Comparison of the Therapeutic Effects of Urethral Injections of 50 and 100 Units of Botulinum A Toxin for Voiding Dysfunction

ObjectivesUrethral injection of botulinum A toxin (BoNT-A) has therapeutic effects on voiding dysfunction. However, the optimal dose remains to be determined. This study compared the therapeutic results of urethral injections of 50 U and 100 U of BoNT-A.Materials and MethodsSixty-six patients with voiding dysfunction were randomly treated with urethral injections of 50 U (n = 33) or 100 U (n = 33) of BoNT-A (BOTOX). The therapeutic results and changes in the urody-namic parameters were compared between these two groups of patients.ResultsThe overall therapeutic results in the 100 U and 50 U injection groups were excellent in 20 (60.6%) and 23 (69.7%) patients, improved in 10 (30.3%) and 5 (15.2%), and failed in 3 (9%) and 5 (15.2%), respectively. Significant reductions in the voiding pressure, postvoid residual volume, and maximal urethral closure pressure as well as improvement in the quality of life index and increases in the maximum flow rate were noted after treatment in both groups. No significant between-group differences were noted in the net changes of the urodynamic parameters after treatment. Excellent results were noted in 68% and 33% of patients with detrusor underactivity, and in 71.4% and 70.8% of patients with hyperactive urethral sphincter who received injections of 50 U and 100 U, respectively. The mean durations of therapeutic effect were 6.4 ± 3.6 months and 8.4 ± 3.4 months in the 50 U and 100 U groups, respectively (p = 0.022).ConclusionUrethral injection of 50 U of BOTOX is as effective as 100 U in the treatment of voiding dysfunction of any etiology, but the duration of therapeutic effect was significantly shorter in the group who received 50 U.