Drugs for Coagulation Disorders Flashcards
1
Q
what is hemostasis?
A
- vessel spasms, constricting the vessel and limiting blood flow to the site of injury
- platelets bind with high affinity to the damaged vessel; activated platelets release ADP and thromboxane A2 which stimulate the activation of new platelets, platelet aggregation and vasoconstriction
- thrombin is produced, thrombin will convert fibrinogen into fibrin, fibrin provides the scaffolding that forms a clot
2
Q
when is the extrinsic pathway activated?
A
- triggered when tissue thromboplastin is released from damaged cells (outside the circulation)
- catalyzes for formation of factor Xa
3
Q
when is the intrinsic pathway activated?
A
- triggered when collagen is exposed at the site of vascular injury to blood components (inside the circulation)
- catalyzes formation of factor Xa
4
Q
when is the common pathway activated?
A
- synthesis of factor Xa
5
Q
TPA
A
- cells adjacent to the clot release tissue plasminogen activator
- converts plasminogen into plasmin
6
Q
what is the mechanism of action of plasmin?
A
- plasmin digests fibrin and destroys the clot
7
Q
when is fibrinolysis initiated?
A
- 24 to 48 hours after clot formation
8
Q
what is included with thromboembolic disorders?
A
- formation of non-therapeutic clots
- occlusion of arterial vessels lead to MI and stroke
- embolus; piece of stable thrombi breaks off and lodges in smaller blood vessels
9
Q
what is included in bleeding disorders?
A
- thrombocytopenia (bone marrow suppression)
10
Q
what are the most commonly prescribed coagulation modifiers?
A
- anticoagulants
11
Q
what drug class would be given to inhibit specific clotting factors?
A
- anticoagulants
12
Q
what drug class would be given to inhibit platelet actions?
A
- anticoagulants
- antiplatelets
13
Q
what drug class would be given to dissolve a clot?
A
- thrombolytics
14
Q
what drug class would be given to inhibit the destruction of fibrin?
A
- antifibrinolytics
15
Q
what is the mechanism of action of anticoagulant drugs?
A
- modulate coagulation cascade and thrombin formation
- lengthen clotting times and prevent thrombi from forming in veins and arteries
16
Q
in cases of MI or stroke, how would anticoagulants be administered? give an example
A
- IV or SC for rapid onset of action (ex. heparin)
17
Q
what are the 5 anticoagulant drugs?
A
- heparin
- warfarin
- low molecular weight heparins
- direct thrombin inhibitors
- direct acting factor Xa inhibitors
18
Q
how is heparin administered?
A
- IV or SC
19
Q
where is heparin made?
A
-found in liver and lining of blood vessels
20
Q
what is heparin’s antidote?
A
- protamine sulphate
21
Q
how is warfarin administered?
A
- PO
22
Q
what is warfarin’s antidote?
A
- vitamin K
23
Q
what is a low molecular weight heparin antidote?
A
- protamine sulphate
24
Q
what is the mechanism of action of heparin?
A
- catalyzes the inactivation of thrombin
- enhances the ability of antithrombin III to inactivate thrombin and clotting factors
- thrombin no longer available to convert fibrinogen into fibrin
- inhibition of factor Xa, inhibits intrinsic and extrinsic pathways of the clotting cascade
25
what is heparin prescribed for?
- used for prevention of venous thrombosis, pulmonary embolism, disseminated intravascular coagulation, treatment in MI and stroke
26
what is it important to monitor for with heparin?
- bleeding
27
what is the mechanism of action of low molecular weight heparins?
- same mechanism of action as heparin, but more specific to factor Xa
- produces a more stable response than unfractioned heparin since thrombin remains active
28
what are some benefits of low molecular weight heparin?
- reduced risk for thrombocytopenia
- longer duration of action, reduced dosing frequency
- drug class of choice for the prevention of DVT
29
what is the mechanism of action of warfarin?
- blocks synthesis of clotting factors thrombin, VIIa, IXa and Xa
- precursors require carboxylation to become active
- carboxylation linked to oxidation of vitamin K to vitamin K epoxide
- inhibits vitamin K epoxide reductase
30
what is vitamin K essential for?
