What is the recommended dose of aspirin (acetylsalicylic acid) for stroke prevention?

Recommended Aspirin Dose for Stroke Prevention

For stroke prevention, aspirin 75-100 mg daily is the recommended dose, balancing efficacy with safety across both primary and secondary prevention settings. 1, 2

Secondary Prevention (After Stroke or TIA)

Patients with prior ischemic stroke or TIA should receive aspirin 75-100 mg daily for long-term secondary prevention. 1, 3 This dose range provides equivalent stroke risk reduction compared to higher doses (up to 1500 mg daily) while minimizing bleeding complications. 1

Acute Phase Dosing

• Administer aspirin 160-325 mg as a single loading dose immediately after ruling out intracranial hemorrhage on neuroimaging. 3
• Transition to maintenance dose of 75-100 mg daily (typically 81 mg in the US) after the acute phase. 2, 3

Special Circumstances in Secondary Prevention

• For minor ischemic stroke or high-risk TIA, consider dual antiplatelet therapy with aspirin 81 mg daily plus clopidogrel 75 mg daily for 21 days, then transition to single antiplatelet therapy. 3
• For patients with mechanical prosthetic heart valves who experience stroke despite adequate anticoagulation, add aspirin 75-100 mg daily to warfarin (INR 2.5-3.5) if bleeding risk is acceptable. 1

Primary Prevention

For primary stroke prevention in high-risk individuals, aspirin 75-100 mg daily is recommended when cardiovascular risk is sufficiently elevated to outweigh bleeding risks. 1, 2, 4

Specific High-Risk Populations Warranting Primary Prevention

• Women ≥65 years with controlled blood pressure (<150/90 mmHg) and 10-year cardiovascular risk >6-10%. 2, 3
• Patients with high-risk antiphospholipid profile (triple-positive or double-positive antiphospholipid testing, or isolated lupus anticoagulant). 1
• Patients with systemic lupus erythematosus and high-risk antiphospholipid profile. 1
• Diabetic patients ≥50 years with hypertension plus at least one additional major cardiovascular risk factor. 2

Why This Dose Range is Optimal

The 75-100 mg daily dose represents the sweet spot where:

• Efficacy is maintained: Meta-analyses demonstrate that aspirin doses from 50 mg to 1500 mg provide similar relative risk reduction (approximately 15%) for stroke prevention. 1, 5
• Toxicity is minimized: Gastrointestinal bleeding risk is dose-dependent, with higher doses (≥325 mg) conferring 2.5 times the bleeding risk compared to non-users, while lower doses (75-100 mg) reduce this risk substantially. 1, 2
• Hemorrhagic stroke risk is acceptable: While aspirin increases hemorrhagic stroke risk by 0-2 per 1,000 persons over 5 years, this is outweighed by ischemic stroke prevention benefits at the 75-100 mg dose. 2

Common Pitfalls to Avoid

• Do not use doses <75 mg daily: Evidence for doses below 75 mg is limited and may be insufficient for stroke prevention. 1
• Avoid routine use of high doses (≥325 mg) for chronic prevention: Higher doses increase bleeding risk without additional efficacy for long-term stroke prevention. 1, 2
• Do not initiate aspirin in low-risk individuals: For patients with 10-year cardiovascular risk <6%, bleeding risks outweigh minimal benefits. 2, 4
• Always rule out intracranial hemorrhage before administering aspirin in acute stroke settings. 3

Bleeding Risk Assessment

Before initiating aspirin, assess for contraindications and high bleeding risk:

• Absolute contraindications: Active gastrointestinal bleeding, documented aspirin allergy, bleeding disorders, clinically active hepatic disease. 2
• High bleeding risk factors: Age >70 years, uncontrolled hypertension, concomitant NSAIDs or anticoagulants, history of gastrointestinal bleeding. 2, 4
• Expected bleeding rates: Major gastrointestinal bleeding occurs at approximately 2-4 per 1,000 middle-aged persons (4-12 per 1,000 older persons) over 5 years with aspirin therapy. 2

Alternative for Aspirin-Intolerant Patients

For patients with documented aspirin allergy requiring antiplatelet therapy, substitute clopidogrel 75 mg daily. 2, 4