Neurotoxin treatments for urinary incontinence in subjects with spinal cord injury or multiple sclerosis: A systematic review of effectiveness and adverse effects

Background/Objective: The objective was to evaluate the effectiveness of neurotoxin treatments of urinary incontinence (UI) in individuals with spinal cord injury (SCI) or multiple sclerosis (MS). Methods: Studies were included if published in English, presented randomized adults with SCI or MS, and reported UI outcomes. Results: Ten trials randomizing 288 subjects with SCI (43%), MS (52%), or other spinal conditions (5%) and UI refractory to oral antimuscarinics were included. The overall mean age was 41 years, and 46% were women. Study durations ranged from 1 to 18 months. Treatments included botulinum toxin-A (BTX-A, 2 trials) and 2 vanilloid compounds, capsaicin (6 trials) and resiniferatoxin (4 trials). BTX-A was superior to placebo and resiniferatoxin in reducing daily UI episodes, mainly in individuals with SCI, although significant reductions vs placebo were not evident throughout the study duration. There were 1.1 fewer daily UI episodes in the BTX-A 200 unit group vs 0.1 fewer for the placebo group at the final week 24 assessment. Capsaicin was generally superior to placebo. The weighted difference between capsaicin and placebo in a pooled analysis of 2 trials enrolling subjects with either paraplegia or tetraplegia (n = 32) was -3.8 daily UI episodes [95% CI -4.7 to -2.9] after 30 days. Capsaicin was comparable to resiniferatoxin. Pelvic pain and facial flushing were associated with capsaicin. Conclusion: Neurotoxins may improve refractive UI in adults with SCI or MS, although trial results were inconsistent. Trials were small in size and relatively short in duration. Further studies are needed to determine the efficacy and tolerability of long-term application.