Antiarrhythmic Pregnancy: Contraindicated in pregnancy unless clearly necessary; crosses the placenta and may cause neonatal hypothyroidism, bradycardia and prolonged QT. Breast-feeding should be stopped if therapy required.

Amiodarone

Brand names: Cordarone X

Used in: Atrial Fibrillation

Amiodarone is a class III antiarrhythmic used for serious atrial and ventricular tachyarrhythmias, including in acute settings such as resuscitation and rate or rhythm control of atrial fibrillation.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Oral changeover: 200 mg three times a day (usual oral loading dose), then phased out gradually

Route: Oral (changeover from IV) / IV

Frequency: Three times a day (oral loading)

Max: IV: up to 1200 mg/24 hours

Use only where cardiac monitoring, defibrillation and pacing facilities exist. IV loading dose: 5 mg/kg bodyweight by IV infusion over 20 minutes to 2 hours, diluted in 250 ml 5% dextrose; may be followed by repeat infusion up to 1200 mg (~15 mg/kg) in up to 500 ml 5% dextrose per 24 hours, rate adjusted to response. IV maintenance dose: 10-20 mg/kg/24 hours in glucose solution (on average 600-800 mg/24 hours, max 1200 mg/24 hours) for a few days. In extreme emergency, slow IV injection 150-300 mg (or 2.5-5 mg/kg) in 10-20 ml 5% glucose over minimum 3 minutes, not repeated for at least 15 minutes. Administer by central venous route (except peripheral route in cardiac arrest due to refractory VF). Changeover to oral: as soon as adequate response obtained (if possible commence oral maintenance on first day of infusion), start oral therapy at 200 mg three times a day and phase out infusion gradually. Do not exceed simvastatin 20 mg/day with concomitant amiodarone. Safety and efficacy in children not established; IV contraindicated in neonates, infants and children up to 3 years (benzyl alcohol).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Known hypersensitivity to iodine or amiodarone (one ampoule contains ~56 mg iodine)
Sinus bradycardia, sino-atrial heart block; severe conduction disturbances or sinus node disease without a pacemaker
Combination with drugs that may induce torsades de pointes
Severe respiratory failure, circulatory collapse, or severe arterial hypotension (bolus injection contraindications also include hypotension, heart failure, cardiomyopathy)
Evidence or history of thyroid dysfunction
Neonates, infants and children up to 3 years (benzyl alcohol)
Pregnancy (except exceptional circumstances) and lactation

Side effects

Corneal micro-deposits (very common; may cause coloured halos or blurred vision)
Hypothyroidism; hyperthyroidism (sometimes fatal)
Bradycardia (generally moderate)
Injection site reactions (pain, erythema, oedema, phlebitis, thrombophlebitis)
Extrapyramidal tremor; nightmares, sleep disorders, decreased libido

Interactions

Drugs that prolong QT / induce torsades de pointes (class I and III antiarrhythmics, phenothiazines, tricyclic antidepressants, certain fluoroquinolone and macrolide antibiotics, azole antifungals) — contraindicated / increased risk of torsades
Negative chronotropes (digoxin, beta blockers, verapamil, diltiazem) — bradycardia, sinus arrest, AV block
Simvastatin — increased risk of myopathy/rhabdomyolysis; do not exceed 20 mg/day
CYP450 inhibitors (grapefruit juice, cimetidine, certain protease inhibitors) — increased amiodarone exposure
Cyclosporine — increased cyclosporine plasma levels

Clinical monograph

How it works

It predominantly blocks potassium channels to prolong the cardiac action potential and refractory period, with additional sodium and calcium channel blockade and non-competitive beta-adrenergic antagonism.

Prescribing in practice

Amiodarone causes serious cumulative organ toxicity (thyroid, hepatic, pulmonary and ocular) and prolongs the QT interval, so it requires baseline assessment, ongoing surveillance and careful review of QT-prolonging and interacting drugs.
Its very long half-life means effects and interactions, including potentiation of warfarin and raised digoxin levels, persist for weeks after stopping.
Intravenous use can cause severe hypotension and, with peripheral lines, phlebitis, so central access is preferred for prolonged infusion.

Monitoring

Monitor thyroid and liver function at baseline and periodically, with chest imaging and ophthalmic review as indicated, alongside ECG surveillance.

Counselling the patient

Use sun protection as the skin becomes very sensitive to sunlight.
Report breathlessness, persistent cough, visual changes or symptoms of thyroid disturbance.
Avoid grapefruit juice and tell any prescriber you take amiodarone, as interactions persist after stopping.

Evidence & guidelines

Amiodarone features in resuscitation guidance for shock-refractory ventricular fibrillation and pulseless ventricular tachycardia and in NICE atrial fibrillation guidance, with MHRA advice reinforcing its monitoring requirements.

Reference: ERC Resuscitation Guidelines 2021; MHRA Amiodarone Safety Update; ESC 2020 AF Guidelines; SPC Cordarone X; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Drugs

Pathways