Darifenacin HBr (UK-88525) is a selective M3 muscarinic receptor antagonist with pKi of 8.9.
Darifenacin exerts non-parallel rightward displacement of the agonist curve and also significant depression of the maximum response (+)-cis-Dioxolane produced concentration-dependent contraction of the isolated bladder of rat. [1] Darifenacin produces a concentration dependent increase in R123 (P-gp probe) accumulation in MDCK cells. Darifenacin stimulates ATPase activity in P-gp membrane in a clear concentration dependent response manner with an estimated ED50 value of 1.6??M. Darifenacin (100 nM) shows a significantly greater permeability for darifenacin in the basolateral to apical direction resulting in an efflux ratio in BBMEC monolayers of approximately 2.6. [2]
Darifenacin produces dose-dependent inhibition of amplitude of volume-induced bladder contractions(VIBCAMP), producing 35% inhibition at dose of 283.3 nmol/kg and maximal inhibition of approximately 50–55%. [1] Darifenacin (0.1 mg/kg i.v.) reduces bladder afferent activity in both Aδ and C fibers in female Sprague-Dawley rats, the decrease in afferent spikes in C fibers may be more pronounced than that in Aδ fibers. [3] Darifenacin (7.5 mg and 15 mg, daily) reduces the number of incontinence episodes per week from baseline by 67.7% and 72.8% respectively compared with 55.9% with placebo in patients with overactive bladder (OAB). Darifenacin (7.5 mg and 15 mg, daily) also shows significantly superior to placebo for improvements in micturition frequency, bladder capacity, frequency of urgency, severity of urgency and number of incontinence episodes leading to a change in clothing or pads in patients with overactive bladder (OAB). [4]
[1] Hegde SS, et al. Br J Pharmacol, 1997, 120(8), 1409-1418. [2] Miller DW, et al. Neurourol Urodyn, 2011, 30(8), 1633-1638. [3] Iijima K, et al. Eur Urol, 2007, 52(3), 842-847.