Drug interactions between Betapace AF and diltiazem

MONITOR CLOSELY: Additive reductions in heart rate, cardiac conduction, and cardiac contractility may occur when calcium channel blockers, especially verapamil and diltiazem, are used concomitantly with beta blockers. While this combination may be useful and effective in some situations, potentially serious cardiovascular adverse effects such as congestive heart failure, severe hypotension, and/or exacerbation of angina may occur. Ventricular asystole, sinus arrest, and heart block have also been reported. The risk is increased with high dosages, IV administration, left ventricular dysfunction, or AV conduction abnormalities. Beta blocker ophthalmic solutions may also interact, as they are systemically absorbed and can produce clinically significant systemic effects even at low or undetectable plasma levels. Bradycardia (36 bpm) with wandering atrial pacemaker occurred in a patient taking oral verapamil and timolol ophthalmic drops. The proposed mechanisms include additive slowing in AV conduction, reduced cardiac contractility secondary to beta-blockade, and decreased peripheral vascular resistance secondary to calcium channel blockade. Verapamil and diltiazem may also decrease the clearance of some beta blockers. MANAGEMENT: Close clinical monitoring of patient hemodynamic response and tolerance is recommended if these agents are used together, and the dosage of one or both agents adjusted as necessary. Patients should be advised to promptly report any symptoms including fatigue, headache, fainting, swelling of the extremities, weight gain, shortness of breath, chest pain, increased or decreased heartbeat, or irregular heartbeat.