Overview Flexibly adding-on Second Antimuscarinic Agent to the First Antimuscarinics for Refractory Overactive Bladder Syndrome Status: Completed Trial end date: 2017-02-01 Target enrollment: Participant gender: Summary To investigate if oxybutynin ER adding on antimuscarinics is more effective than mono-antimuscarinic treatment for patients with refractory OAB Phase: Phase 4 Details Lead Sponsor: Buddhist Tzu Chi General HospitalTreatments: Mandelic AcidsMuscarinic AntagonistsOxybutyninTolterodine Tartrate