Drugs in Coagulation Disorders (PHRC-5832)

Questions and Answers

What is the primary role of the vascular phase in hemostasis?

Breakdown of the clot after vessel repair

Reduction of blood flow through vasoconstriction (correct)

Aggregation of platelets to form a plug

Formation of a fibrin clot

Which substance released from endothelial cells contributes to vasoconstriction during hemostasis?

Fibrin

Endothelin (correct)

Thromboxane A2

Serotonin

In which phase does platelet aggregation occur to form a plug?

Fibrinolytic phase

Coagulation phase

Platelet phase (correct)

Vascular phase

What is the significance of collagen exposure during the hemostatic process?

It facilitates adhesion of platelets to the damaged area. Signup and view all the answers

What is one of the key actions of thromboxane A2 during hemostasis?

It facilitates platelet aggregation. Signup and view all the answers

Which of the following best describes the coagulation phase in hemostasis?

Activation of clotting factors to form a fibrin clot Signup and view all the answers

What occurs during the fibrinolytic phase of hemostasis?

The clot is broken down after vessel repair. Signup and view all the answers

Which of the following correctly represents the sequence of phases in normal hemostasis?

Vascular phase → Platelet phase → Coagulation phase → Fibrinolytic phase Signup and view all the answers

What initiates the intrinsic pathway of coagulation?

Exposure of clotting factors to negatively charged surfaces Signup and view all the answers

Which of the following factors is responsible for activating factor XI in the intrinsic pathway?

Factor XIIa Signup and view all the answers

What role does thrombin play in the coagulation process?

Converts fibrinogen into fibrin Signup and view all the answers

Which component is involved in the positive feedback loop during coagulation?

Thrombin Signup and view all the answers

What is activated by factor XIII once thrombin acts upon it?

Fibrin monomers Signup and view all the answers

What initiates the common pathway in coagulation?

Activation of factor X Signup and view all the answers

Which elements are required for the activation of factor X in the common pathway?

Factor V, calcium ions, platelet membrane phospholipids Signup and view all the answers

What is the final structural component formed from fibrinogen during coagulation?

Fibrin meshwork Signup and view all the answers

What component is primarily responsible for stabilizing the blood clot?

Factor XIII Signup and view all the answers

What is a 'thrombin burst'?

Rapid generation of thrombin from thrombin Signup and view all the answers

What is the role of thromboxane A2 in the platelet activation process?

It enhances platelet activation. Signup and view all the answers

Which receptor on platelets is responsible for binding to collagen?

GP Ia / GPVI receptor Signup and view all the answers

What substance is released by platelets that activates the coagulation cascade?

Adenosine diphosphate (ADP) Signup and view all the answers

What is the main role of Nitric Oxide (NO) in hemostasis?

To prevent platelet activation and aggregation Signup and view all the answers

Which of the following is NOT a factor dependent on hemostasis?

High Levels of Oxygen Signup and view all the answers

Which process involves the temporary formation of a platelet plug at a site of vascular injury?

Thrombus formation Signup and view all the answers

What is the primary component of the mesh that traps cells and reinforces the platelet plug?

Fibrin Signup and view all the answers

What prevents thrombin from diffusing to surrounding areas during hemostasis?

Adsorption to fibrin Signup and view all the answers

What effect does the release of serotonin have during the activation of platelets?

Enhances platelet activation. Signup and view all the answers

What is a defining characteristic of a pulmonary embolism?

A clot that floats within the blood in the lungs Signup and view all the answers

Which structure in blood vessels do platelets primarily adhere to during the platelet phase?

Subendothelial matrix Signup and view all the answers

Which anticoagulant is released from mast cells to inactivate thrombin?

Heparin Signup and view all the answers

What does the fibrinolytic system do during hemostasis?

Activates plasminogen to form plasmin Signup and view all the answers

What mechanism triggers the release of granules containing ADP and serotonin from platelets?

Collagen activation Signup and view all the answers

What primarily forms a white clot in the circulatory system?

Aggregated platelets in arterial blood Signup and view all the answers

Which substance plays a crucial role in preventing platelet adherence to uninjured endothelial cells?

