What the FDA labels say about taking them together
Azathioprine and peginterferon alfa 2a
Peginterferon alfa 2a's FDA label of September 2, 2026 names azathioprine in its warnings and precautions section; the azathioprine label PlainMeds reads does not name peginterferon alfa 2a. The peginterferon alfa 2a label: “Pancytopenia and bone marrow suppression have been reported in the literature to occur within 3 to 7 weeks after the concomitant administration of pegylated interferon/ribavirin and azathioprine.”
Check it at the source: the azathioprine FDA label on DailyMed (effective November 8, 2025, Sebela Pharmaceuticals Inc.); the peginterferon alfa 2a FDA label on DailyMed (effective September 2, 2026).
What does the azathioprine label say about peginterferon alfa 2a?
Azathioprine's label (effective November 8, 2025) does not name peginterferon alfa 2a 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 peginterferon alfa 2a label say about azathioprine?
Peginterferon alfa 2a label, warnings and precautionsPancytopenia (marked decreases in RBCs, neutrophils and platelets) and bone marrow suppression have been reported in the literature to occur within 3 to 7 weeks after the concomitant administration of pegylated interferon/ribavirin and azathioprine.
Source: FDA drug label (Pegasys), pharmaand GmbH, effective September 2, 2026 (SPL set d9290e5b-6d40-2318-e053-2995a90a9916), 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 | Peginterferon alfa 2a | |
|---|---|---|
| Labeled for | Organ transplant rejection, Rheumatoid arthritis | Hepatitis C, Hepatitis B |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.124 per tablet 50 mg tablet | n/a |
| Shortage now | No current entry | Resolved |
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