From the Guidelines
The most common complication of long-term Amiodarone use is pulmonary toxicity, which may result from direct drug-induced phospholipidosis or immune-mediated hypersensitivity, as reported in a study published in the American Family Physician in 2003 1. This complication can manifest as subacute cough and progressive dyspnea, with associated patchy interstitial infiltrates on chest radiographs. The frequency of pulmonary toxicity in amiodarone therapy was found to be 2 to 17 percent in early studies, but more recent studies have shown a lower incidence in patients receiving dosages of 300 mg per day or less 1. Some key points to consider about pulmonary toxicity include:
- Reduced diffusing capacity on pulmonary function tests
- A much less common presentation is adult respiratory distress syndrome, with a frequency of 1 percent annually 1
- Routine screening for adult respiratory distress syndrome is of limited value, because pulmonary toxicity can develop rapidly with no antecedent abnormalities on chest radiographs or pulmonary function tests
- Any report from the patient of worsening dyspnea or cough should elicit a prompt assessment for pulmonary toxicity
- Congestive heart failure can mimic amiodarone pneumonitis and, thus, must be ruled out early in the evaluation
- High-resolution computed tomographic scanning can be helpful in making a diagnosis The primary treatment for pulmonary toxicity is withdrawal of amiodarone and provision of supportive care and, in some cases, corticosteroids 1. It is essential to monitor patients on long-term amiodarone regularly, including baseline and periodic pulmonary function tests, chest X-rays, and clinical assessment of respiratory symptoms, to promptly identify and manage pulmonary toxicity.
From the FDA Drug Label
Pulmonary toxicity is a well-recognized complication of long-term amiodarone use (see labeling for oral amiodarone). The most common complication of long-term Amiodarone is pulmonary toxicity.
- This includes conditions such as pulmonary fibrosis and adult respiratory distress syndrome (ARDS).
- The FDA drug label recommends close monitoring of patients on amiodarone, especially with regard to pulmonary function 2.
From the Research
Amiodarone-Induced Pulmonary Toxicity
The most common complication of long-term Amiodarone use is pulmonary toxicity, which can manifest in various forms, including:
- Chronic interstitial pneumonitis
- Organizing pneumonia
- Acute respiratory distress syndrome (ARDS)
- Diffuse alveolar hemorrhage
- Pulmonary nodules or masses
- Pleural effusion
Incidence and Risk Factors
The incidence of Amiodarone-induced pulmonary toxicity is estimated to be around 5-15% 3, 4, 5. Risk factors include:
- Older age
- Duration of treatment
- Cumulative dosage
- Pre-existing lung disease
- History of cardiothoracic surgery
- Use of high oxygen mixtures
- Use of iodinated contrast media
Diagnosis and Treatment
Diagnosis is typically made by excluding other causes of pulmonary symptoms, such as infection or heart failure, and by identifying characteristic radiographic features, such as diffuse infiltrates or ground-glass opacities on chest X-ray or high-resolution computed tomography (HRCT) 4, 5, 6. Treatment consists of discontinuing Amiodarone and, in severe cases, administering corticosteroids 3, 4, 5, 6.
Monitoring and Prevention
Regular monitoring of pulmonary function, including chest X-rays and pulmonary function tests, is recommended to detect early signs of pulmonary toxicity 3, 4, 7. A baseline pulmonary function test (PFT) and diffusion capacity for carbon monoxide (DLCO) can help identify patients at risk of developing pulmonary toxicity 5.