Amiodarone Use and Dosage for Arrhythmias
Amiodarone is indicated for life-threatening ventricular arrhythmias and atrial fibrillation, particularly in patients with structural heart disease, with recommended dosing of 800-1600 mg/day loading dose followed by 200-400 mg/day maintenance for ventricular arrhythmias, and 600-800 mg/day loading followed by 200 mg/day maintenance for atrial fibrillation. 1
Indications
Amiodarone is used for:
- Life-threatening ventricular arrhythmias refractory to other treatments
- Atrial fibrillation, particularly in patients with structural heart disease
- More effective than sotalol or propafenone for maintaining sinus rhythm (65% success rate at 16 months vs. 37%) 1
Dosage Regimens
Oral Administration
Ventricular Arrhythmias:
- Loading dose: 800-1600 mg/day in divided doses until total of 10g
- Maintenance dose: 200-400 mg/day 1
Atrial Fibrillation:
- Loading dose: 600-800 mg/day in divided doses until total of 10g
- Maintenance dose: 200 mg/day 1
Recommended lowest effective dose: ≤300 mg/day when possible 1
Intravenous Administration
- Loading dose: 150 mg IV bolus over 10 minutes (can be repeated in 10-30 minutes if needed)
- Followed by: 1 mg/minute for 6 hours, then 0.5 mg/minute for 18 hours
- Administration requirements:
Monitoring Requirements
Baseline Testing
- Thyroid function (TSH, free T4, T3)
- Pulmonary function tests including DLCO
- Chest imaging (X-ray or high-resolution CT)
- Liver function tests 1
Follow-up Monitoring
- Thyroid function every 3-6 months
- Pulmonary function tests every 3-6 months
- Clinical assessment for respiratory symptoms
- Chest imaging 1
Management of Side Effects
Thyroid Abnormalities
- Normal TSH with elevated free T4: Continue amiodarone with monitoring
- Hyperthyroidism (suppressed TSH + symptoms): Consider antithyroid medications, prednisone, or amiodarone discontinuation
- Hypothyroidism (elevated TSH): Continue amiodarone and add levothyroxine 1
Pulmonary Toxicity
- If suspected: Immediately discontinue amiodarone
- Provide supportive care
- Consider corticosteroids in severe cases 1
Important Drug Interactions
- Warfarin: Increased anticoagulant effect
- Digoxin: Increased serum levels
- Statins: Risk of myopathy/rhabdomyolysis
- Beta-blockers and calcium channel blockers: Potentiation of bradycardia 1
Common Side Effects
- Gastrointestinal: Constipation, GI upset (80% of patients) 3
- Neurological: Tremor, ataxia (74% of patients) 3, 4
- Ocular: Corneal microdeposits (nearly all patients with long-term use) 3
- Cardiovascular: Bradycardia, AV block, QT prolongation
- Pulmonary: Cough, dyspnea, interstitial infiltrates (5-7% of patients) 1, 4
- Cutaneous: Photosensitivity, blue-gray skin discoloration 3
Contraindications
- Known hypersensitivity to amiodarone or iodine
- Cardiogenic shock
- Marked sinus bradycardia
- Second- or third-degree AV block without a functional pacemaker
- Pregnancy and lactation 1
Clinical Pearls
- Use the lowest effective dose to minimize side effects
- Side effects are extremely common (93% of patients in some studies) 3
- Amiodarone has a narrow therapeutic-toxic range
- The drug has an extremely long half-life (up to 100 days) due to its lipophilic nature 5
- QT prolongation is common but rarely causes torsades de pointes
- Amiodarone can be safely used in patients with left ventricular dysfunction 5
Administration Cautions
- Higher concentrations (>2 mg/mL) should only be administered via central venous catheter
- Infusions exceeding 2 hours must be administered in glass or polyolefin bottles containing D5W
- Amiodarone adsorbs to polyvinyl chloride (PVC) tubing 2
- Rapid infusions at high concentrations have resulted in hepatocellular necrosis and acute renal failure 2