Solifenacin: Selective M3 Muscarinic Antagonist for Overactive Bladder
Solifenacin (Vesicare) is a selective muscarinic M3 receptor antagonist used for overactive bladder (OAB). It preferentially inhibits M3 receptors in the detrusor muscle, reducing involuntary bladder contractions, urgency, and incontinence.
One of the best-tolerated anticholinergic bladder medications, with a selectivity profile that minimises salivary gland (dry mouth) and CNS (cognitive) side effects compared to older agents.
Mechanism of Action
Competitively antagonises M3 muscarinic receptors in bladder detrusor muscle, reducing involuntary contractions and increasing bladder capacity. Also has some M1 receptor activity (cognition — monitor in elderly). Does not affect M2 receptors significantly (cardiovascular).
Indications & Use
Overactive bladder (OAB) with symptoms of urgency, urge incontinence, and increased urinary frequency. Also used in combination with mirabegron (beta-3 agonist) for inadequate responders. Neurogenic detrusor overactivity (off-label).
Dosage
Standard: 5 mg once daily. Increase to 10 mg once daily if 5 mg tolerated but response inadequate after 4 weeks. Renal impairment (GFR <30 mL/min) or moderate hepatic impairment: maximum 5 mg/day. Severe hepatic impairment: not recommended. CYP3A4 inhibitors: maximum 5 mg/day.
Side Effects
Dry mouth (most common — ~11%), constipation, blurred vision. Urinary retention (rare but serious — screen for BPH before use in men). Cognitive impairment (elderly — anticholinergic burden concern — prefer mirabegron for cognitive vulnerability). QT prolongation at high doses.
Drug Interactions
CYP3A4 inhibitors (ketoconazole, clarithromycin): increase solifenacin levels — maximum 5 mg/day. Other anticholinergics: additive effects (dry mouth, constipation, urinary retention, cognitive). QT-prolonging drugs: additive risk.
Contraindications
Urinary retention, gastric retention, uncontrolled narrow-angle glaucoma, myasthenia gravis, severe hepatic impairment, severe renal impairment (GFR <10 mL/min). Caution in elderly (anticholinergic cognitive effects — Beers Criteria).
Frequently Asked Questions
How is solifenacin different from oxybutynin?
Oxybutynin is a non-selective muscarinic antagonist with M1/M2/M3 activity and crosses the blood-brain barrier, causing more cognitive side effects and dry mouth. Solifenacin is more bladder-selective (M3) and has lower CNS penetration — better tolerated, particularly in elderly patients.
Is solifenacin safe in elderly patients?
Anticholinergic medications, including solifenacin, are listed on the Beers Criteria as potentially inappropriate in elderly patients due to cognitive impairment risk. The beta-3 agonist mirabegron is preferred in cognitively vulnerable elderly patients.
How long does solifenacin take to work?
Symptom improvement (reduced urgency, frequency, incontinence) typically begins within 2–4 weeks. Full benefit is assessed at 4–6 weeks. Up to 12 weeks may be needed for maximum effect.
References
- EMA Vesicare SPC 2023
- EAU Guideline OAB 2022
- Chapple CR et al. Eur Urol 2004
Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice.