Are 200 units of onabotulinumtoxin A sufficient for the suppression of neurogenic detrusor overactivity in individuals with established 300-unit botulinum toxin treatment? A retrospective cohort study.

[STUDY DESIGN] Retrospective cohort study.

[OBJECTIVES] To investigate the effects of 200-unit onabotulinumtoxin A detrusor injections on neurogenic detrusor overactivity (NDO) in patients who have previously been treated with 300-unit injections.

[SETTING] Tertiary urologic referral center in Switzerland.

[METHODS] The patient database was screened for patients with NDO as a result of chronic (≥ 12 months) spinal cord injury (SCI), who had been treated with 300- followed by 200-unit onabotulinumtoxin A detrusor injections. Patient characteristics, bladder management data and concurrent bladder medication as well as urodynamic data were collected. The percent changes in the urodynamic parameters from the 300- to the 200-unit treatment phase were calculated to test for non-inferiority of the 200-unit treatment.

[RESULTS] The data of 61 individuals with a mean age of 44 ± 15 years (range 18-73 years) and a mean 13.2 ± 9.5 years (range 2-43 years) since SCI were analyzed. The 200-unit treatment was not inferior regarding the urodynamic parameters compared to the 300-unit treatment. Furthermore, the proportion of patients with urinary incontinence was similar for both doses. There was no significant difference in the number of daily bladder evacuations (p = 0.13) or used incontinence pads (p = 0.43) between the two dosage phases. Moreover, there was no significant (p = 0.19) increase in the use of concurrent NDO medication (antimuscarinics or mirabegron) during the 200-unit treatment.

[CONCLUSIONS] The treatment of NDO with 200 units of onabotulinumtoxin A was not inferior to a 300-unit treatment regarding urodynamic parameters in patients with chronic SCI.