Figure 1.

The traditional in vitro coagulation activation showing targets of new anticoagulants. PK = prekallikrein, HMWK = high molecular weight kininogens, TF-VII = tissue factor – factor VI complex, TF-VIIa = tissue factor – activated factor VII complex. Rivaroxaban and apixaban are direct activated factor X (Xa) inhibitors. Dabigatran is a direct thrombin inhibitor. Activated protein C inactivates activated factors VIII and V (VIIIa, Va). Fondaparinux and idrabiotoparinux do not inhibit any coagulation factor but potentiate the activity of antithrombin which, in turn antagonizes thrombin and Xa. Whether inactivation of an activated coagulation factor or potentiation of a naturally occurring anticoagulant (such as antithrombin), the net effect is to limit thrombin generation