Nitrofurantoin-induced alterations in pulmonary tissue. A report on five patients with acute or subacute reactions.

Three patients with acute and two with subacute nitrofarantoin-induced pulmonary reactions were studied clinically and by examinining microcoscopically needle biopsy specimens of their lungs. In all five patients slight vasculitis and a few interstitial eosinophils were found in the pulmonary tissue 1-2 weeks after the withdrawal of nitrofurantion therapy. Alveolitis, fibrinous alveolar exudate and perivascular granulomas were also seen in some specimens. The patients with acute reactions had marked blood eosinophilia. In all patients, pulmonary diffusing capacity (DLCO) was below normal, but ventilatory function was not appreciably affected. Withdrawal of nitrofurantion resulted in complete or partial improvement in 4-8 weeks. Our clinical and histological findings support the suggestion that a type III immune-complex-mediated reactions is involved in acute and subacute hypersensitivity reactions to nitrofurantoin.