Anticoagulants and Blood Coagulation
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Questions and Answers

Why is heparin not taken orally?

  • Because it is destroyed by gastric HCl (correct)
  • Because it has a delayed onset of action
  • Because it is not absorbed orally
  • Because it does not pass the blood-brain barrier

    • What is the mechanism of action of heparin?

  • Inhibiting the action of vitamin K
  • Activating Anti-Thrombin III to inhibit clotting factors (correct)
  • Inhibiting the synthesis of clotting factors
  • Inhibiting the action of vitamin K epoxide reductase

    • What is the effect of warfarin on vitamin K?

  • Warfarin converts vitamin K to its oxidized form
  • Warfarin inhibits the conversion of vitamin K to its oxidized form
  • Warfarin activates vitamin K
  • Warfarin inhibits vitamin K epoxide reductase (correct)

    • What is the result of warfarin's inhibition of vitamin K epoxide reductase?

    <p>Decreased synthesis of clotting factors</p> Signup and view all the answers

    What is the duration of action of heparin?

    <p>Short duration of action (4-8 hours)</p> Signup and view all the answers

    What is the mechanism of action of heparin on clotting factors?

    <p>Heparin activates Anti-Thrombin III to inhibit clotting factors</p> Signup and view all the answers

    What is the primary function of anticoagulants?

    <p>To interfere with the coagulation of blood</p> Signup and view all the answers

    How many proteins are responsible for blood coagulation?

    <p>12</p> Signup and view all the answers

    Which pathway is activated after tissue injury, releasing factor III?

    <p>Extrinsic pathway</p> Signup and view all the answers

    What is the final product of the coagulation cascade?

    <p>Fibrin</p> Signup and view all the answers

    What is the source of heparin?

    <p>Mast cells</p> Signup and view all the answers

    How is heparin administered?

    <p>Parenteral (I.V.) administration</p> Signup and view all the answers

    Study Notes

    Anticoagulants

    • Anticoagulants are drugs that interfere with the coagulation of blood.

    Blood Coagulation

    • There are two pathways: Extrinsic and Intrinsic.
    • 12 proteins are responsible for blood coagulation.

    Extrinsic Pathway

    • After tissue injury, factor III is released from the injured tissue.
    • Factor III activates factor VII, which activates factor VIII, then factor X, and finally factor II (prothrombin).
    • Prothrombin is converted to thrombin, which activates factor I (fibrinogen) to form fibrin (blood clot).

    Intrinsic Pathway

    • After tissue injury, factor XII is released from the injured tissue, which activates factor XI, then factor IX, and finally factor X.
    • Factor X is activated, leading to the formation of thrombin and fibrin.

    Heparin vs Warfarin

    • Heparin: natural, stored in mast cells, parenteral (I.V. or S.C.), immediate onset of action, short duration (4-8 hours).
    • Warfarin: synthetic, oral (100% absorbed), delayed onset of action (1-2 days), long duration (5-7 days).

    Heparin Mechanism

    • Inhibits the activity of coagulation factors by activating anti-thrombin III.
    • Anti-thrombin III inhibits the activity of factors II, X, XI, XII, and XIII (mainly factor X).

    Warfarin Mechanism

    • Liver synthesizes clotting factors (1, 9, 7, 2) with the aid of vitamin K.
    • Vitamin K is converted to its oxidized form (vitamin K epoxide) during synthesis.
    • Warfarin inhibits vitamin K epoxide reductase enzyme, preventing the regeneration of reduced form of vitamin K.
    • As a result, the synthesis of clotting factors is stopped.

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    Description

    Learn about anticoagulants, their role in interfering with blood coagulation, and the two pathways of blood coagulation: extrinsic and intrinsic.

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