For how long should aspirin (acetylsalicylic acid) be administered in a patient with non‑ST‑elevation myocardial infarction (NSTEMI)?

Aspirin Duration in NSTEMI

Aspirin should be continued indefinitely after NSTEMI, starting with a loading dose of 162-325 mg (non-enteric-coated, chewable) at presentation, followed by a maintenance dose of 81 mg daily. 1

Initial Dosing

• Loading dose: 162-325 mg non-enteric-coated, chewable aspirin should be given as soon as possible after presentation
• Avoid enteric-coated formulations initially due to delayed absorption
• This is a Class I, Level A recommendation from the 2014 AHA/ACC NSTEMI guidelines 1

Maintenance Therapy

The maintenance dose of 81 mg daily should be continued indefinitely - meaning lifelong therapy for all NSTEMI patients without contraindications 1. This represents the strongest level of evidence (Class I, Level A) in cardiovascular guidelines.

Key Dosing Details:

• Maintenance range: 81-325 mg daily, but 81 mg is preferred 2, 1
• When used with ticagrelor specifically, the recommended aspirin dose is 81 mg daily (not higher doses) 1
• High-dose aspirin (≥160 mg) increases bleeding risk without improving outcomes 1

Duration Context: Aspirin vs. P2Y12 Inhibitors

It's critical to distinguish aspirin duration from dual antiplatelet therapy (DAPT) duration:

• Aspirin alone: Indefinite (lifelong) 2, 1
• P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) in addition to aspirin: At least 12 months 2, 1
• After 12 months of DAPT, the P2Y12 inhibitor may be discontinued, but aspirin continues indefinitely 2

DAPT Duration Nuances:

• The 12-month DAPT duration applies regardless of whether the patient underwent PCI, received medical therapy alone, or had bypass surgery 2
• Extension beyond 12 months may be reasonable in select patients without high bleeding risk 2
• Recent evidence (3) suggests emerging strategies of early aspirin discontinuation with P2Y12 monotherapy, but this is not yet standard guideline-based care and should not be applied routinely

Common Pitfalls

1. Confusing DAPT duration with aspirin duration: The 12-month recommendation refers to dual therapy; aspirin itself continues indefinitely
2. Using enteric-coated aspirin initially: This delays absorption when rapid platelet inhibition is critical 1
3. Using excessive maintenance doses: Doses >81 mg increase bleeding without added benefit, especially with ticagrelor 1
4. Stopping aspirin after completing 12 months of DAPT: This is incorrect - only the P2Y12 inhibitor is discontinued

Special Circumstances

• Aspirin allergy/intolerance: Use clopidogrel as monotherapy with appropriate loading and maintenance dosing 1
• High bleeding risk: Aspirin should still be continued indefinitely unless absolute contraindications exist; the duration of the P2Y12 inhibitor may be shortened to 6 months 4