The Long-Term, Real-World Effects of Oxybutynin on Pressure Reservoir Function in the Neurogenic Bladder after Spinal Cord Injury: A Retrospective Cohort Study

Background/Objectives: Data on the long-term effects of oxybutynin in patients with neurogenic bladder (NGB) due to spinal cord injury (SCI) are limited. This study aimed to evaluate the long-term effects of oxybutynin and the combination of oxybutynin with trospium in these patients, under real-world medical conditions. Methods: A total of 107 patients with NGB due to SCI were included. The mean treatment duration was 2.8 years +/- 0.8 years. The patients were categorized into three groups: (1) low-dose oxybutynin (5-15 mg/day), (2) high-dose oxybutynin (20-40 mg/day), and (3) oxybutynin combined with trospium. The main outcomes were maximal detrusor pressure (MDP) and cystometric bladder capacity (CBC). Both were assessed at baseline and at three subsequent follow-up visits. Generalized estimation equation models were used to estimate the overall mean reduction in MDP and CBC for each group. Results: The overall adjusted mean reduction from baseline of MDP in groups 1, 2, and 3 were 2.5 (95% CI: -5.4 to 10.4; p = 0.540), 16.9 (95% CI: 4.4 to 29.4; p = 0.008), and 21.9 (95% CI: 4.1 to 39.8; p = 0.016) cmH2O, respectively. For the CBC, the mean reduction was not significant in any group at any visit, nor were the overall mean reductions. Conclusions: These findings suggest that high-dose oxybutynin and oxybutynin-trospium combination achieve a significant long-term reduction in MDP in patients with NGB after SCI. The effects were sustained across all three follow-up periods.