Prostacyclin Signup and view all the answers

What is the primary composition of a red clot?

Fibrin strands with trapped blood cells Signup and view all the answers

Which class of drugs is primarily used to treat red clots?

Anticoagulants Signup and view all the answers

Which of the following is a direct thrombin inhibitor?

Bivalirudin Signup and view all the answers

Deep vein thrombosis (DVT) is often associated with which of the following factors?

Stasis Signup and view all the answers

What is the primary action of thrombolytics?

Lyse thrombi Signup and view all the answers

Which anticoagulant is an indirect thrombin inhibitor?

Enoxaparin Signup and view all the answers

Which of the following is NOT an antifibrinolytic agent?

Urokinase Signup and view all the answers

What type of antiplatelet drug is Ticagrelor?

PAR-1 inhibitor Signup and view all the answers

Study Notes

Hemostasis and Coagulation Overview

Hemostasis prevents or stops bleeding through a complex process involving clotting factors.
Phases of hemostasis:
- Vascular phase: Vasospasm reduces blood flow.
- Platelet phase: Platelet aggregation forms a plug.
- Coagulation phase: Fibrin clot formation occurs.
- Fibrinolytic phase: Breakdown of the clot post-repair.

Vascular Phase

Injury to blood vessels triggers vasoconstriction to decrease blood flow, aided by:
- Endothelin released from endothelial cells.
- Thromboxane A2 and serotonin from activated platelets enhance vasoconstriction.

Platelet Phase

Steps in platelet adhesion and activation:
- Damage exposes collagen in the vessel wall.
- Platelets adhere to collagen, morph into a spiky shape, and release substances like ADP and thromboxane A2.
- Platelet aggregation is crucial for clot formation.

Coagulation Cascade

Intrinsic pathway activated by vascular damage and negatively charged subendothelial surfaces.
- Contributions of factors: XII, XI, IX, and VIII lead to activation of factor X.
Common pathway involves:
- Factor Xa converting prothrombin into thrombin.
- Thrombin transforms fibrinogen into fibrin to form the clot structure.

Major Components of Hemostasis

Stable hemostasis relies on:
- Integrity of the vessel wall.
- Adequate platelet counts and function.
- Sufficient levels of clotting factors and fibrinolytic activity.

Pathological Thrombus Formation

Thrombus: Fixed clot on a vessel wall; embolus: Free-floating clot.
Risks include obstruction of blood vessels, leading to conditions like pulmonary embolism.
Anticoagulants help prevent thrombus formation.

Types of Blood Clots

White clots (arterial) consist mainly of platelets; red clots (venous) consist largely of fibrin and trapped blood cells.
Treatment differs by clot type: antiplatelet agents for white clots and anticoagulants for red clots.

Anticoagulant Classification

Anticoagulants reduce blood coagulability, divided into:
- Indirect thrombin inhibitors (e.g., heparins).
- Direct thrombin inhibitors (e.g., hirudin).
Antiplatelet agents interfere with platelet function; notable examples include aspirin and clopidogrel.
Thrombolytics dissolve existing clots.

Common Anticoagulant Drugs

Parenteral options include unfractionated heparin and low molecular weight heparins (e.g., enoxaparin).
Oral options include Warfarin and direct oral anticoagulants (e.g., rivaroxaban, apixaban).

Reversal Agents for Oral Anticoagulants

Idarucizumab for direct thrombin inhibitors.
Andexanet alfa for factor Xa inhibitors.

Antiplatelet Classification Mechanisms

Varying action mechanisms including GP receptor inhibitors (e.g., Abciximab, Eptifibatide) and specific receptor antagonists (e.g., Vorapaxar).

Thrombolytics and Antifibrinolytic Agents

Thrombolytic agents like streptokinase and tissue plasminogen activator promote clot lysis.
Antifibrinolytics such as aminocaproic acid help prevent clot breakdown.

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Description

This quiz covers the mechanisms of coagulation and hemostasis, focusing on major classes of antiplatelet and anticoagulant medications. You will explore their mechanisms of action along with associated toxicities and drug interactions. Test your knowledge of pharmacology in these critical areas.