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[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# Overactive bladder agents

Medicines that calm an overactive bladder: antimuscarinics block detrusor contraction and beta-3 agonists relax it during filling.

Updated 2026-11-01

## What they are

Overactive bladder is urgency, usually with frequency, night-time voiding and sometimes urge incontinence. Two drug groups are used: antimuscarinics (oxybutynin, tolterodine, solifenacin, darifenacin, fesoterodine, trospium) and beta-3 adrenergic agonists (mirabegron, vibegron).

## Mechanism of action

Acetylcholine from parasympathetic nerves contracts the detrusor through M3 (and M2) receptors. Antimuscarinics block these receptors, lowering bladder pressure, raising capacity and reducing urgent contractions. Mirabegron stimulates beta-3 adrenergic receptors on the detrusor, relaxing it during the storage phase and increasing capacity without anticholinergic effects.

Target: Muscarinic M3 receptor (antimuscarinics); beta-3 adrenergic receptor (mirabegron)

## Key points

- Antimuscarinics are contraindicated in urinary retention, gastric retention and uncontrolled narrow-angle glaucoma.
- Dry mouth is the most common reason people stop antimuscarinics; constipation and blurred vision follow.
- Confusion and drowsiness are a particular problem in older adults; trospium (quaternary) and the M3-preferring solifenacin and darifenacin seem to cause fewer brain effects.
- Oxybutynin is the oldest and has the most anticholinergic side effects; skin forms cause fewer.
- Mirabegron can raise blood pressure and inhibits CYP2D6, raising levels of drugs such as metoprolol; it has no anticholinergic effects.

## Drugs in this class

- [**Oxybutynin** The oldest antimuscarinic for the overactive and neurogenic bladder. It works well but often causes dry mouth… Muscarinic M3 receptor of the bladder detrusor](https://durgical.com/en/pharmacology/oxybutynin/)
- [**Solifenacin** A once-daily antimuscarinic for overactive bladder with some preference for M3 receptors and a long half-life. Muscarinic M3 receptor of the bladder detrusor](https://durgical.com/en/pharmacology/solifenacin/)
- [**Tolterodine** An antimuscarinic for overactive bladder whose active metabolite is made by CYP2D6, so genetics and interacting drugs… Muscarinic receptors of the bladder (M3)](https://durgical.com/en/pharmacology/tolterodine/)
- [**Mirabegron** A beta-3 adrenergic agonist that relaxes the bladder during filling. It avoids anticholinergic effects but can raise… Beta-3 adrenergic receptor](https://durgical.com/en/pharmacology/mirabegron/)

## Others in the class

- Trospium (quaternary, cleared by the kidney)
- Darifenacin
- Fesoterodine (prodrug of the active tolterodine metabolite)
- Vibegron (beta-3 agonist)

## Test yourself

Think of the answer, then tap the question to see it.

## Which three conditions contraindicate antimuscarinics for overactive bladder?

Urinary retention, gastric retention and uncontrolled narrow-angle glaucoma.

## Which overactive bladder drug works through beta-3 receptors rather than muscarinic ones?

Mirabegron.

## What is the most common reason for stopping an antimuscarinic?

Dry mouth.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 11 (McGraw Hill, 2023); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=G04BD) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [DailyMed - MIRABEGRON tablet, film coated, extended release](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e597023d-6dcc-4d9e-8ce0-2d28a5d862f3) (DailyMed (U.S. National Library of Medicine), 2026).

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