Anticoagulants and anti platelet drugs

Question 1

Describe the role of platelets and coagulation pathways in normal blood clotting

Answer 1

1. Damaged endothelium reveals underlying collagen & other proteins that are recognised as foreign
2. Platelets aggregate and adhere to the surface to form a temporary seal
3. Stimulated by platelets and intrinsic clotting factors Blood clotting factors form strong, durable thrombin‐fibrin clot

Question 2

Describe the role of platelets and coagulation pathways in pathological
blood clotting

Answer 2

1. Damaged endothelium reveals underlying collagen & other proteins that are recognised as foreign
2. platelets and blood clotting factors aggregate and seal the damage
3. the mass occludes the blood vessel (‘thrombosed’) creating a clot the prevents BF
   Causing:
   Venous thrombosis
   Myocardial infarction (heart attack)
   Cerebral artery occlusion (stroke)
   Peripheral artery thrombosis

Question 3

Describe the roles of thromboxane A2 and ADP in platelet function

Answer 3

Signal aggregation of platelets to site of damage
thromboxane A2: (aspirin)
ADP: (clopidogrel)

Question 4

Describe the mechanism of action of aspirin

Question 5

Describe the mechanisms of action of warfarin

Answer 5

Vitamin K is a cofactor for post‐
translational carboxylation of glutamic
acid groups on Factors II (prothrombin), VII, IX & X

Warfarin inhibits Vitamin K recycling
from KO (inactive) to KH2 (active)

Trapping Vitamin K in its inactive unoxidised form KO

Question 6

Describe the mechanisms of action of heparin

Answer 6

Heparin binds to Lysine on Antithrombin III (ATIII) causing:
- Conformational change to ATIII.
increasing affinity for activated factors of the intrinsic arm, esp. Xa & thrombin
- this accelerated inactivation prevents thrombin from activating fibrinogen (to fibrin) in a thrombin-fibrin clot

Question 7

Identify the clinical indications for heparin and warfarin

Answer 7

patients with preexisting clots or with serious clinical implications that they will (anti-coagulation disorder)

Question 8

Describe the clinical monitoring of warfarin

Question 9

Describe the adverse effects of heparin and warfarin

Question 10

Identify and describe the mode of action of drugs that block thrombin and Xa.

Question 11

Explain the action of clopidogrel on platelets

Question 12

Explain the mechanism of action of the thrombolytic drug, tPA

Answer 12

• Recombinant human protein
• delivered by IV Administration
  Immediate onset of action by relieving blockage of critical vessels, e.g. coronary artery occlusion (heart attack)
• activates plasminogen to form plasmin (enzyme to break down clot)