THE VASOCONSTRICTOR AND PRESSOR EFFECTS OF NYLIDRIN, MEDIATED BY ITS ALPHA-ADRENERGIC ACTION, MAY BE ENHANCED BY THE CONCOMITANT ADMINISTRATION OF DRUGS WITH SIMILAR EFFECTS, SUCH AS ERGOT ALKALOIDS OR OXYTOCIN. SEVERE HYPERTENSION MAY ALSO DEVELOP IF NYLIDRIN IS GIVEN WITH A BETA BLOCKER SINCE THE BETA BLOCKER OPPOSES THE BETA ADRENERGIC ACTION OF NYLIDRIN. ADMINISTRATION OF NYLIDRIN OR NORADRENALINE WITH TRICYCLIC ANTIDEPRESSANTS CARRIES A RISK OF INDUCING HYPERTENSION AND ARRHYTHMIAS. THE ACTION OF NYLIDRIN OR NORADRENALINE MAY BE ONLY SLIGHTLY ENHANCED BY AN MAOIS. THE HYPOKALAEMIC EFFECT OF NYLIDRIN MAY BE POTENTIATED BY OTHER DRUGS THAT CAUSE POTASSIUM LOSS, INCLUDING CORTICOSTEROIDS, POTASSIUM-DEPLETING DIURETICS.