What are the potential side effects of an Amiodarone (antiarrhythmic medication) infusion?

Amiodarone Infusion Side Effects

Intravenously administered amiodarone causes heart block or bradycardia in 4.9% of patients and hypotension in 16% of patients, requiring discontinuation or reduction of infusion rate if these conditions occur. 1

Cardiovascular Side Effects

• Hypotension (16% of patients) is the most common adverse reaction leading to discontinuation of IV amiodarone therapy 2
• Bradycardia and heart block (4.9% of patients) can occur during infusion and may require temporary pacing in some cases 1
• QT interval prolongation is common, though torsades de pointes occurs in less than 2% of patients 2
• Proarrhythmic effects can occur, including worsening of existing arrhythmias or precipitation of new arrhythmias 2
• Contraindicated in patients with bradycardia or heart block who do not have a pacemaker 1

Pulmonary Side Effects

• Acute-onset pulmonary injury can develop within days to weeks, presenting with pulmonary infiltrates, bronchospasm, fever, dyspnea, cough, and hypoxia 2
• Adult respiratory distress syndrome (ARDS) occurs in approximately 2% of patients during 48 hours of therapy 1
• Early pulmonary fibrosis (within 1-3 months) has been reported but is rare with short-term IV use 2
• Pulmonary toxicity is the most serious potential adverse effect of amiodarone therapy, typically presenting as subacute cough and progressive dyspnea 1

Hepatic Side Effects

• Elevated liver enzymes (ALT, AST, GGT) are common in patients receiving IV amiodarone 2
• Approximately 54% of patients have baseline liver enzyme elevations, and 13% develop clinically significant elevations 2
• Acute centrolobular confluent hepatocellular necrosis leading to hepatic coma, acute renal failure, and death has been reported 2
• If liver enzyme levels are three times higher than normal, amiodarone should be discontinued unless the patient is at high risk for recurrence of life-threatening arrhythmia 1

Thyroid Side Effects

• Amiodarone can cause both hyperthyroidism and hypothyroidism due to its high iodine content and effects on peripheral conversion of thyroid hormones 2
• Hyperthyroidism occurs in about 2% of patients and can precipitate arrhythmias 2
• Thyroid function should be evaluated prior to treatment and periodically thereafter 2

Neurologic Side Effects

• Tremor, ataxia, paresthesias can occur and are often dose-related 1
• Peripheral neuropathy has been reported at a rate of 0.3% annually 1
• Other reported neurologic effects include increased intracranial pressure, pseudotumor cerebri, and dizziness 2

Ocular Side Effects

• Optic neuropathy and optic neuritis can occur, sometimes progressing to permanent blindness 2
• Visual impairment should prompt ophthalmologic evaluation 1

Dermatologic and Infusion Site Reactions

• Infusion site reactions including thrombosis, phlebitis, thrombophlebitis, cellulitis, pain, and inflammation can occur 2
• Phlebitis may occur, so administration through a central venous line is preferred when possible 1

Drug Interactions

• Amiodarone inhibits metabolism of several drugs through cytochrome P450 pathways 1
• Warfarin: Reduces clearance leading to sudden increases in prothrombin time and INR, peaking around 7 weeks after initiation 1
• Digoxin: Levels typically double due to inhibition of renal tubular secretion 1
• Close monitoring of digoxin levels, prothrombin time, and INR is essential 1

Monitoring Recommendations

• Baseline assessment should include complete history and physical examination, chest radiograph, thyroid and liver function tests 1
• During infusion, monitor for hypotension, bradycardia, and QT prolongation 2
• For patients on warfarin, monitor prothrombin time and INR at least weekly for the first 6 weeks 1
• For patients on digoxin, monitor levels closely 1

Special Considerations

• IV amiodarone should not be used in patients with bradycardia or heart block without a pacemaker 1
• Correct electrolyte abnormalities (particularly hypokalemia, hypomagnesemia, hypocalcemia) before initiating treatment to reduce risk of torsades de pointes 2
• Use with caution in patients with thyroid disorders or liver disease 2