ABSTRACT
Factors that affect the development of a drug-induced interstitial lung disease include the patient’s age, the initial dosing, the cumulative dose, and associated conditions. For example, patients who receive cytotoxic chemotherapy for underlying malignancy with either bleomycin, busulfan, or carmustine are at risk of developing an acute interstitial pneumonitis with underlying diffuse alveolar damage after radiation therapy or treatment with high concentrations of oxygen. Further, the use of several cytotoxic drugs in combina tion also enhances the development of an interstitial lung reaction. Other conditions en hance the development of a drug-induced interstitial lung disease. Patients being treated with amiodarone, for example, who undergo a surgical procedure are at risk of developing a picture resembling that of acute respiratory distress syndrome (ARDS) owing to diffuse alveolar damage. This was first described in patients receiving chronic amiodarone ther apy, who required cardiac surgery or underwent pneumonectomy. In systemic diseases, which in themselves are associated with an interstitial reaction (the collagen vascular dis eases), it is often difficult to distinguish between a drug-induced pneumonitis and one that is due to the underlying disease. This is often the case in patients receiving weekly methotrexate therapy for the treatment of either rheumatoid arthritis or polymyositis or where gold therapy is used for the treatment of rheumatoid arthritis. Withdrawal of the drug followed by improvement and eventual resolution of the interstitial lung disease confirms the diagnosis of drug toxicity. Further proof of a drug-related interstitial lung disease is the return of the pneumonitis with reinstatement of the drug (not recommended).
