protease inhibitors such as ritonavir, ketoconazole, itraconazole) — contraindicated; co-administration of darifenacin 7.5 mg with ketoconazole 400 mg produced a 5-fold increase in steady-state darifenacin AUC (about 10-fold in poor metabolisers), and the effect is expected to be more pronounced with the 15 mg dose
Potent P-glycoprotein inhibitors such as ciclosporin and verapamil — should also be avoided
Moderate CYP3A4 inhibitors (erythromycin, clarithromycin, telithromycin, fluconazole, grapefruit juice) — start at 7.5 mg daily and titrate cautiously (SPC text truncated at the source-fetch limit)
Potent CYP2D6 inhibitors (paroxetine, terbinafine, cimetidine, quinidine) — start at 7.5 mg daily; exposure increases (e.g. by 33% with paroxetine 20 mg at the 30 mg darifenacin dose)
US label additions: caution with drugs predominantly metabolised by CYP2D6 that have a narrow therapeutic window, such as flecainide, thioridazine and tricyclic antidepressants; concomitant anticholinergic agents may increase the frequency and/or severity of dry mouth, constipation, blurred vision and other anticholinergic effects. SPC §4.4 also warns about concurrent medicinal products that can cause or exacerbate oesophagitis, such as oral bisphosphonates

Clinical monograph

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.

Reference: NICE NG123 (Urinary Incontinence and OAB); EAU OAB Guidelines 2024; 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).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways