Major
Bisoprolol × diltiazem
Selective beta-adrenergic blockers×Calcium channel blocker, non-DHP (benzothiazepine derivative)
Mechanism
Non-dihydropyridine calcium channel blocker (diltiazem) + beta-blocker (bisoprolol) – additive AV node blockade and negative inotropic effect.
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 For atrial fibrillation rate control, choose bisoprolol + digoxin (without diltiazem) or diltiazem with bisoprolol withdrawn.