THE HYPOTENSIVE EFFECTS MAY ALSO BE ANTAGONISED BY TRICYCLIC ANTIDEPRESSANTS, MAOIS AND PHENOTHIAZINE & RELATED ANTIPSYCHOTICS. ORAL CONTRACEPTIVES MAY REDUCE THE HYPOTENSIVE ACTION OF GUANETHIDINE. CONCURRENT ADMINISTRATION WITH DIGITALIS MAY CAUSE EXCESSIVE BRADYCARDIA. THE HYPOTENSIVE EFFECTS OF IT MAY BE ENHANCED BY THIAZIDE DIURETICS, OTHER ANTIHYPERTENSIVES AND LEVODOPA. ALCOHOL MAY CAUSE ORTHOSTATIC HYPOTENSION IN PATIENTS TAKING GUANETHIDINE. PATIENTS TAKING GUANETHIDINE MAY SHOW INCREASED SENSITIVITY TO THE ACTION OF ADRENALINE, AMPHETAMINE AND OTHER SYMPATHOMIMETICS RESULTING IN EXAGGERAT-
ED PRESSOR EFFECTS.