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Vitamin K deficiency amplifies anticoagulation response to ximelagatran: possible implications for direct thrombin inhibitors and their clinical safety

Lookup NU author(s): Professor Farhad Kamali, Peter Wood, Alan Ward

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Abstract

Dietary vitamin K is known to influence the anticoagulation response to warfarin. It is possible that dietary vitamin K availability also influences the pharmacological activity of other oral anticoagulants, which target the vitamin-K dependent clotting proteins in the coagulation cascade. This study examined whether vitamin K insufficiency affected anticoagulation response to the direct thrombin inhibitor, ximelagatran. Anticoagulation response to ximelagatran and warfarin in rats on a normal diet was compared to those on a vitamin K deficient diet. Ximelagatran and warfarin increased prothrombin time (PT) by 1.4- and 1.3-fold, activated partial thromboplastin time (APTT) by 1.8- and 1.4-fold and ecarin clotting time (ECT) by 6.8- and 1.2-fold, respectively, in rats on normal diet. Vitamin K deficient diet alone caused modest increases in PT, APTT and ECT. The anticoagulant activity of both ximelagatran and warfarin was significantly greater in rats on vitamin K deficient diet (6.1- and 12.3-fold for PT, 2.6- and 5.1-fold for APTT and 2.9- and 1.6-fold for ECT, respectively) compared to those on normal diet. Factor II activity was reduced by both ximelagatran (58%) and warfarin (44%) in rats on normal diet. However, factor II activity was virtually abolished (<0.1%) by both drugs in rats on vitamin K deficient diet. The results suggest that oral anticoagulant drugs, whose primary site of action is not within the vitamin K cycle, may also exhibit variability in clinical response due to dietary variation as the established coumarin drugs such as warfarin. © 2008 Springer-Verlag.

Publication metadata

Author(s): Kamali F, Wood P, Ward A

Publication type: Article

Publication status: Published

Journal: Annals of Hematology

Year: 2009

Volume: 88

Issue: 2

Pages: 141-149

ISSN (print): 0939-5555

ISSN (electronic): 1432-0584

Publisher: Springer

URL: http://dx.doi.org/10.1007/s00277-008-0565-x

DOI: 10.1007/s00277-008-0565-x

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