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Br J Clin Pharmacol. 2010 May;69(5):508-15. doi: 10.1111/j.1365-2125.2010.03620.x.

Pharmacokinetic and pharmacodynamic interactions of echinacea and policosanol with warfarin in healthy subjects.

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  • 1Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia.



This study investigated the pharmacokinetic and pharmacodynamic interactions of echinacea and policosanol with warfarin in healthy subjects.


This was an open-label, randomized, three-treatment, cross-over, clinical trial in healthy male subjects (n= 12) of known CYP2C9 and VKORC1 genotype who received a single oral dose of warfarin alone or after 2 weeks of pre-treatment with each herbal medicine at recommended doses. Pharmacodynamic (INR, platelet activity) and pharmacokinetic (warfarin enantiomer concentrations) end points were evaluated.


The apparent clearance of (S)-warfarin (90% CI of ratio; 1.01, 1.18) was significantly higher during concomitant treatment with echinacea but this did not lead to a clinically significant change in INR (90% CI of AUC of INR; 0.91, 1.31). Policosanol did not significantly affect warfarin enantiomer pharmacokinetics or warfarin response. Neither echinacea nor policosanol had a significant effect on platelet aggregation after 2 weeks of pre-treatment with the respective herbal medicines.


Echinacea significantly reduced plasma concentrations of S-warfarin. However, neither echinacea nor policosanol significantly affected warfarin pharmacodynamics, platelet aggregation or baseline clotting status in healthy subjects.

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