Effect on AV conduction time may be potentiated & -ve inotropic effect be increased w/ class I antiarrhythmics (quinidine, hydroquinidine, cibenzoline, flecainide, disopyramide, lidocaine, mexiletine, propafenone). -ve influence on contractility & AV conduction w/ Ca channel antagonists of verapamil/diltiazem type. May worsen heart failure by a decrease in central sympathetic tonus w/ centrally-acting antihypertensives (clonidine, guanfacine, moxonidine, methyldopa, rilmenidine). Effect on AV conduction time may be potentiated w/ amiodarone. May attenuate reflex tachycardia & increase risk of hypotension w/ volatile halogenated anaesth. May mask certain symptoms of hypoglycemia (palpitations, tachycardia) w/ insulin & oral antidiabetic drugs. Increased fall in BP w/ baclofen & amifostine. Concomitant use w/ digitalis glycosides, Ca antagonists of the dihydropyridine type (amlodipine, felodipine, lacidipine, nifedipine, nicardipine, nimodipine, nitrendipine), antipsychotics, antidepressants (tricyclics, barbiturates & phenothiazines), NSAIDs, sympathomimetic agents. May lead to increased plasma levels w/ bupropion, paroxetine, fluoxetine, thioridazine, quinidine, chloroquine, levomepromazin, terbinafine & cimetidine. Slightly increased plasma levels of both nebivolol & nicardipine when co-administered.