 Overactive bladder, OAP, is characterized by the presence of bothersome urinary symptoms. The three-adrenergic agonist merabrine is a moderate cytochrome P for 50, CYP, 2D6 inhibitor. Co-administration of drugs with CYP 2D6 substrates may lead to adverse drug effects. This article was authored by Mary E. Richie, Jingjun Wang, Jessica C. Young, and others.