What the FDA labels say about taking them together
Azathioprine and cyclophosphamide
Azathioprine's FDA label of November 8, 2025 names cyclophosphamide in its contraindications section, and cyclophosphamide's label names azathioprine too. The cyclophosphamide label: “Acute water intoxication has been reported with concomitant use of indomethacin Increase in other toxicities: ● Azathioprine:”
Check it at the source: the azathioprine FDA label on DailyMed (effective November 8, 2025, Sebela Pharmaceuticals Inc.); the cyclophosphamide FDA label on DailyMed (effective January 19, 2026, Amneal Pharmaceuticals LLC).
What does the azathioprine label say about cyclophosphamide?
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 cyclophosphamide label say about azathioprine?
Frindovyx label (AVYXA Pharma, LLC, August 26, 2026), drug interactionsAcute water intoxication has been reported with concomitant use of indomethacin Increase in other toxicities: ● Azathioprine:
Cyclophosphamide label (Eugia US LLC, April 21, 2025), drug interactionsAzathioprine: Increased risk of hepatotoxicity (liver necrosis) Busulfan: Increased incidence of hepatic veno-occlusive disease and mucositis has been reported.
Source: FDA drug label (Frindovyx, NDA210852), AVYXA Pharma, LLC, effective August 26, 2026 (SPL set 5ad8ea65-4c98-487a-9c8d-df778765ec5e), via openFDA
Source: FDA drug label (Cyclophosphamide, NDA210735), Eugia US LLC, effective April 21, 2025 (SPL set 3c1eb470-0bba-457d-94e3-b9508f0d398a), via openFDA
Source: FDA drug label (Cyclophosphamide), Amneal Pharmaceuticals LLC, effective January 19, 2026 (SPL set 520bfe39-dfd5-4a20-9a37-80078afded0d), 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 | Cyclophosphamide | |
|---|---|---|
| Labeled for | Organ transplant rejection, Rheumatoid arthritis | Leukemia, lymphoma and myeloma |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.124 per tablet 50 mg tablet | $1.67 per capsule 50 mg capsule |
| 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