Efficacy and Adherence of Flexibly Adding on a Second Antimuscarinic Agent for Patients with Refractory Overactive Bladder.

OBJECTIVES

To evaluate the efficacy and adverse events (AE) of flexibly adding on oxybutynin ER in patients with overactive bladder (OAB) refractory to monotherapy with the first muscarinic antagonist.

METHODS

A total of 129 patients with refractory OAB were enrolled in a prospective, open-label protocol. Inclusion criteria were persistent symptoms or partial response to 3-month behavioral therapy and an optimized dose of one antimuscarinic agent. At baseline, weeks 4, and 12 after the oxybutynin ER (5-15 mg once a day) was flexibly added, we assessed the OAB symptom indexes and Patient Perception of Bladder Condition, uroflowmetry, and post-void residual, along with the therapeutic effect, AE, and tolerability. Patients continuing combined antimuscarinic therapy were followed up to 12 months.

RESULTS

Compared with baseline, all OAB symptom indexes significantly decreased at all visits. A total of 32 (24.8%) and 25 (19.4%) patients reported successful therapeutic effect at weeks 4 and 12, respectively. Twenty-four (18.6%) and 44 (34.1%) patients discontinued therapy at weeks 4 and 12, respectively. Only 31 (24.0%) patients continued the combined medication for up to 12 months. Discontinuation of the combined medication was noted in 28 (21.7%) patients due to AE and in 70 (54.3%) due to lack of efficacy.

CONCLUSIONS

Flexibly adding on a second antimuscarinic agent is effective and safe for only some OAB patients dissatisfied with the first antimuscarinic treatment in the short-term period. The patients' dropout rate is high and the long-term efficacy of the combination of two antimuscarinic agents is limited.