1. Introduction
Amiodarone is a class III antiarrhythmic drug used to manage serious ventricular and atrial arrhythmias. It works by prolonging the cardiac action potential and refractory period, stabilising the heart’s electrical activity.
2. Indications
- Ventricular Arrhythmias
- Ventricular Tachycardia (VT)
- Ventricular Fibrillation (VF) (Resistant to other treatments)
- Atrial Arrhythmias
- Atrial Fibrillation (AF) (Rate & Rhythm Control, Especially in Heart Failure)
- Atrial Flutter
- Supraventricular Tachycardia (SVT) (Resistant to other treatments)
3. Dosage
Adults:
- Ventricular Arrhythmias (VT/VF):
- Loading dose: 800–1600 mg/day for 1–3 weeks, then 600–800 mg/day for 1 month.
- Maintenance dose: 200–400 mg/day.
- Atrial Fibrillation (Rhythm Control):
- Loading dose: 600–800 mg/day for 1–2 weeks.
- Maintenance dose: 100–400 mg/day.
- IV (Acute Life-Threatening Arrhythmias):
- 300 mg IV over 1 hour, followed by 900 mg over 23 hours, then maintenance 200–400 mg/day.
Elderly:
- Use lower maintenance doses (100–200 mg/day).
Renal Impairment:
- No dose adjustment needed, but monitor for toxicity.
Hepatic Impairment:
- Use with caution—risk of hepatotoxicity.
- Monitor liver function regularly.
4. Administration
- Oral tablets: Take with food to reduce stomach upset.
- IV infusion: Must be diluted in D5W (dextrose) and given via a central line to avoid vein irritation.
- Do not stop suddenly—risk of rebound arrhythmia.
5. Forms Available
- Tablets: 100 mg, 200 mg, 400 mg
- IV Injection: 50 mg/mL in 3 mL ampoule (150 mg), 50 mg/mL in 10 mL vial (500 mg)
6. Side Effects
6.1 Common Side Effects:
- Fatigue
- Bradycardia (slow heart rate)
- Nausea, vomiting
- Skin photosensitivity (blue-grey skin pigmentation)
6.2 Less Common Side Effects:
- Hypotension (IV use)
- Thyroid dysfunction (hypothyroidism or hyperthyroidism)
- Pulmonary toxicity (cough, dyspnoea)
6.3 Rare but Serious Side Effects:
- Liver toxicity (elevated ALT/AST, hepatitis, jaundice)
- Pulmonary fibrosis (irreversible lung scarring, persistent cough, breathlessness)
- QT prolongation (risk of torsades de pointes arrhythmia)
- Corneal deposits (visual disturbances, halos around lights)
- Peripheral neuropathy (tingling, weakness in limbs)
7. Warnings
- Pulmonary Toxicity:
- Can cause fatal pulmonary fibrosis—chest X-ray and lung function tests required before & during therapy.
- Thyroid Dysfunction:
- Amiodarone contains iodine and may cause hypothyroidism or hyperthyroidism—monitor TSH levels.
- Hepatotoxicity:
- Risk of severe liver injury—monitor liver function tests every 6 months.
- Ocular Toxicity:
- Corneal microdeposits are common; regular eye exams recommended.
- QT Prolongation:
- Increases risk of torsades de pointes—avoid combining with other QT-prolonging drugs.
8. Precautions
- Avoid in pregnancy—can cause fetal thyroid dysfunction and bradycardia.
- Caution in patients with lung disease—risk of pulmonary fibrosis.
- Use sunscreen—prevents skin discolouration and photosensitivity reactions.
- Avoid grapefruit juice—can increase drug levels and toxicity risk.
9. Interactions
- Warfarin: Increases INR—reduce warfarin dose by 30–50% and monitor INR frequently.
- Digoxin: Increases digoxin toxicity risk—reduce digoxin dose by 50%.
- Beta-blockers & Calcium Channel Blockers: Increased risk of severe bradycardia and heart block.
- QT-Prolonging Drugs (e.g., macrolides, fluoroquinolones, antipsychotics): Avoid due to torsades risk.
- Statins (Simvastatin, Atorvastatin): Increased risk of rhabdomyolysis—limit simvastatin to 20 mg/day.
10. Monitoring Parameters
- ECG (QT interval, heart rate) every 3–6 months.
- Chest X-ray & Pulmonary Function Tests every 6–12 months.
- Liver function tests (ALT, AST, bilirubin) every 6 months.
- Thyroid function (TSH, free T4, free T3) every 6 months.
- Eye exams (Corneal deposits, optic neuropathy) annually.
11. Use in Children
- Used in paediatric arrhythmias under specialist supervision.
- Lower doses required—start at 5 mg/kg loading, then 2.5 mg/kg/day.
12. Use in Pregnancy
- Category D: Avoid unless life-threatening indication.
- Risk of fetal hypothyroidism, bradycardia, and neurodevelopmental issues.
13. Use in Elderly
- Start with lower doses (100–200 mg/day).
- Increased risk of bradycardia, lung fibrosis, and thyroid dysfunction.
14. Use in Kidney Disease
- No dose adjustment needed, but monitor for toxicity.
15. Use in Liver Disease
- Use with caution—monitor ALT, AST, bilirubin every 3–6 months.
16. Patient Counselling Points
- Take at the same time daily with food.
- Wear sunscreen and protective clothing—reduces risk of photosensitivity & skin discolouration.
- Report shortness of breath or persistent cough immediately (lung toxicity risk).
- Monitor thyroid function regularly—watch for signs of weight gain (hypothyroidism) or sweating, anxiety (hyperthyroidism).
- Avoid grapefruit juice—can increase drug levels.
- Do not stop suddenly—consult your doctor before stopping.
17. Table of Brand Names, Manufacturer, and Prices in USD
Brand Name | Manufacturer | Strength/Dosage Form | Price (USD) |
---|---|---|---|
Cordarone | Sanofi | 100 mg, 200 mg Tablets | $80 (30 tabs) |
Pacerone | Upsher-Smith | 100 mg, 200 mg Tablets | $70 (30 tabs) |
Nexterone | Baxter | 50 mg/mL IV Solution | $200 (150 mg vial) |
Generic Amiodarone | Various | 100 mg, 200 mg Tablets | $40 (30 tabs) |
18. 15 FAQs (Frequently Asked Questions)
1. What is Amiodarone used for?
It is used for serious ventricular and atrial arrhythmias.
2. How does Amiodarone work?
It prolongs the action potential and refractory period, stabilising heart rhythms.
3. How long does it take for Amiodarone to work?
Effects may take days to weeks due to a long half-life (up to 50 days).
4. Does Amiodarone cause lung damage?
Yes, pulmonary fibrosis is a serious long-term risk.
5. Can I drink alcohol while on Amiodarone?
Limit alcohol, as both can affect the liver.