Hem 2 - Anticoagulant Drugs Flashcards
What is the mechanism of heparin?
Cofactor for the activation antithrombin; it supercharges it. Very short half-life. Can be used during pregnancy.
What is the reason why you can use heparin during pregnancy?
Because it does not cross the placenta.
How do we measure the effectiveness of Heparin?
Monitor the PTT.
What are the side effects of Heparin?
Bleeding. Osteoporosis. Heparin-induced thrombocytopenia (HIT); heparin binds to platelet factor 4, which then auto Ab to that complex are generated which can then activate the platelets and get them destroyed; therefore they are also in a hypercoagulable state.
What are Lepirudin, Bivalirudin, and Desirudin?
They are thrombin inhibitors. They are derivatives of hirudin (an anticoagulant of leeches). Hirudin directly inhibits thrombin.
What are two low molecular weight heparins and how do they work?
Enoxaparin. Dalteparin. They work by stimulating antithrombin to inactivate factor 10a. They have longer half-life, therefore can be given as subcutaneous injection and based on patient’s weight instead of IV like heparin and doing a PTT test every 6 hours.
If by some reason you want to monitor the low molecular weight heparins, how do you do it?
Anti-factor Xa activity.
What is Fondaparinux?
Works like heparin derivative but it is not one. It activates antithrombin by inhibiting factor 10a.
What are two direct factor 10a inhibitors? How is it administered?
Rivaroxaban. Apixaban. They work by inhibiting factor 10a. They are given orally.
How does Warfarin work?
Inhibits epoxide reductase, an enzyme responsible for recycling vitamin K. Vitamin K is used in the synthesis and gamma carboxylation of vitamin k-dependent clotting factors (2,9,7,10, Protein C and S). This affects PT (prothrombin time).
When is Warfarin used for?
Chronic anticoagulation. Atrial fibrillation. DVT prophylaxis/treatment. PE treatment.
Why is warfarin contraindicated in pregnant women?
Because it crosses the placenta, and is also teratogenic.
What is the difference b/w Heparin and Warfarin?
H is given IV or SC. W is given orally. H has a short half-life. W has a long half-life. H has a rapid onset. W has a very slow onset. Incase of overdose, in H, you give protamin sulfate. In W, give oral vitamin K + fresh frozen plasma.
Why do you need to give heparin or enoxaparin when starting a warfarin?
Because when you start taking warfarin, the first factors affected are Protein C and Protein S, therefore leading to a transient hypercoagulable state causing skin necrosis. Heparin or enoxaparin will combat the transient hypercoagulable state. Once the INR is between 2 to 3, you can stop.
What are three thrombolytics? How do they work?
Streptokinase. Urokinase. tPA (alteplase). They activate plasmin, which degrades fibrin, breaking up the clot.
