What is the recommended dose of Aspirin (acetylsalicylic acid) for an adult patient with a history of Transient Ischemic Attack (TIA) and cardiovascular disease risk factors?

Aspirin Dosing After TIA

For adults with TIA, initiate aspirin 160-325 mg as a loading dose within 48 hours of symptom onset, followed by a maintenance dose of 75-100 mg daily for long-term secondary prevention. 1, 2

Acute Phase Management (First 48 Hours)

• Loading dose: 160-325 mg aspirin should be administered immediately after excluding intracranial hemorrhage, ideally within 24-48 hours of symptom onset 1, 2
• The aspirin should be chewed (non-enteric-coated formulation) for faster buccal absorption and more rapid platelet inhibition 1, 2
• For patients unable to swallow, use rectal aspirin 325 mg or enteral tube aspirin 81 mg 2
• If thrombolysis was administered, delay aspirin for 24 hours post-alteplase 2

High-Risk TIA: Consider Dual Antiplatelet Therapy

For patients with high-risk TIA (ABCD2 score >4 or symptom onset within 24 hours):

• Load with aspirin 160-325 mg PLUS clopidogrel 300-600 mg within 12-24 hours of symptom onset 3, 2
• Continue dual therapy (clopidogrel 75 mg + aspirin 75-100 mg daily) for 21-30 days only 3
• After 21-30 days, transition to single antiplatelet therapy (either aspirin alone or clopidogrel alone) 3
• Never continue dual antiplatelet therapy beyond 90 days due to dramatically increased bleeding risk (pooled RR 2.42 for major bleeding) without additional stroke prevention benefit 3

Long-Term Maintenance Dosing (After Acute Phase)

The optimal maintenance dose is 75-100 mg daily for noncardioembolic TIA 1, 2

First-Line Options for Long-Term Prevention:

• Aspirin 75-100 mg daily alone (Class I, Level A) 1, 2
• Aspirin 50 mg + extended-release dipyridamole 200 mg twice daily (preferred first-line option per ACC) 2
• Clopidogrel 75 mg daily (alternative if aspirin not tolerated or as first choice) 1, 3, 2

Evidence Supporting Lower Maintenance Doses:

• Doses as low as 30 mg daily are equally effective as 283 mg daily for preventing vascular events (14.7% vs 15.2% event rate), with significantly fewer bleeding complications and gastrointestinal side effects 4, 5
• No dose-response relationship exists above 30 mg daily - higher doses do not provide proportionally greater benefit 5, 6
• The 75-100 mg range balances efficacy with safety, as gastrointestinal hemorrhage risk increases with doses above 100 mg 1, 7

Critical Clinical Scenarios

Cardioembolic TIA (Atrial Fibrillation):

• Anticoagulation (apixaban, warfarin) is superior to aspirin for cardioembolic stroke prevention 3, 8
• If anticoagulation is contraindicated, use aspirin 325 mg daily 2
• Do not combine aspirin with anticoagulation unless there is a concurrent acute coronary syndrome or recent coronary stent - this increases bleeding without reducing stroke risk 8

TIA While Already on Aspirin:

• Switch to clopidogrel 75 mg daily OR aspirin 25 mg + extended-release dipyridamole 200 mg twice daily 2
• This indicates aspirin failure and requires escalation of antiplatelet therapy 2

Perioperative (Carotid Endarterectomy):

• Continue aspirin 50-325 mg daily beginning before surgery 2

Common Pitfalls to Avoid

• Do not use enteric-coated aspirin for the loading dose - it has slower onset of action 2
• Do not continue dual antiplatelet therapy indefinitely - the bleeding risk outweighs benefit after 21-30 days unless there is a separate cardiac indication 3
• Do not reflexively add aspirin to anticoagulation "for extra protection" in atrial fibrillation patients - this is a common error that increases bleeding without benefit 8
• Do not use doses below 30 mg daily in acute stroke patients - suppression of thromboxane synthesis may be inadequate in the hyperacute phase 6