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Does Azathioprine Interact with Allopurinol?

Azathioprine and Allopurinol have a major drug interaction according to U.S. FDA drug labeling data. Concomitant use requires dose reduction of azathioprine as recommended in its prescribing information. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.

Severity
Major
Azathioprine Class
Purine Antimetabolite
Allopurinol Class
Xanthine Oxidase Inhibitor
Management
Close medical supervision required
Data Source
U.S. FDA via OpenFDA

What To Tell Your Doctor or Pharmacist

If you are taking Azathioprine and your doctor is considering prescribing Allopurinol (or vice versa), make sure to:

  • Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
  • Ask whether the benefits of combining these medications outweigh the risks for your specific situation
  • Ask what symptoms to watch for that would indicate the interaction is causing problems
  • Ask how frequently you should be monitored while these are co-prescribed
  • Ask whether any dosage adjustments are needed
  • Never stop or change either medication without first consulting your healthcare provider
💊 Azathioprine(Imuran)+💊 Allopurinol(Zyloprim)

Severity & Interaction Details

⚠️
major
Use with caution — major interaction
Serious risk of clinically significant harm. Generally avoid; if used, monitor closely.
Severity scale
MinorContra
On record
Yes
Drug A class
Purine Antimetabolite
Drug B class
Xanthine Oxidase Inhibitor
Source
NLP:allopurinol

What this means in plain English

Concomitant use requires dose reduction of azathioprine as recommended in its prescribing information.

About Azathioprine and Allopurinol

Azathioprine is a Purine Antimetabolite, while Allopurinol is a Xanthine Oxidase Inhibitor. You may recognize them by the brand names Imuran and Zyloprim. Both medications are taken by mouth. Both Azathioprine and Allopurinol carry an FDA boxed warning — the agency's most serious safety designation.

Recent research & FDA safety updates

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Auto-aggregated from PubMed E-utilities and FDA safety data.

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Data integrity: Every interaction shown is extracted directly from official U.S. FDA drug labeling via openFDA and the U.S. National Library of Medicine (NIH) — no interactions are invented, inferred, or manually edited. Maintained by CheckDrugInteractions.com. See our methodology or report a correction at support@checkdruginteractions.com.

Data sourced from U.S. FDA drug labeling via openFDA and the NIH National Library of Medicine, supplemented with a small number of well-established interactions from curated clinical references. For informational purposes only. Always consult your pharmacist or physician.