Sir, in BDJ 2004, 197: 62 the letter detailing hemorrhagic tendencies states that the Vitamin K dependant factors are factor II, factor V, factor VII, factor IX and factor X. Factor V is actually a non- vitamin K dependant cloning factor. It acts on both the intrinsic and extrinsic pathways as a cofactor in the activation of prothrombin to thrombin.

Vitamin K has a bifunctional role in the coagulation pathway. Specifically, the vitamin K dependant pro-coagulants are factors II, VII, IX and X. Proteins C and S are also vitamin K dependant, having a role in the regulation of anti-coagulation i.e. inhibition of the cloning process. Protein C degrades factors V and VIII in the presence of calcium while protein S acts synergistically with protein C. Despite this dual role, the overriding tendency of a deficiency in utilisable vitamin K is to cause an increased propensity to bleed. Warfarin is a commonly used oral anti-coagulant which is, in basic terms, a vitamin K antagonist.