Duration of High-Dose Aspirin (160-325 mg) in Acute Ischemic Stroke
High-dose aspirin (160-325 mg) should be used for only the first 1-2 days after acute ischemic stroke, then transitioned to low-dose aspirin (75-100 mg daily) for long-term secondary prevention. 1, 2
Acute Phase Dosing (First 24-48 Hours)
- Administer aspirin 160-325 mg as a single loading dose within 24-48 hours of stroke onset after brain imaging excludes intracranial hemorrhage 3, 1
- The American Heart Association/American Stroke Association specifically recommends doses between 160-300 mg based on landmark trials (CAST and IST) 2
- This initial high dose achieves rapid inhibition of thromboxane biosynthesis and immediate antiplatelet effect 4
Transition to Maintenance Therapy
- After the initial loading dose, transition immediately to low-dose aspirin (75-100 mg daily) for indefinite secondary stroke prevention 1, 2
- The lower maintenance dose provides equivalent efficacy to higher doses (300-325 mg) but with significantly reduced bleeding risk 2
- Long-term use of doses above 325 mg increases bleeding without improving efficacy 1
Critical Timing Considerations
- If IV thrombolysis (alteplase) is administered, delay any aspirin for 24 hours after thrombolytic therapy to avoid increased bleeding risk 1, 2
- Aspirin should not be used as adjunctive therapy within 24 hours of thrombolytic treatment 1
- For patients unable to swallow, use rectal or nasogastric administration during the acute phase 2
Evidence Quality
- This recommendation is based on Class I, Level A evidence from two large randomized trials (CAST and IST) involving over 40,000 patients 2
- These trials demonstrated that aspirin 160-300 mg initiated within 48 hours reduces mortality and recurrent stroke by approximately 10 events per 1,000 patients treated 4
Common Pitfall to Avoid
Do not continue high-dose aspirin (160-325 mg) beyond the initial loading dose. The high dose is only needed acutely for rapid platelet inhibition; continuing it long-term unnecessarily increases gastrointestinal bleeding and other side effects without additional benefit 1, 2, 5