Botulinum Toxin A Injection Treatment in Chronic Pelvic Pain Patients: Open-Label Extension Study and 12-Month Follow-Up After RCT

INTRODUCTION AND HYPOTHESIS: A recent randomized controlled trial (RCT) demonstrated that while botulinum toxin A (BTA) significantly reduced pelvic floor muscle activity compared to placebo, it did not provide greater pain relief than placebo at 26 weeks. This study evaluates the effect of BTA combined with pelvic floor muscle therapy (PFMT) in placebo nonresponders and investigates long-term outcomes of BTA versus placebo in women with CPP. METHODS: This open-label extension (n = 27) and long-term follow-up study (initial responders n = 18 and BTA nonresponders n = 31) was conducted in the Netherlands as part of an RCT. Placebo nonresponders received 100 units of BTA injected into the pelvic floor muscles during the open-label extension study. PFMT was provided at 4, 8, 12, and 26 weeks post-injection, with validated questionnaires completed at each time point and at 12 months follow-up. Primary outcomes were average pain score (0-10) and Patient Global Impression of Improvement. Secondary outcomes included quality-of-life questionnaires and pelvic floor muscle function. Data were analysed using mixed models. RESULTS: No serious safety concerns were observed. In placebo nonresponders, pain improved after BTA injections, with sustained improvement at 12 months. Among initial responders in the RCT, pain improvement persisted up to 12 months after both BTA and placebo treatment, with no significant difference between treatment groups. CONCLUSION: Our findings support the safety of BTA treatment for women with CPP. When effective, both BTA and placebo injections combined with PFMT were associated with sustained benefits for up to 1 year, although these exploratory findings should be interpreted with caution.