(4.5) ANTIPLATELET DRUGS (HARD QUIZ)
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Questions and Answers

Which of the following components play a role in platelet plug formation?

  • Antithrombin III
  • Protein C
  • Thrombin
  • PDE (correct)

What is the role of arachidonic acid in platelet activation?

  • Inhibits platelet aggregation
  • Precursor for TxA2 synthesis (correct)
  • Decreases intracellular calcium concentration
  • Stabilizes platelet membranes

Which of the following antiplatelet drugs primarily acts by inhibiting the P2Y12 receptor?

  • Aspirin
  • Glycoprotein IIb/IIIa inhibitors
  • Clopidogrel (correct)
  • Dabigatran

What is the inhibition mechanism of action for aspirin in antiplatelet therapy?

<p>Irreversibly inhibits cyclooxygenase-1 (A)</p> Signup and view all the answers

Which of the following best describes the function of glycoprotein IIb/IIIa on platelets?

<p>Mediates platelet aggregation by binding to fibrinogen (D)</p> Signup and view all the answers

What is a significant adverse event associated with clopidogrel therapy?

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

Which metabolic pathway is clinically significant for the activation of clopidogrel?

<p>P450 enzymatic pathway (D)</p> Signup and view all the answers

The structure of the active metabolite of clopidogrel is primarily derived from which substance?

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

Which of the following factors does NOT directly influence platelet activation?

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

Which antiplatelet agent works primarily by inhibiting the glycoprotein IIb/IIIa receptor?

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

What is the primary abnormality associated with hemostasis?

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

Which type of thrombus is primarily associated with myocardial infarction?

<p>Platelet-rich clots (A)</p> Signup and view all the answers

What are the three main steps in the formation of a hemostatic plug?

<p>Adhesion, Granule Release, Aggregation &amp; Consolidation (A)</p> Signup and view all the answers

Which two molecular interactions are essential for platelet adhesion?

<p>Von Willebrand Factor and Platelet Glycoprotein VI (B)</p> Signup and view all the answers

What role does von Willebrand Factor (vWF) play in hemostasis?

<p>Facilitates platelet adhesion (C)</p> Signup and view all the answers

What is a characteristic feature of red thrombus?

<p>Rich in fibrin (C)</p> Signup and view all the answers

Which condition is primarily linked with cardioembolic strokes?

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

What is the effect of activated platelets on von Willebrand Factor?

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

Which thrombosis is associated with the risk of pulmonary embolism?

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

Which interaction is particularly important for platelet Glycoprotein VI?

<p>Interaction with collagen (B)</p> Signup and view all the answers

What is the mechanism by which aspirin reduces platelet activation?

<p>It inhibits the synthesis of thromboxane A2 by irreversibly acetylating COX-1. (B)</p> Signup and view all the answers

What is the primary role of phospholipase A2 (PLA2) in platelet activation?

<p>To liberate arachidonic acid and activate glycoprotein IIb/IIIa (B)</p> Signup and view all the answers

Which antiplatelet drug is classified as an irreversible P2Y12 blocker?

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

Which of the following best describes the action of vorapaxar?

<p>It targets thrombin-mediated platelet activation through PAR-1. (C)</p> Signup and view all the answers

Which of the following antiplatelet agents irreversibly inhibits the ADP receptor?

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

Which drugs act by blocking the final common pathway of platelet aggregation?

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

What is the mechanism of action of aspirin in the context of antiplatelet therapy?

<p>Decreasing thromboxane A2 production via acetylation of COX-1 (D)</p> Signup and view all the answers

What unique property differentiates ticagrelor from other P2Y12 blockers?

<p>It acts as a reversible inhibitor. (C)</p> Signup and view all the answers

What is a common adverse effect of P2Y12 receptor inhibitors?

<p>Risk of treatment failure in CYP2C19 poor metabolizers (A)</p> Signup and view all the answers

Which dosage form is common for GPIIb/IIIa inhibitors like Abciximab?

<p>Intravenous bolus followed by infusion (B)</p> Signup and view all the answers

Which receptor does ticlopidine specifically target to exert its antiplatelet effects?

<p>P2Y12 ADP receptor (A)</p> Signup and view all the answers

What is the result of reduced thromboxane A2 release in the context of platelet activity?

<p>Decreased platelet activation (B)</p> Signup and view all the answers

Cilostazol primarily functions by inhibiting which enzyme?

<p>Phosphodiesterase-3 (PDE3) (D)</p> Signup and view all the answers

Which statement about thromboxane A2 is true?

<p>It is produced from arachidonic acid via COX-1. (A)</p> Signup and view all the answers

Which drug is a reversible inhibitor of P2Y12?

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

What role does eptifibatide play in platelet aggregation?

<p>It obstructs fibrinogen and vWF binding to glycoprotein IIb/IIIa. (D)</p> Signup and view all the answers

What happens during platelet degranulation?

