Darifenacin-d4 is intended for use as an internal standard for the quantification of darifenacin by GC- or LC-MS. Darifenacin is an antagonist of M3 muscarinic acetylcholine receptors (mAChRs; Ki = 0.76 nM).1 It is selective for M3 over M1, M2, M4, and M5 mAChRs (Kis = 7.08, 44.67, 45.71, and 9.33 nM, respectively). Darifenacin selectively inhibits contractions in isolated guinea pig ileum, bladder, and trachea (pA2s = 9.44, 8.66, and 8.7, respectively), tissues that endogenously express high levels of M3 mAChRs, over isolated rabbit vas deferens and isolated guinea pig atria (pA2s = 7.9 and 7.48, respectively), which endogenously express M1 and M2 mAChRs, respectively. It inhibits micturition pressure (ED50 = 0.089 mg/kg, i.v.), as well as micturition interval and volume in rats. Formulations containing darifenacin have been used in the treatment of overactive bladder.
1.Wallis, R.M., and Napier, C.M.Muscarinic antagonists in development for disorders of smooth muscle functionLife Sci.64(6-7)395-401(1999)