What is the standard dose of amiodarone (antiarrhythmic medication) for converting atrial fibrillation (a fib) to sinus rhythm?

From the Guidelines

The standard dose of amiodarone for atrial fibrillation conversion to sinus rhythm typically involves a loading dose of 400-600 mg orally three times daily for 1 week, followed by 200 mg twice daily for 1-2 weeks, and then a maintenance dose of 200 mg once daily. This dosing regimen is based on the most recent and highest quality study available, which suggests that amiodarone is effective in maintaining sinus rhythm in patients with atrial fibrillation 1. The use of low-dose amiodarone (200 mg daily or less) may be effective and associated with fewer side effects, as suggested by several studies 1.

Some key points to consider when prescribing amiodarone for atrial fibrillation conversion include:

• Monitoring for QT prolongation, thyroid dysfunction, pulmonary toxicity, and liver function abnormalities during treatment
• Dose adjustments may be necessary based on individual patient response, age, and comorbidities
• Amiodarone works by blocking multiple ion channels in cardiac tissue, prolonging the action potential and refractory period, which helps maintain sinus rhythm
• The medication has a very long half-life (approximately 58 days), so effects persist long after discontinuation

It's also important to note that amiodarone is associated with a relatively high incidence of potentially severe extracardiac toxic effects, making it a second-line or last-resort agent in many cases 1. However, in patients with left ventricular hypertrophy, heart failure, coronary artery disease, and/or previous myocardial infarction, amiodarone is associated with a low risk of proarrhythmia, making it an appropriate initial choice to prevent recurrent atrial fibrillation in these situations 1.

For more rapid conversion, an intravenous loading dose of 150 mg over 10 minutes, followed by 1 mg/minute for 6 hours, then 0.5 mg/minute for 18 hours may be used, as suggested by the guidelines 1. After IV administration, patients should transition to oral therapy. Overall, the dosing regimen for amiodarone in atrial fibrillation conversion should be individualized based on patient-specific factors and guided by the most recent and highest quality evidence available 1.

From the FDA Drug Label

DOSAGE & ADMINISTRATION Amiodarone shows considerable interindividual variation in response. Thus, although a starting dose adequate to suppress life-threatening arrhythmias is needed, close monitoring with adjustment of dose as needed is essential The standard dose of amiodarone for a fib to sinus rhythm conversion is not explicitly stated in the provided drug label for oral administration. The label provided is for intravenous administration.

• The recommended starting dose of amiodarone HCl injection is about 1000 mg over the first 24 hours of therapy. However, this information is for intravenous administration and may not be applicable to oral administration. The FDA drug label does not answer the question.

From the Research

Standard Dose of Amiodarone for Atrial Fibrillation to Sinus Rhythm Conversion

The standard dose of amiodarone for converting atrial fibrillation to sinus rhythm varies depending on the administration route and patient characteristics.

• Intravenous amiodarone has been used as a bolus only or as a bolus followed by a continuous infusion until conversion or up to 24 hours, with a bolus dose ranging from 3 to 7 mg/kg body weight and an infusion dose ranging from 900 to 3000 mg/day 2.
• The oral regimen of 25-30 mg/kg body weight administered as a single loading-dose has been reported to have a high conversion rate (>85%) 2.
• High-dose intravenous or combined intravenous and oral administration may be effective as early as 8 hours in patients with recent-onset atrial fibrillation of <48 hour duration, without contraindications to these high-dose regimens 3.
• Predictors of successful conversion include shorter duration of atrial fibrillation, smaller left atrial size, and higher amiodarone dose 2.

Administration Considerations

• Amiodarone is not superior to other antiarrhythmic drugs conventionally used for pharmacological cardioversion of recent-onset atrial fibrillation, but it is relatively safe in patients with structural heart disease and in those with depressed left ventricle function 2.
• The use of amiodarone should be limited to symptomatic patients who are refractory to electrical conversion, especially in patients with an ejection fraction of <40% or clinical heart failure 3.
• Pre-treatment with low-dose oral amiodarone can increase the efficacy of direct-current cardioversion in restoring sinus rhythm in patients with chronic atrial fibrillation 4.