Increased anticholinergic effect of tetra- & TCAs, antihistamine, antipsychotic, quinidine, amantadine, disopyramide, other anticholinergics (eg, tiotropium, ipratropium, atropine-like compd). Co-administration w/ dopamine antagonists eg, metoclopramide deprive effects of each other in GIT. Increased tachycardia effects of β-adrenergic drugs.