QuestionSBA
QuestionChoice
Incorrect - A direct thrombin inhibitor works through thrombin inhibition. LMWH binds and activates antithrombin III, through induction of conformational change. Heparin-activated antithrombin III binds to factor Xa directly, inactivating it. Although this indirectly brings about a reduction in thrombin activation, LMWH does not directly inhibit it.
10008327
c
Limits secondary haemostatic plug formation through thrombin inhibition
QuestionChoice
Incorrect - Fibrinogen is converted into fibrin by thrombin, which drives clot formation. LMWH inhibits this process.
10008326
b
Converts fibrinogen into fibrin
QuestionChoice
Correct - LMWH binds and activates antithrombin III, through induction of a conformational change. This activated antithrombin III then binds to Factor Xa directly, preventing its activation. Factor Xa plays a role in thrombin generation, which drives platelet activation and clot formation. LMWH, therefore, inhibits this process, exerting its anticoagulant effects.
10008325
a
Limits secondary haemostatic plug formation through Factor Xa inhibition
QuestionChoice
Incorrect - LMWH does not inactivate Factor VIIa. LMWH binds and activates antithrombin III, through induction of conformational change. Heparin-activated antithrombin III binds to factor Xa directly, inactivating it.
10008329
e
Limiting primary haemostatic plug formation through factor VIIa inhibition
QuestionChoice
Incorrect - While unfractionated heparin inactivates both thrombin and factor Xa, LMWH primarily works through factor Xa inactivation.
10008328
d
Limits secondary haemostatic plug formation through thrombin and factor Xa inhibition
Concept
Chapter
2693
4608
Low molecular weight heparin
Topic
203
Pharmacology of Haemostasis and Thrombosis
14212
A 53-year-old man is admitted to the respiratory ward for the management of a pulmonary embolism. He is commenced on treatment dose low molecular weight heparin (LMWH).

Which of the following describes the mechanism of action of LMWH?
a