Should a patient already on aspirin (acetylsalicylic acid) who experiences an acute ischemic stroke be loaded with additional aspirin?

Should You Load Aspirin in a Patient Already on Aspirin Who Has an Acute Ischemic Stroke?

Yes, administer a loading dose of aspirin (at least 160 mg) even if the patient is already on aspirin therapy, as soon as brain imaging excludes hemorrhage and dysphagia screening is passed. 1

Rationale for Loading Dose in Aspirin-Naive vs. Already-on-Aspirin Patients

The evidence strongly supports aspirin loading in acute ischemic stroke, but the guidelines make an important distinction:

• For patients NOT already on antiplatelet therapy: Give at least 160 mg aspirin immediately after excluding hemorrhage 1
• For patients ALREADY on aspirin prior to stroke: The 2018 Canadian guidelines explicitly state "all acute stroke patients not already on an antiplatelet agent" should receive the loading dose 1, which implies those already on aspirin may not require additional loading

However, the 2025 ACS guidelines provide relevant context: aspirin loading doses (162-325 mg) should be administered even to patients already on aspirin therapy 1. While this is from cardiac literature, the principle of ensuring adequate platelet inhibition in acute thrombotic events applies.

The Evidence Base for Early Aspirin in Acute Stroke

Aspirin initiated within 24-48 hours of stroke onset prevents approximately 9 deaths or recurrent strokes per 1,000 patients treated 1, 2, 3:

• Reduces recurrent ischemic stroke by approximately 7 per 1,000 patients 3
• Reduces death without further stroke by approximately 4 per 1,000 patients 3
• Small increase in hemorrhagic transformation of only 2 per 1,000 patients 3
• Net benefit of 9 fewer strokes or deaths per 1,000 treated 1, 3

The combined analysis of 40,000 patients from the Chinese Acute Stroke Trial and International Stroke Trial demonstrated these benefits were consistent across all subgroups, including elderly patients, those with atrial fibrillation, and varying stroke subtypes 3.

Practical Dosing Algorithm

Step 1: Immediate Assessment

• Confirm acute ischemic stroke with brain imaging (exclude hemorrhage) 1
• Perform dysphagia screening 1

Step 2: Determine Aspirin Status

• If NOT on aspirin: Give 160-325 mg loading dose immediately 1
• If ALREADY on aspirin: The most conservative approach based on stroke-specific guidelines is to continue current aspirin without additional loading 1, though cardiac literature supports loading even in this scenario 1

Step 3: Route of Administration

• Oral (preferred): 160-300 mg, chewed if possible for faster absorption 2
• Rectal suppository: 325 mg if unable to swallow 1
• Enteral tube: 80 mg daily if dysphagia present 1

Step 4: Maintenance Therapy

• Continue 81-325 mg daily indefinitely 1
• Current evidence favors 75-100 mg daily for long-term maintenance 1

Critical Timing Considerations

Do NOT give aspirin if:

• Patient received or is planned for thrombolytic therapy (tPA) - delay aspirin until 24 hours post-thrombolysis after repeat imaging excludes hemorrhage 1
• Brain imaging shows intracranial hemorrhage 1
• Patient has hemorrhagic transformation on imaging 4

Special Consideration: Minor Stroke or TIA

For patients with minor stroke (NIHSS ≤3) or high-risk TIA, dual antiplatelet therapy (aspirin + clopidogrel) for 21 days is superior to aspirin alone 1, 5, 6:

• Loading: Aspirin 160-325 mg + clopidogrel 300-600 mg 1, 5
• Maintenance: Aspirin 81 mg + clopidogrel 75 mg daily for 21 days only 1, 5
• After 21 days, switch to single antiplatelet agent 1, 5

The CHANCE trial demonstrated dual therapy reduced stroke risk from 11.7% to 8.2% at 90 days (HR 0.68) without increasing hemorrhage 6. However, duration should not exceed 21-30 days due to increased bleeding risk 1, 5.

Common Pitfalls to Avoid

• Don't withhold aspirin in patients without CT scan: Among 9,000 patients randomized without prior CT, aspirin showed net benefit with no unusual excess of hemorrhagic stroke 3
• Don't use aspirin as substitute for thrombolysis: Aspirin should not delay or replace IV tPA in eligible patients 1
• Don't continue dual antiplatelet beyond 21-30 days: Bleeding risk (HR 2.32) outweighs benefit after this period 1, 5