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Methotrexate and Trimethoprim: Drug Interaction Guide

Quick answer: This is a major interaction — avoid combining Methotrexate and Trimethoprim unless specifically directed by your doctor.

Interaction severity: Major — avoid combination

How Methotrexate interacts with Trimethoprim

Both inhibit folate metabolism — risk of severe pancytopenia.

What you should do

Avoid combination. If essential, monitor blood counts weekly.

Key facts

Severity

Major — avoid combination

Mechanism

Both inhibit folate metabolism — risk of severe pancytopenia.

Action

Avoid combination. If essential, monitor blood counts weekly.

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 Methotrexate and Trimethoprim together?

No — this combination should generally be avoided. Avoid combination. If essential, monitor blood counts weekly.

What is the severity of this interaction?

The interaction between Methotrexate and Trimethoprim is classified as Major — avoid combination. Both inhibit folate metabolism — risk of severe pancytopenia.

What should I do if I'm prescribed both?

Avoid combination. If essential, monitor blood counts weekly. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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