What is the recommended dose of aspirin (acetylsalicylic acid) for suspected cardiac-related chest pain?

Aspirin Dosing for Chest Pain

For suspected cardiac chest pain, administer 160-325 mg of non-enteric aspirin, chewed immediately, unless there is a known aspirin allergy or active/recent gastrointestinal bleeding. 1

Recommended Dose and Administration

EMS providers should administer 160-325 mg of non-enteric aspirin (chewed) to all patients with suspected acute coronary syndrome. 1 The American Heart Association guidelines provide Class I, Level of Evidence B-C recommendation for this dose range. 1

• The aspirin tablet must be chewed rather than swallowed whole to achieve rapid buccal absorption and faster antiplatelet effect. 1
• Non-enteric formulations are specifically recommended because enteric-coated aspirin delays absorption during the critical early phase. 1
• For acute STEMI, a loading dose of 162-325 mg achieves the rapid clinical antithrombotic effect needed. 2

Pre-Hospital Administration

It is reasonable for 9-1-1 dispatchers to instruct patients to chew aspirin (160-325 mg) while awaiting EMS arrival, provided there is no aspirin allergy or signs of active/recent gastrointestinal bleeding. 1 This represents a Class IIa recommendation from the American Heart Association. 1

• Early aspirin administration—ideally within 4 hours of symptom onset—has been shown to delay approximately 13,000 deaths annually in the United States. 3
• The mortality benefit of early aspirin administration significantly outweighs bleeding risk by a factor of 10:1. 3

Absolute Contraindications

Do not administer aspirin if:

• Known aspirin allergy or hypersensitivity exists. 1
• Active gastrointestinal bleeding is present or recent bleeding has occurred. 1, 4
• Recent subdural hematoma or other intracranial bleeding—explicit neurosurgical clearance is required before aspirin administration in these cases. 4

The American Heart Association explicitly states aspirin should only be given when there is "no allergy or contraindication to aspirin, such as recent bleeding." 4

Alternative Antiplatelet Therapy

For patients unable to take aspirin due to hypersensitivity or major gastrointestinal intolerance, administer clopidogrel 300 mg orally. 1, 5 This represents a Class IIa, Level of Evidence B recommendation from the American College of Cardiology. 1

Special Populations

Dialysis patients: The same 160-325 mg aspirin dose applies regardless of dialysis status, as the American Heart Association guidelines make no distinction for renal failure patients with suspected ACS. 5

Elderly patients: The standard 160-325 mg dose remains appropriate, though clopidogrel dosing for STEMI patients receiving fibrinolysis is limited to those ≤75 years of age. 1

Common Pitfalls to Avoid

• Never delay aspirin administration to obtain physician consultation if the patient meets criteria and has no contraindications—time to treatment directly correlates with mortality reduction. 1, 3
• Do not use enteric-coated formulations for acute presentation, as they significantly delay absorption during the critical early phase. 1
• Do not give aspirin to patients with recent bleeding even if cardiac symptoms are severe—mortality from rebleeding can equal or exceed cardiac mortality in this population. 4
• Ensure the patient chews the aspirin—swallowing whole tablets delays the antiplatelet effect when rapid action is most critical. 1