Antithrombin binds to and inactivates ACTIVATED clotting factors: XIIa, XIa, IXa, XA, and IIA (Thrombin)
Binds to antithrombin and speeds up these reactions
Increases activity of antithrombin 3 of 1000X
Inactivate, activating clotting factors
What is the mechanism of action for warfarin?
Inhibits Vitamin K Oxide (epoxide) Reductase
Means decreased levels of Active Vitamin K
Means decreased levels of Vitamin K Dependent Clotting Factors II, VII, IX, X (also anticoagulant proteins C & S)No effect on already synthesized clotting factors; so therapeutic effects not seen until these factors are depleted
3-4 days until effect is seen
What are the main adverse effects from heparin?
HIT (Heparin-induced thrombocytopenia) - Heparin binds to platelet factor 4. And body makes antibodies for it. Which binds to platelets.
1. Removed by the spleen and drops platelet count. Outcome is Thrombocytopenia
2. Platelet is activated and stimulates blood clotting. Outcome is Thrombosis
Cause of HIT is having a thromboembolic event
What are the main adverse effects from warfarin?
Warfarin Skin Necrosis - caused by depletion of Protein C by Warfarin
What is the time to steady-state anticoagulant effects during a heparin IV infusion?
What is the time to steady-state anticoagulant effects during a oral warfarin regimen?
How does warfarin have a pro-coagulant effect early in therapy?
Decreases level of Protein C (Anticoagulant)
What are the lab tests used to monitor and adjust doses for heparin?
Activated partial thromboplastin time (aPTT or PTT)
Anti-Factor Xa levels
What are the lab tests used to monitor and adjust doses for warfarin?
Prothrombin Time (ProTime or PT) - measured in seconds