Reversible interstitial lung disease with prolonged use of nitrofurantoin: Do the benefits outweigh the risks?
A 70-year-old man was admitted for the evaluation of dry cough and progressive shortness of breath of 8 weeks duration. His past medical history was remarkable for diabetes mellitus, hypertension and benign hyperplasia of prostate (BHP). He underwent trans-urethral resection of the prostate 1 year back for BHP. He had recurrent urinary tract infections and was on nitrofurantoin, 100 mg at night, for 6 months preceding the onset of symptoms. There was no significant work place exposure, previous lung disease or significant smoking history. Physical examination revealed a respiratory rate of 20 breaths/min, blood pressure of 140/90 mmHg, pulse of 100/min and a saturation of 93% while room air. Respiratory system revealed bibasilar fine end-inspiratory, velcro crackles. Rest of the physical examination was unremarkable. His routine biochemistry and hemogram were normal. Arterial blood gas analysis while breathing room air showed a pH of 7.43, PaO2 of 64 mm Hg, PaCO2 of 37 mm Hg, and bicarbonate of 25 mEq. Chest radiograph carried out revealed bilateral lower zone reticulo-nodular opacities []. He was euthyroid and enzyme-linked immuno sorbent assay for human immunodeficiency virus was negative. Antinuclear antibody, antineutrophil cytoplasmic antibody and rheumatoid factor were normal. Computed tomography of the chest demonstrated symmetric bilateral reticulation, architectural distortion, and honeycombing involving mainly the subpleural lung regions and lower lobes []. Pulmonary function tests showed moderate restrictive defect (forced vital capacity was 58% predicted) with severe reduction carbon monoxide diffusion capacity (DLCO 48%, diffusing capacity corrected for alveolar volume (DLCO/VA), 49% predicted). Electrocardiograph and echocardiography were normal. Open lung biopsy was offered to the patient, but he didn’t agree to it. Nitrofurantoin-induced lung disease was suspected and the drug was discontinued and prednisone 40 mg daily was initiated. Follow chest radiograph [] and computed tomography [] at 1 month showed significant improvement.