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Antiplatelets Drugs


Platelet Aggregation
Platelet function is regulated by three categories of substances:


Agents Outside Platelets

Agents Generated Inside Interacting With Platelet Membrane

Agents Generated Inside And Acting Inside The Platelets





Gpiib/iiia Ligand





Thromboxane A2






  1. Thromboxane A2 Inhibitors (Aspirin)
    1. Only NSAID which is irreversible inhibitor (covalent acetylation) of COX enzyme
    2. Prophylaxis of myocardial infarction
    3. Dose 75 – 325 mg. 
  2. Glycoproteins (Gp IIb/IIIa) inhibitors
    The IIb/IIIa complex functions as a receptor mainly for fibrinogen and vitronectin but also for fibronectin and von Willebrand factor. Activation of this receptor complex is the “final common pathway” for platelet aggregation. Persons lacking this receptor have a bleeding disorder called Glanzmann’s thrombasthenia.
    1. Abxciximab        
    2. Tirofiban            
    3. Epatifibatide  
      1. Short acting
      2. Given parenterally
      3. Used in PTCA, unstable angina, Acute coronary syndromes
      4. S/E: Bleeding  
      5. Most potent drugs is abciximab. 
      6. All GPIIb/IIIa inhibits are eliminated by kidney except abciximab.
  1. Phosphodiesterase inhibitors
    1. Dipyridamole: Vasodilator that also inhibits platelet function by inhibiting adenosine uptake and cGMP phosphodiesterase activity.
      Therapeutic use: Primarily in combination with aspirin to prevent cerebrovascular ischemia.
      It may also be used in combination with warfarin for primary prophylaxis of thromboemboli in patients with prosthetic heart valves.
    2. Cilastazole: Newer phosphodiesterase inhibitor, Useful for intermittent claudication
  2. ADP blockers
    Reduce platelet aggregation by inhibiting the ADP pathway of platelets. These drugs    irreversibly block the ADP receptor on platelets.




Approved for prevention of stroke in patients with a history of a transient ischemic attack (TIA) or thrombotic stroke,

In combination with aspirin for prevention of coronary stent thrombosis.


Clopidogrel is approved for patients with unstable angina or non-ST-elevation acute myocardial infarction (NSTEMI) in combination with aspirin

Patients with ST-elevation myocardial infarction (STEMI)

Recent myocardial infarction, stroke, or established peripheral arterial disease.

Prasugrel, similar to clopidogrel, is approved for patients with acute coronary syndromes.


Adverse effects of ticlopidine include nausea, dyspepsia, hemorrhage and, most seriously, leukopenia. The leukopenia is detected by regular monitoring of the white blood cell count during the first 3 months of treatment.

Development of thrombotic thrombocytopenic purpura


Clopidogrel has fewer adverse effects than ticlopidine and is rarely associated with neutropenia. Thrombotic thrombocytopenic purpura has been reported. Because of its superior side effect profile and dosing requirements, clopidogrel is frequently preferred over ticlopidine.

Clopidogrel is a prodrug that requires activation via the cytochrome P450 enzyme isoform CYP2C19

Prasugrel is contraindicated in patients with history of TIA or stroke because of increased bleeding risk.


Because of the significant side effect profile, the use of ticlopidine for stroke prevention should be restricted to those who are intolerant of or have failed aspirin therapy.




  1. Platelet maturation inhibitor
    i. Anagrelide
  2. New Drugs
    1. Prasugel              
    2. Ticagrelor            
    3. Cangrelor
      1. ADP receptor (P2Y12) inhibitors
      2. Better anti-platelet activity than clopidogrel
      3. More chances of bleeding so monitoring is required in CRF patient because all these drugs are eliminated by kidney.
  3. Thromboxane A2 (TxAr) receptor inhibitor (PAR-1 inhibitors) atopaxar, varopaxar



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