Mercaptopurine and Xanthine Oxidase Inhibitors: Drug Interaction Guide

Quick answer: This is a major interaction — avoid combining Mercaptopurine and Xanthine Oxidase Inhibitors unless specifically directed by your doctor.

Interaction severity: Major — avoid combination

How Mercaptopurine interacts with Xanthine Oxidase Inhibitors

Xanthine oxidase inhibitors such as allopurinol or febuxostat inhibit a major metabolic pathway for mercaptopurine. This increases active thiopurine exposure and can cause severe myelosuppression.

What you should do

Avoid unless intentionally co-managed by specialists. If combined, use a major mercaptopurine dose reduction and frequent full blood count monitoring.

Key facts

Severity

Major — avoid combination

Mechanism

Xanthine oxidase inhibitors such as allopurinol or febuxostat inhibit a major metabolic pathway for mercaptopurine. This...

Action

Avoid unless intentionally co-managed by specialists. If combined, use a major mercaptopurine dose reduction and frequen...

Important medical disclaimer: This page provides educational information about drug interactions for general reference. It is not a substitute for professional medical advice, diagnosis, or treatment. Always discuss your specific medications with a qualified healthcare provider before starting, stopping, or changing any treatment. About our editorial team.

Frequently asked questions

Can I take Mercaptopurine and Xanthine Oxidase Inhibitors together?

No — this combination should generally be avoided. Avoid unless intentionally co-managed by specialists. If combined, use a major mercaptopurine dose reduction and frequent full blood count monitoring.

What is the severity of this interaction?

The interaction between Mercaptopurine and Xanthine Oxidase Inhibitors is classified as Major — avoid combination. Xanthine oxidase inhibitors such as allopurinol or febuxostat inhibit a major metabolic pathway for mercaptopurine. This increases active thiopurine exposure and can cause severe myelosuppression.

What should I do if I'm prescribed both?

Avoid unless intentionally co-managed by specialists. If combined, use a major mercaptopurine dose reduction and frequent full blood count monitoring. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

Last reviewed: by iMedic Medical Editorial Team. Our editorial process.