Amiodarone

Antiarrhythmics
Antiarrhythmics
High alert
An error with this medicine can cause serious harm: double checks and protocols are used.

A broad antiarrhythmic for ventricular and atrial arrhythmias. Very effective, but it builds up in tissues and can damage the lungs, liver, thyroid and eyes.

Updated Nov 1, 2026

Quick facts

Group: Antiarrhythmics
Target: Cardiac potassium (hERG/IKr), sodium and L-type calcium channels; β-adrenergic receptors (the L-type calcium channel Cav1.2 is shown)
Used for: Recurrent · Atrial fibrillation
Key effects: Nausea · Photosensitivity and · Corneal microdeposits
Monitor: ECG · Liver enzymes at baseline
ATC: C01BD01

No doses: the clinician sets them by the current guideline.

Mechanism of action

Cardiac potassium (hERG/IKr), sodium and L-type calcium channels; β-adrenergic receptors (the L-type calcium channel Cav1.2 is shown)Amiodarone

The figure shows amiodarone bound to the human L-type calcium channel Cav1.2, one of the several cardiac channels it blocks; the hepatitis C drug sofosbuvir is also bound in this structure, which relates to the severe bradycardia seen when the two are combined.

Target in 3D: Cardiac potassium (hERG/IKr), sodium and L-type calcium channels; β-adrenergic receptors (the L-type calcium channel Cav1.2 is shown). PDB structure 8FHS (RCSB PDB, public domain). View the structure at RCSB PDB

Amiodarone is classed as a class III drug because, with chronic use, it lengthens the action potential and refractory period in all cardiac tissues (longer QT). It also blocks sodium channels at fast rates (class I), has a non-competitive antisympathetic effect (class II) and slows the sinus and AV nodes like calcium channel blockers (class IV). Intravenously it also relaxes vascular smooth muscle and can lower blood pressure.

Amiodarone blocks potassium channels: longer action potential and QT
It also blocks sodium and calcium channels and β-adrenergic effects
The sinus rate falls and AV conduction slows
Tissue stores build up slowly, so the effect starts and fades over weeks

Indications

Recurrent, life-threatening ventricular fibrillation Cardiac arrest (VF, pulseless VT, asystole, PEA) →
Recurrent haemodynamically unstable ventricular tachycardia Ventricular tachycardia →
Atrial fibrillation (rhythm control; widely used, though not a labelled US indication) Atrial fibrillation →

Adverse effects

Common

Nausea, constipation and poor appetite
Photosensitivity and, with long use, blue-grey skin discolouration
Corneal microdeposits (common, reversible)
Bradycardia
Tremor and fatigue
Hypotension with intravenous use

Contraindications

Cardiogenic shock
Sick sinus syndrome, second- or third-degree AV block, or bradycardia with syncope, without a working pacemaker
Hypersensitivity to amiodarone or iodine

Key interactions

Warfarin: Stronger anticoagulant effect and serious bleeding; the warfarin dose is lowered and the INR checked closely
Digoxin: Higher digoxin levels and toxicity; the digoxin dose is reduced or stopped
Sofosbuvir (hepatitis C): Symptomatic, sometimes severe bradycardia
Other QT-prolonging drugs (class I and III antiarrhythmics, some macrolides, fluoroquinolones, azoles, antipsychotics): Higher risk of torsades de pointes; avoided
Simvastatin, lovastatin and other CYP3A substrates: Higher statin levels and risk of myopathy
Beta blockers, verapamil, diltiazem, ivabradine: Additive bradycardia, sinus arrest and AV block

What is monitored

ECG: heart rate, PR, QRS and QT
Chest X-ray and pulmonary function tests at baseline, then if symptoms appear
Liver enzymes at baseline and periodically
Thyroid function at baseline and periodically
Eye examination if vision changes
Potassium and magnesium; INR and digoxin levels when combined

Administration and safety

Intravenous amiodarone is given by infusion pump, ideally through a dedicated central line, with an in-line filter.
It irritates peripheral veins (phlebitis); the site is watched closely when a peripheral line is used.
Long infusions are mixed in glass or polyolefin containers; the drug leaches plasticisers (DEHP) from PVC tubing.
Hypotension during the infusion is managed first by slowing the infusion.
The injection contains benzyl alcohol, which is dangerous for neonates.

Pregnancy and breastfeeding

It crosses the placenta and can cause fetal thyroid problems, slow fetal heart rate and growth restriction, so it is used in pregnancy only when other options fail.

Nursing care

Continuous ECG and blood pressure during intravenous use; report bradycardia, AV block, QT prolongation or hypotension.
Correct low potassium and magnesium before starting, as ordered.
Ask about new cough or breathlessness, yellow skin or dark urine, visual changes, and signs of an over- or underactive thyroid.
Teaching: sun protection, avoid grapefruit juice, and tell every prescriber about amiodarone, since interactions last for months.

Pharmacokinetics

Absorption: Slow and variable by mouth; food increases absorption, so it is taken the same way with respect to meals
Distribution: Highly protein bound with a huge volume of distribution: it accumulates in fat, liver, lung and other tissues
Metabolism: Liver, by CYP3A and CYP2C8, to the active metabolite desethylamiodarone
Half-life: Weeks to months, so effects, toxicity and interactions persist long after stopping
Onset and duration: Oral antiarrhythmic effect takes days to weeks, even with a loading phase

Test yourself

Think of the answer, then tap the question to see it.

Why does amiodarone affect the thyroid?

It is rich in iodine and alters thyroid hormone metabolism, so it can cause hypothyroidism or hyperthyroidism.

Which tests are taken before long-term amiodarone?

Chest X-ray and pulmonary function tests, liver enzymes, thyroid function and an ECG.

What happens to warfarin and digoxin when amiodarone is added?

Both rise: the INR goes up with bleeding risk and digoxin levels increase, so their doses are reduced and levels checked.

Why do amiodarone's interactions and toxicity last long after it is stopped?

Its half-life is weeks to months because it accumulates in fat and other tissues.

What is the most common adverse effect of intravenous amiodarone and its first management?

Hypotension; the infusion is slowed first.

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Connections

← Back to the class: Antiarrhythmics

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - AMIODARONE HYDROCHLORIDE tablet (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - AMIODARONE HYDROCHLORIDE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); 8FHS: Human L-type voltage-gated calcium channel Cav1.2 in the presence of amiodarone and sofosbuvir at 3.3 Angstrom resolution (RCSB Protein Data Bank, 2023).

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Representative model, for educational purposes only.