What drugs can cause eosinophilic pneumonitis?

Drugs That Cause Eosinophilic Pneumonitis

NSAIDs (particularly naproxen, ibuprofen, and diclofenac), antibiotics (especially beta-lactams, nitrofurantoin, minocycline, daptomycin, and imipenem/cilastatin), methotrexate, 5-ASA compounds (sulfasalazine), anti-TNF biologics, and antituberculosis agents are the primary drugs that cause eosinophilic pneumonitis. 1, 2, 3

High-Risk Medication Classes

NSAIDs

• Naproxen is the most commonly reported NSAID causing eosinophilic pneumonitis, with 8 published cases plus 3 additional cases in the French pharmacovigilance database 2, 3
• Ibuprofen (3 published cases, 2 in French database) and diclofenac (2 published cases) are also significant culprits 2
• Fenbufen (4 cases), piroxicam (1 case), and other NSAIDs have been documented 2
• The FDA label for naproxen specifically lists "eosinophilic pneumonitis" as an adverse reaction 4

Antibiotics

• Beta-lactam antibiotics are common causes of drug-induced eosinophilic pneumonitis 1, 5
• Nitrofurantoin is a well-established cause 1, 5
• Daptomycin and minocycline are commonly reported antibiotic causes 6
• Imipenem/cilastatin can cause acute eosinophilic pneumonia, with recurrence upon rechallenge 6

Immunosuppressive and Anti-Inflammatory Agents

• Methotrexate causes severe hypersensitivity pneumonitis or pulmonary fibrosis 1
• 5-ASA compounds (sulfasalazine, mesalamine) induce different types of interstitial lung disease, with peripheral eosinophilia in almost half of cases 1
• Anti-TNF monoclonal antibodies can cause granulomatous inflammation and organizing pneumonia patterns 1

Cancer Therapeutics

• EGFR-TKIs (gefitinib, erlotinib, osimertinib, afatinib) cause pneumonitis with pulmonary eosinophilia patterns in 0.55-4.77% of patients 1
• ALK inhibitors (alectinib, brigatinib, ceritinib, crizotinib) cause pneumonitis in 1.14-6.25% of patients 1
• PD-1 inhibitors (nivolumab, pembrolizumab) cause pneumonitis in 2.7-6.6% of patients 1
• Bleomycin is a classic anticancer agent causing eosinophilic pneumonitis 1, 3

Other Medications

• Anticonvulsants, particularly phenytoin 5
• Sulfonamide-containing antibiotics 5
• Gold salts (historically important, now less common) 7
• Chinese herbal medicines 7
• Antituberculosis agents 7

Clinical Presentation and Timing

Onset Patterns by Drug Class

• Anti-inflammatory drugs, analgesics, and antibiotics: Typically develop at 1-2 weeks after starting administration 7
• Anticancer and immunosuppressive agents: Often delayed onset with features of diffuse interstitial pneumonia 7
• Chinese herbal medicines, gold salts: Intermediate timing at 2-6 months 7

Key Clinical Features

• Dyspnea, fever, chest pain, and cough are the most common symptoms 1
• Peripheral eosinophilia is found in almost half of cases with 5-ASA compounds 1
• Bronchoalveolar lavage shows elevated eosinophils (>15% is diagnostic) 2, 6
• Ground-glass opacities and consolidation on chest CT 1, 6

Diagnostic Approach

The diagnosis requires temporal relationship to drug exposure, exclusion of infections and other causes, and demonstration of eosinophilia in blood or bronchoalveolar lavage. 1, 2, 3

• Obtain detailed medication history including exact timing of drug initiation 1
• Perform chest CT showing organizing pneumonia, NSIP, DAD, hypersensitivity pneumonitis, or simple pulmonary eosinophilia patterns 1
• Check peripheral eosinophil count (though may be normal) 7
• Bronchoscopy with BAL showing >15% eosinophils is diagnostic 2, 6
• Drug lymphocyte stimulation test (DLST) has high sensitivity for NSAIDs, antibiotics, and anti-inflammatory drugs but low sensitivity for anticancer agents 7

Management Algorithm

1. Immediately discontinue the suspected offending drug 2, 3, 6
2. Initiate corticosteroid therapy for severe or refractory cases (typically prednisolone 30 mg daily, then taper) 8, 2, 3
3. Monitor for clinical improvement within days to weeks 2, 6
4. Never rechallenge with the causative drug, as recurrence is expected 3, 6

Critical Pitfalls

• Do not assume eosinophilia is drug-related without first excluding helminthic infections, especially in travelers or migrants 5
• Infections (particularly opportunistic infections in immunosuppressed patients) must always be excluded before attributing pneumonitis to drugs 1
• Japanese patients have significantly higher incidence of EGFR-TKI pneumonitis (4.77% vs 0.55% in non-Japanese) 1
• Metastatic disease can mimic drug-induced pneumonitis on imaging 1
• Tapering corticosteroids too rapidly can cause recurrence, as demonstrated in the rheumatoid arthritis case where symptoms returned when prednisolone was reduced to 5 mg daily 8

Prognosis

• Anti-inflammatory drugs, analgesics, and antibiotics: Generally good outcome with drug discontinuation and corticosteroids 7
• Anticancer and immunosuppressive agents: Generally poor outcome with higher mortality 7
• All patients in published NSAID-induced eosinophilic pneumonitis cases recovered with appropriate management 2