Prescription ·Strong evidence ·Reviewed May 2026
Amiodarone is the most effective antiarrhythmic drug available, possessing properties of all four Vaughan-Williams antiarrhythmic classes. It is used for life-threatening ventricular arrhythmias and atrial fibrillation. However, its extensive side effect profile including thyroid, pulmonary, hepatic, and ocular toxicity requires careful long-term monitoring.
The bottom line
Evidence rating strong. Most-documented uses: most effective antiarrhythmic for ventricular and atrial arrhythmias, reduces mortality from ventricular arrhythmias (meta-analyses), maintains sinus rhythm in atrial fibrillation. 9 sources indexed (2017–2024), with 8 interaction records on file.
Core mechanism
Primarily a class III antiarrhythmic (potassium channel blocker) that prolongs the action potential duration and effective refractory period. Also exhibits class I (sodium channel blocking), class II (non-competitive beta-blocking), and class IV (calcium channel blocking) activity. Contains iodine (37% by weight), which contributes to thyroid effects. Extremely lipophilic with massive tissue distribution.
Food increases absorption; extremely long tissue loading period; avoid grapefruit juice
Amiodarone has mitochondrial effects, and CoQ10 is involved in mitochondrial electron transport. Direct evidence that CoQ10 changes amiodarone outcomes is limited.
Recommendation: Discuss CoQ10 with the prescriber managing amiodarone, especially if heart-failure, arrhythmia, or anticoagulant issues are present; do not assume it changes amiodarone safety or effectiveness.
St. John's Wort induces CYP3A4, which is a major metabolic pathway for amiodarone. This can significantly reduce amiodarone plasma levels, potentially causing loss of antiarrhythmic control and life-threatening recurrence of cardiac arrhythmias.
Recommendation: Do not combine St. John's Wort with amiodarone. Loss of arrhythmia control can be life-threatening. Discuss alternative mood support options with your cardiologist.
Both amiodarone and fluoroquinolones independently prolong the QT interval. Concurrent use creates additive QT prolongation risk, potentially leading to torsades de pointes, a life-threatening ventricular arrhythmia.
Recommendation: Avoid concurrent use if possible. If unavoidable, perform baseline ECG, monitor QTc closely, and discontinue if QTc exceeds 500 ms. Ensure electrolytes (K+, Mg2+) are normal.
Both amiodarone and escitalopram can prolong the QT interval. Combined use increases the risk of dangerous cardiac arrhythmias, particularly torsades de pointes.
Recommendation: Monitor ECG closely if combined. Consider alternative antidepressant with lower QT prolongation risk (e.g., sertraline). Keep electrolytes balanced.
Amiodarone increases digoxin levels by 70-100% through inhibition of P-glycoprotein and reduction of renal and non-renal clearance. This can cause potentially fatal digoxin toxicity with cardiac arrhythmias.
Recommendation: Reduce digoxin dose by 50% when starting amiodarone. Monitor digoxin levels closely. Watch for toxicity signs (nausea, visual changes, bradycardia, arrhythmias).
Amiodarone can prolong the QT interval and rarely trigger torsades de pointes. Low potassium greatly increases that risk because it reduces the heart's repolarization reserve. Potassium supplementation is useful only when potassium is low or intake is inadequate; too much potassium can be dangerous, especially with kidney disease or RAAS-blocking drugs.
Recommendation: Keep potassium in the normal range while taking amiodarone, and have levels checked if you use diuretics, have vomiting or diarrhea, or have kidney disease. Do not start potassium tablets or high-dose electrolyte powders unless your prescriber is monitoring your blood potassium.
Amiodarone can prolong cardiac repolarization, and low magnesium makes torsades de pointes more likely. Maintaining normal magnesium status helps stabilize repolarization and supports potassium balance. Oral magnesium is preventive support when intake is low; acute torsades requires emergency care and intravenous magnesium.
Recommendation: Maintain adequate magnesium intake while taking amiodarone, especially if you also take diuretics, PPIs, or have diarrhea. Ask your prescriber about checking magnesium periodically, and do not use high-dose magnesium if you have significant kidney disease unless monitored.
Amiodarone contains a large iodine load and is strongly associated with thyroid dysfunction. Extra iodine from supplements can further increase iodine exposure and may precipitate hypothyroidism or thyrotoxicosis, especially in people with nodular thyroid disease or autoimmune thyroid disease. Thyroid shifts can destabilize heart rhythm and worsen heart failure symptoms.
Recommendation: Avoid iodine supplements while taking amiodarone unless your prescriber specifically treats a documented deficiency. Follow the thyroid lab schedule your clinician recommends, and report new palpitations, heat or cold intolerance, weight change, tremor, or unusual fatigue.
Numbered references. Citations throughout the page link here.
Widiarti W, Saputra PBT, Mustofa A et al.. The roles of thyroidectomy in patients with amiodarone-induced thyrotoxicosis: A systematic review. Current problems in cardiology. 2024
Mohammadi K, Shafie D, Vakhshoori M et al.. Prevalence of amiodarone-induced hypothyroidism; A systematic review and meta-analysis. Trends in cardiovascular medicine. 2023
Alshehri M, Joury A. Ocular Adverse Effects of Amiodarone: A Systematic Review of Case Reports. Optometry and vision science : official publication of the American Academy of Optometry. 2020
Ruzieh M, Moroi MK, Aboujamous NM et al.. Meta-Analysis Comparing the Relative Risk of Adverse Events for Amiodarone Versus Placebo. The American journal of cardiology. 2019
Khan SU, Winnicka L, Saleem MA et al.. Amiodarone, lidocaine, magnesium or placebo in shock refractory ventricular arrhythmia: A Bayesian network meta-analysis. Heart & lung : the journal of critical care. 2017
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