digoxin and amiodarone

Amiodarone inhibits P-glycoprotein-mediated renal and biliary excretion of digoxin, increasing digoxin plasma concentrations. Additionally, both drugs have additive negative chronotropic and dromotropic effects on the atrioventricular node, potentially causing bradycardia or heart block.

Digoxin toxicity may occur, manifesting as nausea, vomiting, visual disturbances, and cardiac arrhythmias (e.g., bradycardia, AV block, ventricular ectopy). The risk is particularly high in patients with renal impairment or when loading doses are used.

If co-prescription is necessary, consider reducing the digoxin maintenance dose by approximately 50% (or use a lower starting dose) and monitor serum digoxin concentrations, renal function, and ECG. Monitor for signs of digoxin toxicity. Adjust digoxin dose based on levels and clinical response. Alternative antiarrhythmics may be considered to avoid the interaction.

The interaction is well established through clinical studies and case reports. Amiodarone has been shown to increase digoxin levels in a dose-dependent manner. Guidelines from major cardiology societies recommend dose reduction and monitoring when these drugs are combined.