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Therapeutics of Cardiovascular Diseases
Thrombosis and Haemostasis
2008
Dr. George Hsiao
Principles of haemostasis
The three stages invoved in haemostasis are blood vessel constriction, formation of a platelet plug, and formation of a clot.
Coagulation vs Platelet
Thrombosis Thrombosis is the pathological formation of a
clot known as a thrombus. Arterial occlusion, which may lead to
myocardial infarction, stroke, and peripheral ischemia.
Venous occlusion, which may lead to deep venous thrombosis and pulmonary embolism.
AnticoagulantsVitamin K antagonists Warfarin, acenocoumarol (nicoumalone), and phenindione
are examples of vitamin K antagonists. Mechanism of action: Vitamin K antagonists block the
reduction of vitamin K epoxide, which is necessary for its action as a cofactor in the synthesis of factors II, VII, IX, and X.
Heparin and the low-molecular weight heparins Mechanism of action: Heparin activates antithrombin III,
which limits blood clotting by inactivating thrombin and factor X. Heparin also inhibits platelet aggregation, possibly as a result of inhibiting thrombin. Low-molecular weight heparins are simply fragments of heparin which exhibit very similar activity to heparin.
Hirudins Mechanism of action: Derived from the medical leech,
hirudin, or rather its recombinant derivatives, desirudin and lepirudin, inactivate thrombin.
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