Whilst various agents such as ^-adrenoceptor agonists, oestrogens and tricyclic antidepressants have all been used anecdotally in the past for the treatment of stress incontinence duloxetine is the first drug to be specifically developed and licensed for this indication.
Duloxetine is a potent and balanced serotonin (5-Hydroxytryptamine) and noradrenaline reuptake inhibitor (SNRI) which enhances urethral striated sphincter activity via a centrally mediated pathway . The efficacy and safety of duloxetine (20 mg, 40 mg, 80 mg) has been evaluated in a double-blind randomized parallel group placebo controlled phase II dose finding study in 48 centres in the United States involving 553 women with stress incontinence . Duloxetine was associated with significant and dose dependent decreases in incontinence episode frequency. Reductions were 41% for placebo and 54%, 59% and 64% for the 20,40 and 80 mg, groups respectively. Discontinuation rates were also dose dependent; 5% for placebo and 9%, 12% and 15% of 20 mg, 40 mg and 80 mg respectively, the most frequently reported adverse event being nausea.
A further global phase III study of 458 women has also recently been reported . There was a significant decrease in incontinence episode frequency and improvement in quality of life in those women taking duloxetine 40 mg od. when compared to placebo. Once again nausea was the most frequently reported adverse event occurring in 25.1% of women receiving duloxetine compared to a rate of 3.9% in those taking placebo. However, 60% of nausea resolved by 7 days and 86% by 1 month. These findings are supported by a further double-blind, placebo controlled study of 109 women awaiting surgery for stress incontinence . Overall there was a significant improvement in incontinence episode frequency and quality of life in those women taking duloxetine when compared to placebo. Furthermore, 20% of women who were awaiting continence surgery changed their mind whilst taking duloxetine. More recently the role of synergistic therapy with pelvic floor muscle training and duloxetine has been examined in a prospective study of 201 women with stress incontinence. Women were randomized to one of four treatment combinations; duloxetine 40 mg bd, PFMT, combination therapy or placebo. Overall duloxetine, with or without PFMT was found to be superior to placebo or PFMT alone whilst pad test results and quality of life analysis favoured combination therapy to single treatment .
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