Antiplatelet, Anticoagulant and Thrombolytic Drugs Flashcards
Haemostasis
Arrest of blood loss from a damaged vessel
Types of thrombosis
Arterial thrombosis - white thrombus: mainly platelets in a fibrin mesh
Venous thrombosis - red thrombus: white head, jelly-like red tail, fibrin rich
How does Aspirin work
Aspirin decreases production of prostaglandins and Thromboxane A2 (TXA2).
When are antiplatelets more effective than anticoagulants?
Antiplatelet agents are often the best treatment for disease involving white thrombus, whereas red thrombi may better treated by anticoagulation.
What is the international normalized ratio?
International normalized ratio (INR) is a calculation made to standardize prothrombin time. INR is based on the ratio of the patient’s prothrombin time and the normal mean prothrombin time. Prothrombin time is a test to learn how fast the blood clots in patients receiving oral anticoagulant medication.
Heparin mechanism of action
Heparin binds to the enzyme inhibitor antithrombin III (AT), causing a conformational change that results in its activation through an increase in the flexibility of its reactive site loop. Antithrombin III (AT III) is an important inhibitor of coagulation which neutralises all serine protease factors in the coagulation cascade.
A major disorder caused by use of Heparin
Heparin Induced Thrombocytopenia - Development of thrombocytopenia (a low platelet count). Body makes antibodies to Heparin when its bound to platelet-derived protein called platelet factor-4 complexes. This causes formation of unwanted clots by platelets clumping together and hence reduction in platelet count
Why use factor Xa and IIa, indirect Thrombin inhibitors over Heparin, a direct Thrombin inhibitor?
They dont bind to platelet factor 4 and can be used to treat Heparin induced thrombocytopenia. However, they can cause bleeding
What enzyme does Warfarin inhibit?
Vitamin K epoxide reductase
Heparin vs LMWH in renal failure
Heparin is preferred as LMWH is excreted renally
Antidote for Heparin
Protamine Sulphate IV
Why choose Rivaroxaban and Dabigatran > Heparin?
Oral administration and predictable degree of anticoagulation
Main adverse effect of Aspirin
Main adverse effect is gastrointestinal bleeding and ulceration
What drug can be given to patients intolerant to Aspirin?
Clopidogrel - Prodrug requires hepatic metabolism
Maximum number of days Streptokinase can be administered
Reduces mortality in acute M.I. (given IV, or intracoronary) but action blocked after 4 days by the generation of antibodies. Further doses not to be given after this time
