What is the role of long-term aspirin (acetylsalicylic acid) therapy in patients who have experienced a Transient Ischemic Attack (TIA)?

Long-Term Aspirin Therapy After TIA

All patients with noncardioembolic TIA should receive immediate and indefinite antiplatelet therapy, with aspirin (50-325 mg daily) being an effective and acceptable option, though combination aspirin/extended-release dipyridamole or clopidogrel monotherapy may offer superior stroke prevention. 1

Immediate Initiation is Critical

• Start antiplatelet therapy immediately upon TIA diagnosis—never delay while awaiting diagnostic workup. 2
• Aspirin should be initiated within 48 hours of symptom onset at a dose of 160-325 mg initially, then continued long-term at 50-100 mg daily. 1
• Early aspirin therapy (within 48 hours) reduces stroke risk more effectively than delayed treatment or no treatment. 1

Optimal Aspirin Dosing for Long-Term Use

• For long-term secondary prevention, aspirin 50-100 mg daily is as effective as higher doses (up to 1300 mg daily) but causes significantly fewer gastrointestinal bleeding complications and adverse effects. 1, 3
• A landmark trial comparing 30 mg versus 283 mg daily found equivalent efficacy (14.7% vs 15.2% event rates) but significantly fewer bleeding complications and gastrointestinal symptoms with the lower dose. 3
• Doses above 100 mg daily increase hemorrhagic risk without additional benefit. 1

When Aspirin Alone May Not Be Optimal

Combination aspirin (25-50 mg) plus extended-release dipyridamole (200 mg twice daily) is preferred over aspirin monotherapy as it reduces stroke risk more effectively without increasing major bleeding. 1, 2

• This combination is recommended as first-line therapy by multiple guidelines for noncardioembolic TIA. 1, 2
• Clopidogrel 75 mg daily is slightly more effective than aspirin alone and represents an appropriate alternative, particularly for patients with peripheral arterial disease or prior myocardial infarction. 1, 2
• However, with long-term use beyond 5 years, aspirin-containing regimens may reduce cancer-related mortality, potentially offsetting clopidogrel's vascular benefits. 1

Critical Contraindications to Aspirin

Never use aspirin in patients with active bleeding, severe uncontrolled hypertension, hemophilia, or aspirin allergy—use clopidogrel 75 mg daily instead. 4, 5

• Patients with known bleeding disorders should receive alternative antiplatelet therapy. 4
• Severe hypertension (>180/110 mmHg) must be controlled before initiating antiplatelet therapy due to intracranial hemorrhage risk. 4

Cardioembolic TIA Requires Different Management

For TIA patients with atrial fibrillation (persistent or paroxysmal), oral anticoagulation with target INR 2.5 (range 2.0-3.0) is mandatory—not aspirin. 1, 2

• Anticoagulation is superior to aspirin for preventing recurrent stroke in atrial fibrillation patients. 1, 5
• Aspirin 325 mg daily (or clopidogrel 75 mg if aspirin-intolerant) should only be used when anticoagulation is contraindicated or refused. 1
• For mechanical heart valves, target INR 3.0 (range 2.5-3.5) is required; aspirin 75-100 mg may be added if recurrent events occur despite adequate anticoagulation. 1, 2

Dual Antiplatelet Therapy: A Critical Pitfall

Never combine aspirin and clopidogrel for long-term secondary prevention after TIA—bleeding risk outweighs any potential benefit. 2, 6, 7

• The MATCH and CHARISMA trials demonstrated that aspirin plus clopidogrel provides no significant benefit over monotherapy but significantly increases major bleeding complications. 6, 7
• Dual antiplatelet therapy may have a limited role (approximately 3 months) immediately after TIA in highly selected patients with symptomatic large artery atherothromboembolism, but this remains investigational. 7

Essential Concurrent Interventions

• Initiate statin therapy immediately targeting LDL <100 mg/dL regardless of baseline cholesterol. 2
• Start blood pressure-lowering medication 7-14 days post-TIA with ACE inhibitor or ARB plus thiazide diuretic, targeting <140/90 mmHg (<130/80 mmHg if diabetic). 2
• Address modifiable risk factors including smoking cessation, diabetes control (fasting glucose <126 mg/dL), and regular physical activity. 2

Drug Interactions to Avoid

Herbal supplements including feverfew, garlic, ginkgo biloba, ginger, and ginseng alter bleeding time and must be discontinued when taking aspirin or other antiplatelet agents. 4

• St. John's wort interferes with warfarin metabolism and should be avoided in patients requiring anticoagulation. 4

Duration of Therapy

Antiplatelet therapy after TIA is lifelong unless contraindications develop or the patient transitions to anticoagulation for a cardioembolic source. 1, 5

• There is no defined endpoint for discontinuation in noncardioembolic TIA patients. 1
• Continuous adherence is essential as stroke risk remains elevated indefinitely. 8