What is the typical dose of Amiodarone for treating arrhythmias?

Amiodarone Dosing for Arrhythmias

For ventricular arrhythmias, start with an oral loading dose of 800-1600 mg daily in divided doses until a cumulative total of 10 grams is reached, then transition to maintenance therapy of 200-400 mg daily. 1, 2

Loading Dose Regimens by Arrhythmia Type

Ventricular Arrhythmias (VT/VF)

• Begin with 800-1600 mg per day in divided doses until a total cumulative dose of 10 grams has been administered 1, 2
• This loading phase typically takes 1-2 weeks depending on the daily dose used 2
• Higher loading doses (up to 1200 mg daily) may be considered in monitored inpatient settings, though this increases adverse effect risk 1

Atrial Fibrillation

• Use 600-800 mg per day in divided doses until a total of 10 grams has been given 1
• Then reduce to maintenance dose of 200 mg daily 1

General Arrhythmias (Alternative Regimen)

• The American Heart Association supports a more conservative approach of 400-600 mg daily in divided doses for 2-4 weeks, followed by maintenance of 100-200 mg daily 1
• This lower-dose regimen may be appropriate for less severe arrhythmias or patients at higher risk for toxicity 1

Intravenous Dosing for Acute Management

Hemodynamically Stable Monomorphic VT

• Administer 150 mg IV over 10 minutes, which can be repeated if necessary 2
• Follow with 1 mg/min infusion for 6 hours, then 0.5 mg/min infusion 2
• Total dose over 24 hours should not exceed 2.2 grams 2
• Onset of antiarrhythmic effect occurs rapidly, typically in less than 30 minutes 2

Transitioning from IV to Oral Therapy

The oral dose depends on duration of IV therapy:

• IV therapy <1 week: Transition to 800-1600 mg oral daily 1, 2
• IV therapy 1-3 weeks: Transition to 600-800 mg oral daily 1, 2
• IV therapy >3 weeks: Transition to 400 mg oral daily 1, 2

Maintenance Dosing

• Standard maintenance: 200-400 mg daily for ventricular arrhythmias 1, 2
• Lower maintenance: 100-200 mg daily may be sufficient for some patients, particularly those with atrial fibrillation 1
• The full antiarrhythmic effect may take days to weeks to develop despite adequate serum levels due to amiodarone's very long half-life 1

Critical Monitoring Requirements

During Loading Phase

• Watch for bradycardia, QT prolongation, hypotension, and heart block 1
• Monitor closely as the first sign of antiarrhythmic failure may manifest as sudden cardiac death 3

Long-Term Monitoring

• Screen for pulmonary toxicity (subacute cough, progressive dyspnea, interstitial infiltrates on chest radiograph) - the most serious adverse effect 2
• Monitor thyroid function - dysfunction occurs in a small but significant percentage of patients 1, 2
• Check hepatic function regularly during long-term therapy 1
• Assess for bradycardia and QT prolongation - common cardiovascular effects 2

Dose Adjustment Strategy

• Reduce the dose if side effects occur rather than discontinuing therapy when possible 1
• Adverse effects correlate with total amiodarone exposure (dosage and duration), so use the lowest effective dose possible 2
• In clinical practice, maintenance doses often need reduction from initial targets: one study showed doses decreased from 572 mg/day at 45 days to 372 mg/day at 6 months due to side effects 3

Important Drug Interactions

• Avoid coadministration with other QT-prolonging medications without expert consultation 1
• Be aware of significant interactions with warfarin and digoxin - dose adjustments of these medications will be necessary 1

Common Pitfall to Avoid

The major pitfall is using maintenance doses that are too high (≥600 mg daily), which leads to adverse effects in virtually all patients. While older studies from the 1980s used 600-800 mg daily maintenance doses, these resulted in side effects in over 90% of patients and discontinuation rates of 10-19% 3, 4, 5. Modern guidelines recommend lower maintenance doses of 200-400 mg daily to minimize toxicity while maintaining efficacy 1, 2.