ADDITIVE DEPRESSANT EFFECT WITH SEDATIVES, HYPNOTICS, ANTIHISTAMINES, OPIATES AND ALCOHOL. POTENTIATION OF ANTICHOLINERGIC EFFECTS OF ANTIPARKINSON AGENTS. ADDITIVE ORTHOSTATIC HYPOTENSIVE EFFECT WITH MAOI. REVERSES ANTIHYPERTENSIVE EFFECT OF GAUENTHIDINE, METHYLDOPA AND CLONIDINE. INCREASED RISK OF ARRHYTHMIAS WITH ANTIMALARIALS, TRICYCLIC ANTIDEPRESSANTS, ANTIHISTIMINES AND CISAPRIDE.