- clotting
31
how is vitamin K epoxide recycled to its reduced form?
- vitamin K epoxide is not used in the body
| - vitamin k epoxide reductase recycles it back to vitamin K
32
what do you closely monitor for when patient is on both heparin and warfarin?
- spontaneous bleeding
33
what should patients avoid when taking warfarin?
- avoid vitamin-K rich foods because it reduces the effectiveness of the drug
- strenuous activities that could result in an injury
34
what is the mechanism of action for direct acting thrombin inhibitors?
- prevents conversion of fibrinogen to fibrin, inhibiting clot formation
35
direct acting thrombin inhibitors are used to reduce the risk of what?
- stroke, systemic embolism in clients with A fib, DVT, pulmonary embolism
36
what circumstance are direct acting thrombin inhibitors used as an alternative therapy?
- heparin induced thrombocytopenia
37
when would praxbind (direct acting thrombin inhibitor antagonist) be used?
- life threatening bleeding or uncontrolled bleeding
| - emergency surgeries
38
what is the mechanism of action of the direct acting factor Xa inhibitors?
- inhibits intrinsic and extrinsic pathways of the coagulation cascade
- reduces thrombin formation and development of thrombi; no direct effects on thrombin or platelets
39
direct acting factor Xa inhibitors are used to to prevent/ treat what?
- deep vein thrombosis
| - reduces the risk of pulmonary emboli in patients undergoing knee or hip replacements
40
what caution precautions should be taken with anticoagulant drugs?
-patients with hemorrhagic disorders, recent trauma, spinal puncture, GI ulcers, recent surgery
41
what is warfarin contraindicated with?
- pregnancy and during lactation
42
what are some common adverse effects with anticoagulant drugs?
- bleeding
- international normalized ratio (measures prothrombin levels)
- prothrombin time (time required for clotting to occur)
43
what are the three drug classes for anti platelet drugs?
- irreversible cyclooxygenase inhibitors
- adenosine diphosphate receptor antagonists
- glycoprotein IIb and IIIa receptor antagonists
44
what is the mechanism of action of irreversible cyclooxygenase inhibitors (ASPARIN)?
- irreversibly blocks the activity of COX 1 and COX 2 enzymes
- inhibits the synthesis of prostaglandins and thromboxane A2
45
what are the benefits of irreversible cyclooxygenase inhibitors?
- patients with established cardiovascular disease
46
what is the mechanism of action for an ADP receptor antagonist?
- irreversibly change the molecular conformation of ADP receptors present on platelets
- platelets no longer receive chemical signal to aggregate, thereby inhibiting thrombus formation
47
- what is the mechanism of action of glycoprotein IIb and IIIa receptor antagonists?
- glycoprotein IIb and IIIa enzymes are involved in platelet aggregation
- antagonist activity at receptors prevents platelet aggregation and thrombus formation
48
how are glycoproteins administered?
- IV route
49
what are caution precautions with antiplatelet drugs?
- presence of any known bleeding disorders
- recent surgery
- closed head injuries
50
what is the mechanism of action for thrombolytics drugs?
- promote fibrinolysis by converting plasminogen to plasmin
| - dissolve insoluble fibrin with intravascular emboli and thrombi
51
when are thrombolytics drugs administered?
- to dissolve pre-existing clots
| - MI, pulmonary embolism, ischemic CVS, DVT
52
what is the mechanism of action of streptokinase?
- enzyme made by bacteria
- can cause an immunological reaction
- may result in systemic fibrinolysis
53
what is the mechanism of action of the tissue plasminogen activators?
- identical to human TPA
- converts plasminogen to plasmin, which dissolves clots
- specific to fibrin bound plasminogen
54
what is contraindicated with thrombolytic drugs?
- recent trauma or bleeding disorders
55
what do you monitor for with thrombolytic drugs?
- cerebral hemorrhage
56
what is the antidote for thrombolytic drugs?
- aminocaproic acid
57
what is the mechanism of action for an antifibrinolytic drug and when is it used?
- used to facilitate blood clotting and shorten bleeding time
- post surgery to reduce bleeding at surgical sites
58
what does aminocaproic acid do?
- an enzyme inhibitor that inactivates plasmin
