Positive Health Online

Abstract

JIANG and colleagues, Faculty of Pharmacy, The University of Sydney, NSW 2006, Australia, have studied the effects of St John's wort and ginseng on the pharmacokinetics of warfarin.

Background

The aim of the study was to investigate the interactions between St John's wort and ginseng and warfarin, an anti-thrombosis drug that many people have to take.

Methodology

In this open-label, three-way crossover randomized study, 12 healthy male patients received a single 25-mg dose of warfarin alone or after 14 days' pretreatment with St John's wort, or 7 days' pretreatment with ginseng. Dosing with St John's wort or ginseng was continued for 7 days after administration of the warfarin. Blood coagulation parameters, pharmacokinteic paramteres of warfarin and warfarin metabolites were measured.

Results

Blood coagulation parameters were not affected by treatment with St John's wort or ginseng. Warfarin appeared to be cleared out from the system faster with St John's wort but not with ginseng. The mean ratio of apparent clearance for S-warfarin was 1.29 and for R-warfarin it was 1.23 when St John's wort was co-administered. St John's wort and ginseng did not affect the apparent volumes of distribution or protein binding of warfarin.

Conclusion

St John's wort significantly induced the apparent clearance of warfarin, which in turn resulted in a significant reduction in the pharmacological effect of warfarin. Coadministration of warfarin with ginseng did not affect the pharmacokinetics or pharmacodynamics of warfarin.

References

Jiang X, Williams KM, Liauw WS, Ammit AJ, Roufogalis BD, Duke CC, Day RO, McLachlan AJ. Effect of St John's wort and ginseng on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects. British Journal of Clinical Pharmacology 57 (5): 592-599, May 2004.