What is the role of aspirin (acetylsalicylic acid) in preventing another stroke in patients who have had an ischemic stroke or transient ischemic attack (TIA)?

Role of Aspirin in Secondary Stroke Prevention

Aspirin is a first-line antiplatelet agent for preventing recurrent stroke in patients with ischemic stroke or transient ischemic attack (TIA), with doses ranging from 50-325 mg daily being effective and appropriate for most patients. 1

Antiplatelet Therapy for Secondary Stroke Prevention

Efficacy and Recommendations

• For patients with noncardioembolic ischemic stroke or TIA, antiplatelet agents are recommended over oral anticoagulation to reduce the risk of recurrent stroke and other cardiovascular events (Class I, Level of Evidence A) 1
• Aspirin (50 to 325 mg/d) is an acceptable option for initial therapy (Class IIa, Level of Evidence A) 1
• Low-dose aspirin (50-325 mg) is as effective as higher doses for stroke prevention while causing fewer gastrointestinal side effects 1, 2
• Aspirin reduces the relative risk of stroke, MI, or death by approximately 22% in patients with prior stroke or TIA 1

Alternative Antiplatelet Options

• Besides aspirin, other acceptable first-line options include:
  • The combination of aspirin and extended-release dipyridamole (Class IIa, Level of Evidence A) 1
  • Clopidogrel 75 mg daily (Class IIb, Level of Evidence B) 1
• For patients allergic to aspirin, clopidogrel is a reasonable alternative (Class IIa, Level of Evidence B) 1, 3
• For elderly patients (>75 years) experiencing bleeding complications on aspirin, the risk-benefit ratio shifts toward increased harm, and alternative agents may be considered 3

Clinical Considerations

Dosing

• Aspirin doses ranging from 50-325 mg daily are equally effective for stroke prevention 1, 2
• Lower doses (50-100 mg) are associated with fewer gastrointestinal side effects while maintaining efficacy 1, 2
• There is no evidence that increasing the dose of aspirin provides additional benefit for patients who have a stroke while taking aspirin 1

Special Populations

• For patients with mechanical prosthetic heart valves who have had an ischemic stroke, warfarin (INR 2.5-3.5) plus aspirin 75-100 mg/day is reasonable if the patient is not at high bleeding risk 1
• For patients with arterial dissections causing ischemic stroke, antiplatelet therapy is an acceptable treatment option 1

Common Pitfalls and Caveats

• Adding aspirin to clopidogrel increases bleeding risk and is not routinely recommended for ischemic stroke or TIA patients (Class III, Level of Evidence A) 1
• Higher doses of aspirin (>325 mg) increase the risk of gastrointestinal bleeding without providing additional stroke prevention benefits 1, 2
• For patients experiencing a stroke while on aspirin, switching to an alternative antiplatelet agent (clopidogrel or aspirin plus extended-release dipyridamole) may be considered, although there is limited evidence supporting this approach 1
• In elderly patients with bleeding complications, the American College of Chest Physicians recommends stopping aspirin as the risks of continued bleeding may outweigh the benefits of stroke prevention 3

Decision Algorithm for Antiplatelet Selection

1. For most patients with noncardioembolic ischemic stroke or TIA:

   • Start aspirin 50-325 mg daily (81 mg daily is commonly used) 1

2. If patient has aspirin allergy or significant gastrointestinal intolerance:

   • Use clopidogrel 75 mg daily 1, 3

3. If patient has high risk of recurrent stroke:

   • Consider aspirin plus extended-release dipyridamole 1, 4
   • OR clopidogrel monotherapy 1

4. If patient experiences recurrent stroke while on aspirin:

   • Consider switching to clopidogrel or aspirin plus extended-release dipyridamole 1, 4

5. If patient experiences bleeding complications on aspirin:

   • Consider dose reduction if on higher dose aspirin 1, 2
   • If bleeding persists, consider switching to clopidogrel 3