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개요Fesoterodine, launched for the treatment of OAB, is an orally active pro-drug that is converted in vivo to its active metabolite 5-HMT through hydrolysis by non-specific esterases. 5-HMT is also an active metabolite of tolterodine (Detrol), which has been marketed for the treatment of OAB since 1998. 5-HMT is a potent muscarinic antagonist, with essentially equivalent affinity for M1, M2, M3, M4, and M5 receptors (Ki＝0.32, 0.63, 1.26, 2, and 0.63 nM, respectively). The binding of 5-HMT is stereoselective; the corresponding S-enantiomer has at least 100 times lower binding affinity for all five receptors. Fesoterodine is supplied as its fumarate salt in an extended release tablet form. The recommended starting dose is 4 mg once daily. On the basis of individual response and tolerability, the dose may be increased to 8 mg once daily. Following oral administration, fesoterodine is not detected in the peripheral blood, thereby indicating a rapid and complete bioconversion to 5-HMT. Bioavailability of 5-HMT is about 52%. After single- or multiple-dose oral administration of fesoterodine in doses from 4 to 28 mg, plasma concentrations of 5-HMT are proportional to the dose. Maximum plasma levels are reached after approximately 5 h. No accumulation occurs after multiple-dose administration. 5-HMT is further metabolized in the liver through oxidation of the hydroxymethyl group and oxidative cleavage of N-alkyl groups mediated by CYP2D6 and CYP3A4. 5-HMT and its metabolites are primarily eliminated through renal excretion.The most common adverse events associated with fesoterodine include dry mouth, constipation, and dyspepsia. Fesoterodine is contraindicated in patients with urinary retention, gastric retention, or uncontrolled narrow-angle glaucoma.