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Antiplatelet agents

Last updated: June 10, 2021

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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 antiinflammatory actions. Low-dose aspirin is used in the management of cardiovascular events (e.g., acute MI) 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 usually contraindicated in patients who have thrombocytopenia or active/recent bleeding (e.g., hemorrhagic stroke, major surgery within the past 30 days).

For the mechanisms of platelet activation, platelet adhesion, platelet aggregation, and clot formation, see “Hemostasis.”

Overview of antiplatelet agents

Group

Agents

Indications

Adverse effects

Irreversible cyclooxgenase inhibitors

P2Y12 receptor antagonists

(ADP receptor inhibitors)

Glycoprotein IIb/IIIa inhibitors

Agents [1]

Acetylsalicylic acid (ASA, aspirin)

Mechanism of action [2][3]

ASA covalently attaches an acetyl group to COX.

Effects

Indications

Adverse effects

Contraindications

  • Febrile illness in individuals < 19 years of age
  • Acute gout attack [6]

Complications

Aspirin-exacerbated respiratory disease (AERD) [7][8][9]

Reye syndrome [12][13]

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 correction of the antiplatelet effect of aspirin can only be achieved by administering platelet concentrates.

To memorize the symptoms of Reye syndrome, remember that “It’s never Rainy (Reye) in CHILE”: Coma, Hepatomegaly/Hypoglycemia, history of viral Infection, Liver failure, Encephalopathy.

Agents [17][18]

Mechanism of action

Indications

Adverse effects

Agents

Mechanism of action [20]

Indication [21]

Adverse effects

To remember that ABCiximab targets glycoproteins IIb/IIIa, think ABC rhymes with 123!

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

Eptifibatide and tirofiban are fibrinogen receptor blockers.

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

  1. Acetylsalicylic acid. https://www.drugbank.ca/drugs/DB00945. Updated: February 19, 2017. Accessed: February 20, 2017.
  2. Ferreira SH, Moncada S, Vane JR. Prostaglandins and the mechanism of analgesia produced by aspirin-like drugs. Br J Pharmacol. 1997; 120 (S1): p.401–412. doi: 10.1111/j.1476-5381.1997.tb06823.x . | Open in Read by QxMD
  3. Cashman JN. The Mechanisms of Action of NSAIDs in Analgesia. Drugs. 2012; 52 (Suppl 5): p.13-23. doi: 10.2165/00003495-199600525-00004 . | Open in Read by QxMD
  4. Powers WJ, Rabinstein AA, Ackerson T, et al. 2018 Guidelines for the Early Management of Patients With Acute Ischemic Stroke: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association. Stroke. 2018; 49 (3). doi: 10.1161/str.0000000000000158 . | Open in Read by QxMD
  5. Aspirin Use for the Primary Prevention of Cardiovascular Disease and Colorectal Cancer: U.S. Preventive Services Task Force Recommendation Statement. http://annals.org/aim/article/2513179/aspirin-use-primary-prevention-cardiovascular-disease-colorectal-cancer-u-s. Updated: June 21, 2016. Accessed: February 20, 2017.
  6. Zhang Y, Neogi T, Chen C, Chaisson C, Hunter DJ, Choi H. Low-dose aspirin use and recurrent gout attacks. Ann Rheum Dis. 2013; 73 (2): p.385-390. doi: 10.1136/annrheumdis-2012-202589 . | Open in Read by QxMD
  7. Babu KS, Salvi SS. Aspirin and asthma. Chest. 2000; 118 (5): p.1470-1476.
  8. Aspirin-Exacerbated Respiratory Disease (AERD). https://www.aaaai.org/conditions-and-treatments/library/asthma-library/aspirin-exacerbated-respiratory-disease. Updated: February 20, 2017. Accessed: February 20, 2017.
  9. Lee RU, Stevenson DD. Aspirin-exacerbated respiratory disease: evaluation and management. Allergy Asthma Immunol Res. 2011; 3 (1): p.3-10. doi: 10.4168/aair.2011.3.1.3 . | Open in Read by QxMD
  10. Spies JW, Valera FC, Cordeiro DL, et al. The role of aspirin desensitization in patients with aspirin-exacerbated respiratory disease (AERD). Braz J Otorhinolaryngol. 2016; 82 (3): p.263-268. doi: 10.1016/j.bjorl.2015.04.010 . | Open in Read by QxMD
  11. Williams AN, Woessner KM. The clinical effectiveness of aspirin desensitization in chronic rhinosinusitis. Curr Allergy Asthma Rep. 2008; 8 (3): p.245-252.
  12. Reye Syndrome. http://www.merckmanuals.com/professional/pediatrics/miscellaneous-disorders-in-infants-and-children/reye-syndrome. Updated: May 1, 2014. Accessed: February 20, 2017.
  13. Glasgow JFT, Middleton B. Reye syndrome: insights on causation and prognosis. Archives of Disease in Childhood . 2001; 85 (5): p.351-353. doi: 10.1136/adc.85.5.351 . | Open in Read by QxMD
  14. Schrör K. Aspirin and Reye syndrome: a review of the evidence. Paediatr Drugs. 2007; 9 (3): p.195-204.
  15. Reye Syndrome. https://rarediseases.org/rare-diseases/reye-syndrome/. . Accessed: January 21, 2021.
  16. The Mechanism for Aspirin or Salicylates Induced Reye's Syndrome in Children with Viral Infections. http://www.ebmconsult.com/articles/reye-syndrome-asa-aspirin-mechanism-liver-encephalopathy. Updated: August 1, 2015. Accessed: February 20, 2017.
  17. Aggrastat (tirofiban HCl Injection premixed), Aggrastat (tirofiban HCl Injection).
  18. Lippi G, Montagnana M, Danese E, Favaloro EJ, Franchini M. Glycoprotein IIb/IIIa inhibitors: an update on the mechanism of action and use of functional testing methods to assess antiplatelet efficacy. Biomark Med. 2011; 5 (1): p.63-70. doi: 10.2217/bmm.10.119 . | Open in Read by QxMD
  19. Stangl PA, Lewis S. Review of Currently Available GP IIb/IIIa Inhibitors and Their Role in Peripheral Vascular Interventions. Semin Intervent Radiol. 2010; 27 (4): p.412-421. doi: 10.1055/s-0030-1267856 . | Open in Read by QxMD
  20. Wijeyeratne YD, Heptinstall S. Anti-platelet therapy: ADP receptor antagonists. Br J Clin Pharmacol. 2011; 72 (4): p.647-657. doi: 10.1111/j.1365-2125.2011.03999.x . | Open in Read by QxMD
  21. Damman P, Woudstra P, Kuijt WJ, De winter RJ, James SK. P2Y12 platelet inhibition in clinical practice. J Thromb Thrombolysis. 2012; 33 (2): p.143-153. doi: 10.1007/s11239-011-0667-5 . | Open in Read by QxMD