What are the contraindications for Amiodarone?

Amiodarone Contraindications

Amiodarone is 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 unless a functioning pacemaker is available. 1

Absolute Contraindications

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

Relative Contraindications and Precautions

Cardiovascular Conditions

• Prolonged QT interval - Amiodarone prolongs QT interval in almost all patients, though torsades de pointes is rare 2
• Combination with other QT-prolonging drugs - Should not be used with procainamide or other QT-prolonging medications without expert consultation 2

Pulmonary Conditions

• Pre-existing lung disease - Increases risk of amiodarone pulmonary toxicity 3
• Inflammatory lung disease - May exacerbate underlying condition 2

Hepatic Conditions

• Severe hepatic dysfunction - Amiodarone is metabolized in the liver and can cause hepatotoxicity 2

Thyroid Conditions

• Hypothyroidism or hyperthyroidism - Amiodarone contains iodine and can affect thyroid function 2

Other Considerations

• Peripheral neuropathy - Amiodarone can cause or worsen neurological symptoms 2
• Optic neuritis - Visual changes have been reported with amiodarone use 2
• Abnormal gait/ataxia - Neurological effects may be exacerbated 2

Special Populations and Monitoring Requirements

Patients on Concomitant Medications

• Warfarin therapy - Amiodarone reduces warfarin clearance and can significantly increase INR; warfarin dose typically needs to be reduced by 50% 2
• Digoxin therapy - Amiodarone typically doubles digoxin levels; digoxin dose should be reduced by 50% when starting amiodarone 2
• Statins - Increased risk of myopathy/rhabdomyolysis due to CYP3A4 inhibition 2

Monitoring Requirements

• Baseline assessment before starting amiodarone 2:

  • Complete history and physical examination
  • Chest radiograph
  • Thyroid studies and liver transaminase levels
  • Pulmonary function tests including diffusing capacity (DLCO)
  • Ophthalmologic examination (if pre-existing visual impairment)

• Regular monitoring during treatment 2:

  • Thyroid studies and liver transaminase levels every 6 months
  • Chest radiograph if pulmonary toxicity is suspected
  • Heart rate surveillance, especially during the first week of treatment

Important Clinical Considerations

• Pulmonary toxicity is one of the most serious adverse effects, occurring in 5-15% of patients, and presenting as interstitial pneumonitis with cough, dyspnea, and infiltrates on imaging 3

• Intravenous administration requires special precautions:

  • May cause hypotension (16% of patients) and bradycardia (4.9% of patients) 2
  • Should be given through a central venous line when possible to avoid phlebitis 2
  • Continuous electrocardiographic monitoring should be employed 2

• Drug interactions are extensive due to amiodarone's inhibition of multiple cytochrome P450 enzymes (CYP2C9, CYP2D6, CYP3A4) and P-glycoprotein 2

• Long half-life (weeks to months) means effects persist long after discontinuation 4, 5