Study design, materials and methods
The Institutional Review Board and Ethics Committee of the hospital approved this study. Thirty-three OAB patients, who received intravesical 100 U onabotulinumtoxinA injection one month ago, were consecutively invited to a prospective, randomized, open-label study. They were randomly treated with solifenacin 5 mg QD in 11 patients (group 1), mirabegron 50 mg QD in 11 patients (group 2) and without medication in 11 patients (group 3). All enrolled patients were asked to complete 3-day voiding diary, the Overactive Bladder Symptom Score (OABSS), Urgency Severity Scale (USS) questionnaires, and uroflowmetry at baseline and 3-month. Videourodynamic study was performed before intravesical onabotulinumtoxinA injection. The primary endpoint was changes of Global Response Assessment (GRA) at 3-month. The secondary endpoint included changes of OABSS, USS and the parameters of voiding diary.
Results
The mean patients’ age was 73.9±9.8, 66.9±13.4 and 71.2±10.2 (p=0.35) in group 1,2 and 3 respectively. The baseline data were comparable in three groups. Compared with baseline, OABSS in group 1 and 2 was significantly decreased at 3-month but not in group 3. At 3-month, GRA in group 1 and 2 was significantly higher than group 3 (1.3 ± 0.7, 1.8 ± 1.0 versus 0.1 ± 1.6, p=0.04) (Table 1). The differences of OABSS, functional bladder capacity and nocturia episodes between baseline and 3-month in group 1 and 2 were also significantly different from those in group 3.
Interpretation of results
AUA/SUFA OAB guideline suggests that specialists may offer intradetrusor onabotulinumtoxinA (100 U) as third-line treatment in patients refractory to first- and second-line OAB treatments. This recommendation implies that no pharmacological therapy is needed after patients received intradetrusor onabotulinumtoxinA injection. However, our study showed patients resuming antimuscarinics or beta-3 agonist after intravesical onabotulinumtoxinA injection had better therapeutic effects than those without any medication. Due to the different mechanisms involving OAB pathophysiology, combined the second-line and third-line treatment might be another choice for refractory OAB patients.