Aspirin Dosing for Secondary Prevention
For long-term secondary prevention after ischemic stroke, TIA, or cardiovascular disease, use aspirin 75–100 mg daily (typically 81 mg in the United States). 1
Recommended Maintenance Dose
Aspirin 75–100 mg once daily is the evidence-based dose for secondary prevention in patients with non-cardioembolic ischemic stroke, TIA, myocardial infarction, or established coronary artery disease 1
The 81 mg tablet is the most common low-dose formulation in the United States and provides equivalent efficacy to higher doses while minimizing bleeding complications 1
Doses above 100 mg (such as 325 mg) increase gastrointestinal bleeding risk without providing additional cardiovascular protection 1
Loading Dose in Acute Settings
For acute ischemic stroke or TIA, administer a single loading dose of 160–325 mg aspirin after intracranial hemorrhage has been excluded on neuroimaging 1, 2
If the patient received intravenous alteplase, delay aspirin until at least 24 hours post-thrombolysis to reduce hemorrhagic risk 1, 2
After the loading dose, transition to maintenance therapy of 75–100 mg daily starting on day 2 1, 2
Special Circumstances: Dual Antiplatelet Therapy
For minor stroke (NIHSS ≤3) or high-risk TIA (ABCD2 ≥4) presenting within 24 hours, use dual antiplatelet therapy: loading doses of aspirin 160–325 mg plus clopidogrel 300–600 mg, followed by aspirin 75–100 mg daily plus clopidogrel 75 mg daily for exactly 21 days 1, 2
After 21 days of dual therapy, switch to single antiplatelet therapy (aspirin 75–100 mg daily OR clopidogrel 75 mg daily) indefinitely 1, 2
Do not extend dual antiplatelet therapy beyond 21–30 days because bleeding risk outweighs benefit (hazard ratio for major hemorrhage 2.22–2.32) 1, 2
Alternative Antiplatelet Agents
Clopidogrel 75 mg daily is an equally effective alternative for patients with aspirin allergy, intolerance, or diabetes 1, 3
Aspirin 25 mg plus extended-release dipyridamole 200 mg twice daily is another acceptable alternative regimen 1, 2
Diabetes-Specific Recommendations
For diabetic patients with established cardiovascular disease, use aspirin 75–162 mg daily for secondary prevention 1
The dose range of 75–162 mg is acceptable, but 75–100 mg is preferred to minimize bleeding while maintaining efficacy 1
Common Pitfalls to Avoid
Never use aspirin doses below 75 mg daily because efficacy data are limited 1, 3
Never routinely prescribe 325 mg daily for chronic maintenance because this increases bleeding without improving outcomes 1
Never continue dual antiplatelet therapy indefinitely in stable patients without a specific cardiac indication (e.g., recent stent placement) 1, 2
Never substitute aspirin for thrombolysis or mechanical thrombectomy in eligible acute stroke patients 1, 2
Evidence Quality
The 75–100 mg daily maintenance dose recommendation is supported by Class I, Level A evidence from multiple large randomized trials and international guidelines 1, 3
The ADAPTABLE trial (38% diabetic patients) showed no difference in cardiovascular events or bleeding between 81 mg and 325 mg daily, supporting use of the lower dose 1