Major
diltiazem × Propranolol
Calcium channel blocker, non-DHP (benzothiazepine derivative)×Non-selective beta blocker
Mechanism
Non-dihydropyridine calcium channel blocker (diltiazem) + non-selective beta-blocker (propranolol) – marked additive bradycardia, AV block, negative inotropic effect. Risk of symptomatic AV block, especially in older patients and left ventricular dysfunction.
Symptoms
Bradycardia (heart rate below 50/min), dizziness, syncope. ECG: first- to second-degree AV block. Older patients: fall risk.
Management
Avoid the combination. For atrial fibrillation rate control, propranolol + digoxin (without diltiazem) or diltiazem with propranolol withdrawn. In heart failure, a selective beta-blocker (bisoprolol) or carvedilol is preferable.