<p>Numerous chemical mediators, including Ca2+ and vWF, are released. (A)</p> Signup and view all the answers

Which of the following correctly describes the route of action for antiplatelet drugs like abciximab?

<p>They inhibit glycoprotein IIb/IIIa receptor binding. (B)</p> Signup and view all the answers

Which medication is an active drug that mimics adenosine?

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

What is the primary indication for using GPIIb/IIIa inhibitors during percutaneous coronary intervention (PCI)?

<p>As an alternative to P2Y12 inhibitors. (B)</p> Signup and view all the answers

Flashcards

Platelet plug formation

A process where platelets clump together to stop bleeding.

cAMP role in platelets

cAMP inhibits platelet activation and aggregation

Ca2+ role in platelets

Ca2+ promotes platelet activation and aggregation.

vWF role in platelets

vWF facilitates platelet adhesion to the damaged blood vessel.

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Antiplatelet Drugs

Drugs that prevent blood clots by interfering with platelet function.

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Clopidogrel mechanism

Clopidogrel inhibits platelet activation and aggregation by blocking ADP receptors, interfering with platelet signaling.

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Arachidonic Acid Pathway

A metabolic pathway that produces various molecules, including TxA2, crucial for platelet aggregation.

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TXA2

A molecule that promotes platelet aggregation from arachidonic acid.

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Platelet Glycoprotein Ib

Mediates the adhesion of platelets to damaged blood vessels by binding to von Willebrand factor.

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Platelet Glycoprotein IIb/IIIa

Plays a central role in platelet aggregation by forming cross-links between platelets.

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Aspirin's antiplatelet mechanism

Aspirin inhibits thromboxane A2 (TXA2) synthesis by targeting cyclooxygenase-1 (COX-1).

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Ticlopidine's action

Ticlopidine irreversibly blocks the P2Y12 receptor on platelets.

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Clopidogrel's function

Clopidogrel is an irreversible inhibitor of the P2Y12 receptor on platelets.

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Prasugrel's mechanism

Prasugrel is an irreversible blocker of the P2Y12 ADP receptor on platelets.

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Cangrelor's role

Cangrelor is a reversible inhibitor of the P2Y12 ADP receptor on platelets.

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Ticagrelor's action

Ticagrelor is a reversible inhibitor of the P2Y12 receptor on platelets.

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Platelet aggregation inhibition (Abciximab, etc.)

Blocking fibrinogen and vWF binding to GP IIb/IIIa inhibits platelet aggregation.

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Vorapaxar's function

Vorapaxar inhibits thrombin-mediated platelet activation by targeting PAR-1.

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Antiplatelet drugs' target

Antiplatelet drugs target various steps in platelet activation and aggregation pathways.

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Platelet activation pathway

Platelet activation involves complex signaling cascades and interactions with various molecules within blood vessels.

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Hemostasis

The process of stopping bleeding.

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Thrombosis

Abnormal blood clot formation.

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White thrombus

Platelet-rich clot.

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Myocardial Infarction (MI)

Heart attack.

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Platelet Activation

The process where platelets change shape and release chemicals to initiate blood clotting.

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Granule Release

The platelets release stored substances (like ADP) to support coagulation.

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Transient Ischemic Attack (TIA)

Temporary interruption in blood supply to the brain.

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Red thrombus

Fibrin-rich clot.

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Aggregation & Consolidation

Platelets clump together (aggregate) and are stabilized in the area of injury.

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Cardioembolic stroke

Stroke caused by a blood clot moving from the heart.

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COX-1 Inhibitors (e.g., Aspirin)

Decrease Thromboxane A2 (TxA2) production by acetylating COX-1, preventing platelet activation.

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Deep Vein Thrombosis (DVT)

Blood clot in a deep vein, often in the leg.

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P2Y12 Inhibitors (e.g., Clopidogrel)

Block ADP receptors on platelets, reducing platelet activation and aggregation.

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GPIIb/IIIa Inhibitors (e.g., Abciximab)

Prevent platelet aggregation by blocking the ability to bind fibrinogen.

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Platelet Adhesion

Platelets sticking to the damaged blood vessel wall.

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von Willebrand Factor (vWF)

A protein that helps platelets stick to the damaged blood vessel.

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Phosphodiesterase Inhibitors (e.g., Cilostazol)

Increase cAMP levels, inhibiting platelet activation by causing smooth muscle relaxation.

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Hemostatic Plug Formation

The process of forming a blood clot to stop bleeding, involving adhesion, granule release, and aggregation.

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Platelet Aggregation Inhibitors

Drugs that reduce the clumping action of platelets, used to prevent blood clots(thrombosis).

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Thromboxane A2 (TxA2)

A potent platelet aggregating agent produced by platelets.

