amiodarone × digoxin

Amiodarone inhibits intestinal and renal P-glycoprotein – plasma digoxin concentration rises 1.7–2.5-fold over 1–2 weeks. Risk of digitalis toxicity: nausea, visual disturbances, AV block, ventricular arrhythmias. The effect persists for weeks after amiodarone withdrawal due to tissue accumulation.

When starting amiodarone, immediately reduce the digoxin dose by 50 %. Monitor digoxin level (target 0.5–0.9 ng/mL in HF) at 7–10 days, then every 2–3 weeks. Maintain potassium and magnesium in the upper-normal range – hypokalemia sharply increases digoxin's arrhythmogenic potential.