Which mechanism describes how low molecular weight heparin exerts its anticoagulant effect?

Which mechanism describes how low molecular weight heparin exerts its anticoagulant effect?

• A. Inhibits factor Xa
• B. Inhibits thrombin (IIa)
• C. Antagonizes vitamin K
• D. Inhibits platelet aggregation

Answer: (A)

Low molecular weight heparin works mainly by binding to antithrombin III and accelerating its inhibition of factor Xa. Because LMWH has shorter polysaccharide chains, it more effectively blocks factor Xa than thrombin, so its primary anticoagulant action is preventing the formation of thrombin rather than directly inhibiting thrombin itself. In contrast, antagonizing vitamin K is the mechanism of warfarin, and inhibiting platelet aggregation is the domain of antiplatelet drugs. So the best description is inhibition of factor Xa.

Low molecular weight heparin works mainly by binding to antithrombin III and accelerating its inhibition of factor Xa. Because LMWH has shorter polysaccharide chains, it more effectively blocks factor Xa than thrombin, so its primary anticoagulant action is preventing the formation of thrombin rather than directly inhibiting thrombin itself. In contrast, antagonizing vitamin K is the mechanism of warfarin, and inhibiting platelet aggregation is the domain of antiplatelet drugs. So the best description is inhibition of factor Xa.