- Clinical science
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).
Irreversible cyclooxgenase inhibitors
(ADP receptor inhibitors)
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- Known allergy against an antiplatelet agent
- Active/recent hemorrhage within the past 30 days (e.g., gastric ulcers or intracranial bleeding)
- Major surgery/severe trauma within the past 30 days
- Severe hypertension
- Aortic dissection
- Aspirin: patients < 19 years of age with a febrile illness (risk of )
We list the most important contraindications. The selection is not exhaustive.