L19: Pharmacology of Anticoagulants Flashcards
What are 3x physiological mechanisms that cause haemostasis
- Vasoconstriction
- Platelet adhesion & activation
- Fibrin formation
Which clotting pathway is more rapid & why?
Extrinsic –> has less steps
How is Vit K a pro-coagulant
Essential for the carboxylation and thus functionality of clotting factors 2, 7, 9, 10
How is Heparin an anti-coagulant
enhances activity of antithrombin III (a natural inhibitor that inactivates Xa & thrombin)
How is warfarin an anti-coagulant
Inhibits the reduction of Vit K which inhibits the carboxylation and functionality of clotting factors 2, 7, 9, 10 thus breaking the coagulation cascade
Why does warfarin take a while to take effect?
only affects the formation/ pathway of clotting factors so won’t affect already active ones
what is an example of an anti platelet drug?
thromboxane synthesis inhibitor eg/ aspirin
how do thromboxane synthesis inhibitor drugs work?
- thromboxane is a potent platelet activator
- thromboxane is synthesised by arachidonic acid (A2) which is catalysed by cyclo-oxygenase
- aspirin is a COX inhibitor
therefore decrease thromboxane synthesis, platelet aggregation, vasoconstriction
what is an example of fibrinolytic drugs
streptokinase
how do fibrinolytic drugs such as streptokinase work?
activates plasminogen –> activates normal biological pathway responsible for lysis of fibrin
how are fibrinolytic drugs administered?
intravenously
how many times can fibrinolytic drugs be used?
only once - they are antigenic
how can you measure evidence of warfarin exposure?
measure prothrombin time Pt
–> time for clot formation of plasma after addition of Ca2+ tissue factor
it is measure of the extrinsic factor
how can you monitor the effect of anticoag effects of heparin?
measure activated partial thromboplastin time
–> time for clot formation in citrated plasma after addition of Ca
measure of intrinsic pathway
