Darifenacin has a low affinity for muscarinic M1 receptors in dog saphenous vein confirming its M3 selectivity

Darifenacin for the treatment of overactive bladder

Overactive bladder is a debilitating disorder affecting 16.5% of adults and increasing in prevalence with age. Symptoms, including urgency, urge incontinence and frequency can result from detrusor overactivity with contraction of the bladder mediated primarily by activation of muscarinic M(3) receptors. Antimuscarinic agents are therefore an important approach to treating overactive bladder, but a lack of M(3) receptor subtype selectivity with these agents can generate a range of side effects that limits their effectiveness. This review describes an alternative approach to treating overactive bladder using the selective muscarinic M(3) receptor antagonist darifenacin. The M(3) receptor selectivity of darifenacin improves the symptoms of overactive bladder while reducing the potential for deleterious effects of non-M(3) muscarinic receptor antagonism in the brain or heart. The pharmacology and pharmacokinetics of darifenacin are summarized, and the its clinical efficacy and demonstrated safety profile are described.

Darifenacin: a novel M3muscarinic selective receptor antagonist for the treatment of overactive bladder

Darifenacin is a novel M3 muscarinic selective receptor antagonist for once-daily treatment of overactive bladder (OAB), a highly prevalent, chronic and debilitating disease defined by urinary urgency with or without urge incontinence, usually with increased frequency of micturition and nocturia. In vitro, darifenacin is a potent and specific muscarinic receptor antagonist with </= 59-fold higher selectivity for muscarinic M3 receptors relative to other muscarinic receptor subtypes. This profile may, therefore, confer clinical efficacy in the treatment of OAB, with a lower propensity for adverse effects and safety issues related to blockade of other muscarinic receptor subtypes. Indeed, consistent with its low relative affinity for M1 and M2 receptors, no effects on cognitive function and heart-rate variability, respectively, have been observed with darifenacin. Subsequent large-scale clinical trials have confirmed that darifenacin (at doses of 7.5 and 15 mg/day) results in central nervous system and cardiac adverse events comparable to placebo, and provides early and meaningful improvement across a range of OAB symptoms including incontinence episodes, urgency and urinary frequency. On the basis of such findings, darifenacin would appear to meet the current need for an effective OAB pharmacotherapy that is efficacious, well-tolerated and, more importantly, minimises the risk of safety-related adverse effects.

Darifenacin: in the treatment of overactive bladder

Darifenacin is a selective muscarinic M3-receptor antagonist that has been evaluated in clinical trials in patients with overactive bladder syndrome (OAB) using a controlled-release formulation. In multicentre, randomised, double-blind trials in patients with OAB, darifenacin 7.5 or 15 mg once daily for 12 weeks significantly reduced the frequency of urinary incontinence, frequency of micturition and frequency and severity of urgency versus placebo. A significant difference from placebo was apparent 2 weeks after starting treatment. At a dosage of 30 mg once daily, darifenacin significantly prolonged warning time compared with placebo. Darifenacin 15 mg once daily for 2 weeks was as effective as oxybutynin 5 mg three times daily at reducing the frequency of urinary incontinence and frequency and severity of urgency in patients with OAB. Darifenacin was generally well tolerated in clinical trials. The most common adverse events were dry mouth and constipation. CNS tolerability appeared to be similar to that of placebo. Darifenacin had no adverse effect on cognitive function in healthy elderly volunteers.