What the FDA labels say about taking them together
Mercaptopurine and warfarin
Mercaptopurine's FDA label of July 20, 2026 names warfarin in its drug interactions section; the warfarin label PlainMeds reads does not name mercaptopurine. The mercaptopurine label: “Monitor INR and adjust warfarin dose as appropriate. See FDA approved patient labeling and”
Check it at the source: the mercaptopurine FDA label on DailyMed (effective July 20, 2026, Nova Laboratories, Ltd); the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC).
What does the mercaptopurine label say about warfarin?
Mercaptopurine label, drug interactionsMonitor INR and adjust warfarin dose as appropriate. ( 7.2 ) See FDA approved patient labeling and
Mercaptopurine label (Florida Pharmaceutical Products, LLC, January 30, 2026), drug interactionsThe concomitant administration of mercaptopurine tablets and warfarin may decrease the anticoagulant effectiveness of warfarin.
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 warfarin label say about mercaptopurine?
Warfarin's label (effective May 29, 2026) does not name mercaptopurine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Warfarin Sodium), Amneal Pharmaceuticals LLC, effective May 29, 2026 (SPL set 558b7a0d-5490-4c1b-802e-3ab3f1efe760), 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 | Warfarin | |
|---|---|---|
| Labeled for | Leukemia, lymphoma and myeloma | Blood clots (DVT and PE), Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.07 per tablet 50 mg tablet | $0.093 per tablet 2 mg tablet |
| 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