2012 Drugs that promote or inhibit coagulation

Example QuestionDrugs that interfere with platelet function
ASA, ABCIXIMAB, CLOPIDOGREL, DIPYRIDAMOLE, EPTIFIBATIDE,
PRASUGREL, TICLOPIDINE, TIROFIBAN

Drugs that inhibit platelet adhesion and/or aggregation are used for prophylactic and/or long term anticlotting treatment. As with thrombolytic and anticoagulant drugs, their major side effect is BLEEDING. Antiplatelet drugs are often used in combination with other agents:  ABCIXIMAB and EPTIFIBATIDE with HEPARIN or ASA, DIPYRIDAMOLE with either WARFARIN or ASA.
Critical fact icon

Mechanism of action of antiplatelet drugs

Mechanism of action

Inhibit platelet adhesion and aggregation by:

  1. Decreasing production of thromboxane A2 by inhibiting cyclooxygenase
    e.g. ASA

  2. Antagonism of glycoprotein IIb/IIIa receptor
    e.g. ABCIXIMAB, EPTIFIBATIDE, TIROFIBAN

  3. Inhibiting the activation of GPIIb/IIIa by ADP
    e.g. CLOPIDOGREL
    , PRASUGREL, TICLOPIDINE

  4. Inhibiting cyclic nucleotide phosphodiesterase
    e.g. DIPYRIDAMOLE
Alternative view of platelet aggregation
ANOTHER WAY OF LOOKING AT IT:
  • collagen and thrombin initiate platelet aggregation via 3 primary mechanisms:
    1. thromboxane A2
      • cyclooxygenase inhibitors (esp. ASA) inhibit TXA2 synthesis
    2. ADP
      • ADP receptor antagonists (e.g. ticloplidine) can block GPIIb/IIIa activation
    3. thrombin
  • the final common pathway in platelet activation/aggregation is conformational activation of GPIIb/IIIa
      • specific antagonists of this receptor block platelet aggregation IRRESPECTIVE OF THE ACTIVATION MECHANISM
Email: Dr. Janet Fitzakerley | ©2012 University of Minnesota Medical School Duluth | Last modified: 4-jun-13 11:12 AM