Evidence available on the use of the selective β3-adrenoceptor agonist mirabegron for the treatment of overactive bladder.

CONTEXT: Mirabegron, the selective β3-adrenoceptor agonist, heralds the latest development for the treatment of overactive bladder (OAB).

OBJECTIVE: To present the evidence available on the efficacy and tolerability of mirabegron and to discuss this treatment's potential in our setting.

EVIDENCE ACQUISITION: We reviewed 11 studies conducted with mirabegron in patients with OAB (2 phase II, 9 phase III), all studies were compared to placebo with 6 studies also including tolterodine as an additional arm. Greater emphasis shall be given to the main phase III trials performed in Europe, the USA and Australia evaluating efficacy and safety after 12 weeks (NCT00662909, NCT00689104, NCT00912964) and safety after 12 months (NCT00688688). The combined analyses of these 12 week studies is also available, with emphasis on global efficacy (FAS), efficacy with regard to incontinence (FAS i) and safety (SAF). More than 50% of patients had previously discontinued anticholinergics medication for OAB, thus allowing us to obtain data on the effectiveness of mirabegron in patients already treated with anticholinergics.

EVIDENCE SYNTHESIS: Mirabegron is an efficacious drug which presents a statistically significant reduction in the number of incontinence episodes and in urinary frequency as of 4 weeks, with a higher percentage of dry patients and a higher percentage of patients with reduction ≥50% in the number of incontinence episodes than placebo. The efficacy of mirabegron 50 and 100mg in the reduction of incontinence episodes occurs in de novo patients and who have received antimuscarinics, with adjusted mean difference and improvement in urinary frequency greater in treated patients. Its tolerability is very similar to placebo particularly for the adverse effects of the antimuscarinics (dry mouth, constipation and blurred vision). A minimal, non-clinically significant change is observed in systolic and diastolic blood pressure and pulse. Its efficacy is long-term. Mirabegron at the doses of 50 and 100mg presents an improvement versus placebo in patient satisfaction, health-related quality of life (HRQoL), symptom bother and patient's perception of bladder condition (PPBC). In the 12 week Phase III European study tolterodine delivered a lesser degree of improvement than mirabegron versus placebo in patient satisfaction, HRQoL, symptom bother and PPBC.

CONCLUSIONS: Mirabegron is the first of a new class of compounds with a novel mechanism of action that is different to the antimuscarinics. It presents significant and clinically important efficacy in the treatment of the symptoms of OAB. It has advantages with regard to the results described by the patient in treatment satisfaction. Studies on its combined use with anticholinergics are ongoing.