Capecitabine and Phenytoin: Drug Interaction Guide

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

Interaction severity: Moderate — caution required

How Capecitabine interacts with Phenytoin

Capecitabine or its fluorouracil metabolites can inhibit CYP2C9-mediated phenytoin metabolism, increasing phenytoin concentrations and toxicity.

What you should do

Monitor phenytoin concentrations and clinical signs of toxicity closely. Adjust the phenytoin dose as necessary during and after capecitabine treatment.

Key facts

Severity

Moderate — caution required

Mechanism

Capecitabine or its fluorouracil metabolites can inhibit CYP2C9-mediated phenytoin metabolism, increasing phenytoin conc...

Action

Monitor phenytoin concentrations and clinical signs of toxicity closely. Adjust the phenytoin dose as necessary during a...

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 Capecitabine and Phenytoin together?

With caution. Monitor phenytoin concentrations and clinical signs of toxicity closely. Adjust the phenytoin dose as necessary during and after capecitabine treatment.

What is the severity of this interaction?

The interaction between Capecitabine and Phenytoin is classified as Moderate — caution required. Capecitabine or its fluorouracil metabolites can inhibit CYP2C9-mediated phenytoin metabolism, increasing phenytoin concentrations and toxicity.

What should I do if I'm prescribed both?

Monitor phenytoin concentrations and clinical signs of toxicity closely. Adjust the phenytoin dose as necessary during and after capecitabine treatment. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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