Brief communication: American ginseng reduces warfarin's effect in healthy patients: a randomized, controlled Trial.
BACKGROUND
People using prescription medication often concurrently take herbal supplements. In a case report, the anticoagulant effect of warfarin decreased after patients consumed ginseng.


OBJECTIVE
To evaluate the interactions between American ginseng and warfarin.


METHODS
Randomized, double-blind, placebo-controlled trial.


METHODS
General Clinical Research Center, University of Chicago, Chicago, Illinois.


METHODS
20 healthy patients.


METHODS
In this 4-week study, 20 patients received warfarin for 3 days during weeks 1 and 4. Beginning in week 2, patients were assigned to receive either American ginseng or placebo.


METHODS
International normalized ratio (INR) and plasma warfarin level.


RESULTS
The peak INR statistically significantly decreased after 2 weeks of ginseng administration compared with placebo (difference between ginseng and placebo, -0.19 [95% CI, -0.36 to -0.07]; P = 0.0012). The INR area under the curve (AUC), peak plasma warfarin level, and warfarin AUC were also statistically significantly reduced in the ginseng group as compared with the placebo group. Peak INR and peak plasma warfarin level were positively correlated.


CONCLUSIONS
The study sample consisted of young, healthy volunteers in a research setting rather than patients taking therapeutic doses of warfarin.


CONCLUSIONS
American ginseng reduces warfarin's anticoagulant effect. When prescribing warfarin, physicians should ask patients about ginseng use.
Yuan
Chun-Su
CS
Tang Center for Herbal Medicine Research, Committee on Clinical Pharmacology and Pharmacogenomics, Anticoagulation Consult Service, Pritzker School of Medicine, The University of Chicago, Chicago, Illinois 60637, USA. cyuan@uchicago.edu
Wei
Gang
G
Dey
Lucy
L
Karrison
Theodore
T
Nahlik
Linda
L
Maleckar
Spring
S
Kasza
Kristen
K
Ang-Lee
Michael
M
Moss
Jonathan
J
D000328:Adult; D000925:Anticoagulants / Q000493:pharmacokinetics / Q000494:pharmacology*; D019540:Area Under Curve; D004347:Drug Interactions; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D005894:Panax / Q000009:adverse effects*; D008517:Phytotherapy / Q000009:adverse effects*; D028321:Plant Preparations / Q000009:adverse effects*; D014859:Warfarin / Q000493:pharmacokinetics / Q000494:pharmacology*
D000925:Anticoagulants; D028321:Plant Preparations; D014859:Warfarin