The randomized phase III SYNERGY II study is the first to assess the long-term safety and therapeutic efficacy of mirabegron plus solifenacin versus each monotherapy for overactive bladder (OAB). Over 12 months, the combination was well tolerated, with only a slightly higher frequency of treatment-related adverse events in the combination arm compared with mirabegron and solifenacin alone (49% versus 41% versus 44%, respectively). The combination significantly reduced the mean number of incontinence episodes and micturitions compared with each monotherapy.