What the FDA labels say about taking them together
Azathioprine and chlorambucil
Azathioprine's FDA label of November 8, 2025 names chlorambucil in its contraindications section; the chlorambucil label PlainMeds reads does not name azathioprine. The azathioprine label: “Patients with rheumatoid arthritis previously treated with alkylating agents may have a prohibitive risk of malignancy if treated with IMURAN.”
Check it at the source: the azathioprine FDA label on DailyMed (effective November 8, 2025, Sebela Pharmaceuticals Inc.); the chlorambucil FDA label on DailyMed (effective January 8, 2025, Waylis Therapeutics LLC).
What does the azathioprine label say about chlorambucil?
Azathioprine label, contraindicationsPatients with rheumatoid arthritis previously treated with alkylating agents (cyclophosphamide, chlorambucil, melphalan, or others) may have a prohibitive risk of malignancy if treated with IMURAN.
Source: FDA drug label (IMURAN), NDA016324 (Legacy), as published by Sebela Pharmaceuticals Inc., effective November 8, 2025 (SPL set 606101a0-6244-7eff-e053-2a91aa0acadd), via openFDA; the full label on DailyMed
What does the chlorambucil label say about azathioprine?
Chlorambucil's label (effective January 8, 2025) does not name azathioprine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (LEUKERAN), Waylis Therapeutics LLC, effective January 8, 2025 (SPL set 58a3c995-5ad6-465d-8437-5970c9088213), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Azathioprine | Chlorambucil | |
|---|---|---|
| Labeled for | Organ transplant rejection, Rheumatoid arthritis | Leukemia, lymphoma and myeloma |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.124 per tablet 50 mg tablet | n/a |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once