Azathioprine and Febuxostat interaction
Azathioprine and Febuxostat: 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 Azathioprine (IMURAN) label · effective 2025-11-08
Concomitant use of IMURAN and febuxostat is not recommended.
It is recommended that a further dose reduction or alternative therapies be considered for patients with low or absent TPMT activity receiving IMURAN and xanthine oxidase inhibitors because both TPMT and XO inactivation pathways are affected (see CLINICAL PHARMACOLOGY, WARNINGS, PRECAUTIONS: Laboratory Tests and ADVERSE REACTIONS sections).
Drug Interactions: Use with xanthine oxidase (XO) inhibitors: One of the pathways for inactivation of azathioprine is inhibited by XO inhibitors (allopurinol or febuxostat).
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) ] .
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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.