What are the contraindications for Amiodarone (antiarrhythmic medication) administration?

Contraindications for Amiodarone Administration

Amiodarone is absolutely contraindicated in patients with cardiogenic shock, marked sinus bradycardia, and second- or third-degree AV block without a functioning pacemaker, as well as in those with known hypersensitivity to amiodarone or iodine. 1

Absolute Contraindications

The FDA label and major guidelines identify the following as absolute contraindications:

• Cardiogenic shock is an absolute contraindication to amiodarone use 1
• Marked sinus bradycardia without pacemaker support contraindicates amiodarone administration 1
• Second- or third-degree AV block without a functioning pacemaker is an absolute contraindication 2, 1
• Known hypersensitivity to amiodarone, any of its components, or iodine contraindicates its use 1
• Severe sinus node dysfunction is a contraindication per pediatric guidelines 2
• Heart transplant patients should not receive amiodarone 2

Critical Relative Contraindications and High-Risk Situations

Pre-excitation Syndromes

• Amiodarone should not be administered intravenously to patients with pre-excitation syndromes (e.g., Wolff-Parkinson-White) presenting with atrial fibrillation, as it may paradoxically increase ventricular response and potentially precipitate ventricular fibrillation 2
• In WPW patients with AF, procainamide or ibutilide are preferred agents, while amiodarone may only be considered in hemodynamically stable patients with expert consultation 3

Pregnancy

• Amiodarone should be avoided in pregnancy, especially during the first trimester, due to significant risk of congenital malformations 2

Severe Organ Dysfunction

• Severe hepatic dysfunction requires extreme caution, as amiodarone can cause hepatotoxicity 2
• Pre-existing inflammatory lung disease may be exacerbated by amiodarone 2

Important Precautions Requiring Careful Risk-Benefit Assessment

Cardiovascular Precautions

• Prolonged QT interval requires caution, though amiodarone paradoxically has lower torsades de pointes risk than other QT-prolonging agents despite causing marked QT prolongation 2
• Patients with bradycardia (HR <60 bpm), hypotension (SBP <100 mmHg), or moderate-to-severe left ventricular failure require careful monitoring 2
• Severe peripheral vascular disease and insulin-dependent diabetes warrant caution 2

Pulmonary Precautions

• Pre-existing pulmonary disease significantly increases the risk of pulmonary toxicity, the most serious non-cardiac adverse effect occurring in 2-17% of patients 2, 4
• Severe chronic obstructive pulmonary disease and history of asthma require careful consideration 2

Thyroid Risk Factors

• Patients with risk factors for thyrotoxicosis (female sex, cyanotic heart disease, low BMI, prior Fontan procedure) require particularly close monitoring 2

Mandatory Drug Interaction Considerations

These interactions may constitute functional contraindications without dose adjustment:

• Concurrent use with procainamide or other QT-prolonging medications should not occur without expert consultation 2
• Warfarin dose must be reduced by 50% when initiating amiodarone, with weekly INR monitoring for 6 weeks 2, 4
• Digoxin dose must be reduced by 50% when starting amiodarone, as levels typically double 2, 4
• Statin use (particularly simvastatin and atorvastatin) requires caution due to increased myopathy/rhabdomyolysis risk 2, 5
• HIV antiretroviral medications have significant interactions with amiodarone 5

Required Baseline Assessment Before Administration

Before initiating amiodarone, the following must be documented to identify contraindications:

• Complete cardiovascular examination including ECG to assess for conduction abnormalities 2
• Chest radiograph and pulmonary function tests to establish baseline pulmonary status 2, 4
• Thyroid function studies (TSH, free T4) 2, 4
• Liver transaminase levels 2, 4
• Ophthalmologic examination if pre-existing visual impairment exists 2
• Electrolyte panel to identify hypokalemia or hypomagnesemia, which significantly increase torsades risk 2

Special Population Considerations

Cancer Patients

• In cancer patients, AF or AF risk does not represent a contraindication to continuing cancer treatment, and amiodarone discontinuation must be exceptional and weighed against cancer progression risk 3
• Rate control may be preferable to rhythm control in cancer patients on arrhythmogenic chemotherapy, as the substrate persists with continued drug exposure 3

Hemodialysis Patients

• Amiodarone is not contraindicated in hemodialysis patients and does not require dose adjustment for renal dysfunction 2
• Standard loading and maintenance doses can be used with appropriate monitoring 2