St John S Wort and Warfarin: Drug Interaction Guide

Quick answer: This combination requires caution. St John S Wort and Warfarin can be used together with adjustments and monitoring.

Interaction severity: Moderate — caution required

How St John S Wort interacts with Warfarin

St John's wort induces CYP3A4, CYP2C9, and P-glycoprotein through pregnane X receptor activation. This can reduce warfarin exposure and lower INR.

What you should do

Avoid St John's wort in patients taking warfarin. If started or stopped, monitor INR closely and adjust warfarin as needed.

Key facts

Severity

Moderate — caution required

Mechanism

St John's wort induces CYP3A4, CYP2C9, and P-glycoprotein through pregnane X receptor activation. This can reduce warfar...

Action

Avoid St John's wort in patients taking warfarin. If started or stopped, monitor INR closely and adjust warfarin as need...

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 St John S Wort and Warfarin together?

With caution. Avoid St John's wort in patients taking warfarin. If started or stopped, monitor INR closely and adjust warfarin as needed.

What is the severity of this interaction?

The interaction between St John S Wort and Warfarin is classified as Moderate — caution required. St John's wort induces CYP3A4, CYP2C9, and P-glycoprotein through pregnane X receptor activation. This can reduce warfarin exposure and lower INR.

What should I do if I'm prescribed both?

Avoid St John's wort in patients taking warfarin. If started or stopped, monitor INR closely and adjust warfarin as needed. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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