Amiodarone × Digoxin

Amiodarone blocks P-glycoprotein in the intestine and renal tubules – the main dabigatran-style clearance route of digoxin. Digoxin plasma levels rise 1.7- to 2.5-fold. The narrow therapeutic window of digoxin turns any rise into a risk of acute toxicity.

Nausea, anorexia, visual disturbances (yellow-green halos around lights), arrhythmias ranging from premature beats to ventricular tachycardia. In older adults: confusion, dizziness. Symptoms appear 1–2 weeks after starting amiodarone.

When amiodarone is started, halve the digoxin dose immediately. Measure digoxin level after 1 week (target 0.5–0.9 ng/mL in heart failure). Check potassium and magnesium monthly: hypokalaemia worsens digoxin toxicity.