NEW YORK (Reuters Health) – Intravesical botulinum toxin improves overactive bladder symptoms, but with a significant risk of urinary retention, according to a meta-analysis reported April 19th in The Journal of Urology.

Treatment reduced voiding frequency and pad use, and it increased quality of life – but it also increased the odds of post-void residual urine nearly nine-fold compared to placebo.

Off-label use of botulinum toxin for refractory overactive bladder has been reported in numerous case series and observational studies, and now Dr. Jennifer T. Anger from University of California, Los Angeles and colleagues have synthesized the results of 23 studies (3 randomized controlled trials and 20 observational/case series) involving 951 patients.

The subjects ranged in age from 44 to 81years; they all had refractory idiopathic overactive bladder. Botulinum toxin was injected transurethrally in all cases, but the doses, concentrations, and locations in the bladder varied from study to study. Follow-up intervals were generally 6 to 9 months (range, 1 month to 6 years). Unfortunately, outcomes were not recorded in a consistent way. Seven studies involved only women.

Pooled analysis of the 3 randomized placebo-controlled trials (with 99 patients) showed that patients treated with botulinum toxin had 3.88 fewer incontinence episodes daily compared with patients treated with placebo.

Quality of life in these 3 trials (assessed with standard instruments) improved with a pooled effect size of 0.6, which translates into a 15 point decrease on the Urogenital Distress Inventory-6 short form (maximum score, 100 points).

Eleven case series included 749 patients (70% of the total in all the case series). In 10 of the 11, treatment produced a significant decrease in the mean number of daily voids from baseline, with an absolute reduction in voiding frequency of 1.2 to 7.0 (a decrease of 12% to 50%).

In 7 case studies, the average number of pads used daily fell from a range of 3.9 to 5.0 at baseline to a range of 0 to 3.0 at follow-up.

Like the controlled trials, the case series showed significant improvements in quality of life after botulinum toxin injection.

But the overall pooled analysis showed that the botulinum toxin group had an 8.55-fold increase in the odds of urinary retention compared with the placebo group. Patients with post-void retention of 200 cc or more received clean intermittent catheterization. The researchers report that rates of postoperative clean intermittent catheterization ranged from 0% to 41% and lasted up to 6 months. One study was terminated early because the rate of post-void retention was so high.

“Since retention is not a rare consequence, patients should be willing to perform clean intermittent catheterization or maintain an indwelling catheter before undergoing intravesical (botulinum therapy),” the researchers write.

They add, “Given these estimates of benefits and harms, botulinum toxin deserves more study as a potential treatment option for those who do not desire, are not candidates for, or experience failure of sacral neuromodulation, and who understand and are willing to accept the potential for an increased risk of urinary retention.”

But “clearly,” they conclude, “more level I data from randomized controlled trials are needed to guide management.”

Reference:

J Urol 2010;183:2258-2264.