There have been only a couple of randomized controlled trials of intravesical onabotulinumtoxinA injections in this setting, note Dr. Sender Herschorn, at the University of Toronto, Ontario, and colleagues in the June issue of the Journal of Urology.
To investigate further, they conducted a prospective double-blind trial in 19 patients with MS and 38 with spinal cord injury who had urinary incontinence despite antimuscarinic treatment. They were randomized to receive an injection of onabotulinumtoxinA 300 U or placebo via cystoscopy at 30 intradetrusor sites, sparing the trigone.
At baseline, the mean number of urinary incontinence episodes was 5.6/day in the onabotulinumtoxinA group and 5.7/day in the placebo group. At week 6, the frequency had dropped to 1.3/day compared with 4.8/day in the two groups, respectively (p<0.0001).
The between-group difference diminished over time but was still significant at 36 weeks (2.37/day vs 4.21/day; p=0.0443), according to the report.
Significantly greater improvement from baseline in total incontinence-related quality-of-life scores was also seen in recipients of onabotulinumtoxinA vs placebo at weeks 6, 24 and 36, the team notes
At 36 weeks, all patients remaining in the study were offered open-label onabotulinumtoxinA. By week 48, urinary incontinence frequency was 1.56 episodes/day in the original onabotulinumtoxinA group and 1.86 in the former placebo group.
Urinary tract infection was the most common adverse event and it occurred in 16 patients in each group, the investigators report. Muscle weakness that was probably or possibly treatment related was reported by three patients in the onabotulinumtoxinA group.
OnabotulinumtoxinA intradetrusor injections, Dr. Herschorn and colleagues conclude, “are well tolerated and provide clinically beneficial improvements in adults with neurogenic detrusor overactivity and incontinence refractory to antimuscarinics. These improvements are seen up to 9 months after injection.”
Efficacy of Botulinum Toxin A Injection for Neurogenic Detrusor Overactivity and Urinary Incontinence: A Randomized, Double-Blind Trial
J Urol 2011;185:229-2235.