ANAESTHETICS THAT CAUSE MYOCARDIAL DEPRESSION, SUCH AS CYCLOPROPANE AND TRICHLOROETHYLENE. CONCOMITANT USE OF LEVOBUNOLOL WITH ANTIARRHYTHMIC DRUGS AFFECTING CARDIAC CONDUCTION CAN PRECIPITATE BRADYCARDIA AND HEART BLOCK. CONCURRENT ADMINISTRATION OF CALCIUM-CHANNEL BLOCKERS AND BETA BLOCKERS HAS RESULTED IN HYPOTENSION, BRADYCARDIA, CONDUCTION DEFECTS, AND CARDIAC FAILURE. THE ANTIHYPERTENSIVE EFFECT OF BETA BLOCKERS MAY BE IMPAIRED BY CONCURRENT ADMINISTRATION OF SOME NSAIDS. ORAL BETA BLOCKERS, CONCOMITTANT THERAPY WITH LEVOBUNOLOL AND ENINEPHRINE, CATECHOLAMINE - DEPLETING DRUGS.