Duration of Aspirin Therapy After Ischemic Stroke
For patients with a history of noncardioembolic ischemic stroke, aspirin should be continued indefinitely as long-term secondary prevention therapy at a dose of 75-100 mg once daily. 1
Acute Phase Treatment (First 48 Hours)
Initiate aspirin within 48 hours of stroke onset at a loading dose of 160-325 mg to achieve rapid platelet inhibition and reduce early recurrent stroke risk by approximately 60%. 1, 2
This early aspirin therapy prevents approximately 10 deaths and early recurrent strokes per 1,000 patients treated, with the greatest benefit occurring in the first 2-3 days after stroke. 3, 2
The reduction in early recurrent ischemic stroke is not offset by any significant increase in intracranial hemorrhage (approximately 2 additional hemorrhagic strokes per 1,000 patients). 3, 4
Transition to Long-Term Therapy
After the acute phase, transition to a maintenance dose of 75-100 mg daily for indefinite secondary prevention. 1
The American College of Chest Physicians guidelines (Grade 1A recommendation) specify that this long-term antiplatelet therapy should continue lifelong in patients with a history of noncardioembolic ischemic stroke or TIA. 1
Alternative Antiplatelet Regimens
While aspirin is recommended indefinitely, clopidogrel (75 mg once daily) or aspirin/extended-release dipyridamole (25 mg/200 mg twice daily) are preferred over aspirin monotherapy for long-term secondary prevention (Grade 2B). 1
Clopidogrel 75 mg daily is recommended as a safe and effective alternative to aspirin monotherapy for patients who cannot tolerate aspirin. 1
With long-term use exceeding 5 years, the benefit of clopidogrel over aspirin in preventing major vascular events may be offset by a reduction in cancer-related mortality with aspirin-containing regimens. 1
Duration Considerations for Dual Antiplatelet Therapy
Dual antiplatelet therapy (aspirin plus clopidogrel) is NOT recommended for routine long-term use after ischemic stroke, as it increases bleeding risk without proportionate benefit beyond the acute period. 1
For minor ischemic stroke (NIHSS ≤3) or high-risk TIA, dual antiplatelet therapy may be used for only 21 days, followed by transition to single antiplatelet therapy indefinitely. 5, 6
Short-term dual antiplatelet therapy (≤3 months) reduces ischemic stroke recurrence by 41% without increasing intracranial hemorrhage risk, while prolonged dual therapy (≥1 year) increases major bleeding and intracranial hemorrhage risk. 6
Special Circumstances
Hemorrhagic Transformation
For lower-grade hemorrhagic transformation (HI1), initiate aspirin within 24-48 hours after confirming no progression on follow-up imaging. 5
For higher-grade hemorrhagic transformation (HI2, PH1, PH2), delay aspirin for 7-10 days and restart with single antiplatelet therapy rather than dual therapy. 5
Cardioembolic Stroke with Atrial Fibrillation
Switch from aspirin to oral anticoagulation (warfarin with INR 2.0-3.0 or direct oral anticoagulant) for long-term therapy, as anticoagulation is superior to aspirin in this population. 1
Bridge with aspirin until anticoagulation reaches therapeutic levels, typically initiating anticoagulation within 1-2 weeks after stroke onset. 1, 5
Common Pitfalls to Avoid
Do not discontinue aspirin after an arbitrary time period (e.g., 6 months or 1 year) in patients with noncardioembolic stroke—the benefit persists indefinitely. 1
Avoid using dual antiplatelet therapy (aspirin plus clopidogrel) for long-term secondary prevention beyond 21-90 days, as bleeding risk outweighs benefit. 1, 6
Do not delay aspirin initiation in the acute phase while waiting for CT results in patients with suspected ischemic stroke, as early treatment (within 48 hours) provides maximal benefit. 3, 2, 4
Do not use subtherapeutic aspirin doses (<75 mg) for long-term secondary prevention, as efficacy is reduced. 1