From the Guidelines
Diagnosis of amiodarone lung should be suspected in patients taking amiodarone who develop respiratory symptoms, and a prompt assessment for pulmonary toxicity is crucial. The diagnosis is typically made through a combination of clinical evaluation, imaging studies, and sometimes lung biopsy. Patients on amiodarone who develop new or worsening dyspnea, cough, or chest pain should be promptly evaluated, as stated in the guidelines for use and monitoring of amiodarone 1.
Key Diagnostic Features
- Chest X-rays may show bilateral interstitial or alveolar infiltrates
- High-resolution CT scans often reveal ground-glass opacities, interstitial thickening, or consolidation, typically in the upper lobes
- Pulmonary function tests usually demonstrate a restrictive pattern with decreased diffusion capacity, as evidenced by reduced diffusing capacity on pulmonary function tests 1
- Laboratory tests may show elevated inflammatory markers, but these are nonspecific
Diagnostic Approach
- Bronchoalveolar lavage can help exclude infection and may show foamy macrophages, though these can be present in asymptomatic patients as well
- In unclear cases, a lung biopsy showing foamy macrophages, interstitial inflammation, and fibrosis may be necessary
- The diagnosis is often one of exclusion after ruling out other causes of pulmonary disease, such as congestive heart failure, which can mimic amiodarone pneumonitis 1
Risk Factors
- Higher doses (>400 mg/day)
- Longer duration of therapy (>2 months)
- Pre-existing lung disease
- Older age Early recognition is crucial as discontinuation of amiodarone is the primary treatment, though the drug's long half-life means that symptoms may persist or even worsen initially after discontinuation. 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 1.
From the FDA Drug Label
There have been postmarketing reports of acute-onset (days to weeks) pulmonary injury in patients treated with intravenous amiodarone. Findings have included pulmonary infiltrates and/or mass on X-ray, bronchospasm, wheezing, fever, dyspnea, cough, hemoptysis, and hypoxia. Two percent (2%) of patients were reported to have adult respiratory distress syndrome (ARDS) during clinical studies involving 48 hours of therapy. Pulmonary Fibrosis Only 1 of more than 1000 patients treated with amiodarone HCl injection in clinical studies developed pulmonary fibrosis. Pulmonary toxicity is a well-recognized complication of long-term amiodarone use
The diagnosis of amiodarone lung is based on findings such as pulmonary infiltrates, bronchospasm, wheezing, fever, dyspnea, cough, hemoptysis, and hypoxia.
- Pulmonary function tests and imaging studies (e.g. X-ray) may be used to support the diagnosis.
- A high index of suspicion is necessary to diagnose amiodarone lung, especially in patients with respiratory symptoms and a history of amiodarone use 2.
From the Research
Diagnosis of Amiodarone Lung
The diagnosis of amiodarone-induced lung toxicity is based on a combination of clinical, radiological, and histological data. Some key features that support a clinical diagnosis include:
- New onset dyspnea 3, 4
- Exclusion of lung infection 3, 4
- Exclusion of heart failure 3, 4
- New radiographic features, such as ground-glass opacities and interstitial thickening on computed tomography (CT) scans 3, 5, 4
- Improvement with withdrawal of amiodarone 3, 5, 4
Radiological Findings
Radiological findings in amiodarone-induced lung toxicity may include:
- Bilateral infiltrates on chest x-ray 3
- Ground-glass opacities on high-resolution computed tomography (HRCT) scans 3, 5, 4
- Interstitial thickening on CT scans 5, 4
- Pleural effusions on chest x-ray or CT scans 3
Pulmonary Function Tests
Pulmonary function tests may show:
- A restrictive pattern of lung function 3
- A decrease in diffusing capacity (DLCO) 3, 6, 7
- A decrease in total lung capacity (TLC) 7
Treatment
Treatment of amiodarone-induced lung toxicity typically involves: