Episode 6 Anticoagulants, Thrombolytics (Fibrinolytics), Antiplatelet Agents and Antifibrinolytics Flashcards
What are the four major categories of Anticoagulants?
Indirect Thrombin Inhibitors (heparin), Coumarin Anticoagulants (warfarin), Direct Thrombin Inhibitors, and Direct Factor X Inhibitors
Why can’t heparin be administered orally?
It is a protein which will be broken down in the GI tract
What are the two most common heparin preparations?
Ufractionated heparin (UFH) - Heparin Sodium. Low-molecular-weight heparin (LMWH) - Fragmin, Innohep, Lovenox
How does heparin work?
It stimulates Antithrombin, which shuts down FX (and other clotting factors as well)
What does the lack of thrombin result in?
Inability to convert fibrinogen into fibrin
Why is heparin called an indirect thrombin inhibitor?
B/c stimulates Antithrombin to inhibit FX, which inhibits, Prothrombin from becoming thromobin. Without thrombin there is no fibrin conversion from fibrinogen. Therefore it is an indirect inhibitor
What does heparin stimulate also besides antithrombin?
Heparin cofactor II (which inhibits thrombin)
Why is UFH monitored with APPT?
UFH response varies greatly among patients
What is the main difference in how UFH and LMWH can be used?
UFH is mainly used in hospitals and LMWH can be used both in hospital or on an outpatient basis
How are LMWH administered?
Subcutaneously but not intravenous
What is the difference between UFH and LMWH?
UFH is isolated from different animals and vary in size. LMWH is selected for small (low molecular weight) heparins. LMWH will not interact (thereby reducing its anticoagulation effectiveness) with plasma proteins as much as UFH.
T/F LMHWs do not need to be monitored with lab tests such as APPT, while UFH do.
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T/F Warfarin is found in rodent poison
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How does warfarin affect the blood clotting cascade?
It works in the liver by preventing the liver to make vitamin K dependent clotting factor (II, VII, IX, X)
What is warfarin used for prophylactially?
Venous thrombosis and Pulmonary Embolism
What is the ideal INR for someone taking warfarin?
2.0-3.0 - a balance between reducing clot formation and not causing spontaneous bleeding
What is a major disadvantage of warfarin?
Has many drug-drug interactions
What is a common effect of DDIs on warfarin?
Inhibition of warfarin breakdown (INR will go up very high)
Which two drugs stimulate warfarin metabolism?
Chronic alcohol use and Phenytoin (Dilantin)
What effects do oral contraceptive have on warfarin?
Increase synthesis of many clotting factors and can reduce the effects of warfarin
What effects to foods rich in vitamin K (green leafy vegetables and cereals) have on warfarin?
Decrease effects of warfarin by stimulating synthesis of vitamin K dependent clotting factor
How can warfarin overdoses be treated?
with vitamin K and transfusions
Why is warfarin contraindicated during pregnancy?
It can cross the placenta and is teratogenic (causes birth defects)
What is the first direct thrombin inhibitor to come on to the market?
Pradaxa (dabigatran)
