Pharmacology · Overactive bladder agents
Mirabegron !
A beta-3 adrenergic agonist that relaxes the bladder during filling. It avoids anticholinergic effects but can raise blood pressure.
Updated 2026-11-01
The figure shows mirabegron bound to the dog beta-3 adrenergic receptor in its active state with a G protein; the drug pocket is very similar in the human receptor.
Mechanism of action
Mirabegron activates beta-3 adrenergic receptors on the detrusor muscle. During the storage phase of the bladder cycle this relaxes the detrusor and increases bladder capacity, reducing urgency and leakage. It does not block muscarinic receptors, so it does not cause the dry mouth and confusion of antimuscarinics, but it can raise blood pressure.
- Activates beta-3 receptors on the detrusor
- Detrusor relaxes during bladder filling
- Bladder capacity increases
- Urgency and leakage ease, without anticholinergic effects
Pharmacokinetics
- Absorption
- Extended-release tablets by mouth, with or without food
- Metabolism
- Several pathways; CYP2D6 and CYP3A4 play a limited role. It is itself a moderate CYP2D6 inhibitor
- Half-life
- About 50 hours in adults
Indications
- Overactive bladder in adults Overactive bladder and urge incontinence →
- Neurogenic detrusor overactivity in children aged three and older above a minimum weight Neurogenic bladder →
Adverse effects
Common
- High blood pressure
- Urinary tract infection
- Headache
- Nasopharyngitis
Contraindications
- Hypersensitivity to mirabegron
- Not recommended in severe uncontrolled hypertension
Key interactions
- Drugs metabolized by CYP2D6 with a narrow margin (metoprolol, desipramine, flecainide, thioridazine)
- Higher exposure to those drugs; monitoring and dose adjustment may be needed
- Digoxin
- Digoxin levels rise; the lowest digoxin dose is used first and levels are checked
- Antimuscarinics for overactive bladder
- Higher risk of urinary retention
What is monitored
- Blood pressure before and periodically during treatment
- Voiding in men with prostate enlargement
- Digoxin level if taken together
Administration and safety
- Tablets are swallowed whole with water, not chewed or crushed
Nursing care
- Measure blood pressure at visits, especially in hypertension
- Review other medicines for CYP2D6 substrates
- Teach to report swelling of face or tongue and inability to pass urine
Pregnancy and breastfeeding
No studies in pregnant women; animal effects occurred only at exposures far above human ones.
Test yourself
Think of the answer, then tap the question to see it.
Which receptor does mirabegron activate, and with what effect on the bladder?
The beta-3 adrenergic receptor; it relaxes the detrusor during filling and increases capacity.
Which vital sign must be checked during mirabegron treatment?
Blood pressure, which it can raise.
Why can mirabegron raise metoprolol levels?
It is a moderate CYP2D6 inhibitor, and metoprolol is a CYP2D6 substrate.
Related drugs
Related conditions
← Back to the class: Overactive bladder agents
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - MIRABEGRON tablet, film coated, extended release (DailyMed (U.S. National Library of Medicine), 2026); Mirabegron: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); RCSB PDB - 7DH5: Dog beta3 adrenergic receptor bound to mirabegron in complex with a miniGs heterotrimer (RCSB Protein Data Bank, 2026).
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Representative model, for educational purposes only.