*2.1.1.1. Mechanism of action*

Warfarin is a racemic mixture of two optically active isomers, the R and S enantiomers, and it produces its anticoagulant effect by interfering with the cyclic interconversion of vitamin K and vitamin K-2,3-epoxide. Warfarin blocks vitamin K epoxide reductase (VKOR), and the consequent conversion of oxidized vitamin K epoxide into its reduced form, vitamin K hydroquinone [2]. However, warfarin also has a simultaneous procoagulant effect caused by blocking the activation of protein C and S, two endogenous anticoagulants. A rapid depletion of these proteins leads to a transient hypercoagulable state in the first 1 or 2 days of therapy.
