Wein AJ et al. (2007) Achieving continence with antimuscarinic therapy for overactive bladder: effects of baseline incontinence severity and bladder diary duration. BJU Int 99: 360–363

Urge urinary incontinence (UUI) is a symptom of overactive bladder. Antimuscarinic agents are the first-line therapy for patients with overactive bladder, and the continence rate (the percentage of patients who record no urinary incontinence episodes during a diary period) is often used as a measure of treatment success. Wein and colleagues examined whether continence rates truly reflect the efficacy of antimuscarinic treatment.

The authors performed a post-hoc analysis of data from a 12-week, multinational, randomized, double-blind trial. Participants (mean age 61 years) with urinary frequency (≥8 voids per 24 h) and UUI (≥5 episodes per week) were randomly allocated to receive 4 mg extended-release tolterodine or placebo once daily. The authors conducted intention-to-treat and per-protocol analyses of weekly UUI episodes at baseline and week 12. Patients kept voiding diaries, and these data were analyzed for the 3, 5, and 7-day periods immediately preceding both assessments.

In the intention-to-treat and per-protocol analyses 503 and 374 patients received placebo and 502 and 398 patients received tolterodine, respectively. The overall continence rate decreased with increasing number of UUI episodes at baseline and increased diary duration. Higher continence rates were observed in the per-protocol analysis than in the intention-to-treat analysis.

The authors conclude that diary duration, baseline frequency of UUI and the patient population analyzed all influence continence rates—which, therefore, might not be a valid measure of efficacy in trials of antimuscarinic drugs, unless standard methodology and a placebo-controlled design are used.