Enoxaparin is a low molecular weight heparin. Enoxaparin is used to prevent and treat deep vein thrombosis or pulmonary embolism, and is given as a subcutaneous injection. Enoxaparin binds to and accelerates the activity of antithrombin III. By activating antithrombin III, enoxaparin preferentially potentiates the inhibition of coagulation factors Xa and IIa. Factor Xa catalyzes the conversion of prothrombin to thrombin, so enoxaparin's inhibition of this process results in decreased thrombin and ultimately the prevention of fibrin clot formation. Low molecular weight heparins are less effective at inactivating factor IIa due to their shorter length compared to unfractionated heparin.