Anticoagulants and Fibrinolytics Flashcards
1
Q
Platelets
A
- Immediate responders
- Adhere to site of tissue damage
- Activated platelets initiate the coagulation cascade
2
Q
Coagulation Cascade
A
- Needs to be inactive under normal conditions: factors circulate in inactive form (Factor X => Xa)
- Needs to activate quickly when bleeding occurs: one pathway is short and fast (extrinsic)
- Cascade needs to amplify when bleeding occurs (fast pathway leads to “feed-forward” response that is longer and sustained (intrinsic)
Pathways converge at factor X
3
Q
Extrinsic Pathway
A
- Forms fibrin quickly
- One step to activate Factor X and three to make a clot
- Tissue factor is a potent initiator of clotting cascade which binds to factor VII and activates factor X
4
Q
Intrinsic Pathway
A
- Long and amplified response
- Four steps to activate Factor X and seven steps to make a clot
- Activated by thrombin and activated platelets
5
Q
Vitamin K
A
-Required for the activation of factor VII, X, and thrombin (II)
6
Q
PT
A
- Prothrombin Time
- Monitoring Test
- Used to assess the activity of pathway 1
- Detects/diagnoses bleeding or clotting disorders
7
Q
Anti-Thrombin
A
- Inactivates two factors in intrinsic pathway
- Inactivates thrombin IIa and Factor Xa
8
Q
aPTT
A
- Activated partial thromboplastin time
- Montiroing test to assess the activity of pathway 2
9
Q
Process for Monitoring Tests
A
- Draw venous blood sample
- Blue cap = citrate bind calcium and prevent clotting
- Add “Kaolin” (activates factor XII or add “thromboplastin” (tissue factor + phospholipids) depending on test
- Add calcium and measure the time it takes to clot
10
Q
Anticoagulation Drug Classes
A
- Indirect Factor Xa and Thrombin Inhibitions (UF Heparin)
- Factor Xa Inhibitors
- Direct Thrombin Inhibitors (Argatroban, bivalirudin)
- Vitamin K Inhibitors (Warfarin)
11
Q
Unfractionated Heparin (UFH)
A
- Indirect Factor Xa and Thormbin Inhibitor
- Activates anti-thrombin
- Subsequently inactivates two factors in intrinsic pathway: thrombin IIa and Factor Xa
12
Q
LMWH
A
- Indirect Factor Xa and Thormbin Inhibitor
- Low molecular weight heparin
- Activates anti-thrombin
- Inactivates Factor Xa and inactivating thrombin
13
Q
Fondaparinux
A
- Indirect Factor Xa Inhibitor
- Activates anti-thrombin
- But only inactivates Factor Xa
14
Q
Direct Factor Xa Inhibitors
A
- Oral anti-coagulants with predictable anti-coagulant effects, eliminating the need for monitoring
- Site of action: blood stream
- Andexanet - antidote for life-threatening bleeding, inactive/truncated form of Factor Xa that competes for drug binding
15
Q
Direct Factor Xa Inhibitor Examples
A
- Rivaroxaban (antidote approved)
- Apixaban (antidote approved)
- Edoxaban (off-label)
- Betrixaban (off-label)
