An investigation of dose titration with darifenacin, an M3-selective receptor antagonist

To evaluate the efficacy, tolerability and safety of a flexible-dosing strategy with darifenacin, an M(3)-selective receptor antagonist, in patients with symptoms of overactive bladder (OAB).

In this multicentre double-blind 12-week study, 395 patients (aged 22-89 years; 84% female) with OAB symptoms for >6 months were randomized (2 : 1) and received once-daily treatment with darifenacin controlled-release tablets 7.5 mg (268 patients) or matching placebo (127). After 2 weeks of treatment, the efficacy, safety and tolerability were assessed and the dose increased to 15 mg once daily (pseudo-increase for placebo recipients) if additional efficacy was required by both the patient and physician. In the week before clinic visits (at 2 and 12 weeks), patients recorded incontinence episodes (primary efficacy endpoint) and several secondary efficacy variables in an electronic daily diary. Safety and tolerability were evaluated from withdrawal rates and adverse-event reports.

The treatment groups had comparable baseline characteristics. Similar proportions of darifenacin (59%) and placebo (68%) recipients increased the dose at 2 weeks; at 12 weeks patients on darifenacin (overall group) had a significantly greater reduction in the median number of incontinence episodes per week than had those on placebo, at - 8.2 (-62.9%) and - 6.0 (-48.1%), respectively (P = 0.035). There were also significant improvements in voiding frequency (P = 0.001), bladder capacity (volume voided; P = 0.036), frequency of urgency (P < 0.001), severity of urgency (P = 0.013) and number of significant leaks/week (i.e. incontinence episodes needing a change of clothing or pads, per week; P = 0.010) for darifenacin over placebo. Subset analysis suggested that some patients (those remaining on darifenacin 7.5 mg) were more sensitive to darifenacin than those who increased the dose, based on both efficacy and adverse events. Continued treatment with 7.5 mg for 'sensitive' patients, and an increased dose (to 15 mg) for remaining patients, resulted in comparable outcomes by 12 weeks. The most common treatment-related adverse events were mild-to-moderate dry mouth and constipation, which led to discontinuation in < 3.0% of darifenacin-treated patients and < 1.0% of the placebo group. Central nervous system and cardiovascular adverse events were comparable to those with placebo.

Darifenacin appears to be an effective, well-tolerated and flexible treatment for patients with OAB, allowing individualized dosing according to patient needs.