Can aspirin (acetylsalicylic acid) be started in the first few days after an acute ischemic stroke?

Aspirin Initiation After Acute Ischemic Stroke

Yes, aspirin should be started within 24-48 hours after acute ischemic stroke onset in most patients, with an initial dose of 160-325 mg. 1, 2

Timing and Dosing

• Initiate aspirin between 24-48 hours after stroke symptom onset for the majority of patients with acute ischemic stroke 1
• Loading dose: 160-325 mg initially, followed by maintenance dosing 1, 2
• For patients with impaired swallowing, use rectal aspirin 325 mg daily or aspirin 81 mg via enteral tube as alternatives 1
• Non-enteric-coated formulations provide more rapid buccal absorption and are preferred for initial dosing 1

Evidence for Early Aspirin Use

The benefit of early aspirin is substantial and time-sensitive:

• Aspirin reduces 6-week risk of recurrent ischemic stroke by approximately 60% and disabling/fatal ischemic stroke by 70% when started early 3
• Greatest benefit occurs within the first 2-3 days after treatment initiation, with hazard ratio of 0.37 for recurrent ischemic stroke 3
• The primary mechanism is prevention of early recurrent stroke rather than limitation of the initial stroke's neurological consequences 1, 2
• Early aspirin also reduces stroke severity if recurrence does occur 3

Critical Contraindications and Timing Restrictions

Do NOT give aspirin in these situations:

• Within 24 hours of IV thrombolytic therapy (rtPA) - this is an absolute contraindication 1, 2
• Before brain imaging has excluded intracranial hemorrhage 1
• As a substitute for IV rtPA when the patient is eligible for thrombolysis 1

Special Consideration: Minor Stroke and High-Risk TIA

For patients with minor stroke (NIHSS ≤3) or high-risk TIA (ABCD2 ≥4), dual antiplatelet therapy is superior:

• Initiate aspirin 81 mg + clopidogrel 75 mg daily within 12-24 hours of symptom onset 1, 4
• Loading doses: aspirin 160-325 mg and clopidogrel 300-600 mg at initiation 1, 2
• Continue dual therapy for 21 days only, then transition to single antiplatelet agent 1, 2
• This regimen reduces stroke risk from 11.7% to 8.2% at 90 days without increasing hemorrhage risk 4

Safety Profile

• Aspirin causes a small (0.1% absolute) increase in intracranial hemorrhage risk 1
• Modest increase in systemic hemorrhage is noted but does not offset the benefit of reduced recurrent stroke 1
• The net benefit strongly favors aspirin use, with approximately 10 fewer deaths and recurrent strokes per 1,000 patients treated 5

Clinical Algorithm

1. Confirm ischemic stroke with brain imaging (CT or MRI) to exclude hemorrhage 1
2. Assess thrombolysis eligibility - if eligible and within 3-hour window, prioritize IV rtPA 1
3. If thrombolysis given: Wait 24 hours before starting aspirin 1
4. If no thrombolysis: Start aspirin 160-325 mg within 24-48 hours 1, 2
5. For minor stroke (NIHSS ≤3) or high-risk TIA: Use dual antiplatelet therapy (aspirin + clopidogrel) for 21 days 1, 4
6. For moderate-severe stroke: Use aspirin monotherapy 1

Common Pitfalls to Avoid

• Do not delay aspirin beyond 48 hours - the benefit diminishes rapidly with time, with greatest effect in the first 2-3 days 3
• Do not use clopidogrel monotherapy or dual antiplatelet therapy for moderate-severe strokes - this is not recommended outside of minor stroke/high-risk TIA 1, 2
• Do not give aspirin before imaging - hemorrhagic stroke must be excluded first 1
• Do not combine aspirin with thrombolytics within 24 hours - this significantly increases bleeding risk 1