Beta-3 adrenoceptor agonist (bladder relaxant) Pregnancy: Avoid — limited safety data.

Mirabegron

Brand names: Betmiga

Adult dose

Dose: 25 mg once daily; increase to 50 mg after 4–8 weeks if needed

Route: Oral

Frequency: Once daily

Max: 50 mg/day

OAB (urgency, frequency, urge incontinence): 25 mg OD for 4–8 weeks. If insufficient, increase to 50 mg OD. Max 25 mg/day if on strong CYP3A4 inhibitors. Do not crush or chew tablets.

Paediatric dose

Route: Not applicable

Frequency: Not licensed in children

Max: Not applicable

Not licensed in children. Some specialist use in neurogenic bladder under paediatric urology supervision.

Dose adjustments

Renal

Max 25 mg/day if severe renal impairment (eGFR <30).

Hepatic

Max 25 mg/day for moderate hepatic impairment; avoid severe.

Clinical pearls

Alternative to antimuscarinics — fewer dry mouth, constipation, and cognitive side effects
Preferred in elderly patients where anticholinergic burden is a concern
Monitor blood pressure (mild increase expected)
Can be combined with antimuscarinics if monotherapy insufficient
No contraindication in narrow-angle glaucoma unlike antimuscarinics

Contraindications

Severe uncontrolled hypertension (>180/110 mmHg)
Hypersensitivity to mirabegron

Side effects

Hypertension (increases blood pressure)
Tachycardia and palpitations
UTI
Nasopharyngitis
Dry mouth (much less than antimuscarinics)
Urinary retention (uncommon)

Interactions

Strong CYP3A4 inhibitors (ketoconazole) — max 25 mg/day
Digoxin — increases digoxin exposure (check digoxin levels)
Warfarin — increased warfarin exposure (monitor INR)
Metoprolol — increased levels

Monitoring

Blood pressure
Urinary symptoms and incontinence episodes
Digoxin levels (if co-prescribed)

Reference: BNFc; BNF; NICE NG123; EAU Guidelines; NICE TA290. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways