Definition
Anti-platelet agents inhibit platelet aggregation and activation, thereby preventing thrombus formation.
Classes of Anti-Platelet Agents
1) Aspirin (Acetylsalicylic Acid):
Mechanism: Irreversibly inhibits cyclooxygenase-1 (COX-1), reducing thromboxane A2 synthesis, which decreases platelet aggregation.
Use: Prevention of AMI, stroke, and in peripheral arterial disease.
Side Effects: Gastrointestinal ulcers, bleeding, Reye’s syndrome in children.
2) P2Y12 Inhibitors (e.g., Clopidogrel, Prasugrel, Ticagrelor):
Mechanism: Block the ADP receptor on platelets, inhibiting platelet activation and aggregation.
Use: Acute coronary syndrome, post-percutaneous coronary intervention (PCI), stroke prevention.
Side Effects: Bleeding, thrombotic thrombocytopenic purpura (rare with some agents).
3) Glycoprotein IIb/IIIa Inhibitors (e.g., Abciximab, Eptifibatide, Tirofiban):
Mechanism: Block the final common pathway for platelet aggregation by inhibiting glycoprotein IIb/IIIa receptors.
Use: During PCI, acute coronary syndromes.
Side Effects: Bleeding, thrombocytopenia.
4) Phosphodiesterase Inhibitors (e.g., Dipyridamole):
Mechanism: Increase cyclic AMP levels in platelets, inhibiting aggregation.
Use: Often combined with aspirin for stroke prevention.
Side Effects: Headache, dizziness, gastrointestinal upset.
5) Thienopyridines (e.g., Ticlopidine):
Mechanism: Similar to clopidogrel; inhibit ADP-mediated platelet activation.
Use: Similar to other P2Y12 inhibitors.
Side Effects: Neutropenia, thrombotic thrombocytopenic purpura.
Clinical Indications:
Primary and Secondary Prevention of Atherosclerotic Events: Including AMI, stroke, and peripheral arterial disease.
Acute Coronary Syndromes (ACS): Used in combination with other therapies during and after interventions like PCI.
Atrial Fibrillation: As an alternative to anticoagulation in certain cases.
Clinical Considerations:
Combination Therapy: Often used alongside anticoagulants (e.g., dual antiplatelet therapy with aspirin and clopidogrel).
Bleeding Risk: Increased risk of gastrointestinal bleeding, intracranial hemorrhage.
Resistance and Non-responsiveness: Some patients exhibit resistance to aspirin or clopidogrel, necessitating alternative therapies.
Side Effects: Gastrointestinal irritation (aspirin), bleeding complications, thrombocytopenia (GP IIb/IIIa inhibitors).