by Pravin Shukle, MD

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    Let's move on to heparin. So heparin is a huge molecule, you can see the chemical structure here. Obviously you don't need to know the chemical structure, just know that unfractionated heparin can have a multiplicity of molecular weight. Some of the heparin molecules are 3000 Daltons in weight. Some of the molecular weight are 25000. We call that unfractionated heparin. It's old school. It is highly acidic so it's neutralized by a base, and that base can be protamine. So protamine zinc is commonly as an antidote to heparin. Now heparin binds to antithrombin III and it forms a complex. And that complex inactivates thrombin. And it also inhibits factor Xa and other factors that we won't get into right now. The important point is, is that unfractionated heparin has a multiplicity of molecular weights, and it's a large molecule. It's always given subcutaneously. We never ever want to give this drug intramuscularly. It may cause a moderate, transient thrombocytopenia. And the thing that we always bring up in exams is heparin induced thrombocytopenia and thrombosis. It's a potentially fatal complication. I've had a few patients actually with HITT, and they are not fun to manage. This is something that we often ask on exams, so when you have a patient, clinical scenario on an exam, where they are starting to have thrombocytopenia and thrombosis and purpura, and they are on heparin, you should think about HITT. Heparin, the unfractionated version may also be linked to osteoporosis when you use it chronically. So, we had problems with unfractionated heparin, so we came up with a new type of heparin called low molecular weight heparin. They don't bind to thrombin but they do still inactivate factor Xa. Therefore the APTT test is not a reliable test when we are using...

    About the Lecture

    The lecture Anticoagulants by Pravin Shukle, MD is from the course Pharmacology of Blood Coagulation. It contains the following chapters:

    • Anticoagulants: Heparins and Fondaparinux
    • Anticoagulants: Direct Thrombin Inhibitors
    • Anticoagulants: Warfarin
    • Anticoagulants: NOAC's – Factor Xa Inhibitors

    Included Quiz Questions

    1. Osteoporosis
    2. Thrombocytosis
    3. Thrombosis
    4. Vitamin K deficiency
    5. Injection site reaction
    1. Dabigatran
    2. Dalteparin
    3. Fondaparinux
    4. Enoxaparin
    5. Unfractionated heparin
    1. Factor Xa
    2. aPTT
    3. Adenosine
    4. Fibrinogen
    5. INR
    1. Direct thrombin inhibitors
    2. Warfarin
    3. PDE inhibitors
    4. COX inhibitors
    5. Unfractionated heparin
    1. Factor C & S
    2. Factor II
    3. Factor X
    4. Factor IX
    5. Factor VII

    Author of lecture Anticoagulants

     Pravin Shukle, MD

    Pravin Shukle, MD

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