II. Epidemiology
- Occurs in 1-2% of patients on Amiodarone per year
III. Pathophysiology
- Acute or subacute pneumonitis related to pulmonary drug deposition
V. Differential Diagnosis
VI. Imaging
-
Chest XRay
- Diffuse Pulmonary Infiltrates
- In some cases may appear similar to lobar Pneumonia
- CT Chest
- Extensive bilateral alveolar and Interstitial Infiltrates
- Ground-glass opacities
VII. Diagnosis
- Clinical diagnosis only (no lab or imaging study is diagnostic)
-
Pulmonary Function Tests
- Restrictive Lung Disease pattern with decreased DLCO
- Bronchoscopy with bronchoalveolar lavage (BAL)
- Evaluates for other causes of diffuse lung disease
- Absence of foamy Macrophages makes Amiodarone toxicity unlikely
- However foamy Macrophages are also seen in up to 50% of patients on Amiodarone
VIII. Precautions
- Often mis-diagnosed as Pneumonia or Congestive Heart Failure
- Consider Amiodarone toxicity in refractory Pneumonia or CHF
IX. Management
- Discontinue Amiodarone (best prognosis with early discontinuation)
- Prednisone 40-60 mg orally daily and slowly tapered over 4-12 months
X. Prognosis
- Most cases, if discontinued early, improve after discontinuation of Amiodarone
- Improvement may take months due to the Amiodarone long Half-Life
- Amiodarone Pulmonary Toxicity is fatal in some cases
XI. Prevention
- Obtain baseline tests before starting Amiodarone
XII. References
- Weinstock, Orman, Frank and Greenwald in Herbert (2016) EM:Rap 16(1):9-11
- Wolkove (2009) Can Respir J 16(2): 43–8 +PMID:19399307 [PubMed]