Class III Antiarrhythmic (Iodine-containing) 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 Hydrochloride

Brand names: Cordarone X

Amiodarone hydrochloride is the salt form of the class III antiarrhythmic amiodarone, available as oral and intravenous preparations for serious atrial and ventricular tachyarrhythmias.

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 mainly blocks cardiac potassium channels to prolong the action potential and refractory period, with additional sodium and calcium channel blocking and beta-adrenergic antagonist actions.

Prescribing in practice

Cumulative thyroid, hepatic, pulmonary and ocular toxicity together with QT prolongation mandates baseline checks, periodic monitoring and avoidance of unnecessary QT-prolonging combinations.
The extremely long half-life means drug interactions, including with warfarin and digoxin, continue for weeks after discontinuation.
The intravenous route may cause profound hypotension and venous irritation, so dilute appropriately and prefer central administration for continued infusion.

Monitoring

Check thyroid and liver function before treatment and periodically thereafter, with ECG monitoring and chest or eye review where clinically indicated.

Counselling the patient

Protect skin from sunlight to reduce photosensitivity reactions.
Report new cough, breathlessness, visual disturbance or signs of an over- or under-active thyroid.
Avoid grapefruit juice and inform other prescribers about long-lasting interactions.

Evidence & guidelines

Use is supported by NICE guidance on arrhythmia management and resuscitation algorithms, with MHRA communications underlining the need for organ-toxicity monitoring.

Reference: NICE NG196 (Atrial fibrillation, 2021 updated 2024); ESC Guidelines on AF (2020 updated 2024); MHRA Drug Safety Update (amiodarone thyroid, 2015); 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.

Calculators

Pathways