Antiplatelet Agents

Antiplatelet Agents

David Ray Velez, MD

Table of Contents

Definitions
Aspirin (ASA)
Thienopyridines
Holding and Reversal

Definitions

Definitions

  • Antithrombotic Agents (“Blood Thinners”): Prevents Thrombosis/Blood Clots
    • Includes Both Antiplatelet and Anticoagulant Drugs
  • Antiplatelet Medication: Prevents Platelet Aggregation
    • Not Technically “Anticoagulation”
  • Anticoagulant Medication: Inhibits Clotting Factors

Aspirin (ASA)

Mechanism of Action

  • Irreversibly Inhibits Cyclooxygenase (COX)
  • Causes Permanent Inhibition of Prostaglandin (PGH2) Synthesis
  • Decreases Synthesis of Thromboxane A2 (TXA2) Inhibits Platelet Aggregation

Other Effects

  • Nonsteroidal Anti-Inflammatory Drug (NSAID) and Analgesia
  • Anti-Pyretic

Dose

  • Low-Dose (“Baby Aspirin”): 81 mg
  • High-Dose: 325-650 mg

Complications

  • Bleeding
  • GI-Bleed – From Upregulation of COX-2
  • Aspirin-Induced Asthma

Thienopyridines

Agents

  • Clopidogrel (Plavix)
  • Ticagrelor (Brilinta)
  • Prasugrel (Effient)

Mechanism of Action

  • Inhibits P2Y12 ADP Receptors on Platelets
  • Inhibits IIb/IIIa Complex (Functionally Similar to Glanzmann Thrombocytopenia)
  • Reversibility:
    • Irreversible Inhibition: Clopidogrel (Plavix) and Prasugrel (Effient)
    • Reversible Inhibition: Ticagrelor (Brilinta)

Holding and Reversal

Holding Prior to Surgery

  • Low Bleeding Risk Procedure: Hold Clopidogrel for 5 Days but Continue ASA
  • High Bleeding Risk Procedure: Hold ASA and Clopidogrel for 5 Days

Bleed Treatment While on Antiplatelet Agents

  • Effects Last 5-7 Days Due to Irreversible Binding (Platelet Half-Life is 1 Week)
    • *Ticagrelor is Shorter Due to Reversible Binding
  • Treatment Options:
    • Platelet Transfusion
    • Desmopressin (DDAVP)
    • *Controversial with Limited Data to Support
  • Reversal Agents are Being Produced and Researched