Drug-induced interstitial pneumonia.

(1) Interstitial pneumonia usually develops gradually. The signs and symptoms are non-specific, and generally include dyspnea, cough, fatigue, and weight loss. In other cases onset is acute, sometimes beginning with a flu-like syndrome. Interstitial pneumonia can lead to acute respiratory failure, sometimes gradual deterioration of respiratory function, and pulmonary fibrosis progressing to respiratory failure. The fibrosis does not regress when the causal factor is withdrawn. (2) There are numerous causes of interstitial pneumonia, including medicinal drugs. (3) Amiodarone generally induces slow and insidious lung disease. (4) Methotrexate induces lung disease. Most cytotoxic drugs cause chronic dose-dependent lung disease and fibrosis, in some cases long after treatment cessation. (5) The many other implicated drugs include nitrofurantoin, Nonsteroidal antiandrogens, drugs that induce connective tissue diseases, laxatives based on mineral oil, and many other drugs, some of which are known to cause hypersensitivity reactions. (6) In practice, a drug-related cause should be kept in mind in cases of interstitial pneumonia, as symptoms generally improve after drug withdrawal, unless fibrosis has already started to develop.