Botulinum toxin type A and neurogenic urinary incontinence: sometimes beneficial, if used safely

Patients with spinal cord injury or multiple sclerosis are often troubled by urinary incontinence due to detrusor (bladder muscle) overactivity. For patients who use intermittent self-catheterisation, empirical treatments for urinary incontinence include: optimisation of catheterisation; anticholinergic drugs; and, in some cases, surgery. The indications of botulinum toxin type A (Botox, Allergan) in France have been extended to cover this situation when anticholinergic drugs are ineffective. Clinical evaluation is based on 2 double-blind randomised placebo-controlled trials in a total of 691 patients who had an average of about 32 episodes of urinary incontinence per week.These trials tested the efficacy of a total dose of 300 or 200 units of botulinum toxin type A. Six weeks after toxin injection into the bladder wall, about 40% of patients had no further episodes of incontinence, compared to 10% of patients who received placebo injections. The median duration of the effect was 42 to 48 weeks after a dose of 200 units (13 to 18 weeks with placebo). It remains to be shown whether botulinum toxin has any long-term benefits in terms of complications (hospitalisation, urinary tract infections, etc.). The main adverse effects of botulinum toxin injections in these patients were urinary tract infections (51% versus 36% with placebo) and urinary retention (18% versus 3%). Both differences were statistically significant, and these events were most frequent in patients who had not yet started to self-catheterise (mainly patients with multiple sclerosis). Cases of autonomic hyperreflexia with favourable outcome were also reported. Botulinum toxin type A has been marketed since the 1990s in other indications. It has been linked to life-threatening adverse effects on tissues at a distance from the injection site, following its diffusion throughout the body. Muscle weakness, asthenia and constipation have been reported. A negative effect on the course of multiple sclerosis cannot be ruled out. Botulinum toxin type A injection into the bladder wall necessitates cystoscopy, an invasive and very inconvenient procedure that requires antibiotic prophylaxis and sometimes anaesthesia. Cystoscopy also carries a risk of punctures and tears, etc. In practice, existing treatment options are unsatisfactory for patients in whom anticholinergic drugs fail to control urinary incontinence due to neurogenic detrusor overactivity. Botulinum toxin type A temporarily prevents incontinence for a few months in about one-third of patients, but it is difficult to administer. In experienced hands, it may be beneficial for patients with very troublesome incontinence who self-catheterise.