Heparin/fondaparinux mechanism of action

Schematic representation of anticoagulant mechanisms. Heparins bind to antithrombin (AT) and induce a conformational change that makes AT an efficient inactivator of coagulation factors. Unfractionated heparin inhibits thrombin (factor IIa) by forming a ternary complex. The inhibitory effect of LMW heparins on thrombin is variable, with longer products such as tinzaparin having greater inhibition than the shorter products such as enoxaparin. All heparins and fondaparinux efficiently inactivate factor Xa. Refer to UpToDate topics on use of heparins and fondaparinux for details.