Coagulation and Aggregation - 3rd Year Medicine
42 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

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 (A)</p> Signup and view all the answers

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

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

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

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

Which of the following factors decreases the effectiveness of warfarin?

<p>Pregnancy (B), Increased hepatic P450 activity (C)</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 (A)</p> Signup and view all the answers

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

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

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

<p>Hypothyroidism (D)</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. (C)</p> Signup and view all the answers

Which condition is a contraindication for the use of heparin?

<p>Surgery (A)</p> Signup and view all the answers

What is the mechanism of action of warfarin?

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

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

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

What must be monitored when administering hirudin?

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

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

<p>Hirudin (B)</p> Signup and view all the answers

For which procedure is bivalirudin commonly used?

<p>Percutaneous coronary artery surgery (D)</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 (C)</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 (D)</p> Signup and view all the answers

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

<p>Moxalactam (C)</p> Signup and view all the answers

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

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

Which type of oral anticoagulant directly inhibits thrombin?

<p>Dabigatran (C)</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 (D)</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 (B)</p> Signup and view all the answers

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

<p>Discontinue warfarin (C)</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 (D)</p> Signup and view all the answers

What is the primary mechanism of action of streptokinase?

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

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

<p>Alteplase (D)</p> Signup and view all the answers

What is a common adverse drug reaction of fibrinolytic therapy?

<p>Hypotension (C)</p> Signup and view all the answers

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

<p>Uncontrolled hypertension (D)</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 (A)</p> Signup and view all the answers

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

<p>Fibrinolytics (B)</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. (C)</p> Signup and view all the answers

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

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

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

<p>Binding to antithrombin III (D)</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) (A)</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 (C)</p> Signup and view all the answers

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

<p>It acts immediately upon administration (C)</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 (D)</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) (C)</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 (A)</p> Signup and view all the answers

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

<p>Procoagulants (C)</p> Signup and view all the answers

Flashcards

How do oral anticoagulants work?

Oral anticoagulants, like warfarin and acenocoumarol, work by blocking the regeneration of Vitamin K, which is needed for the production of clotting factors. They reduce the ability of the blood to clot.

What is special about warfarin?

The most important oral anticoagulant, warfarin needs close monitoring with blood tests to adjust the dose. It has a narrow safety margin, meaning it needs to be carefully balanced to be effective but avoid too much bleeding.

How is the effect of warfarin monitored?

The effect of warfarin and acenocoumarol is measured by the prothrombin time (PT). The International Normalized Ratio (INR) standardizes PT across labs for better monitoring.

Why is it important to understand interactions with warfarin?

Many factors can influence how warfarin works, like pregnancy, certain medical conditions, and even other medicines. These factors can affect how the body processes warfarin, making it more or less strong.

Signup and view all the flashcards

What can weaken the effect of warfarin?

Warfarin's effect can be weakened by Vitamin K, drugs that speed up liver enzymes, and certain medications that reduce its absorption. These interactions may require dosage adjustments.

Signup and view all the flashcards

What is Heparin?

Heparin is a family of sulfated glycosaminoglycans that interfere with blood clotting by accelerating the action of antithrombin III, which inhibits thrombin and factor Xa.

Signup and view all the flashcards

What are LMWHs?

Low-molecular-weight heparins (LMWHs) are fragments of heparin that have longer action and are generally preferred over unfractionated heparin.

Signup and view all the flashcards

What is Fondaparinux?

Fondaparinux is a synthetic pentasaccharide that selectively inhibits factor Xa.

Signup and view all the flashcards

What is Unfractionated Heparin (UFH)?

Unfractionated Heparin (UFH) is the full-length version of heparin, used in specific cases like renal failure where LMWHs are not suitable.

Signup and view all the flashcards

How does Heparin work?

Heparin's mechanism of action involves binding to antithrombin III, boosting its ability to inhibit thrombin and factor Xa, thus preventing coagulation.

Signup and view all the flashcards

How is Heparin administered and how long does it last?

Heparin is administered intravenously for immediate effect or subcutaneously for a delayed effect, with a half-life of 40-90 minutes.

Signup and view all the flashcards

What are the benefits of LMWHs compared to UFH?

LMWHs have longer elimination half-lives, leading to more predictable effects and less frequent dosing compared to unfractionated heparin.

Signup and view all the flashcards

How is Heparin dosing managed?

Heparin dosages are adjusted based on individual needs and monitored closely. In urgent situations, a bolus IV dose followed by a constant-rate infusion can be used.

Signup and view all the flashcards

Heparin

Heparin is a medication used to prevent and treat blood clots. It works by interfering with the clotting cascade, making it harder for blood to form clots.

Signup and view all the flashcards

APTT (Activated Partial Thromboplastin Time)

A blood test that measures the time it takes for blood to clot. APTT evaluates the function of certain clotting factors in the intrinsic and common coagulation pathways.

