Injection site number and outcomes of intradetrusor onabotulinumtoxinA for refractory overactive bladder syndrome: a randomized clinical trial

Introduction and hypothesis The optimal number of onabotulinumtoxinA injections for the treatment of refractory overactive bladder syndrome is unknown. Our primary objective was to determine whether 10-injections sites with 100 units of onabotulinumtoxinA each were associated with less pain than 20-injections sites. Methods In a single-blinded randomized trial, 100 units of onabotulinumtoxinA was administered, either as 10 × 1 ml or as 20 × 0.5 ml injections following the instillation of 30 ml of bupivacaine and 5 ml of NaHCO 3 solution for 15 min. The primary outcome was procedural pain, as measured on an 11-point Numerical Pain Rating Scale (NPRS) immediately following the procedure. A power calculation estimated that 16 subjects in each arm were needed to detect a mean difference of 1 with a standard deviation of 1, on the NPRS score between the two treatment groups, with α 0.05 and power 80%. To adjust for an estimated 20% dropout rate, the final sample size was planned for 20 patients per group. Results From October 2020 to November 2022, a total of 56 patients were approached and 40 were enrolled and randomized to two groups (21 in the 10-injections group and 19 in 20-injections group). The difference in the median pain score between the group was not statistically significant (4 [1.5–5] for 10 injections vs 3 [1–4] for 20 injections, p =0.823). Conclusion Patients’ perception of pain, efficacy, and adverse events did not significantly differ between patients receiving 10 and those receiving 20 injections of 100 units of onabotulinumtoxinA.