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Antiplatelet Drugs: Mechanism, Therapeutic Uses, and Adverse Effects

Antiplatelet drugs are used to prevent blood clots by inhibiting platelet aggregation. These drugs are primarily used in the prevention and treatment of cardiovascular events such as stroke, myocardial infarction, and peripheral artery disease.

Classification of Antiplatelet Drugs

1. Aspirin (Acetylsalicylic Acid)

  • Mechanism of Action: Inhibits cyclooxygenase-1 (COX-1), reducing thromboxane A2 and preventing platelet aggregation.
  • Therapeutic Uses:
    • Prevention of cardiovascular events (e.g., myocardial infarction, stroke).
    • Prevention of thrombosis after CABG or PCI.
  • Adverse Effects:
    • Gastrointestinal irritation (ulcers, bleeding).
    • Increased bleeding risk.
    • Reye's syndrome in children with viral infections.

2. P2Y12 Inhibitors

These drugs block the P2Y12 receptor on platelets, preventing ADP-mediated platelet activation and aggregation.

Clopidogrel

  • Mechanism of Action: Prodrug, inhibits P2Y12 ADP receptor irreversibly.
  • Therapeutic Uses:
    • Acute coronary syndrome (ACS).
    • Stroke prevention in atrial fibrillation.
  • Adverse Effects:
    • Increased bleeding risk.
    • Gastrointestinal upset.
    • Rarely, thrombotic thrombocytopenic purpura (TTP).

Prasugrel

  • Mechanism of Action: Similar to clopidogrel, irreversibly inhibits the P2Y12 receptor.
  • Therapeutic Uses:
    • ACS, especially in PCI patients.
  • Adverse Effects:
    • Increased bleeding risk.
    • Not recommended in patients with a history of stroke or TIA.

Ticagrelor

  • Mechanism of Action: Reversible antagonist of the P2Y12 receptor.
  • Therapeutic Uses:
    • ACS and PCI.
  • Adverse Effects:
    • Dyspnea (breathlessness).
    • Increased bleeding risk.

3. Glycoprotein IIb/IIIa Inhibitors

These drugs inhibit the glycoprotein IIb/IIIa receptor on platelets, preventing fibrinogen binding and platelet aggregation.

  • Abciximab, Eptifibatide, Tirofiban
  • Mechanism of Action: Intravenous inhibitors of glycoprotein IIb/IIIa receptor.
  • Therapeutic Uses: Used in acute coronary syndrome and PCI.
  • Adverse Effects:
    • Major bleeding.
    • Thrombocytopenia.
    • Hypotension.

4. Cilostazol

  • Mechanism of Action: Phosphodiesterase III inhibitor, increases cyclic AMP, preventing platelet aggregation.
  • Therapeutic Uses:
    • Intermittent claudication (peripheral artery disease).
  • Adverse Effects:
    • Headache.
    • Diarrhea.
    • Tachycardia.

5. Dipyridamole

  • Mechanism of Action: Inhibits phosphodiesterase and adenosine uptake, increasing cyclic AMP.
  • Therapeutic Uses:
    • Stroke prevention, often in combination with aspirin.
  • Adverse Effects:
    • Headache.
    • Dizziness.
    • Gastrointestinal disturbances.