Abstract
Intravesical onabotulinumtoxinA (BoNT-A) injection can relieve symptoms of interstitial cystitis/bladder pain syndrome (IC/BPS), but lacks sustainability. Repeated injections have been shown to provide a superior outcome to a single injection, but data on long-term efficacy and safety is limited. In this prospective study, we enrolled patients with refractory IC/BPS, and treated them with 100 U of BoNT-A injection plus hydrodistention followed by repeated injections every six months for up to two years or until the patient wished to discontinue. A "top-up" dose was offered after the fourth injection. Of these 104 participants, 56.7% completed four BoNT-A injections and 34% voluntarily received the fifth injection due to exacerbated IC symptoms. With a follow-up period of up to 79 months, O'Leary-Sant symptom and problem indexes (ICSI, ICPI, OSS), pain visual analogue scale (VAS) functional bladder capacity, frequency episodes, and global response assessment (GRA) all showed significant improvement (p < 0.0001). Those who received repeated injections had a better success rate during the long-term follow-up period. The incidence of adverse events did not rise with the increasing number of BoNT-A injections. A higher pre-treatment ICSI and ICPI score was predictive for successful response to repeated intravesical BoNT-A injections plus hydrodistention.