OnabotulinumtoxinA for OAB: Efficacy of the Reduced Injection-Site Protocol

The rationale for reducing the number of onabotulinumtoxinA (onabotA, Botox) injection sites in OAB treatment emerged from direct clinical observation. Steven Bernstein, MD, recognized early in his experience with the standard 20-site protocol that although patients generally tolerated the first half of the procedure well, discomfort increased considerably with the latter injections. After determining that the 20-site convention appeared to be based on an arbitrary starting point rather than established pharmacologic necessity, Bernstein began a methodical, stepwise reduction—first to 10 sites, then to 3, and ultimately to a single posterior bladder wall injection—in each case using 100 units of onabotA reconstituted in preservative-free saline. At each reduction, patient-reported efficacy appeared unchanged while procedural tolerability improved substantially.

The clinical outcomes of this reduced-site approach are described in a retrospective chart review of 90 patients treated with 1 to 3 injection sites. More than 93% of treatments were rated as producing a "great" response (defined as greater than 50% improvement), and an additional approximately 6% of patients reported improvement that fell below this threshold—yielding an overall response rate approaching 99%. Persistence through at least 3 treatment visits was observed in 61% of patients, a rate more than double the approximately 25% 1-year persistence figures reported in published data and insurance database analyses for onabotA administered via the standard protocol. The mean retreatment interval of 7.5 months was consistent with the broader literature for multi-site injection, demonstrating that reducing injection sites did not shorten the duration of therapeutic effect.¹

From a practical standpoint, the single-site protocol transformed the procedural experience in Bernstein's practice. Total door-to-door time for the office visit—including arrival, registration, preparation, and the injection itself—was timed at 13 minutes in one representative patient. No patients in his experience returned to a higher-site protocol after transitioning to fewer sites, and some patients who had progressed through the full evolution from 20 to 10 to 3 to 1 site reported progressive improvement in satisfaction.