What is mechanism of action of vitamin K antagonists?

Several of the protein coagulation factors (including Factors II, VII, IX, and X) require vitamin K as a cofactor for their synthesis by the liver. These factors undergo vitamin K–dependent posttranslational modification, whereby a number of their glutamic acid residues are carboxyated to form γ-carboxyglutamic acid residues Warfarin treatment results in the production of clotting factors with diminished activity (10%– 40% of normal). Unlike heparin, the anticoagulant effects of warfarin are not observed until 8 to 12 hours after drug administration, but peak effects may be delayed for 72 to 96 hours