Objectives

To investigate whether adding an anticholinergic or beta-3 agonist can improve the therapeutic effect of intravesical onabotuliumtoxinA injection in patients with refractory overactive bladder (OAB).

Methods

Ninety OAB patients who received an intravesical 100-U onabotulinumtoxinA injection 1 month previously were consecutively invited into a prospective, randomized, open-label study. They were randomly adding on solifenacin 5 mg daily (QD) (30 patients), mirabegron 50 mg QD (31 patients), or no medication (29 patients, control). All enrolled patients completed a 3-day voiding diary, Overactive Bladder Symptom Score (OABSS) and Urgency Severity Scale (USS) questionnaires, Global Response Assessment (GRA) scale, and uroflowmetry at baseline (1 month after intravesical onabotulinumtoxinA injection) and 3-, 6-, 9-, and 12-month follow-up. The primary end point was the effective therapeutic outcome defined as no OAB wet during the 12-month period. The secondary end point included changes of GRA, OABSS, and the parameters of the voiding diary at 3 months.

Results

The baseline data were comparable among the three groups. The percentage of OAB wet in the mirabegron-added-on group was significantly less than that in the solifenacin-added-on and onabotulinumtoxinA-only groups at four different time points (P = .02). At 3 months, the changes of GRA, OABSS, USS, urge urinary incontinence, frequency, nocturia episodes, and functional bladder capacity in the mirabegron-added-on group were significantly greater than those in the other groups. No serious adverse events were reported.

Conclusions

Adding mirabegron could increase the therapeutic effects, mainly on OAB symptoms and GRA scale, after intravesical onabotulinumtoxinA injection in refractory OAB patients.