Anticoagulants and Antiplatelets Flashcards
How long do platelets survive in plasma?
7 days.
What are anti-platelet drugs?
Inhbits platelet aggregation.
How does aspirin exhibit it’s anti-platelet effect?
Inhibits platelet aggregation- alters balance between thromboxane A2 and prostacyclin.
How does clopidogrel exhibit it’s anti-platelet effect?
Inhibits ADP induced platelet aggregation.
How does dipyridamole exhibit it’s anti-platelet effect?
Inhibits platelet phosphodiesterase.
Why are anti-platelet drugs an issue in dentistry?
Prolong bleeding time following dental extractions.
- drug combination increases the risk.
What is the purpose of Antiplatelet drugs?
Reduce the risk of MI or stroke, in an at risk population.
What do anti-coagulants do?
Inhibits the clotting cascade- doesn’t affect platelets.
- reduce formation of fibrin formation, so the platelet plug will form but it will not stabilise and so, the patient will start bleeding a few hours after the extraction.
Why are anti-coagulants an issue in dentistry?
Won’t affect bleeding time but the patient will have an episode later on where they start bleeding again.
Name the three different components of haemostasis?
Vascular response
Platelet response
Plasma response (coagulation)
What occurs during the vascular response of haemostasis?
Smooth muscle within the vascular wall spasms- releases humeral factor- vasoconstriction.
What occurs during the platelet response in haemostasis?
Damage to a blood vessel during extraction causes turbulent blood flow, platelets come into contact with exposed collagen.
Platelets aggregate and release Thromboxane A2 and ADP- causes vasoconstriction and causes further aggregation of platelets.
Formation of platelet plug.
What occurs in the coagulation phase of haemostasis?
Plasma proteins and tissue components convert fibrinogen to fibrin by thrombin- forms a blood clot.
What does Factor Xa do in the clotting cascade?
Converts prothrombin to thrombin.
Factor Xa is converted from Factor X by intrinsic and extrinsic pathways- which produce phospholipids and calcium ions.
What is the process called whereby the blood clot is dissolved?
Fibrinolysis.
What processes occur during fibrinolysis?
Plasmin converts fibrin to soluble fibrin fragments.
What is Warfarin?
Coumarin base anticoagulant- inhibits synthesis of vitamin K dependent factors.
What are the vitamin K dependent factors?
2, 7, 9 and 10.
Protein C and protein S.
What occurs when the patient first takes warfarin?
Initially the patient is hyperocagulated because of the inhibition of protein C and protein S.
As vitamin K dependent factors are reduced over 2-3 days, the patient will become anti-coagulated.