Anticoagulant

Question 1

explain the difference between the intrinsic and extrinsic clotting pathways

Answer 1

The intrinsic pathway responds to spontaneous, internal damage of the vascular endothelium, whereas the extrinsic pathway becomes activated secondary to external trauma.

• Intrinsic: triggered when collagen is exposed on the wall of the blood vessel; blood in contact w/ negatively-charged collagen of injured vessel (factors XII, XI, IX, VIII)
• Extrinsic: relies on factors outside bloodstream for activation (factor VII)

Question 2

list the steps in the common clotting pathway

Answer 2

• Factors: 10, 5, 2
• Prothrombinase complex formed (Factor X, V, Ca2+)
• Complex converts converts inactive prothrombin (Factor II) to active thrombin
• Thrombin converts fibrinogen to fibrin
• Fibrin are cross-linked to form and stabilize clot

Question 3

understand the role of Ca2+ in coagulation, and the rationale for use of Ca2+ chelators in collection of clinical blood samples

Answer 3

• calcium plays a role in activating platelets & is a cofactor for reactions that lead to the formation of fibrin
• calcium chelators bind to calcium ions, reducing the number of free calcium, which inhibits the coagulation process so the blood remains a liquid

Question 4

ANSWER

define the conditions for each of the following laboratory tests for coagulation and give normal time ranges: prothrombin time, bleeding time, activated partial thromboplastin time

Answer 4

• prothrombin time (PT)
• bleeding time (BT)
• activated partial thromboplastin time (aPTT)

Question 5

define the INR and understand it’s clinical relevance

Answer 5

• International Normalized Ratio
• Shows how long it takes for blood to clot
• Clinical relevance: maintain a balance between preventing clot formation and avoiding excessive bleeding
• Normal: 0.8-1.2
• Therapeutic: ~2-3

Question 6

ANSWER from access pharmacy

explain the MOA for the following anticoagulant drugs: indirect thrombin inhibitors (heparin, LMWH), direct thrombin inhibitors (hirudin, bivalirudin, argatroban, dabigatran), Xa inhibitors (fondaparinux, rivaroxaban, apixaban, edoxaban, betrixaban), and warfarin/coumadin

Question 7

access pharmacy info ANSWER

know the routes of admin and potential side effects of each of the anticoagulant drugs

Answer 7

• Warfarin
• Indirect factor IIa/Xa inhibitors (UFH, enoxaparin, daltaparin, fondaparinux)
• Direct factor Xa inhibitors/DOAC (rivaroxaban, apixaban, edoxaban)
• Direct thrombin inhibitors (bivalirudin, argatroban, dabigatran)