When to Start Single Antiplatelet Therapy in Stroke
For patients with acute ischemic stroke or TIA not receiving thrombolysis, single antiplatelet therapy should be initiated immediately after intracranial hemorrhage is excluded on neuroimaging, with a loading dose of aspirin 160 mg administered as soon as possible. 1, 2
Immediate Initiation (Within 24 Hours)
Standard Acute Stroke/TIA (Not Minor Stroke or High-Risk TIA)
- Administer aspirin 160 mg as a single loading dose immediately after CT/MRI excludes intracranial hemorrhage and dysphagia screening is passed 1, 2
- Continue with aspirin 81-325 mg daily indefinitely or until an alternative antithrombotic regimen is indicated 1
- For patients unable to swallow: use rectal aspirin 325 mg daily OR aspirin 81 mg daily via enteral tube as reasonable alternatives 1
Minor Stroke (NIHSS ≤3) or High-Risk TIA (ABCD2 ≥4)
These patients require dual antiplatelet therapy (DAPT), NOT single antiplatelet therapy initially:
- Start DAPT with loading doses of aspirin 160-325 mg AND clopidogrel 300-600 mg within 12-24 hours of symptom onset 1, 2
- Continue DAPT (aspirin 81 mg + clopidogrel 75 mg daily) for 21 days 1
- After 21 days, transition to single antiplatelet therapy (aspirin 81 mg daily OR clopidogrel 75 mg daily) for long-term secondary prevention 1
Critical Timing Considerations
Patients Receiving Thrombolysis (Alteplase)
- Delay antiplatelet initiation until 24 hours post-thrombolysis after repeat neuroimaging excludes intracranial hemorrhage 1
- This is a crucial safety measure to minimize bleeding risk 1
Extended Time Window (24-72 Hours)
- Recent evidence from the INSPIRES trial demonstrates that DAPT can be initiated up to 72 hours after symptom onset in patients with mild ischemic stroke or high-risk TIA of presumed atherosclerotic cause 3, 4
- However, the greatest benefit occurs when treatment is initiated within the first 24 hours, with diminishing returns thereafter 4, 5
Long-Term Single Antiplatelet Therapy
For Noncardioembolic Stroke
After the initial acute period (and completion of DAPT if indicated), continue indefinitely with ONE of the following options 1:
- Aspirin 81-325 mg daily (most commonly 81 mg) 1
- Clopidogrel 75 mg daily 1, 6
- Aspirin 25 mg + dipyridamole 200 mg twice daily 1
Special Populations Requiring Single Antiplatelet Therapy
- Embolic stroke of undetermined source (ESUS): Use antiplatelet therapy, NOT anticoagulation 1
- Extracranial artery dissection: Either antiplatelet therapy or anticoagulation for at least 3 months 1
- Carotid web: Antiplatelet therapy recommended 1
- Fibromuscular dysplasia: Antiplatelet therapy plus lifestyle modification 1
Common Pitfalls to Avoid
Do NOT Use Single Antiplatelet Therapy Alone in These Situations:
- Minor stroke (NIHSS ≤3) or high-risk TIA (ABCD2 ≥4) within 24 hours: These patients benefit significantly from DAPT for 21 days, with absolute risk reduction of 1.42% in the first week alone 4, 5
- Patients with atrial fibrillation: These require anticoagulation, not antiplatelet therapy 1
Critical Safety Checks Before Administration:
- Always exclude intracranial hemorrhage on neuroimaging first 1, 2
- Perform dysphagia screening before oral administration 1
- Do NOT give aspirin within 24 hours of thrombolysis 1
Loading Dose Importance:
- The loading dose is essential - standard 75 mg daily clopidogrel dosing takes approximately 5 days to achieve maximal platelet inhibition 2
- Without a loading dose of aspirin, antiplatelet effect is delayed by several days 6
- Avoid enteric-coated aspirin for loading doses due to slower onset of action 2
Duration of Benefit
The benefit-risk profile of antiplatelet therapy varies by timing 4, 5:
- First week: Maximum benefit with DAPT (ARR 1.42%) 4
- Second week: Continued benefit but lesser degree (ARR 0.49%) 4
- Third week: Minimal additional benefit (ARR 0.29%) 4
- Beyond 21-30 days: Single antiplatelet therapy is appropriate, as DAPT increases bleeding risk without additional ischemic benefit 1, 5