Fluorouracil and Warfarin: Drug Interaction Guide

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

Interaction severity: Moderate — caution required

How Fluorouracil interacts with Warfarin

Fluorouracil can increase warfarin anticoagulant activity, possibly through reduced CYP2C9-mediated clearance and chemotherapy-related changes in vitamin K intake or absorption.

What you should do

Monitor the INR frequently during chemotherapy and for several weeks after treatment changes, with prompt warfarin dose adjustment.

Key facts

Severity

Moderate — caution required

Mechanism

Fluorouracil can increase warfarin anticoagulant activity, possibly through reduced CYP2C9-mediated clearance and chemot...

Action

Monitor the INR frequently during chemotherapy and for several weeks after treatment changes, with prompt warfarin dose ...

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 Fluorouracil and Warfarin together?

With caution. Monitor the INR frequently during chemotherapy and for several weeks after treatment changes, with prompt warfarin dose adjustment.

What is the severity of this interaction?

The interaction between Fluorouracil and Warfarin is classified as Moderate — caution required. Fluorouracil can increase warfarin anticoagulant activity, possibly through reduced CYP2C9-mediated clearance and chemotherapy-related changes in vitamin K intake or absorption.

What should I do if I'm prescribed both?

Monitor the INR frequently during chemotherapy and for several weeks after treatment changes, with prompt warfarin dose adjustment. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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