Aim: Fesoterodine is one of the most novel antimuscarinic agents approved for the treatment of overactive biadder.Fesoterodine is rapidly and extensively converted by ubiquitous nonspecific esterase to its active metabolite, 5-hydroxymethyl toherodine (5-HMT), which is also active metabolite of tolterodine.Both agents may contribute sigrificantly to the pharmacological effects in the bladder after oral administration of fesoterodine.