Coagulation and Aggregation - 3rd Year Medicine
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What is the primary mechanism of action of tranexamic acid?

  • Stimulates thrombus formation
  • Inhibits vitamin K synthesis
  • Prevents activation of plasminogen (correct)
  • Increases fibrinolysis

    • In which scenario is tranexamic acid NOT typically used?

  • Life-threatening bleeding after thrombolytic therapy
  • Hypoprothrombinemic hemorrhage (correct)
  • Menorrhagia
  • Hereditary angioedema

    • Which factors are synthesized in the liver under the influence of vitamin K?

  • II, VI, IX, X
  • I, III, VIII, X
  • II, VII, IX, X (correct)
  • I, II, V, VII

    • What most significantly affects the absorption of vitamin K?

    <p>Reduced bile salts due to colelithiasis</p> Signup and view all the answers

    What is a potential risk associated with the administration of antifibrinolytics like tranexamic acid?

    <p>Thrombus formation</p> Signup and view all the answers

    What is the primary mechanism of action of acenocoumarol and warfarin?

    <p>Vitamin K antagonist</p> Signup and view all the answers

    Which of the following factors decreases the effectiveness of warfarin?

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

    What significant monitoring is required during therapy with oral anticoagulants like warfarin?

    <p>Prothrombin time (PT) measured as INR</p> Signup and view all the answers

    What is the peak pharmacological effect timing after administration of warfarin?

    <p>48 hours</p> Signup and view all the answers

    Which patient condition requires careful dose adjustment of warfarin to avoid excessive effects?

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

    What is a primary reason that LMWH has a lower incidence of HIT compared to standard heparin?

    <p>It has reduced interaction with PF4.</p> Signup and view all the answers

    Which condition is a contraindication for the use of heparin?

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

    What is the mechanism of action of warfarin?

    <p>Inhibits vitamin K epoxide reductase.</p> Signup and view all the answers

    Which factor is NOT dependent on vitamin K for its synthesis?

    <p>Factor V</p> Signup and view all the answers

    What must be monitored when administering hirudin?

    <p>Activated partial thromboplastin time (APTT)</p> Signup and view all the answers

    Which anticoagulant is specifically indicated for patients with type II HIT?

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

    For which procedure is bivalirudin commonly used?

    <p>Percutaneous coronary artery surgery</p> Signup and view all the answers

    What is the potential complication associated with over-anticoagulation of direct thrombin inhibitors?

    <p>Bleeding or hypersensitivity reactions</p> Signup and view all the answers

    Which condition can lead to an increased effect of warfarin due to increased plasma concentration?

    <p>Liver disease</p> Signup and view all the answers

    Which of the following antibiotics is known to inhibit platelet function?

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

    What is a critical adverse effect of warfarin that requires immediate intervention?

    <p>Life-threatening bleeding</p> Signup and view all the answers

    Which type of oral anticoagulant directly inhibits thrombin?

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

    What effect do broad-spectrum antibiotics have on vitamin K levels?

    <p>Decrease the availability of vitamin K</p> Signup and view all the answers

    Which of the following is NOT a known adverse reaction (ADR) of direct oral anticoagulants (DOACs)?

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

    What is the appropriate response for minor hemorrhagic events associated with warfarin therapy?

    <p>Discontinue warfarin</p> Signup and view all the answers

    Which of these drugs displaces warfarin from plasma albumin binding sites, potentially increasing its effect?

    <p>Chloral hydrate</p> Signup and view all the answers

    What is the primary mechanism of action of streptokinase?

    <p>It activates plasminogen, increasing plasmin formation.</p> Signup and view all the answers

    Which of the following drugs is considered 'clot selective'?

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

    What is a common adverse drug reaction of fibrinolytic therapy?

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

    In which condition should the use of fibrinolytic drugs be avoided?

    <p>Uncontrolled hypertension</p> Signup and view all the answers

    What is the recommended time frame for administering fibrinolytic therapy in acute thrombotic stroke?

    <p>Within 3 hours of symptom onset</p> Signup and view all the answers

    What is the main drug class that includes alteplase and reteplase?

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

    What is the clinical significance of waiting a minimum of 6 months before repeating streptokinase therapy?

    <p>Antibodies against the drug may develop.</p> Signup and view all the answers

    What additional treatment is suggested for managing bleeding due to fibrinolytic therapy?

    <p>Fresh plasma</p> Signup and view all the answers

    What is the primary mechanism by which heparin acts as an anticoagulant?

    <p>Binding to antithrombin III</p> Signup and view all the answers

    Which type of heparin is primarily preferred for long-term treatment due to its longer acting properties?

    <p>Low Molecular Weight Heparins (LMWH)</p> Signup and view all the answers

    In which scenario is Unfractionated Heparin (UFH) typically used?

    <p>Patients with renal failure where LMWHs are contraindicated</p> Signup and view all the answers

    What characterizes the administration and action of Heparin when given intravenously?

    <p>It acts immediately upon administration</p> Signup and view all the answers

    Which of the following correctly orders the anticoagulant effect of Heparin types from strongest to weakest for general anticoagulation?

    <p>UFH &gt; LMWH &gt; Fondaparinux</p> Signup and view all the answers

    What action do direct thrombin inhibitors primarily target in the coagulation cascade?

