Background
Overactive bladder (OAB) is a chronic condition requiring long-term treatment, commonly with antimuscarinics. Analysis of responder rates is a useful way of assessing the impact of drug treatment. Darifenacin has been associated with significantly higher responder rates than placebo in 12-week clinical trials in patients with OAB.
Objectives
To assess the effect of darifenacin on responder rates (proportion of patients achieving ≥50%, ≥70% or ≥90% reductions in urge incontinence episodes [IEs]/week) during a 2-year open-label study.
Methods
This multicenter, uncontrolled, open-label, 2-year extension study enrolled patients from two 12-week, double-blind feeder studies that assessed the efficacy, tolerability and safety of controlled-release darifenacin 3.75, 7.5 or 15mg once daily (qd) in patients with OAB symptoms for ≥6 months. All patients entering the extension received darifenacin 7.5mg qd for the first 2 weeks followed by 7.5 or 15mg qd as needed. Efficacy was assessed from diary records of patients remaining on-treatment, compared with feeder study baseline. Tolerability and safety were assessed from adverse events (AEs) and discontinuations.
Results
716 patients entered the extension (mean age 57.3 years; 85.1% female) and 475 (66.3%) completed. Darifenacin treatment significantly reduced the number of IEs/week (primary endpoint) at all study visits (Table). This was accompanied by high percentages of responders (patients achieving ≥50%, ≥70% or ≥90% reductions in IEs/week; Table) and approximately one-third of patients achieving normalisation of micturition frequency
(<8 voids/day; Table).

	Duration of darifenacin treatment in extension study (months)
	0a	3	6	12	24
Median (%) reduction in number of IEs/week	-8.5* (-63.2)	-10.5* (-80.1)	-11.0* (-83.9)	-11.0* (-85.7)	-11.0* (-84.4)
≥50% improvement in IEs/week (% patients)	62.4	74.4	77.3	78.8	77.2
≥70% improvement in IEs/week (% patients)	44.2	59.5	61.7	66.1	62.3
≥90% improvement in IEs/week (% patients)	22.3	36.6	41.8	43.0	43.8
Micturition frequency <8 voids/day (% patients)	33.2	29.8	33.6	34.9	34.9

^aDifferences from baseline to end of 12-week double-blind feeder studies in the extension study population; *p<0.001 using Wilcoxon signed rank test compared with baseline
Darifenacin was well tolerated. There were no new types of AEs in the extension compared with feeder studies. All-causality AEs were most commonly dry mouth (23.3%) and constipation (20.9%), which infrequently resulted in discontinuation (1.3% and 2.4%, respectively).
Conclusions
During 2-year open-label treatment, darifenacin was associated with high responder rates and substantial reductions in OAB symptoms, and was well tolerated. As such, darifenacin represents an important addition to current treatment options for OAB.

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