Betmiga: first-in-class treatment for overactive bladder

Astellas has launched Betmiga (mirabegron) for the symptomatic treatment of urinary frequency, urgency and urge incontinence associated with overactive bladder.

Betmiga (mirabegron) offers an alternative treatment approach to overactive bladder.
Betmiga (mirabegron) offers an alternative treatment approach to overactive bladder.


Mirabegron is a selective beta 3-adrenoceptor agonist. It relaxes smooth muscle in the bladder, enhancing urine storage.1

Mirabegron is unlikely to interfere with the urine voiding phase as it is predominantly the activity of acetylcholine on muscarinic receptors that induces bladder contraction.1


Mirabegron proved efficacious for the treatment of overactive bladder in adults with symptoms of urgency and frequency, with or without incontinence, in three phase III, randomised, double-blind studies of similar design.1

Investigators recruited patients aged 18 years and over who had been experiencing symptoms of overactive bladder, defined as eight or more micturitions and three or more episodes of urgency per day, for at least three months. Patients had a mean age of 59 years and the majority (72%) were female.1

Following a two-week single-blind run-in period, patients were randomised to receive placebo or mirabegron 50mg or 100mg* once daily. One study also included an active control arm in which patients received an oral tolterodine prolonged-release formulation (4mg once daily).1

Patients compiled a micturition diary and completed quality of life assessments. The co-primary efficacy endpoints were reduction from baseline to final visit in mean number of micturitions and mean number of incontinence episodes per day. Change from baseline in mean volume voided per micturition, and change from baseline to week four in mean number of micturitions and incontinence episodes per day were secondary efficacy endpoints.1

Pooled analysis showed that mirabegron 50mg once daily was significantly more effective than placebo for the co-primary endpoints from week four (the first measured time point) and maintained this superiority until study end at week 12 (p<0.001).1

After three months of treatment with mirabegron 50mg daily, the number of urinations was reduced by an average of 1.8 per day, compared with a reduction of 1.2 per day for placebo. The 50mg daily dose resulted in a reduction of 1.5 incontinence episodes per day compared with a reduction of 1.1 incontinence episodes per day for placebo.1

Results from the three key studies showed that mirabegron is generally well tolerated, with a similar rate of adverse events to placebo. Urinary tract infections and tachycardia were the most commonly observed side-effects.1

Longer-term safety and efficacy

A further double-blind phase III study assessed the longer-term safety and efficacy of mirabegron. Patients (n=2,444) were randomised in a 1:1:1 ratio to receive mirabegron 50mg or 100mg* once daily or prolonged-release tolterodine 4mg once daily. The incidence and severity of adverse events were logged over 12 months.2

Treatment-emergent adverse events were reported in 59.7%, 61.3% and 62.6% of patients, respectively. Most reactions were mild to moderate in severity. The incidence of dry mouth and cardiac arrhythmias was lower in patients treated with 50mg or 100mg mirabegron than in those receiving tolterodine (2.8% and 2.3% vs 8.6%; 3.9% and 4.1% vs 6.0%, respectively).2

Mirabegron produced similar reductions to tolterodine in the mean number of micturitions and episodes of incontinence per day from the first measured time point (one month) until study end.2

Lower strength tablet for use in renal and hepatic impairment

Mirabegron is available as a 25mg tablet for use in patients with moderate hepatic or severe renal impairment (GFR 15–29ml/min/1.73m2). Patients taking a strong CYP3A inhibitor who have mild hepatic or mild to moderate renal impairment should also take the reduced 25mg daily dose. Mirabegron is not recommended in patients with moderate hepatic or severe renal impairment who are taking a strong CYP3A inhibitor.1

*Unlicensed dose.


1.    Betmiga Summary of Product Characteristics, January 2013.
2.    Chapple CR et al. Eur Urol 2013; 63: 296-305.

View Betmiga drug record

Further information: Astellas Pharma Ltd

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