Long-term treatment with darifenacin for overactive bladder: results of a 2-year, open-label extension study

To examine, in a 2-year, non-comparative, open-label extension study, the safety, tolerability and efficacy of darifenacin controlled-release (CR) 7.5/15 mg once daily in patients with overactive bladder (OAB) who completed two 12-week randomized, double-blind, placebo-controlled 'feeder' studies.

Patients entering the extension received darifenacin 7.5 mg once daily for 2 weeks, after which a voluntary increase in dose to 15 mg was permitted. Thereafter, patients could adjust the dose (either 7.5 or 15 mg). Safety and tolerability were assessed from adverse events (AEs) and discontinuations. Efficacy was determined using various endpoints.

In all, 716 patients entered the extension (mean age 57.3 years; 85.1% women) and 475 (66.3%) completed it (1089.9 patient-years of exposure). Darifenacin was well tolerated with no significant safety concerns. The most commonly reported AEs were dry mouth and constipation (all-causality rates 23.3% and 20.9%, respectively), leading to discontinuation in 1.3% and 2.4% of patients, respectively. Constipation infrequently required intervention, and analysis of bowel-habit questionnaires revealed that the reporting of constipation was related to minor changes in bowel habit rather than true constipation. The efficacy of darifenacin was maintained, including significant improvements in the number of incontinence episodes/week (median change -84.4% at 2 years, P < 0.001 vs feeder-study baseline). After 2 years, > 40% of patients achieved a > or = 90% reduction in incontinence episodes/week.

In the first published 2-year, open-label study of a CR antimuscarinic agent, darifenacin 7.5/15 mg once daily had a favourable safety, tolerability and efficacy profile during the long-term treatment of OAB. As such, darifenacin represents a valuable therapeutic option for OAB.