What are the contraindications to amiodarone?

Contraindications to Amiodarone

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 following conditions represent absolute contraindications where amiodarone must not be used:

• Cardiogenic shock 1
• Marked sinus bradycardia 1
• Second- or third-degree AV block without a functioning pacemaker 2, 1
• Known hypersensitivity to amiodarone, its components, or iodine 1
• Severe sinus node dysfunction 3
• Heart transplant patients 3

Critical Relative Contraindications

These conditions require extreme caution and often represent practical contraindications in most clinical scenarios:

Cardiovascular Conditions

• Pre-excitation syndromes (e.g., WPW) with atrial fibrillation - IV amiodarone may increase ventricular response and precipitate ventricular fibrillation 3
• Bradycardia (heart rate <60 bpm) - particularly concerning as amiodarone causes bradycardia in 1-3% of patients 3
• Hypotension (systolic BP <100 mmHg) - IV amiodarone causes hypotension in 16% of patients 3
• Moderate to severe left ventricular failure - requires careful assessment 3

Pulmonary Conditions

• Pre-existing inflammatory lung disease - significantly increases risk of potentially fatal pulmonary toxicity 3
• Severe chronic obstructive pulmonary disease 3
• History of asthma 3

Hepatic and Metabolic Conditions

• Severe hepatic dysfunction - amiodarone causes hepatotoxicity at 0.6% annually; discontinue if liver enzymes exceed 3x normal 2, 3
• Hyperthyroidism - amiodarone contains significant iodine and can worsen thyroid dysfunction 3

Other High-Risk Conditions

• Severe peripheral vascular disease 3
• Insulin-dependent diabetes 3

Special Population Considerations

Pregnancy

• Avoid in pregnancy, especially first trimester - risk of congenital malformations 3

Patients on Specific Medications

Amiodarone should not be used without expert consultation in patients taking:

• Procainamide or other QT-prolonging medications 3
• Dronedarone - contraindicated in permanent atrial fibrillation due to increased stroke, MI, and cardiovascular death risk 3

Drug Interaction Warnings Requiring Dose Adjustments

When amiodarone must be used with these medications, mandatory dose reductions are required:

• Warfarin: reduce dose by 50% and monitor INR at least weekly for first 6 weeks 3
• Digoxin: reduce dose by 50% due to significant elevation of digoxin levels 3, 4
• Statins: use with extreme caution due to increased myopathy/rhabdomyolysis risk 3

Mandatory Pre-Treatment Assessment

Before initiating amiodarone, the following baseline evaluations are required to identify contraindications 2, 3:

• Complete history focusing on congestive heart failure, arrhythmia symptoms, and concomitant medications
• Chest radiograph - to establish baseline for pulmonary toxicity monitoring
• Thyroid studies (TSH, free T4) - to identify pre-existing thyroid dysfunction
• Liver transaminase levels - to establish baseline hepatic function
• Pulmonary function tests including DLCO - critical for detecting early pulmonary toxicity
• ECG - to document baseline QT interval and conduction abnormalities
• Ophthalmologic examination - if pre-existing visual impairment present
• Digoxin level, PT/INR - when applicable

Common Pitfalls to Avoid

• Do not overlook subclinical sinus node dysfunction - amiodarone will unmask and worsen this condition 3
• Do not assume QT prolongation alone is a contraindication - while amiodarone prolongs QT in nearly all patients, torsades de pointes is rare (<1% annually) compared to other antiarrhythmics 2, 3
• Do not use in patients with uncorrected hypokalemia or hypomagnesemia - these electrolyte abnormalities significantly increase proarrhythmic risk 3
• Do not initiate without establishing a monitoring plan - pulmonary toxicity can develop rapidly without antecedent abnormalities 2