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Antiplatelet agents

Last updated: January 5, 2020

Summary

Antiplatelet agents are drugs that inhibit enzymes or receptors required for platelet activation, platelet aggregation, and/or thrombus formation. The most commonly used antiplatelet agent is acetylsalicylic acid (aspirin), which is an irreversible cyclooxygenase inhibitor with dose-dependent antiplatelet, antipyretic, analgesic, and anti-inflammatory actions. Low-dose aspirin is used in the management of cardiovascular events (e.g., acute MI, angina) and for primary/secondary prophylaxis of cardiovascular disease. Adverse effects of aspirin include peptic ulcers, hemorrhage, salicylate toxicity, aspirin-exacerbated respiratory disease, and Reye syndrome. P2Y12 receptor antagonists (clopidogrel, prasugrel, ticagrelor) are mainly used in conjunction with aspirin (dual antiplatelet therapy) in the management of acute coronary syndrome and to prevent stent thrombosis in patients after percutaneous coronary intervention (PCI). Although allergic reactions are more common, P2Y12 receptor antagonists cause fewer hemorrhagic/gastrointestinal complications compared to aspirin. Glycoprotein IIb/IIIa inhibitors (abciximab, eptifibatide, and tirofiban) are parenterally administered, rapid-acting antiplatelet agents that are only used in high-risk patients in which PCI is planned. Gp IIb/IIIa inhibitors can cause a sudden drop in platelet counts (acute profound thrombocytopenia), necessitating platelet count monitoring. All antiplatelet agents increase the risk of hemorrhage and are contraindicated in patients who have thrombocytopenia or an active/recent hemorrhagic event (e.g., hemorrhagic stroke, major surgery within the past 30 days).



Overview

For the mechanisms of platelet activation, platelet adhesion, platelet aggregation, and clot formation, see “Pathophysiology” in the article hemostasis and bleeding disorders.

Group

Agents

Indications

Side effects

Irreversible cyclooxgenase inhibitors

P2Y12 receptor antagonists

(ADP receptor inhibitors)

Glycoprotein IIb/IIIa inhibitors

References:[1][2]

Irreversible cyclooxygenase inhibitors

Agents
Effects
Indications
Side effects

The lifespan of a platelet is 7–10 days. If aspirin is held prior to surgery, it should be discontinued one week in advance.

Emergency inhibition of the antiplatelet effect of aspirin can only be achieved by administering platelet concentrates!

References:[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]

P2Y12 receptor antagonists

Agents
  • Clopidogrel
  • Prasugrel
  • Ticagrelor
  • Ticlopidine
Effects
Side effects
Indications

References:[26][27][28][29][30][31][32]

Glycoprotein IIb/IIIa inhibitors

Agents
  • Abciximab
  • Eptifibatide
  • Tirofiban
Effects
Side effects
Indications

Abciximab and tirofiban are contraindicated in patients with thrombocytes < 100,000/mm3!

References:[33][34][35][36][37][38][39]

Contraindications

References:[35][40][41]

We list the most important contraindications. The selection is not exhaustive.

References

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