What the FDA labels say about taking them together
Azathioprine and natalizumab
Natalizumab's FDA label of March 21, 2025 names azathioprine in its drug interactions section; the azathioprine label PlainMeds reads does not name natalizumab. The natalizumab label: “DRUG INTERACTIONS Because of the potential for increased risk of PML and other infections, Crohn’s disease patients receiving natalizumab products should not be treated with concomitant immunosuppressants or inhibitors …”
Check it at the source: the azathioprine FDA label on DailyMed (effective November 8, 2025, Sebela Pharmaceuticals Inc.); the natalizumab FDA label on DailyMed (effective March 21, 2025, Biogen Inc.).
What does the azathioprine label say about natalizumab?
Azathioprine's label (effective November 8, 2025) does not name natalizumab in these sections. A label lists what its studies and reports found; it is not a complete list.
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 natalizumab label say about azathioprine?
Natalizumab label, drug interactionsDRUG INTERACTIONS Because of the potential for increased risk of PML and other infections, Crohn's disease patients receiving TYSABRI should not be treated with concomitant immunosuppressants (e.g., 6-mercaptopurine, azathioprine, cyclosporine, or methotrexate) or inhibitors of TNF-α, and corticosteroids should be tapered in those patients with Crohn's disease who are on chronic corticosteroids when they start TYSABRI therapy [ see Indications and Usage ( 1.2 ), Warnings and Precautions ( 5.1 , 5.6 ) ].
Natalizumab label, warnings and precautionsPrior treatment with an immunosuppressant (e.g., mitoxantrone, azathioprine, methotrexate, cyclophosphamide, mycophenolate mofetil).
Source: FDA drug label (Tyruko, BLA761322), Sandoz Inc, effective October 31, 2025 (SPL set ef653c36-dd4b-4e71-9d2d-40b8fea24b67), via openFDA
Source: FDA drug label (TYSABRI), Biogen Inc., effective March 21, 2025 (SPL set c5fdde91-1989-4dd2-9129-4f3323ea2962), 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 | Natalizumab | |
|---|---|---|
| Labeled for | Organ transplant rejection, Rheumatoid arthritis | Multiple sclerosis |
| 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