When is amiodarone (antiarrhythmic medication) contraindicated?

Amiodarone Contraindications: When Not to Administer

Amiodarone is absolutely contraindicated in patients with known hypersensitivity to any of its components (including iodine), cardiogenic shock, marked sinus bradycardia, and second- or third-degree AV block without a functioning pacemaker. 1

Absolute Contraindications

• Severe sinus node dysfunction - Amiodarone can worsen bradycardia and sinus node function 2
• Second- and third-degree AV block without a functioning pacemaker - Amiodarone can further depress AV nodal conduction 2, 1
• Cardiogenic shock - Amiodarone can worsen hypotension and hemodynamic compromise 1
• Known hypersensitivity to amiodarone or its components (including iodine) - Can cause severe allergic reactions 1
• Heart transplant patients - Specific contraindication noted in guidelines 2

Cardiovascular Contraindications and Precautions

• Pre-excitation syndromes with AF - Intravenous amiodarone should not be administered as it may increase ventricular response and potentially result in ventricular fibrillation 3
• Prolonged QT interval - Amiodarone further prolongs QT interval and requires careful monitoring, though it has lower risk of torsades de pointes compared to other QT-prolonging antiarrhythmics 2
• Bradycardia (heart rate <60 bpm) - Amiodarone can worsen bradycardia 2, 4
• Hypotension (systolic BP <100 mmHg) - Amiodarone can cause or worsen hypotension 2
• Moderate or severe left ventricular failure - Requires careful monitoring 2
• Concomitant use with other QT-prolonging medications - Increases risk of torsades de pointes 2

Pulmonary Contraindications and Precautions

• Inflammatory lung disease - May be exacerbated by amiodarone 2
• Severe COPD or history of asthma - Amiodarone can worsen respiratory conditions 2
• Pre-existing pulmonary disease - Increases risk of pulmonary toxicity, which is the most serious potential adverse effect 3, 2

Hepatic Contraindications and Precautions

• Severe hepatic dysfunction - Amiodarone can cause hepatotoxicity 2
• Active liver disease - May be worsened by amiodarone 2, 5

Thyroid Contraindications and Precautions

• Pre-existing thyroid disorders - Amiodarone contains iodine and can cause both hypo- and hyperthyroidism 2, 6
• Patients with risk factors for thyrotoxicosis - Including female sex, cyanotic heart disease, low body mass index, prior Fontan procedure 3

Special Populations and Monitoring Requirements

• Pregnancy - Amiodarone should be avoided if possible, especially in the first trimester due to risk of congenital malformations 3
• Patients on warfarin - Requires 50% dose reduction of warfarin due to significant drug interaction 2
• Patients on digoxin - Requires 50% dose reduction of digoxin due to increased digoxin levels 2
• Patients on statins - Increased risk of myopathy/rhabdomyolysis 2
• Insulin-dependent diabetes - Requires careful monitoring 2

Permanent AF with Rate Control Strategy

• Dronedarone should not be used to control ventricular rate in patients with permanent AF as it increases the risk of stroke, myocardial infarction, systemic embolism, and cardiovascular death 3

Clinical Decision Algorithm for Amiodarone Use

1. Assess for absolute contraindications:

   • If patient has hypersensitivity to amiodarone/iodine, cardiogenic shock, severe sinus bradycardia, or high-grade AV block without pacemaker → DO NOT USE 1

2. Evaluate cardiac status:

   • If patient has pre-excitation syndrome with AF → DO NOT USE IV amiodarone 3
   • If QTc >500ms → Consider alternative therapy 2
   • If severe LV dysfunction → Use with caution, monitor closely 2

3. Check for organ dysfunction:

   • If severe hepatic dysfunction → Consider alternative therapy 2
   • If inflammatory lung disease/severe COPD → Consider alternative therapy 2
   • If thyroid disease → Use with extreme caution and close monitoring 2

4. Review concomitant medications:

   • If on warfarin → Reduce warfarin dose by 50% 2
   • If on digoxin → Reduce digoxin dose by 50% 2
   • If on other QT-prolonging drugs → Avoid combination if possible 2

5. Establish monitoring protocol:

   • Baseline: ECG, thyroid function, liver enzymes, chest X-ray, pulmonary function tests 3, 2
   • Regular follow-up: ECG, thyroid function, liver enzymes, clinical assessment for pulmonary symptoms 3, 2

Important Considerations

• Despite its efficacy, amiodarone should generally be considered a secondary therapeutic option due to its significant adverse effect profile 7
• Long-term treatment should use minimal effective doses to reduce risk of toxicity 7
• For atrial fibrillation, amiodarone should be reserved for patients with left ventricular dysfunction or when other agents have failed 8, 6
• Patients with pre-existing conduction disorders have a substantially higher risk (24% in one study) of developing symptomatic bradycardia with amiodarone 4
• AV nodal ablation with permanent ventricular pacing should not be performed to improve rate control without prior attempts to achieve rate control with medications 3