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3. Amiodarone lung toxicity
Amiodarone lung toxicity is a clinical diagnosis made with a compatible clinical situation, absence of other likely diagnosis and compatible pathology. This case would fulfill all criteria.
The incidence of amiodarone toxicity is estimated at 1-15%. Risk factors include:
The highest risk is in men over the age of 60 years on who have received amiodarone for 6-12 months. Dose associations can be either accumulative or daily dosing. With higher daily doses (>400mg) there is a 5-15% incidence but with lower doses used today (< 400 mg) the incidence is about 2%.
Several types of lung injury have been reported including:
Clinically 50-75% of patients have progressive dyspnea and nonproductive cough. There may be fever, pleurisy, or weight loss. Physical exam shows hypoxia and bilateral rales. Usually there is no clubbing.
Laboratory findings are nonspecific. KL-6, a mucinous high-molecular weight glycoprotein, expressed on type II pneumonocytes, is often elevated in the serum of patients with amiodarone toxicity, but is nonspecific, being elevated in most active interstitial pneumonias. Amiodarone levels are not useful in diagnosing amiodarone lung toxicity.
Pulmonary function testing usually shows a restrictive pattern with a low FVC, TLC and DLCO. A stable DLCO suggests amiodarone toxicity is unlikely while a decrease of 15% or more is suggestive, but not diagnostic.
Chest x-ray and CT scans may have alveolar, interstitial or mixed opacities. In the case of organizing pneumonia the opacities may be migratory. Pleural effusions are rare.
On bronchoalveolar lavage the inflammatory cell types are highly variable with lymphocytes, neutrophils and eosinophils all reported. Foamy macrophages are present in 50% of patients on amiodarone and are not specific for pulmonary toxicity. However, if absent, amiodarone toxicity is unlikely.
Diagnosis may be made with typical history, clinical findings and imaging and the exclusion of other clinical syndromes cardiogenic pulmonary edema, infection, pulmonary embolus and noncardiogenic pulmonary edema (ARDS). Lung biopsy may be necessary when the diagnosis is unclear.
Which of the following are not recommended therapies for amiodarone lung toxicity?