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Study Notes

Lecture #28: Antiplatelet Pharmacology

  • Presenter: Brian Skinner, PharmD, BCPS
  • Affiliation: Associate Professor of Internal Medicine, Marian University - College of Osteopathic Medicine
  • Course: BMS 551 Med Phys Pharm
  • Year: Fall 2024

Objectives

  • Describe platelet plug formation, identifying the roles of: cAMP, Ca²⁺, vWF, PLA₂, arachidonic acid, TxA₂, ADP, PKC, PKA, PDE
  • Identify the roles of platelet glycoproteins Ib, IIb/IIIa, and VI in platelet plug formation
  • Identify the mechanism of action, dosage forms, adverse events, indications, and contraindications of highlighted antiplatelet drugs
  • Describe the clinically significant metabolic pathway for clopidogrel
  • Identify the structure of the active metabolite of clopidogrel
  • Diagram arachidonic acid pathway relating to PGE₂, TxA₂, and leukotriene synthesis
  • Recommend appropriate pharmacotherapeutic strategies for simplified patient cases

Drug Overview

  • COX Inhibitors: Aspirin
  • P2Y₁₂ Receptors Blockers: Clopidogrel, Prasugrel, Ticlopidine, Ticagrelor, Cangrelor
  • GP IIb/IIIa Inhibitors: Abciximab, Eptifibatide, Tirofiban
  • Phosphodiesterase Inhibitors: Cilostazol, Dipyridamole

Hemostasis and Thrombosis

  • Hemostasis: The process of stopping blood flow
  • Thrombosis: The most common abnormality of hemostasis
  • Types of clots:
    • Platelet-rich (white thrombus): Myocardial Infarction (MI), Transient Ischemic Attacks (TIAs)
    • Fibrin-rich (red thrombus): Peripheral Arterial Clots, Cardioembolic strokes, Deep Vein Thrombosis (DVT), Pulmonary Embolism (PE)

Formation of a Hemostatic Plug

  • Three main steps: Adhesion, Granule Release, Aggregation & Consolidation

Platelet Adhesion

  • vWF secreted by activated platelets and exposed collagen
  • vWF binds to Glycoprotein Ib on activated platelets
  • Platelet Glycoprotein VI (GPVI) expressed on platelet surface interacts with collagen (GPVI:collagen interaction)

Granule Release

  • Numerous chemical mediators released in response to platelet activation
  • ADP, epinephrine, collagen activate phospholipase A₂ (PLA₂)
  • Arachidonic acid converted into thromboxane A₂ by cyclooxygenase-1 (COX-1)
  • ADP, Ca²⁺, ATP, serotonin, vWF, and platelet factor 4 released during degranulation

Aggregation & Consolidation

  • Increased cytosolic calcium and activation of thromboxane A₂ and the GPIIb/IIIa receptors lead to further platelet activation
  • Thrombin, thromboxane A₂, ADP, and other mediators increase Ca²⁺ levels.

COX-1 Inhibitors (Aspirin)

  • Mechanism: Irreversible inhibition of COX-1 enzyme via acetylation
  • Indications: Secondary prophylaxis following MI or stroke, prevention of thrombotic events
  • Adverse Effects: GI bleeding & ulcer formation, increased risk of asthma exacerbations

P2Y₁₂ ADP Receptor Inhibitors (Clopidogrel, Ticagrelor)

  • Mechanism: Clopidogrel is a prodrug activated by CYP2C19, irreversibly binding to and inactivating the ADP receptor; Ticagrelor reversibly binds to the ADP receptor mimicking adenosine
  • Indications: Secondary prophylaxis following MI or stroke, prevention of thrombotic events during PCI
  • Adverse Effects: Bleeding

GPIIb/IIIa Inhibitors (Abciximab, Eptifibatide, Tirofiban)

  • Mechanism: Monoclonal antibodies that reversibly bind to and inactivate GPIIb/IIIa preventing fibrinogen interaction and platelet aggregation
  • Indications: Prevention of thrombotic events during PCI as an alternative to P2Y12 inhibitors
  • Adverse Effects: Bleeding

Phosphodiesterase Inhibitors (Cilostazol)

  • Mechanism: Inhibition of phosphodiesterase-3 (PDE3) leading to increased cAMP catabolism
  • Indications: Intermittent claudication
  • Adverse Effects: Bleeding, headache (cerebral vasodilation), contraindicated for heart failure

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Med Phys Pharm L28 Antiplatelet Pharmacology (student) PDF

Description

This quiz focuses on the key concepts of antiplatelet pharmacology covered in Lecture #28 of the BMS 551 course. Students will explore platelet plug formation, the mechanisms of various antiplatelet drugs, and clinical implications related to their use. Prepare to navigate through essential pathways and recommend pharmacotherapeutic strategies based on case studies.

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