Overactive bladder (OAB) in women is often characterized by urgency, frequency, and nocturia, and significantly impacts quality of life. Although antimuscarinic agents such as solifenacin are commonly used, they may exacerbate voiding dysfunction by increasing postvoid residual (PVR) urine volume. Alpha-1 adrenergic receptor blockers, traditionally used in men, have shown promise in improving voiding efficiency in women by reducing urethral resistance. We hypothesized that the combination of silodosin, an alpha-1A receptor blocker, with solifenacin would offer superior efficacy in female OAB patients by improving both storage symptoms and voiding parameters compared to monotherapy with solifenacin.

In this retrospective study, 586 women with newly diagnosed OAB were analyzed between January 2022 and June 2023. Patients received either combination therapy (solifenacin 5 mg + silodosin 8 mg; n=287) or solifenacin monotherapy (5 mg; n=299) for 12 weeks. Exclusion criteria included recurrent UTIs, residual urine >200 mL, neurologic disease, and prior use of antimuscarinics or alpha-blockers. Primary endpoints included changes in Overactive Bladder Symptom Score (OABSS), International Prostate Symptom Score (IPSS), quality of life (QoL), Qmax, voided volume (VV), and PVR.

Both groups showed significant improvements in OABSS and IPSS after 12 weeks. QoL improved in both groups, but more markedly in the combination therapy group (p = 0.031). No significant between-group differences were found in Qmax or VV. Importantly, the combination group showed a significant reduction in PVR (from 25.1 to 24.8 mL), while the monotherapy group showed an increase (from 20.5 to 25.5 mL), with between-group comparison favoring combination therapy (p < 0.001).

Adding silodosin to solifenacin improved storage symptoms and QoL, and prevented the rise in PVR commonly associated with antimuscarinic therapy. This suggests a synergistic effect of the combination, possibly through reduced urethral resistance and improved bladder emptying. The absence of adverse voiding outcomes supports the safety of this regimen.

Combination therapy with silodosin and solifenacin was more effective than solifenacin alone in treating female OAB, especially in preventing increased PVR and improving QoL. This approach may represent a valuable pharmacologic strategy for female patients with mixed storage and voiding symptoms.