Antiplatelet Drugs (Pharmacology)

Mechanism of Platelet Aggregation and Inhibition
Fig.1: Mechanism of Platelet Aggregation and Inhibition
Mechanism of Platelet - Antiplatelet Drugs

Antiplatelet Drugs (Classification):

  • TXA2 synthesis inhibitor:

Low dose aspirin

  • Phosphodiesterase inhibitor:

Dipyridamole, cilostazol

  • Thienopyridine derivatives (ADP antagonists):

Ticlodipine, clopidogrel

  • Gp-IIb/IIIa receptor antagonists

Abciximab, eptifibatide, tirofiban

  • Others

PGI2, Bactroban, dazoxiben, clofibrate


MoA of Aspirin - Antiplatelet Drugs
Fig. MoA of Aspirin

Fig.3: MoA of Aspirin


  • Coronary vasodilator and relatively weak antiplatelet drug.

Mechanism of Action:

  • Potentiates effect of endogenous prostacyclin.
  • In high concentration inhibits Phosphodiesterase, so increases cAMP.
  1. Dose = 100 mg BD/TDS.
  2. Used with aspirin to prevent ischemic stroke in patients of TIA.
 Dipyridamole mechanism of action - Antiplatelet Drugs
Fig.4: Dipyridamole mechanism of action

Ticlodipine and Clopidogrel:

  • ADP antagonists, inhibit the binding of ADP to its receptors irreversibly.
  • Also, Inhibit fibrinogen induced platelet aggregation without modifying GPIIb/IIIa.
  • Synergistic action with aspirin.
  • Both are prodrugs have a long duration of antiplatelet effect.
  • Clopidogrel a congener of felodipine is safer and better tolerated.
Antiplatelet Drugs
Fig.5: MoA of Clopidogrel and Ticlopidine


  • Adverse effects:
  1. Diarrrhoea, vomiting, abdominal pain
  2. Headache, tinnitus, skin rash
  3. Bleeding, neutropenia, thrombocytopenia
  • Dose = 250 mg BD.


  • Adverse effects:
  1. Bleeding most IMP
  2. Less bone marrow toxicity
  3. Diarrhoea, epigastric pain, rashes
  • Dose = 75 mg OD.


  • Fab fragment of Chimeric monoclonal antibody against GP-IIb/IIIa.
  • Used to prevent platelet aggregation in patients having PCI, administered along with aspirin & heparin or LMW heparin.
  • The most common A/E is bleeding.
  • May cause thrombocytopenia, hypotension, bradycardia.
  • Non-antigenic.
Antiplatelet Drugs

Uses of Antiplatelet Drugs:

  • Prosthetic heart valves & A-V shunts
  • Peripheral vascular disease
  • Coronary artery diseases
  1. Myocardial infarction
  2. Unstable angina
  3. Primary & secondary prevention of MI
  • Coronary angioplasty, stents, bypass implants
  • Cerebrovascular transient ischemic attacks
  • Venous thromboembolism.
Make sure you also check our other amazing Article on : Fibrinolytics
Sharing Is Caring:

Leave a Comment