Potentiation of Warfarin by Dong Quai

Authors

  • Dr. Robert Lee Page II Pharm.D.,

    Corresponding author
    1. Department of Pharmacy Practice, School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado
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  • Dr. Julie D. Lawrence Pharm.D.

    1. Department of Pharmacy Services, McClennan-Banks Ambulatory Care Center, and the Medical University of South Carolina, Charleston, South Carolina
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University of Colorado Health Sciences Center, Department of Pharmacy Practice, School of Pharmacy, 4200 East Ninth Avenue, Box C238, Denver, CO 80262

Abstract

Dong quai is a Chinese herbal supplement touted for treatment of menstrual cramping, irregular menses, and menopausal symptoms. Phytochemical analyses found it to consist of natural coumarin derivatives, as well as constituents possessing antithrombotic, antiarrhythmic, phototoxic, and carcinogenic effects. A 46-year-old African-American woman with atrial fibrillation stabilized on warfarin experienced a greater than 2-fold elevation in prothrombin time and international normalized ratio after taking dong quai concurrently for 4 weeks. No identifiable cause was ascertained for the increase except dong quai. The patient's coagulation values returned to acceptable levels 1 month after discontinuing the herb. One animal study suggests a pharmacodynamic interaction between the product and warfarin, but the true mechanism remains unknown. Practitioners should be aware of the possibility of such an interaction and should inform patients of potential hazards of taking the two together.

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