Mesalamine and Azathioprine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Azathioprine
Mesalamine
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
An increased risk of myelosuppression, an increased risk of hepatotoxicity and an increased risk of blood disorders
Interaction Deep Dive
Coadministration of mercaptopurine and mesalamine, an aminosalicylate derivative, may inhibit the thiopurine methyltransferase enzyme (TPMT) and increase the risk of bone marrow suppression (anemia, leukopenia, thrombocytopenia, or any combination) caused by mercaptopurine21. If coadministering, use the lowest effective doses of each drug and closely monitor CBC for signs of bone marrow suppression. Mercaptopurine is hepatotoxic. Hepatotoxicity may be increased when mercaptopurine is coadministered with other products that can cause hepatoxicity, such as mesalamine. Hepatic injury can occur with any dosage but seems to occur with greater frequency when the recommended dosage is exceeded. Monitor serum transaminase levels, alkaline phosphatase, and bilirubin levels at weekly intervals when first beginning therapy and at monthly intervals thereafter. Monitor liver tests more frequently in patients who are receiving mercaptopurine with mesalamine. Withhold mercaptopurine at onset of hepatotoxicity 2. Exert caution when coadministration of mesalamine and azaTHIOprine as this may result in an increased risk of blood disorders 3.
Why it happens (mechanism)
Inhibition of thiopurine methyltransferase (TPMT) by mesalamine; additive myelosuppression and hepatotoxic effects
Literature reports
1 report — tap to read
a) There has been cases of blood disorders reported when mesalamine was coadministered with mercaptopurine 1.
Common questions
Can I take Mesalamine and Azathioprine together?
An increased risk of myelosuppression, an increased risk of hepatotoxicity and an increased risk of blood disorders Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mesalamine and Azathioprine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Mesalamine or Azathioprine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (3)
- Product Information: DELZICOL oral delayed-release capsules, mesalamine oral delayed-release capsules. Warner Chilcott (US), LLC (per FDA), Rockaway, NJ, 2014. DailyMed
- Product Information: PURIXAN(R) oral suspension, mercaptopurine oral suspension. Rare Disease Therapeutics Inc (per FDA), Franklin, TN, 2024. DailyMed
- Product Information: LIALDA(TM) delayed-release oral tablets, mesalamine delayed-release oral tablets. Shire US,Inc, Wayne, PA, 2007. DailyMed
Keep reading about Azathioprine
Keep reading about Mesalamine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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