Fesoterodine fumarate (Toviaz) is the fumarate salt form of fesoterodine, a competitive muscarinic receptor antagonist with muscle relaxant and urinary antispasmodic properties. Fesoterodine is rapidly hydrolyzed in vivo into its active metabolite 5-hydroxymethyl tolterodine, which binds and inhibits muscarinic receptors on the bladder detrusor muscle, thereby preventing bladder contractions or spasms caused by acetylcholine.

Fesoterodine is rapidly and extensively converted to 5-HMT, such that the pharmacologic activity appears to be primarily attributable to 5-HMT. [1] Fesoterodine is a competitive antagonist of cholinergic agonist-stimulated responses in human M1-M5 cell lines and has a similar potency and selectivity profile to the radioligand-binding studies. Fesoterodine causes a rightward shift of the concentration-response curve for carbachol with no depression of the maximum in rat bladder strips, and concentration-dependently reduces contractions induced by electrical field stimulation (EFS). [2] Fesoterodine is hydrolyzed by nonspecific esterases to 5-hydroxmethyl tolterodine (5-HMT), which is the active metabolite and is responsible for all its antimuscarinic activity. [3]