Signup and view all the flashcards

Anticoagulants

A type of drug that prevents the formation of blood clots. Anticoagulants are used to treat various conditions, including deep vein thrombosis and pulmonary embolism.

Signup and view all the flashcards

Heparin-Induced Thrombocytopenia (HIT)

This rare condition is an immune response to heparin, a blood-thinning medicine. It can cause the formation of blood clots, even though heparin is meant to prevent them.

Signup and view all the flashcards

Direct Thrombin Inhibitors

A type of anticoagulant that acts by inhibiting thrombin, a key enzyme in the clotting cascade.

Signup and view all the flashcards

Anti-vitamin K Agents

A group of medications that prevent the formation of blood clots by inhibiting Vitamin K, which is essential for the production of clotting factors.

Signup and view all the flashcards

Warfarin

Warfarin is an anticoagulant that is effective in preventing blood clots by blocking the action of Vitamin K.

Signup and view all the flashcards

Acenocoumarol

Acenocoumarol is a medication that blocks Vitamin K's action, preventing blood clots.

Signup and view all the flashcards

What is plasmin?

A protein that breaks down fibrin, the structural component of blood clots. It also degrades fibrinogen, a protein that forms fibrin, and some clotting factors.

Signup and view all the flashcards

What are fibrinolytic drugs?

A group of medications that dissolve blood clots by activating plasmin, which in turn breaks down fibrin.

Signup and view all the flashcards

What is streptokinase?

A fibrinolytic drug that activates plasminogen, the precursor of plasmin. It binds to circulating plasminogen making it more sensitive to endogenous plasminogen activators, leading to increased plasmin formation.

Signup and view all the flashcards

What is alteplase?

A fibrinolytic drug that specifically targets fibrin-bound plasminogen. It works only in the presence of fibrin clots and does not dissolve circulating plasminogen. This makes it more clot-selective.

Signup and view all the flashcards

What is reteplase?

A fibrinolytic drug administered as a bolus injection. Often used for myocardial infarction.

Signup and view all the flashcards

What's a major risk associated with fibrinolytic drugs?

A common side effect of fibrinolytic drugs, which can range from gastrointestinal bleeding to a hemorrhagic stroke.

Signup and view all the flashcards

What's the main clinical use for fibrinolytic drugs?

Primary use for fibrinolytic drugs. It is most effective when administered within 12 hours of the onset of symptoms.

Signup and view all the flashcards

What are some contraindications for fibrinolytic drugs?

Conditions that prevent the use of fibrinolytic drugs. These include internal bleeding, bleeding disorders, pregnancy, recent trauma, and uncontrolled hypertension.

Signup and view all the flashcards

What drugs can increase Warfarin's effect?

Drugs that inhibit hepatic metabolism can increase the concentration of Warfarin in the blood, leading to an enhanced anticoagulant effect. Examples include Citalopram, Metronidazole, Amiodarone, and antifungal azoles.

Signup and view all the flashcards

How do broad-spectrum antibiotics impact Warfarin?

Broad-spectrum antibiotics can reduce the production of vitamin K in the gut, leading to a heightened anticoagulant effect of Warfarin. This is because vitamin K synthesis relies on the gut bacteria.

Signup and view all the flashcards

What is the mechanism of action of Dabigatran?

Dabigatran is a direct thrombin inhibitor, which prevents the final step in the coagulation cascade. This prevents the formation of blood clots.

Signup and view all the flashcards

What are the main uses of Dabigatran?

Dabigatran is used to prevent blood clots in people who have had hip or knee replacements, and to reduce the stroke risk in people with atrial fibrillation.

Signup and view all the flashcards

How can other drugs affect Warfarin's effect?

Warfarin's effects can be potentiated by drugs that bind to plasma proteins, leading to displacement of Warfarin and an increase in its free concentration. This enhances its anticoagulant effect.

Signup and view all the flashcards

What are some of the adverse effects of Warfarin?

Adverse effects of Warfarin include bleeding, ranging from minor to life-threatening. Hepatotoxicity and teratogenicity are also potential risks.

Signup and view all the flashcards

What are some of the side effects of Dabigatran?

Dabigatran can cause side effects such as nausea, vomiting, constipation, insomnia, and peripheral edema.

Signup and view all the flashcards

Antifibrinolytic Drug

A medication that prevents the breakdown of blood clots (fibrinolysis), helping to stop bleeding.

Signup and view all the flashcards

Tranexamic Acid

This drug stops the activation of plasminogen, which is a protein that breaks down blood clots. It can be given by mouth or intravenously.

Signup and view all the flashcards

Hypoprothrombinemic Hemorrhage

A deficiency of vitamin K, leading to a lack of clotting factors and potential bleeding.

Signup and view all the flashcards

Vitamin K

This fat-soluble vitamin is crucial for the liver to produce clotting factors.

Signup and view all the flashcards

Lack of Bile, Obstructive Jaundice

A condition where the body cannot absorb vitamin K properly, often due to problems with bile production.

Signup and view all the flashcards

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).

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

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.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser