To critically analyse available phase II and III randomised control trials 
(RCTs) reporting clinical data about the efficacy and tolerability of Mirabegron 
(a β₃-adrenoceptor agonist) in the treatment of overactive bladder (OAB) 
syndrome. A review of the literature was performed in September 2013 using the 
MEDLINE database. A 'free text' protocol was used for the search strategy using 
'overactive bladder' and 'Mirabegron' as keywords. Subsequently, the searches 
were pooled and limited to phase II and III RCTs. Two phase II and five phase 
III RCTs were selected and analysed. The available phase II studies showed the 
efficacy and tolerability of different doses of Mirabegron compared with 
placebo. Moreover, a dose-ranging study showed that 50 mg once daily should be 
considered the most promising dose for clinical use. The 12-week phase III 
studies confirmed the effectiveness of Mirabegron to significantly reduce the 
mean number of incontinence episodes/24 h and the mean number of 
micturitions/24 h compared with placebo. A post hoc analysis confirmed that 
favourable results with Mirabegron were reported both in patients with OAB who 
were antimuscarinic naïve and in those who had discontinued prior antimuscarinic 
therapy. Moreover, a phase III trial showed the safety and tolerability of 
12-month treatment of Mirabegron. Discontinuation due to adverse events was low 
both using the 50 and 100 mg dose of Mirabegron. Mirabegron is the first of a 
new class of drugs for the treatment of OAB able to influence non-voiding 
activity and produce an increased storage capacity and inter-void interval. 
Recently published phase II and III RCTs have shown that the 
β₃-adrenoceptor-selective agonist, Mirabegron, is an effective and safe drug for 
the symptomatic treatment of OAB syndrome. Mirabegron represents a valid medical 
option both for patients with OAB who are antimuscarinic naïve, as well as in 
those where antimuscarinics are ineffective or not tolerated.