ASA Dosage for NSTEMI
For patients with NSTEMI, aspirin (ASA) should be prescribed at an initial dose of 162-325 mg followed by a maintenance dose of 75-162 mg daily indefinitely. 1, 2
Initial Dosing
- An immediate loading dose of 162-325 mg should be administered as soon as the diagnosis of NSTEMI is made or suspected 1
- This higher initial dose achieves more rapid and complete platelet inhibition during the acute thrombotic phase 3
- The loading dose can be given orally or intravenously (100 mg) if oral administration is not possible 4
Maintenance Dosing
- After the initial loading dose, maintenance therapy with 75-162 mg daily should be continued indefinitely 2
- Lower maintenance doses (75-100 mg) are preferred over higher doses due to similar efficacy with lower bleeding risk 1, 4
- For medically managed NSTEMI patients (without stenting), ASA 75-162 mg per day should be prescribed indefinitely (Level of Evidence: A) 2
Dosing Based on Treatment Strategy
For Medically Managed NSTEMI (without stenting):
- ASA 75-162 mg daily indefinitely 2
- Should be combined with clopidogrel 75 mg daily for at least 1 month and ideally up to 1 year 2
For NSTEMI Treated with Bare-Metal Stent (BMS):
- Initial ASA 162-325 mg daily for at least 1 month 2
- Then continued indefinitely at 75-162 mg daily 2
- Combined with a P2Y12 inhibitor (clopidogrel 75 mg daily or prasugrel 10 mg daily) for at least 12 months 2
For NSTEMI Treated with Drug-Eluting Stent (DES):
- Initial ASA 162-325 mg daily for at least 3 months after sirolimus-eluting stent or 6 months after paclitaxel-eluting stent 2
- Then continued indefinitely at 75-162 mg daily 2
- Combined with a P2Y12 inhibitor for at least 12 months 2
Special Considerations
Bleeding Risk
- For patients with increased bleeding risk, a lower initial ASA dose of 75-162 mg daily after PCI is reasonable (Level of Evidence: C) 2
- Dose-dependent increase in bleeding has been observed with aspirin: 2.0% with <100 mg, 2.3% with 100-200 mg, and 4.0% with >200 mg daily 1
- The risk of gastrointestinal side effects and bleeding is lower with daily doses of 75-150 mg 4
ASA Allergy
- For ASA-allergic patients, use clopidogrel alone (indefinitely) or try ASA desensitization 2
- ASA desensitization protocols have been developed for patients with NSAID hypersensitivity who require coronary intervention 5
Concomitant Anticoagulation
- For NSTEMI patients who have an indication for anticoagulation, the addition of warfarin may be reasonable to maintain an INR of 2.0-3.0 2
- An INR of 2.0-2.5 is preferable when given with ASA and clopidogrel, especially in older patients and those with other risk factors for bleeding 2
Efficacy Considerations
- No significant difference has been observed in the incidence of stent thrombosis between 81 mg versus 325 mg maintenance doses of aspirin post-PCI with sirolimus-eluting stents 6
- A daily maintenance dose of 75 mg ASA is sufficient to effectively inhibit thromboxane A2 synthesis in long-term treatment 4