digoxin and metoprolol

Pharmacodynamic interaction. Digoxin increases vagal tone, slowing sinus rate and AV nodal conduction. Metoprolol, a beta-1 selective blocker, reduces sympathetic drive, further slowing heart rate and AV conduction. The combined effect is additive depression of the cardiac conduction system.

Additive bradycardia and AV block are the main risks. Patients may develop symptomatic bradycardia, fatigue, dizziness, or syncope. In patients with conduction disease or on other rate-lowering drugs, the risk of complete heart block is increased.

Co-prescription is acceptable but requires monitoring. Check heart rate and ECG before and during treatment, particularly when introducing or adjusting doses. Monitor for signs of bradycardia or heart block. Consider reducing doses of one or both agents if the heart rate is too low. Digoxin levels should be monitored if renal function changes.

Well established by clinical experience and pharmacodynamic principles. This combination is common in heart failure and atrial fibrillation, and guidelines address the need for caution. No specific citations provided.