Nitrofurantoin and Pulmonary fibrosis / interstitial lung disease: is the FAERS signal real?
Nitrofurantoin ↔ Pulmonary fibrosis / interstitial lung disease
Nitrofurantoin can produce an acute pneumonitis and, with prolonged use, a chronic interstitial lung disease that may progress to pulmonary fibrosis — a rare but well-recognised and potentially irreversible toxicity of a drug otherwise regarded as safe and reserved for uncomplicated urinary infection. The chronic form is related to cumulative duration of therapy, which is why long-term prophylaxis is discouraged and lung function is monitored. The 147 co-reports (PRR 9.9) reflect both the true effect and the difficulty of attributing chronic fibrosis to a drug that is often used intermittently.
Regulatory basis: nitrofurantoin prescribing information (acute and chronic pulmonary reactions, including fibrosis). Established nitrofurantoin lung-toxicity literature.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | Chronic lung changes develop after months–years of exposure; acute pneumonitis after days |
| Strength | partial | PRR 10 on a modest co-report count |
| Consistency | met | Reproduced across decades of nitrofurantoin pulmonary-toxicity case series |
| Specificity | met | A recognised drug cause of chronic interstitial lung disease |
| Biological gradient | partial | Cumulative-duration-related for the chronic form |
| Plausibility | met | Repeated oxidant injury and immune reaction in the lung are the proposed mechanisms |
| Coherence | met | Coheres with the labelled pulmonary warnings and periodic lung review |
| Experiment | partial | Dechallenge (withdrawal) may halt or partially reverse it; no randomized trial |
| Analogy | met | Analogous to pulmonary fibrosis from other drugs (amiodarone, methotrexate, bleomycin) |
This page's own qualitative read, not an automated/citation-gated assessment.