Febuxostat and Mercaptopurine interaction
Febuxostat and Mercaptopurine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Febuxostat (ULORIC) label · effective 2025-12-24
ULORIC is contraindicated in patients being treated with azathioprine or mercaptopurine [see Drug Interactions (7) ] .
ULORIC is contraindicated in patients being treated with azathioprine or mercaptopurine.
ULORIC is contraindicated in patients being treated with azathioprine or mercaptopurine [see Contraindications (4) ].
Concomitant administration of ULORIC with XO substrate drugs, azathioprine or mercaptopurine could increase plasma concentrations of these drugs resulting in severe toxicity.
A drug interaction study of ULORIC and azathioprine, also metabolized by XO, showed an increase in exposure of 6-mercaptopurine which may lead to toxicity [see Clinical Pharmacology (12.3) ] .
From the Mercaptopurine label · effective 2026-01-30
Allopurinol Allopurinol can inhibit the first-pass oxidative metabolism of mercaptopurine by xanthine oxidase, which can lead to an increased risk of mercaptopurine adverse reactions (i.e., myelosuppression, nausea, and vomiting) [see Warnings and Precautions (5.1), Adverse Reactions (6.1)] .
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.