Does Allopurinol Interact With Azathioprine?
Concomitant use with allopurinol increases the exposure of either mercaptopurine or azathioprine which may increase the risk of myelosuppression.
Severity: Moderate
Severity basis: warnings section (keywords: may increase). Combining Allopurinol (Xanthine oxidase inhibitor) and Azathioprine (Immunosuppressant) is classified as a moderate interaction.
What to Do
Use this combination with caution. Your prescriber may monitor you more closely or adjust doses.
How This Interaction Works
Interactions like this one can happen when two medicines have overlapping effects, or when one changes how the other is absorbed, broken down, or cleared from the body. Allopurinol is a xanthine oxidase inhibitor and Azathioprine is a immunosuppressant; together they are documented as a moderate interaction. How much this matters depends on your dose, your other medications, and your overall health.
If You Take Both Medications
If you have been prescribed both Allopurinol and Azathioprine, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
From the FDA Label
Concomitant use with allopurinol increases the exposure of either mercaptopurine or azathioprine which may increase the risk of myelosuppression.
Source: FDA structured product labeling (set_id 005048dd-844f-468c-bf56-1a09727e3477).
Check these against your full medication list in our free Interaction Checker
Frequently Asked Questions
Can you take Allopurinol and Azathioprine together?
Allopurinol and Azathioprine have a documented moderate interaction. Use this combination with caution. Your prescriber may monitor you more closely or adjust doses.
How serious is the Allopurinol and Azathioprine interaction?
It is classified as a moderate interaction, based on the FDA label's warnings section (keywords: may increase). A moderate interaction can be clinically meaningful and usually calls for monitoring or a dose adjustment.
What should I do if I'm taking both Allopurinol and Azathioprine?
If you have been prescribed both Allopurinol and Azathioprine, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
This information is educational — not medical advice.
This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.