[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Lung](https://durgical.com/en/general-pathology/areas/lung/) › Drug- and radiation-induced lung injury

# Drug- and radiation-induced lung injury

- Lesion

Some drugs and thoracic radiation injure the lung, causing acute damage that may heal or scar. Always consider them in a treated patient with new infiltrates.

Updated Nov 12, 2026

## Key points

- Bleomycin: direct toxicity and inflammation leading to pulmonary fibrosis.
- Amiodarone: concentrates in the lung; foamy, lipid-laden alveolar macrophages (phospholipidosis) and pneumonitis in a minority of users.
- Methotrexate: hypersensitivity-type pneumonitis with poorly formed granulomas; nitrofurantoin: acute reaction or chronic fibrosis.
- ACE inhibitors: dry cough (bradykinin), not lung damage.
- Acute radiation pneumonitis weeks to months after therapy; chronic radiation fibrosis follows in some.
- Talc and other fillers injected with drugs: foreign-body granulomas around vessels.

## What it is

Drugs and radiation are frequent and avoidable causes of lung disease. They produce a range of patterns: diffuse alveolar damage, NSIP or fibrosis, organizing pneumonia, eosinophilic pneumonia, hypersensitivity-like reactions and bronchiolitis obliterans. Radiation pneumonitis appears weeks to months after treatment of thoracic cancers and may end in fibrosis.

## Structure

- Acute drug or radiation injury: diffuse alveolar damage with markedly atypical, enlarged type II pneumocytes and fibroblasts.
- Radiation: foam cells in vessel walls, vascular sclerosis, then interstitial fibrosis confined to the radiation field.
- Amiodarone: clusters of foamy macrophages in alveoli; lamellar inclusions on electron microscopy.
- Talc granulomatosis: birefringent crystals inside foreign-body giant cells around small vessels.

## Step by step

- Some drugs generate free radicals or are directly toxic to pneumocytes and endothelium (bleomycin, radiation).
- Others act as haptens and trigger hypersensitivity (methotrexate, nitrofurantoin).
- Cationic amphiphilic drugs such as amiodarone accumulate in lysosomes and block phospholipid breakdown.
- The injury evokes inflammation and, if it persists, fibroblast activation and fibrosis.
- Radiation damages DNA in dividing epithelial and endothelial cells, with acute exudation then chronic vascular sclerosis and scar.

## Drugs and the lung lesions they cause

| Agent | Main pattern | Clue |
| --- | --- | --- |
| Bleomycin | Diffuse alveolar damage, fibrosis | Chemotherapy for germ cell tumours and lymphoma |
| Amiodarone | Pneumonitis with foamy macrophages | Antiarrhythmic, cumulative exposure |
| Methotrexate | Hypersensitivity pneumonitis | Fever, eosinophilia, poorly formed granulomas |
| Nitrofurantoin | Acute eosinophilic reaction or chronic fibrosis | Long-term urinary prophylaxis |
| Radiation | Pneumonitis then fibrosis | Limited to the radiation field |

## Clinical notes

- New cough, fever, dyspnoea and infiltrates in a patient on these drugs or after radiotherapy; exclude infection.
- Radiation pneumonitis causes dyspnoea out of proportion to the irradiated volume; many cases resolve with steroids.
- Stopping the drug is the key step; fibrosis that has formed does not reverse.

## Memory aid

B-A-M on the lung: Bleomycin, Amiodarone, Methotrexate.

## Test yourself

Think of the answer, then tap the question to see it.

## What histologic finding is typical of amiodarone lung toxicity?

Foamy, lipid-laden alveolar macrophages from drug-induced phospholipidosis, with interstitial pneumonitis.

## What is typical about the location of radiation fibrosis?

It is largely confined to the area of lung that was in the radiation field.

## What lesion forms in the lungs of people who inject crushed tablets?

Foreign-body granulomas around small vessels containing birefringent filler particles such as talc.

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## Connections

## Related 5

- [Injury by therapeutic drugs: the classic examples](https://durgical.com/en/general-pathology/injury-by-therapeutic-drugs-the-classic-examples/)
- [Ionizing radiation injury](https://durgical.com/en/general-pathology/ionizing-radiation-injury/)
- [Diffuse alveolar damage (ARDS)](https://durgical.com/en/general-pathology/diffuse-alveolar-damage/)
- [Idiopathic pulmonary fibrosis (UIP pattern)](https://durgical.com/en/general-pathology/idiopathic-pulmonary-fibrosis/)
- [Pulmonary eosinophilia](https://durgical.com/en/general-pathology/pulmonary-eosinophilia/)

## Related conditions 1

- [Interstitial lung disease](https://durgical.com/en/conditions/interstitial-lung-disease/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Interstitial Lung Disease](https://www.ncbi.nlm.nih.gov/books/NBK541084/) (StatPearls (NCBI Bookshelf), 2025); [Interstitial Lung Diseases](https://medlineplus.gov/interstitiallungdiseases.html) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/drug-and-radiation-induced-lung-injury/