To compare the therapeutic efficacy and safety of mirabegron monotherapy in male patients with overactive bladder (OAB) with and without bladder outlet obstruction (BOO).

Male patients with OAB aged ≥20 years, with or without BOO, receiving mirabegron 25 mg monotherapy once daily, were prospectively enrolled. The treatment results were assessed using global response assessment, international prostate symptom score and subscores, overactive bladder symptom score, patient perception on intensity of urgency scale, patient perception of bladder condition, and quality of life index at 1 and 3 months after treatment.

Of the 289 enrolled patients (mean age, 71.2 years), 207 did not have BOO (71.6%) and 82 had BOO (28.4%). The baseline OAB symptoms were similar between patients with and without BOO. After mirabegron treatment, the satisfactory rate (global response assessment score ≧1) were similar between those without BOO (61.3%) and with BOO (57.1%). The improvement of quality of life index and patient perception of bladder condition was also found in both groups. However, only patients without BOO had significantly improved international prostate symptom score and subscores, overactive bladder symptom score, and patient perception on intensity of urgency scale. Although most adverse events (AEs) were mild, patients with BOO had significantly higher AEs rate (18.6%) than those without BOO (8.2%, P = .026).

Mirabegron monotherapy in male patients with OAB and BOO was safe. However, the storage symptoms improvement was less in patients with BOO and AEs rate was higher.