An active metabolite of tolterodine and fesoterodine; inhibits M1-5 muscarinic receptors (Kis = 2.3, 2, 2.5, 2.8, and 2.9 nM, respectively); selectively inhibits acetylcholine-induced bladder contraction over electrically induced salivation in anesthetized cats (IC50s = 15 and 40 nmol/kg, respectively)