What is the typical maintenance dose of oral amiodarone?

Oral Amiodarone Maintenance Dosage

The typical maintenance dose of oral amiodarone is 200-400 mg daily. 1

Loading and Maintenance Dosing Protocol

Amiodarone therapy involves a loading phase followed by maintenance dosing:

1. Loading Phase:

   • 800 mg daily for 1 week (total 10g) 2
   • Alternative loading: 600-800 mg daily divided doses until 10g total 2

2. Maintenance Phase:

   • 200-400 mg daily 2, 1
   • Dosing should be adjusted based on clinical response and side effects

The American College of Cardiology/American Heart Association/European Society of Cardiology guidelines recommend this dosing regimen for both inpatient and outpatient settings 2.

Factors Affecting Dosing

Amiodarone shows considerable interindividual variation in response, requiring close monitoring and dose adjustment 3. Key considerations include:

• Patient-specific factors: Age, renal function, hepatic function
• Duration of previous therapy: Longer treatment may require lower maintenance doses
• Concomitant medications: Significant drug interactions with warfarin, digoxin, statins
• Clinical response: Efficacy in controlling arrhythmia
• Side effects: Presence and severity of adverse reactions

Monitoring Requirements

Regular monitoring is essential due to amiodarone's potential toxicities:

• ECG every 3-6 months
• Thyroid function tests every 6 months
• Liver function tests every 6 months
• Pulmonary function tests as clinically indicated
• Annual ophthalmologic examination if therapy continues beyond 1 year 1

Important Considerations

• Long half-life: Terminal half-life of 14-58 days after long-term therapy 4, 5
• Tissue accumulation: Extensively distributes into tissues, particularly adipose tissue, skeletal muscle, and myocardium 5
• Delayed onset and offset: Maximal effects may not appear for 90-150 days, and protection may persist for up to 150 days after discontinuation 6
• Drug interactions: Inhibits multiple CYP450 enzymes and p-glycoprotein, requiring dose adjustments of concomitant medications 1

Pitfalls and Caveats

1. Avoid abrupt discontinuation: Due to long half-life, amiodarone should be tapered rather than stopped suddenly 1

2. Electrolyte monitoring: Maintain potassium and magnesium levels >4.0 mEq/L before and during therapy 1

3. Side effect vigilance: Watch for bradycardia, cardiac block, hypotension, neurological effects, QT prolongation, and organ toxicities 1

4. Contraindications: Severe sinus node dysfunction, AV block (without pacemaker), cardiogenic shock, and severe bradycardia 1

5. Drug interactions: Particularly important with warfarin (increased INR), digoxin (increased levels), and medications metabolized by CYP enzymes 1

The maintenance dose of 200-400 mg daily has been shown to be effective for most patients with atrial fibrillation while minimizing toxicity risk. Higher maintenance doses (400-800 mg daily) may be required for patients with ventricular tachycardia or more refractory arrhythmias 6.