St Johns Wort × Warfarin

Severity: CRITICAL Evidence: well-established

Mechanism

St. John's wort induces CYP2C9 and CYP3A4, increasing warfarin metabolism.

Effect

Reduced anticoagulant effect; subtherapeutic INR

Management

Avoid combination. If used, monitor INR frequently and adjust warfarin dose.

Source

Jiang X et al. Clin Pharmacol Ther 2004

⚠️ CRITICAL INTERACTION: This combination should be AVOIDED.

Disclaimer

This interaction record is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider before starting or stopping any supplement or medication.