Mechanism of Action
Aspirin irreversibly inhibits cyclooxygenase, preventing thromboxane A2 production and platelet aggregation. In acute coronary syndrome, this limits clot growth in a coronary artery. Early administration reduces mortality.
Dose and Route
The typical dose is 324 mg given as four 81 mg chewable tablets. Chewing speeds absorption compared with swallowing. Enteric-coated tablets should not be used for the initial dose because of delayed absorption.
Contraindications
Avoid aspirin in patients with a true aspirin allergy, active gastrointestinal bleeding, or signs of aortic dissection. Asthma with known aspirin sensitivity is also a concern. Document whether the patient already took aspirin that day.