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CYP2C9-mediated warfarin and milk thistle interaction.
David Benjamin Lash1, Shereen Ward1
1Kern Medical, Bakersfield, CA, USA.
Journal of Clinical Pharmacy and Therapeutics
|October 22, 2019
Summary
This case report details a patient experiencing elevated INR levels after starting milk thistle, a popular supplement. This highlights a potential in vivo drug interaction between milk thistle and warfarin.
Area of Science:
- Pharmacology
- Herbal Medicine Interactions
Background:
- In vitro studies suggest that milk thistle may interact with warfarin via CYP2C9.
- No in vivo human studies have confirmed this potential interaction.
Observation:
- A patient on stable warfarin therapy for mitral valve replacement experienced a significant increase in INR after initiating a milk thistle supplement.
- The patient reported no other changes in diet or medication.
Findings:
- The patient's INR normalized after discontinuing the milk thistle supplement.
- This case provides the first in vivo evidence of a drug interaction between milk thistle and warfarin.
Implications:
- Clinicians should be aware of the potential for milk thistle to increase warfarin's anticoagulant effect.
- Patients taking warfarin should be questioned about the use of herbal supplements like milk thistle.
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