Moderate
Established
Descripción
Metoprolol adds to digoxin's rate-slowing effect at the AV node, increasing the risk of bradycardia and AV block in susceptible patients.
Mecanismo
Digoxin increases vagal tone and directly slows AV nodal conduction; metoprolol blocks sympathetic-mediated increases in heart rate and AV nodal conduction. The effects are pharmacodynamically additive.
Relevancia clínica
This combination is used intentionally in rate-controlled AF but can cause excessive bradycardia (<50 bpm) or AV block, particularly in elderly patients or those with pre-existing conduction disease.
Manejo clínico
Monitor heart rate and ECG; target resting heart rate 60–80 bpm in AF; reduce either drug dose if excessive bradycardia develops.