Blood Drugs Flashcards
(35 cards)
What is hemostasis? Thrombosis?
process to prevent and stop bleeding (hemorrhage)
formation or presence of a blood clot in a vessel
How do vein and coronary (artery) thombi compare? What drugs are used on each?
VEIN = red thrombi, RBC embedded in fibrin = anticoagulants
CORONARY = white thrombi, platelets embedded in fibrin = antiplatelets
In what 3 ways do drugs that affect hemostasis and thrombosis act?
- blood coagulation (fibrin formation)
- platelet function (activation, coagulation)
- fibrin removal (fibrinolysis)
What is the difference between red blood cells, white blood cells, and platelets (thrombocytes)?
RBC = erythrocytes; transport oxygen
WBC = leukocytes; fight germs and infections by attacking infected cells
PLATELETS = stop bleeding by forming a blood clot
What is the structure of red blood cells? What is their function?
- disc-shaped with a large surface area
- no nucelus
- contains hemoglobin, which picks up oxygen
transports oxygen from the lungs to the body and carbon dioxide from the body back to the lungs
What is the structure of platelets? Where do they come from?
- colorless and lens-shaped with a small surface area
- no nucleus
fragments of cytoplasm from cells of the bone marrow
What is the function of platelets? In which animals are they found? Where are they not found?
prevents excessive internal or external bleeding after an injury by forming a blood clot
- mammals
- birds and amphibians: present as intact mononuclear cells
What are the 3 types of white blood cells? What is their function?
- granulocytes - neutrophils, eosinophils, basophils
- monocytes
- lymphocytes - B- and T-lymphocytes
work together to fight illness or disease, like infections, inflammation, allergic reactions, and stress
What are the 4 basis steps of hemostasis?
- vascular stage
- platelet stage
- coagulation
- fibrinolysis
What is coagulation? What are the 4 steps?
process by which blood changes from a liquid into a gel, forming a blood clot (fibrin + platelets)
- activation
- adhesion
- aggregation of platelets
- deposition and maturation of fibrin
How do the phases of hemostasis work?
- damaged blood vessels release clotting factors
- clotting factors activate prothrombin into thrombin (IIa)
- vasoconstriction limits blood flow and platelets form a sticky plug, where soluble fibrinogen is activated by thrombin into insoluble fibrin
- fibrin strands adhere to the plug and form an insoluble clot
What are the 5 steps to the clotting cascade?
- wound (vascular injury) causes the endothelium to release tissue factor
- tissue factor activates factor VIIa
- factor VIIa activates factor Xa
- with factor Va, factor X activates prothrombin (factor II) into thrombin (factor IIa)
- thrombin (IIa) then is able to turn soluble fibrinogen into insoluble fibrin to form a clot
Blood coagulation factors:
What are the 3 major steps to clotting? What ion is important for the activation of many zymogen factors?
- activation of prothrombin activators
- conversion of prothrombin into thrombin
- conversion of fibrinogen into fibrin fibers
Ca2+
What is the difference between pro-coagulants and anti-coagulants?
PRO-COAGULANTS promote coagulation: XIIa, XIa, Xa, IXa, and thrombin (IIa)
ANTI-COAGULANTS inhibit coagulation: antithrombin III, fibrinolysis
What conditions require anticoagulants and antiplatelets?
cardiovascular disorders
- thrombosis
- pulmonary thrombosis
- acute coronary syndrome
- arterial fibrillation
- stroke
- ischemic heart disease
- thromboembolic disease in IMHA
- antithombotic prophylaxis
What 4 drugs affect coagulation bleeding?
- anticoagulants
- antiplatelets
- fibrinolytic drugs
- antifibrinolytic
How are anticoagulants used? What are the 4 main classes?
used to modify the coagulation cascade either when there is a defect in coagulation or when there is unwanted coagulation
- heparin and LMWH (Dalteparin, Enoxaparin)
- warfarin and coumarin derivatives (Dicumarol, Menadione, Acenocoumarol)
- thrombin inhibitors
- factor Xa inhibitors
What is antithrombin III? What is its function? What drug potentiates it?
endogenous anticoagulant
inactivates factors IXa, Xa, XIa, XIIa, and thrombin (IIa)
heparin
What is the mechanism of action of heparin? What does this result in?
binds to antithrombin III and causes conformational changes that significantly enhance its inhibitory effects on various activated coagulation factors (~1000-fold)
inactivation of Xa, thrombin (IIa), IXa, XIa, and XIIa
Where is heparin derived from? When is it most commonly used?
proteoglycan from mast cells
excessive clotting or increased risk of clot formation in cats, dogs, and horses, especially disseminated intravascular coagulopathy (DIC)
- thromboembolic problems
- venous thrombosis
- pulmonary thromboembolism
- laminitis
- endotoxic shock
- burns
What are the 2 types of heparin?
- unfractionated heparin (UFH): inactivates thrombin (IIa) and factor Xa
- low-molecular-weight heparin (LMWH): inactivates factor Xa
Why is heparin not a one dose fits all drug? How can we tailor dosages to patients?
- patients with low antithrombin III may not respond as well as those with adequate levels
- variable PK among animals and protein binding
monitor clotting times with activated partial thromboplastin time (aPTT)
What are the 2 most common adverse effects of heparin?
- bleeding problems
- heparin-induced thrombocytopenia (humans)
