Does Injection Number Matter? A Systematic Review and Meta-Analysis of Bladder Botox for Overactive Bladder

INTRODUCTION: Intravesical onabotulinumtoxin A (BoNT-A) is an established treatment for overactive bladder (OAB). Although the standard regimen involves 20 injections, evidence suggests fewer injections may achieve comparable outcomes. OBJECTIVE: To systematically review the literature comparing periprocedural outcomes of the standard 20-injection BoNT-A regimen with reduced-injection techniques for idiopathic OAB. METHODS: PubMed, Scopus, and Embase were searched from their inception through 4/8/2025 using pre-identified search terms. Our population included women undergoing in-office bladder BoNT-A (100 units) for treatment of idiopathic OAB. Our intervention was a reduced number of BoNT-A injections, and our comparator was the standard 20-injection regimen. Outcomes included efficacy, pain at time of injection, urinary tract infections, and retention. Abstracts were doubly screened, full-text articles were doubly screened, and accepted articles were doubly extracted. Quality of studies was assessed using GRADE criteria. In single-arm studies using either reduced injections or standard injections, random-effects meta-analysis of pooled proportions was used to assess periprocedural outcomes. In comparative studies investigating reduced and standard injection protocols, random-effect meta-analysis of pooled risk ratios was used. RESULTS: 3,645 abstracts were screened, 40 full-text papers were assessed, leaving 16 studies (8 RCTs and 3 retrospective cohort studies, 4 prospective cohort studies, and 1 case series) with 1,393 patients. Most outcomes were supported by moderate to high quality evidence (8 Grade A, 7 Grade B, and 1 Grade C). The average follow-up was 8.7±4.3 weeks. The average number of injection sites in the reduced-injection group was 7.3±2.8. At follow-up, on meta-analysis, we found no difference in efficacy between the reduced-injection group and the standard 20-injection group (79% (95% CI 0.66–0.89); P=0.16) (Figure 1). There was no difference in the mean difference in pain scores between the reduced-injection group and the standard-injection group (3 studies, 177 subjects) with mean difference 0 (95% CI −0.36–0.34); P=0.23), with low heterogeneity (I2=29%) (Figure 2). For adverse events, there was no difference between groups in % of patients with a urinary tract infection (UTI) (16% (95% CI 0.12–0.21); P=0.427) or urinary retention (4% (95% CI 0.02–0.06); P=0.591). CONCLUSIONS: Reduced-injection regimens of BoNT-A for treatment of OAB achieve comparable efficacy to the standard 20-injection protocol with no difference in adverse events. Comparable outcomes with fewer injections highlight the potential to simplify bladder BoNT-A delivery while maintaining efficacy and safety.Figure 1Figure 2Table 1