To investigate the effects of mirabegron (50 mg once daily for 12 weeks) in treatment-naïve women with overactive bladder (OAB) based on urodynamic studies.

This was an open-labeled, single-center, prospective study involving 65 recruited outpatients. The OAB symptom score was used for assessing the severity of subjective symptoms. Urodynamic studies, including uroflowmetry, cystometry, and pressure flow study, were conducted to evaluate objective symptoms. The first desire to void, maximum cystometric capacity, and occurrence of detrusor overactivity were measured as storage function parameters, whereas maximum flow rate, detrusor pressure at Qmax, and postvoid residual urine volume were assessed as voiding function parameters.

A total of 60 patients with a mean age of 72.3 years (50-86 years) were included in the analysis. The subjective symptom parameter (ie, the mean OAB symptom score) decreased significantly from 9.4 to 6.2 points (P <.001). In objective symptom parameters, both the first desire to void and maximum cystometric capacity significantly improved after treatment, and detrusor overactivity disappeared in 14 of 35 patients (40.0%) compared with that at baseline (P <.01). The voiding function parameters (ie, mean maximum flow rate, detrusor pressure at Qmax, and postvoid residual urine volume) did not significantly change, demonstrating that mirabegron does not inhibit voiding function.

Mirabegron improves storage function and subjective symptoms, without influencing voiding function, in women with OAB.