ANTACIDS DECREASES ABSORPTION, ADITIVE ANTIMUSCARINIC ACTIVITY WITH TRICYCLIC ANTIDIPRESSANTS, ORTHOSTATIC HYPOTENSION WITH MAOIS. REVERSE ANTIHYPERTENSIVE EFFECT OF GAUNETHIDINE, METHYLDOPA AND CLONIDINE. ADDITIVE CNS DEPRESSION WITH OTHER CNS DEPRESSANTS (SEDATIVE, HYPNOTICS, ANTIHISTAMINES, OPIATES AND ALCOHOL).