Tolerability of 5 mg Solifenacin Once Daily Versus 5 mg Oxybutynin Immediate Release 3 Times Daily: Results of the VECTOR Trial

Abstract

Although antimuscarinic treatment is indicated for overactive bladder, many patients discontinue it because of dry mouth. Of available antimuscarinics oxybutynin is associated with the highest dry mouth rate. We compared the safety and tolerability of 5 mg solifenacin vs 15 mg oxybutynin immediate release. At 12 Canadian centers a total of 132 patients with overactive bladder symptoms (greater than 1 urgency episode per 24 hours, and 8 or greater micturitions per 24 hours) were randomized to 5 mg solifenacin once daily or 5 mg oxybutynin 3 times daily for 8 weeks. The primary end point was the incidence and severity of dry mouth reported after direct questioning. Efficacy end points (3-day diary documented changes in urgency, frequency, incontinence, nocturia and voided volume), and changes on the Patient Perception of Bladder Condition scale and the Overactive Bladder Questionnaire were evaluated secondarily. Of patients on solifenacin vs oxybutynin immediate release 35% vs 83% reported dry mouth (p <0.0001). Of patients reporting dry mouth severity was graded moderate by 13% and 42% of those on solifenacin and oxybutynin immediate release, and severe by 13% and 28%, respectively (p = 0.001). Patients in each group showed improvements in efficacy end points, and Patient Perception of Bladder Condition scale and Overactive Bladder Questionnaire scores from baseline to treatment end. Significantly fewer patients on 5 mg solifenacin once daily reported dry mouth vs those receiving 5 mg oxybutynin immediate release 3 times daily. Significantly fewer patients on solifenacin reported moderate/severe dry mouth. Significantly fewer patients on solifenacin withdrew from study due to dry mouth and there were significantly fewer overall adverse events. Solifenacin and oxybutynin immediate release were efficacious in decreasing efficacy end points, and improved Patient Perception of Bladder Condition scale and Overactive Bladder Questionnaire results from baseline to treatment end.