Anti-Platelet Drugs

Definition

• Anti-platelet agents inhibit platelet aggregation and activation, thereby preventing thrombus formation.

Classes of Anti-Platelet Agents

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).