    <p>Inhibition of Factor IIa (Thrombin)</p> Signup and view all the answers

    What is the key advantage of Low Molecular Weight Heparins (LMWH) over Unfractionated Heparin (UFH)?

    <p>More predictable dosing</p> Signup and view all the answers

    What treatment is indicated for a deficit leading to vascular thrombosis?

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

    Study Notes

    Coagulation and Aggregation

    • Lesson 23 covered in 3rd-year Medicine.
    • Professor: Vittoria Carrabs PhD
    • Academic year: 2024/25

    Pharmacology of Hemostasis

    • Platelet aggregation:
      • Deficit: Hemorrhage
      • Excess: Vascular thrombosis -Drugs: Platelet Concentrate, Antiplatelet agents
    • Coagulation:
      • Deficit: Bleeding
      • Excess: Vascular thrombosis
      • Drugs: Procoagulants, anticoagulants
    • Fibrinolysis:
      • Deficit: Vascular thrombosis
      • Excess: Bleeding
      • Drugs: Fibrinolytics, antifibrinolytics

    Drugs that Act on the Coagulation Cascade

    • Anticoagulants:
      • Heparin:
        • A group of sulfated glycosaminoglycans
        • Dosing in units of activity
        • Types: LMWHs (enoxaparin, dalteparin), fondaparinux, UFH
        • Mechanism: Interferes with blood clotting by binding to antithrombin III, enhancing its effects on factor Ila (thrombin) and factor Xa.
        • Administration: IV (immediate) or subcutaneous (delayed 60 min)
        • Half-life: approximately 40-90 minutes
        • Dosage adjusted as needed
        • Used for shorter-term needs.
        • Alternative administration route (e.g. SC, IV infusion dose) often considered
      • Direct Thrombin Inhibitors:
        • Hirudin, lepirudin (recombinant)
        • Bivalirudin -Used during percutaneous coronary artery surgeries. IV bolus followed by an infusion.
        • Dabigatran -Used for thromboembolic disease, type II HIT patients. Adjusted dosages based on APTT -Causes bleeding or hypersensitivity reactions.
      • Direct Xa Inhibitors:
        • Rivaroxaban, apixaban, edoxaban -Mechanism of action: directly inhibit factor Xa. -Adverse Drug Reactions (ADR): Nausea, tachycardia, anemia, thrombocytopenia, increased transaminases, and hepatoxicity (rivaroxaban in particular).

    Oral Anticoagulants

    • Acenocoumarol, Warfarin:
      • Anti-Vitamin K agents
      • Mechanism: prevent the physiological regeneration of the active form of vitamin K, necessary for the formation of coagulation factors II, VII, IX, and X, protein C, and S which inhibit VKOCR1 (Vitamin K epoxide reductase).
      • Importance: The most important oral anticoagulant drug.
      • Frequent blood tests to individualize the dose.
      • Monitoring of INR (International Normalized Ratio), used for the detection of the effect of the drug.
      • Peak pharmacological effect ~48 hours, lasts 4-5 days.
      • Teratogenic.
      • Appears in milk during lactation.
      • Factors reducing effect: Physiological state/disease (pregnancy, hypothyroidism), several drugs (vitamin K, drugs which induce hepatic P450 enzymes, drugs that reduce absorption).

    Fibrinolysis

    • Mechanism: Fibrinolysis is the breakdown of fibrin clots.
    • Key enzyme: Plasmin, a trypsin-like protease
    • Purpose: Prevents persistence of clots, ensures prompt removal of thrombus
    • Fibrinolytic drugs:
      • Streptokinase: A plasminogen activating protein (non-specific), administered IV, reduces mortality in acute myocardial infarction.
      • Alteplase/Duteplase: Tissue plasminogen activator ("clot selective"). Can be used in patients with antibodies to streptokinase.
      • Reteplase: Administered as bolus, often used in cases of myocardial infarction.
    • Adverse Drug Reactions (ADRs): Bleeding (treated with Tranexamic Acid, Fresh Plasma, Coagulation Factors)
    • Contraindications: Includes internal bleeding, hemorrhagic cerebrovascular disease, bleeding diaseses, pregnancy, uncontrolled hypertension, invasive procedures (where hemostasis is important), recent trauma
    • Clinical uses: treating acute myocardial infarction within 12 hrs of onset; clearing thrombosed shunts/cannulae; acute arterial thromboembolism; and life-threatening deep venous thrombosis and pulmonary embolism
    • Antifibrinolytic drugs: Tranexamic acid

    Vitamin K

    • Importance: Vital for the production of clotting factors (II, VII, IX, X) - "the vitamin of coagulation"
    • Administration: Oral or parenteral
    • Absorption: Requires bile salts.
    • Colelithiasis: Reduces its absorption.
    • Clinical uses: Treating bleeding from excessive oral anticoagulation, preventing hemorrhagic disease in babies, or used to treat deficiencies
    • Sprue, coeliac disease, steatorrhoea or lack of bile (e.g. in obstructive jaundice).

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    Lesson 23- Coagulation and Aggregation (pt.2) PDF

    Description

    This quiz focuses on the pharmacology of hemostasis, including platelet aggregation and coagulation mechanisms as taught in Lesson 23 of the 3rd-year Medicine course. It covers various drugs that influence these processes and describes conditions associated with deficiencies or excesses. Test your understanding of these critical medical concepts.

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