Major
Digoxin × Metoprolol
Cardiac glycosides (digitalis)×Selective β1-adrenoceptor blockers
Mechanism
Additive slowing of atrioventricular (AV) conduction and lowered heart rate. In atrial fibrillation this synergistic ventricular rate control is standard; without atrial fibrillation, bradycardia and AV block risks rise.
Symptoms
Bradycardia (heart rate below 50/min), dizziness, syncope. ECG: first- to second-degree AV block, prolonged PR. Older patients: fatigue, weakness.
Management
The combination is appropriate in atrial fibrillation with preserved or reduced ejection fraction. Check pulse and ECG at 1 and 4 weeks. If pulse drops below 50 or second-degree AV block appears, reduce metoprolol; if symptoms persist, hold digoxin temporarily.
Sources
- ESC: 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure (2021)– Eur Heart J 2021;42(36):3599–3726
- ESC: 2024 ESC Guidelines for the management of atrial fibrillation developed in collaboration with the EACTS (2024)– Eur Heart J 2024;45(36):3314–3414
- RACE II Investigators: Lenient versus Strict Rate Control in Patients with Atrial Fibrillation (2010)– N Engl J Med 2010;362(15):1363–1373