What the FDA labels say about taking them together
Mercaptopurine and mesalamine
Mercaptopurine's FDA label (Mercaptopurine) of January 30, 2026 names mesalamine in its drug interactions section, and mesalamine's label names mercaptopurine too. The mercaptopurine label: “Aminosalicylates may inhibit the TPMT enzyme, which may increase the risk of myelosuppression when coadministered with mercaptopurine tablets.”
Check it at the source: the mercaptopurine FDA label on DailyMed (effective July 20, 2026, Nova Laboratories, Ltd); the mesalamine FDA label on DailyMed (effective August 27, 2026, Salix Pharmaceuticals, Inc.).
What does the mercaptopurine label say about mesalamine?
Mercaptopurine label (Florida Pharmaceutical Products, LLC, January 30, 2026), drug interactionsAminosalicylates (e.g., mesalamine, olsalazine or sulfasalazine) may inhibit the TPMT enzyme, which may increase the risk of myelosuppression when coadministered with mercaptopurine tablets.
Source: FDA drug label (Mercaptopurine, NDA009053), Florida Pharmaceutical Products, LLC, effective January 30, 2026 (SPL set e7309808-5ae8-4a55-90e3-3992ace0da62), via openFDA
Source: FDA drug label (MERCAPTOPURINE), Nova Laboratories, Ltd, effective July 20, 2026 (SPL set 9c6fc66b-522f-499d-961a-cde6ca0ec2e5), via openFDA; the full label on DailyMed
What does the mesalamine label say about mercaptopurine?
Rowasa label (Viatris Specialty LLC, August 3, 2026), drug interactionsAzathioprine or 6-Mercaptopurine The concurrent use of mesalamine with azathioprine or 6‑mercaptopurine and/or any other drugs known to cause myelotoxicity may increase the risk for blood disorders, bone marrow failure, and associated complications.
Source: FDA drug label (Rowasa, NDA019618), Viatris Specialty LLC, effective August 3, 2026 (SPL set e505ab99-1943-4216-a178-4d5dbe64e3b2), via openFDA
Source: FDA drug label (APRISO), Salix Pharmaceuticals, Inc., effective August 27, 2026 (SPL set 7951139c-b271-45a4-b523-34b23800917b), 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
| Mercaptopurine | Mesalamine | |
|---|---|---|
| Labeled for | Leukemia, lymphoma and myeloma | Crohn's disease and ulcerative colitis |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $1.07 per tablet 50 mg tablet | $0.781 per tablet 1.2 g tablet |
| Shortage now | No current entry | A presentation being discontinued |
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