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Class III Antiarrhythmic (Iodine-containing)

Amiodarone Hydrochloride

Brand names: Cordarone X

Adult dose

Dose: Loading: 200 mg 3 times daily for 1 week, then 200 mg twice daily for 1 week. Maintenance: 200 mg once daily (or lowest effective dose). IV (VT/VF): 300 mg in 20 mL glucose 5% over 3 min (resuscitation), or 150 mg over 10 min then 360 mg over 6 h then 540 mg over 18 h
Route: Oral or intravenous
Frequency: See dose detail

Clinical pearls

  • Most effective antiarrhythmic for AF, VT, VF — but extensive toxicity profile limits long-term use
  • Extremely long half-life (40–55 days) — drug interactions persist weeks after stopping
  • Iodine content (75 mg iodine per 200 mg tablet) causes thyroid dysfunction in 15–20% of patients
  • TFT at baseline, then every 6 months (hypothyroidism treated with levothyroxine while continuing amiodarone if essential; hyperthyroidism requires specialist management — may need carbimazole or surgery)
  • Annual chest X-ray; LFTs every 6 months
  • NICE NG196 (AF): amiodarone for long-term rate/rhythm control when other agents inappropriate

Contraindications

  • Sinus bradycardia or sino-atrial block
  • AV block (2nd or 3rd degree) without pacemaker
  • Thyroid dysfunction (caution — may worsen both hyper and hypothyroidism)
  • Iodine hypersensitivity
  • Pregnancy (teratogenic)
  • Breastfeeding

Side effects

  • Pulmonary toxicity (interstitial pneumonitis, ARDS) — life-threatening
  • Thyroid dysfunction (hypo and hyperthyroidism — very common)
  • Hepatotoxicity (raised transaminases, cirrhosis — rare)
  • Corneal microdeposits (very common — benign; blue-grey halos)
  • Photosensitivity (use sunscreen)
  • Peripheral neuropathy
  • QT prolongation (paradoxically low risk of TdP for its degree of QT prolongation)
  • Blue-grey skin discolouration with chronic use
  • Bradycardia

Interactions

  • Warfarin — significantly increases INR; reduce warfarin dose by 30–50% and monitor closely
  • Digoxin — increased digoxin levels; halve digoxin dose
  • Simvastatin — increased myopathy risk; max simvastatin 20 mg/day (or switch statin)
  • QT-prolonging drugs — additive risk (but amiodarone itself has unique pharmacology)
  • Phenytoin — amiodarone increases phenytoin levels; monitor
  • Ciclosporin — increased ciclosporin levels

Monitoring

  • TFTs (TSH, free T3, T4) at baseline and every 6 months
  • LFTs at baseline and every 6 months
  • Chest X-ray at baseline and annually (pulmonary toxicity)
  • ECG (PR, QT interval, QRS duration)
  • Serum creatinine
  • Ophthalmology if visual symptoms (optic neuropathy — rare but serious)

Reference: BNF; NICE NG196 (Atrial fibrillation, 2021 updated 2024); ESC Guidelines on AF (2020 updated 2024); MHRA Drug Safety Update (amiodarone thyroid, 2015); https://bnf.nice.org.uk/drugs/amiodarone-hydrochloride/. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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