CYP2C9‐mediated warfarin and milk thistle interaction

CYP2C9‐mediated warfarin and milk thistle interaction:

Abstract

What is known and objective

In vitro studies suggest a CYP2C9‐mediated interaction between milk thistle and warfarin, but there has been no in vivo case report on this interaction.

Case description

A White Hispanic man in his 30s was well controlled on warfarin therapy for mitral valve replacement. His INR increased from 2.64 to 4.12, and he denied changes to his medications and diet but noted starting a ‘liver cleanse’ supplement which contained milk thistle (200 mg). After stopping the supplement his INR normalized, and he remains on the same warfarin dose.

What is new and conclusion

This is the first in vivo report of an interaction between milk thistle and warfarin.