Mercaptopurine and Trimethoprim: Drug Interaction Guide

Quick answer: This combination requires caution. Mercaptopurine and Trimethoprim can be used together with adjustments and monitoring.

Interaction severity: Moderate — caution required

How Mercaptopurine interacts with Trimethoprim

Trimethoprim-sulfamethoxazole and 6-mercaptopurine both suppress bone marrow; combination causes additive myelosuppression including neutropenia and thrombocytopenia.

What you should do

Avoid combination when possible. If unavoidable for PCP prophylaxis, monitor CBC weekly initially and consider mercaptopurine dose reduction.

Key facts

Severity

Moderate — caution required

Mechanism

Trimethoprim-sulfamethoxazole and 6-mercaptopurine both suppress bone marrow; combination causes additive myelosuppressi...

Action

Avoid combination when possible. If unavoidable for PCP prophylaxis, monitor CBC weekly initially and consider mercaptop...

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 Trimethoprim together?

With caution. Avoid combination when possible. If unavoidable for PCP prophylaxis, monitor CBC weekly initially and consider mercaptopurine dose reduction.

What is the severity of this interaction?

The interaction between Mercaptopurine and Trimethoprim is classified as Moderate — caution required. Trimethoprim-sulfamethoxazole and 6-mercaptopurine both suppress bone marrow; combination causes additive myelosuppression including neutropenia and thrombocytopenia.

What should I do if I'm prescribed both?

Avoid combination when possible. If unavoidable for PCP prophylaxis, monitor CBC weekly initially and consider mercaptopurine dose reduction. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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