Amitriptyline is a tricyclic antidepressant. If taken with Ditropan (an anticholinergic), causes abdominal distension and constipation. Because of a pharmacodynamic interaction: tricyclics inhibit the cholinergic system also via diff mech. Also: tricyclics affect membrane pump that moves nts and antihypertensive drugs into intracellular storage sites. So may alter anti-HTN treatments. Also: metabolized via CYP 2D6, inhibited by Prozac.