Efficacy and duration of response to botulinum neurotoxin A (onabotulinumA) as a treatment for detrusor overactivity in women

Overactive bladder syndrome with urinary incontinence has a number of treatment options. The National Institute for Health and Care Excellence (NICE) in the UK, the American Urological Association (AUA) and the European Association of Urology (EAU) recommend intradetrusor botulinum neurotoxin A (onabotulinumA) injections in women with proven detrusor overactivity (DO) in whom conservative therapies have failed to improve symptoms. However, the effects of individual onabotulinumA treatments are of short duration and patients usually require further treatments. There is little evidence to inform long-term management strategies using onabotulinumA for DO. A retrospective review of patients receiving intradetrusor onabotulinumA injections for DO over a 7-year period was conducted. The primary outcome measures included patient's subjective reports of symptom change following injections (efficacy) and the duration of symptomatic relief following each treatment. The analysis included 136 patients. The mean time between patients receiving intradetrusor onabotulinumA and being added to the surgical waiting list for re-treatment varied between 8.5 and 10.4 months for the first five cycles of treatment with the longest time between the third and fourth cycles. This decreased to 5.5 and 5.25 (ANOVA p = 0.015) between the fifth and sixth cycles and between the sixth and seventh cycles of treatment, respectively. Only 19.9 % of patients continued treatment beyond this, with four patients receiving a seventh treatment. Our results suggest that in patients who respond to onabotulinumA treatment, the duration of response declines after the fifth treatment, suggesting a possible tolerance effect and a subsequent decline in efficacy.