Antiplatelet Drugs

Question 1

Platelet Aggregation Assay

Answer 1

Prepare PRP
Activate platelets (add ADP, TRAP, epi, 5-HT, collagen, ristocetin, AA)
Measure light transmittance (greater transmittance in with aggregation)

Question 2

Antiplatelet Agents

Answer 2

Decrease platelet adhesion, activation, and aggregation
Effective in the arterial circulation (where heparin and oral anticoagulants have little effect)
ASA
COX inhibitors (Celebrex, Vioxx, Dextra)
NSAIDs (ibuprofen, naproxen)
ADP Receptor inhibitors (Ticlopidine, Clopidogrel, Prasugrel, Ticagrelor, and Cangrelor)
Dipyridamole
Cliostazol
GPIIb/IIIa Inhibitors (abciximab, tirofiban, eptifabatide)

Question 3

Dual Antiplatelet Therapy

Answer 3

ASA/ADP receptor inhibitors
ASA/GPIIbIIIa inhibitor
ASA/Dipyridamol

Question 4

Arachidonic Acid and its Metabolites in inflammation and thrombosis

Answer 4

Cell Membrane Phospholipids converted to AA via PLA2

AA can go down lipoxygenase or cyclooxygenase pathway

Question 5

Lipoxygenase Pathway

Answer 5

AA converted to leukotrienes
Vasconstriction, bronchospasm, increased permeability
Zileuton, Montelkast (singulair) and Zarirlukast are lipoxygenase/leukotriene antagonists and are used in the treatment of asthma

Question 6

Cyclooxygenase Pathway

Answer 6

AA converted to prostaglandins
These produce prostacylins PGI2 (vasodilation, inhibits platelet aggregation) and thromboxane A2 TXA2 (vascoconstriction, promotes platelet aggregation)
ASA inhibits this pathway, particularly TXA2 (tilts the balance towards inhibition of platelet aggregation)

Question 7

Pharmacology of fish oil

Answer 7

Its acids compete with AA
Their products inhibit TXA2 (bc they form TXA3 which is inactive)
Molecular mimicry