What is the typical dose of Cordarone (amiodarone) for treating atrial fibrillation?

Cordarone (Amiodarone) Dosing for Atrial Fibrillation

For oral treatment of atrial fibrillation, start with 600-800 mg daily in divided doses until a total loading dose of 10 grams is achieved, then reduce to a maintenance dose of 200 mg daily. 1, 2

Loading Phase Dosing

• Administer 600-800 mg per day in divided doses until a cumulative total of 10 grams has been given 1, 2
• This loading phase typically takes approximately 2 weeks to complete (10,000 mg ÷ 700 mg/day average = ~14 days) 1
• Higher initial dosages may be used in unstable inpatients requiring more rapid control 1
• The loading phase is essential because amiodarone has a very long half-life (approximately 30 days) and therapeutic effects may not be fully apparent for 1-3 weeks 2, 3

Maintenance Phase Dosing

• Reduce to 200 mg daily after completing the loading phase 1, 2
• This lower maintenance dose minimizes long-term toxicity while maintaining efficacy 2
• Some patients may require 200-400 mg daily depending on clinical response, though 200 mg is the standard recommendation 1

Intravenous Dosing for Acute/Unstable Patients

• Initial bolus: 150 mg IV over 10 minutes 1, 2
• Maintenance infusion: 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours 1, 4
• The total first 24-hour dose is approximately 1000 mg 4
• IV administration provides more rapid onset (within days versus 1-3 weeks for oral) 2

Conversion from IV to Oral Therapy

When transitioning from intravenous to oral amiodarone, the dose depends on duration of IV therapy:

• Less than 1 week of IV therapy: 800-1,600 mg oral daily 1, 2
• 1-3 weeks of IV therapy: 600-800 mg oral daily 1, 2
• More than 3 weeks of IV therapy: 400 mg oral daily 1, 2

Clinical Context and Indications

Amiodarone is recommended as a second-line agent for atrial fibrillation, specifically for:

• Patients with structural heart disease where other agents are contraindicated 1
• Highly symptomatic patients without heart disease who have failed other therapies 1
• Patients with heart failure and atrial fibrillation 2

Important caveat: Aggressive rhythm control with amiodarone does not improve outcomes in relatively asymptomatic patients compared to rate-control strategies with anticoagulation 1, 2. Therefore, long-term amiodarone therapy is not justified in patients who can be adequately managed with rate control and anticoagulation 1.

Dose Reduction for Bradycardia

• If bradycardia develops, reduce to 200 mg every 24 hours rather than discontinuing the drug 2
• Bradycardia is a common dose-related adverse effect, particularly in elderly patients and those with paroxysmal atrial fibrillation 2
• Low-dose amiodarone (200 mg daily or less) maintains efficacy with fewer side effects 2

Key Adverse Effects to Monitor

Common dose-related adverse effects include:

• Bradycardia and QT prolongation (monitor ECG regularly) 1, 2
• Gastrointestinal upset and constipation 1
• Tremor or ataxia (35% of patients) 5
• Rarely, torsades de pointes 1

Serious long-term toxicities requiring monitoring:

• Pulmonary toxicity/interstitial infiltrates (5% of patients) 2, 5
• Thyroid dysfunction (6% of patients) 2, 5
• Hepatic dysfunction 2, 5
• Visual disturbances (halos, blurring in 6%) 5

Approximately 35-51% of patients experience adverse effects, with dose reduction required in 41% and discontinuation necessary in 10-14% of cases 2, 5, 6. Regular monitoring of thyroid function, liver enzymes, pulmonary function tests, and ECG is essential 2.

Critical Pitfalls to Avoid

• Do not use drop counter infusion sets for IV administration as surface properties may reduce drop size by up to 30%, leading to underdosing; always use volumetric infusion pumps 4
• Do not exceed 2 mg/mL concentration for peripheral IV administration (concentrations >3 mg/mL cause high incidence of phlebitis); use central venous catheter for higher concentrations 4
• Do not expect immediate effects - maximal antiarrhythmic effects may not occur until 90-150 days of treatment 3
• Remember that antiarrhythmic protection persists for up to 150 days after discontinuation due to the extremely long half-life 3