Hypersensitivity. Resting heart rate <70 beats/min prior to treatment, cardiogenic shock, acute MI, severe hypotension (<90/50 mmHg), severe hepatic insufficiency, sick sinus syndrome, SA block, unstable or acute heart failure, pacemaker-dependent patient, unstable angina, 3rd degree AV-block. Concomitant w/ strong CYP3A4 inhibitors eg, azole antifungals, macrolides, HIV protease inhibitors & nefazodone; concomitant w/ verapamil or diltiazem (moderate CYP3A4 inhibitors w/ heart-rate reducing properties). Severe hepatic insufficiency. Women of childbearing potential not using appropriate contraceptive measures. Pregnancy & lactation.