Enhanced anticholinergic effects of TCAs, tetracyclic antidepressants, antihistamines, antipsychotics, quinidine, amantadine, disopyramide & other anticholinergics (eg, tiotropium, ipratropium, atropine-like compd). Concomitant use w/ dopamine antagonists (eg, metoclopramide) will counteract the effect of both drugs on GIT. Enhanced tachycardiac effects of β-adrenergic agents.