Hemolytic Drugs Flashcards
(34 cards)
1
Q
What is the goal of normal hemostasis?
A
- prevent prolonged hemorrhage
- prevent spontaneous thrombosis
2
Q
What are the stages of hemostasis?
A
- Vasospasm
- Platelet response
- coagulation phase
- clot dissolution (fibrinolysis)
3
Q
What occurs during vasospasm?
A
- vasoconstriction
- sympathetics and local factors respond to restrict blood flow to the area
4
Q
What occurs during platelet response?
A
- forms an initial plug immediately
- platelets adhere to exposed collagen and damaged endothelium
- platelet plug releases chemical mediators to recruit platelets, promote vasoconstriction and initiate the coagulation cascade
5
Q
What happen during the coagulation phase?
A
- conversion of soluble fibrinogen to insoluble fibrin forming a net of organized protein around the platelet plug
- if done correctly this phase results in a clot (thrombus)
6
Q
What happens during clot dissolution/fibrinolysis?
A
- wound healing and restoration of blood flow
- dissolution of clot
7
Q
What are the main causes of excessive bleeding? (3)
A
- platelet deficiency
- clotting factor deficiency
- fibrinolytic hyperactivity
8
Q
What are the two natural forms of Vitamin K that exist?
A
- K1: phytonadione (foods)
- K2: menaquinone (intestinal bacteria)
9
Q
What is the main mechanism of action of vitamin K?-
A
- confers biological activity of multiple factors
- SC is the recommended route because anaphylaxis and hematomas are possible
- it is very fat soluble so considered to be safe
10
Q
When would we use vitamin K?
A
- vitamin k deficiency (rodenticide toxicity or sweet clover poisoning)
- warfarin overdosing
11
Q
What is Desmopressin acetate (DDAVP) used for?
A
- increases Von Willebrand activity (helps platelets stick together)
- used prophylactically to control capillary bleeding during surgery
- injectable or nasal spray
12
Q
What is Protamine Sulfate used for?
A
- used to treat heparin overdoses (binds to heparin neutralizing its anticoagulant effect)
- give IV slowly to avoid adverse reactions that include collapse
13
Q
What do we use fibrinolytic inhibitors for?
A
- plasmin lyses fibrin and fibrinogen
- a fibrinolytic inhibitor like Aminocaproic acid will block lysine binding sites, inhibiting plasmin
- we would use these drugs for bleeding from fibrinolytic therapy or adjunct therapy-hemophiliacs
14
Q
What is thromboembolic disease?
A
- thrombus formation of the “blood clot proper”
- thromboemboli migration of thrombus in the body
15
Q
What does pathogenesis of thrombosis require?
A
Prothrombic factors
16
Q
What are some prothrombic factors?
A
- local vessel injury
- abnormal blood flow (stasis or turbulence)
- altered blood coagulability
17
Q
What does an ideal systemic anticoagulant include?
A
- prevents pathologic thrombosis
- allow normal response to vascular injury and limit bleeding
18
Q
What is the mechanism of action of heparin?
A
- Enhances the action of antithrombin III which inhibits activated clotting factors
19
Q
What do we primarily use heparin for?
A
- initial treatment of thrombosis and thromboembolic disease
- useful as an acute anticoagulant as it has rapid onset
- prevents NEW thrombus formation only, will not lyse existing thrombus
20
Q
What are some adverse effects of heparin?
A
- bleeding tendencies
- 1.8-2.5X the normal mean aPTT
- protamine sulfate can neutralize heparin in overdose
21
Q
What are some key characteristics of Enoxaparin?
A
- systemic anticoagulant
- low molecular weight heparin
- used more commonly due to less bleeding tendencies, protamine sulfate is less active against LMW heparins, less risk of thrombocytopenia, improved pharmokinetics = can give sub q and longer half life
22
Q
What are the key characteristics about Warfarin?
A
- systemic anticoagulant
- oral anticoagulant - antagonizes vitamin K actions
- injectable and oral formulations available
- monitoring using international normalized ratio
23
Q
What are the adverse effects of Warfarin?
A
- bleeding tendencies
- serious bleeding requires fresh blood/plasma
- warfarin crosses placenta therefore do not use in pregnancy (heparin does not cross placenta)
24
Q
What is the mechanism of action of Rivaroxaban?
A
- selective factor Xa inhibitor
25
What are the key characteristics of Rivaroxaban?
- systemic anticoagulant
- inactivate factor Xa directly
- does not interact with ATIII and no thrombin activity
- quick anticoagulant activity
- predictable pharmokinetics
- given orally
- bleeding can occur
26
What are the key characteristics of aspirin?
- cyclooxygenase inhibitor
- irreversibly binds cyclooxygenase-1
- prevents thrombus and re-thrombosis formation
27
What are some adverse effects of aspirin?
- GI ulceration
- renal damage
- bleeding tendencies
28
What are the key characteristics of clopidogrel?
- ADP inhibitors
- reduce platelet aggregation by inhibiting ADP pathways
- "prodrug" which must be activated by liver P450 metabolism
- routinely used for thromboembolic concerns in cats (HCM) and dogs (IMHA)
- fairly safe
29
What do fibrinolytic drugs do?
Rapidly lyse through thrombi by activating plasmin from clot bound plasminogen
30
What are the key characteristics of tissue plasminogen activator?
- proteases that bind fibrin
- can preferentially activate clot bound plasminogen
- short-half life = constant rate infusion
31
What do we use tissue plasminogen activator for?
Thromboembolic therapy for canine pulmonary thromboembolism and feline saddle thrombis
32
What are the adverse effects of tissue plasminogen activator?
- reperfusion injury
- bleeding tendencies
33
What are the key characteristics of erythropoietin?
- erythropoietin is made by the kidney in response to hypoxia
- used commonly in anemias when there is chronic renal failure
- iron supplementation advised with usage
- increases hematocrit and hemoglobin in 2-4 weeks
34
What are the adverse effects of erythropoietin?
- hypertension
- seizure
- therapeutic failure from antibody formation (most common)
