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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Anticoagulant effects of warfarin and kinetics of K vitamins in blood and feces.

Patients (40 cases) were treated with daily dosage of warfarin of 2-7 mg after being undergone artificial valve replacements. Twenty one days after administration of warfarin, we examined the patients for kinetics of K vitamins and vitamin K-dependent coagulation factors in blood, and intestinal flora in feces, as well as the relationship between K vitamins and coagulation activity. The following results were obtained. (1) In warfarin-administered patients (Group B), blood levels of vitamin K1 and menaquinone-7, a vitamin K2 homologue, were similar to those in non-warfarin-administered patients. Therefore, administration of warfarin did not significantly decreased the levels. (2) In patients selected randomly from Group B (Group C), the vitamin K1 level in feces was higher than that in non-warfarin-administered patients. The menaquinone-7 level in feces was similar to that in non-warfarin-administered patients. For the total counts of bacteria and the detection rate of vitamin K2-producing bacteria, there was no significant difference between Group C and non-warfarin-administered patients. (3) The above mentioned results of (1) and (2) suggest that it is important for development of anticoagulant effects by warfarin to inhibit conversion from vitamin K1 to reduced vitamin K1, as well as to inhibit the reducing process from vitamin K1-epoxide to vitamin K1. (4) Vitamin K1-epoxide, a metabolite of vitamin K1, appeared in blood after administration of warfarin; there was a lower correlation between the blood level of vitamin K1-epoxide and the warfarin dosage. Further, PIVKA-II appeared in blood after administration of warfarin; there was a inverse lower correlation between the level of PIVKA-II and HPT, and between PIVIKA-II and TT. In conclusion, it has been clarified that vitamin K1-epoxide and PIVKA-II are useful parameters to evaluate anticoagulant effect of warfarin.[1]


  1. Anticoagulant effects of warfarin and kinetics of K vitamins in blood and feces. Nakamura, K., Toyohira, H., Kariyazono, H., Ishibashi, M., Saigenji, H., Shimokawa, S., Taira, A. Artery (1994) [Pubmed]
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