Heparin is an indirect antithrombotic agent. When antithrombin III binds to thrombin, the thrombin gets broken down. However, this binding reaction happens at a very slow rate. Heparin can sped up this reaction by inducing a confrontational change in antithrombin III.

Warfarin is a vitamin K epoxide reductase inhibitor. It prevents vitamin K from being reduced. Vitamin K is an essential cofactor for gamma-glutamyl carboxylase. This enzyme turns the Glu of Factor X into Gla. The calcium ions can only bind to Gla to enable Factor X to undergo a confrontational change so that it can itneract with the tissue factor and the VIIa cofactor.