Unrecognized Interstitial Lung Disease as a Result of Chronic Nitrofurantoin Use

Drug-induced interstitial lung disease is a rare condition attributed to several medications, including antimicrobial agents such as amphotericin B, anti-inflammatory agents such as methotrexate, biologic agents such as bevacizumab, and cardiovascular agents and chemotherapeutic agents. We describe the case of a 73-year-old female who developed interstitial lung disease following chronic use of nitrofurantoin for a urinary tract infection (UTI). The patient was taking nitrofurantoin 100 mg capsules twice daily for approximately 3 years. She presented to the hospital with complaints of a persistent dry cough that started 2 years previously. Her chest radiograph revealed bilateral reticular opacities and some atelectasis. Computed tomography of the chest demonstrated development of subpleural reticular opacities with minimal honeycombing. The patient had a severe restrictive defect on her pulmonary function tests, with a significant reduction in her carbon monoxide diffusion capacity. Multiple infectious disease and autoimmune tests were negative. Utilizing the algorithm of Naranjo (score of 9), it was determined that chronic use of nitrofurantoin was the definite cause of the patient's interstitial lung disease. Nitrofurantoin was discontinued and she was treated with oxygen and started on an oral steroid, both of which were continued permanently once discharged. Upon discharge, the patient was maintained on 5 L of oxygen at rest and 10 L of oxygen when ambulating. Unfortunately, her lung disease ultimately resulted in her demise several months after her diagnosis. This case report illustrates the importance of rapid recognition of drug-induced lung injuries and discontinuation of the offending agent.