Purpose: Duloxetine, a selective serotonin and norepinephrine reuptake inhibitor, increases rhabdosphincter contractility via the stimulation of pudendal motor neuron alpha-1 adrenergic and 5-hydroxytryptamine-2 receptors. In this first phase 3 study we assessed the efficacy and safety of duloxetine in women with stress urinary incontinence (SUI).
Materials and methods: A total of 683 North American women 22 to 84 years old were enrolled in this double-blind, placebo controlled study. The case definition included a predominant symptom of SUI with a weekly incontinence episode frequency (IEF) of 7 or greater, the absence of predominant symptoms of urge incontinence, normal diurnal and nocturnal frequency, a bladder capacity of 400 ml or greater, and a positive cough stress test and stress pad test. After a 2-week placebo lead-in period subjects were randomly assigned to receive placebo (339) or 80 mg duloxetine daily (344) as 40 mg twice daily for 12 weeks. Primary outcome variables included IEF and an incontinence quality of life questionnaire. Van Elteren's test was used to analyze percent changes in IEF with a stratification variable of weekly baseline IEF (less than 14 and 14 or greater). ANCOVA was used to analyze incontinence quality of life scores.
Results: Mean baseline IEF was 18 weekly and 436 subjects (64%) had a baseline IEF of 14 or greater. There was a significant decrease in IEF with duloxetine compared with placebo (50% vs 27%, p <0.001) with comparably significant improvements in quality of life (11.0 vs 6.8, p <0.001). Of subjects on duloxetine 51% had a 50% to 100% decrease in IEF compared with 34% of those on placebo (p <0.001). These improvements with duloxetine were associated with a significant increases in the voiding interval compared with placebo (20 vs 2 minutes, p <0.001) and they were observed across the spectrum of incontinence severity. The discontinuation rate for adverse events was 4% for placebo and 24% for duloxetine (p <0.001) with nausea the most common reason for discontinuation (6.4%). Nausea, which was also the most common side effect, tended to be mild to moderate and transient, usually resolving after 1 week to 1 month. Of the 78 women who experienced treatment emergent nausea while taking duloxetine 58 (74%) completed the trial.
Conclusions: These phase 3 data are consistent with phase 2 data and they provide further evidence for the safety and efficacy of duloxetine as a pharmacological agent for the treatment of women with SUI.