Characterization of Muscarinic Receptor Binding of Fesoterodine after Oral Administration in Rats

Hypothesis / aims of study Fesoterodine is a relatively novel antimuscarinic agent for the treatment of overactive bladder (OAB) [1]. When administered orally, fesoterodine is rapidly and extensively converted to its active metabolite, 5-hydroxymethyl tolterodine (5-HMT), which is also an active metabolite of tolterodine [2]. Our recent study with radioligand binding assay has shown that fesoterodine and 5HMT have the tissue selectivity for the urinary bladder over parotid gland in human [3]. Furthermore, the intravesical injection of 5-HMT in rats bound the pharmacologically relevant muscarinic receptors in the bladder urothelium and detrusor muscles. Under the clinical setting, oral administration of fesoterodine is useful to treat urinary dysfunction in patients with OAB. Therefore, the current study aimed to characterize the in vivo muscarinic receptor binding by measuring muscarinic receptor binding in several tissues of rats after the oral administration of fesoterodine, .