Class III antiarrhythmic
Amiodarone
Broad-spectrum antiarrhythmic used in life-threatening tachyarrhythmias and atrial fibrillation. Long half-life (≈50 days) and multiple organ toxicities mean monitoring is intensive.
Indications
- Life-threatening ventricular arrhythmias (VT, VF)
- Cardioversion and rhythm control in atrial fibrillation / flutter when other therapies are unsuitable
- Wolff-Parkinson-White syndrome arrhythmias
Dosing
Oral loading
200 mg three times daily for 1 week, then 200 mg twice daily for 1 week, then maintenance 200 mg once daily (or lowest effective dose).
IV
Central line preferred — peripheral administration causes phlebitis. Loading 5 mg/kg over 20–120 min in cardiac arrest / unstable arrhythmia per ALS algorithms.
Always confirm doses against the current BNF — this summary is for study, not prescribing.
Monitoring
- TFTs at baseline and every 6 months (hyper- and hypothyroidism)
- LFTs at baseline and every 6 months
- Chest X-ray at baseline; CXR or pulmonary function tests if dyspnoea / cough
- Annual ophthalmology review for corneal microdeposits / optic neuropathy
- ECG and serum potassium prior to initiation
Contraindications
- Sinus bradycardia, sinoatrial heart block, AV block (without pacing)
- Thyroid dysfunction
- Iodine sensitivity
- Pregnancy and breastfeeding (unless no alternative)
Important interactions
- Warfarin — markedly increases INR; reduce warfarin dose 30–50% and monitor INR closely
- Digoxin — amiodarone roughly doubles digoxin level; halve the digoxin dose
- Statins (simvastatin) — increased myopathy risk; cap simvastatin at 20 mg daily
- Beta-blockers, verapamil, diltiazem — additive bradycardia and AV block
- QT-prolonging drugs (macrolides, fluoroquinolones, methadone, antipsychotics) — torsades risk
- Grapefruit juice — increases amiodarone levels
Counselling points
- Wear high-factor sunscreen — photosensitivity is common and severe
- Report breathlessness or new persistent cough immediately
- Report visual disturbance — corneal deposits and optic neuropathy occur
- Skin discolouration (slate-grey) is a recognised long-term effect
- Avoid grapefruit juice
- Effects persist for weeks after stopping due to long half-life
Red flags
- Pulmonary toxicity (interstitial pneumonitis / pulmonary fibrosis) — stop drug, refer urgently
- Hepatitis with AST/ALT > 3× ULN — stop drug
- Thyrotoxicosis on amiodarone — endocrine review (Type 1 vs Type 2 amiodarone-induced thyrotoxicosis)
Practice for the CRA
Drug-specific questions, calculations, and full mock exams aligned to the GPhC Common Registration Assessment.