What are the contraindications for Amiodarone (antiarrhythmic medication)?

Contraindications for Amiodarone

Amiodarone is contraindicated in patients with marked sinus bradycardia, second- or third-degree AV block without a functioning pacemaker, severe sinus node dysfunction, and cardiogenic shock. 1

Absolute Contraindications

• Hypersensitivity to amiodarone or its components (including iodine)
• Cardiogenic shock
• Marked sinus bradycardia
• Second- or third-degree AV block without a functioning pacemaker
• Severe sinus node dysfunction without a pacemaker 2, 1

Relative Contraindications

Cardiac Conditions

• Preexisting conduction disorders (first-degree AV block, bundle branch blocks) 2
• Prolonged QT interval or conditions predisposing to QT prolongation
• Heart failure (NYHA class III and IV or recently decompensated class II) 3

Pulmonary Conditions

• Severe respiratory failure 4
• History of interstitial lung disease or pulmonary fibrosis

Other Organ Systems

• Hepatocellular failure 4
• Hyperthyroidism 4
• Pregnancy (especially first trimester) due to risk of congenital malformations

High-Risk Patient Populations

Cardiac Patients

• Patients with heart transplants (absolute contraindication) 3
• Patients with ventricular dysfunction and congenital heart disease (higher risk of adverse events) 3

Special Populations

• Patients with cyanotic heart disease (increased risk of thyroid disorders) 3
• Female patients with low body mass index (increased risk of thyrotoxicosis) 3
• Patients with prior Fontan procedure (increased risk of thyroid dysfunction) 3

Drug Interactions to Consider

Amiodarone has significant interactions with multiple medications that may constitute relative contraindications:

• Digoxin (can double digoxin levels, increasing risk of toxicity) 2
• Warfarin and other oral anticoagulants (potentiates anticoagulant effect) 5, 4
• Class I antiarrhythmic drugs (increased risk of proarrhythmia) 5, 4
• Other QT-prolonging medications (additive effect on QT prolongation) 4
• HMG-CoA reductase inhibitors (increased risk of myopathy) 4

Monitoring Recommendations

When amiodarone must be used despite relative contraindications:

• Continuous ECG monitoring during initiation, especially in the first week 2
• Regular thyroid function tests (every 3-6 months)
• Pulmonary function tests and chest X-rays (baseline and periodically)
• Liver function tests (baseline and periodically)
• Drug level monitoring for medications with known interactions

Important Caveats

• The risk of significant bradycardia is higher (24%) in patients with preexisting conduction disorders 2
• Bradycardia risk is highest during the loading phase (32%) compared to maintenance phase (11.2%) 2
• In patients with severe heart failure, amiodarone may be the only antiarrhythmic option, despite the risks 3
• For patients with atrial fibrillation, amiodarone should generally be used when other agents have failed or are contraindicated due to its toxicity profile 3, 6

Remember that amiodarone has a very long half-life (weeks to months), so adverse effects may persist long after discontinuation 7. This should be considered when weighing risks versus benefits in patients with relative contraindications.