Asprin dose in heart attack
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aspirin dose acute myocardial infarction
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Here is a complete, evidence-based summary of aspirin dosing in acute myocardial infarction (MI):
Aspirin in Acute MI (Heart Attack)
Loading Dose (Acute Phase)
| Setting | Dose | How to Give |
|---|---|---|
| STEMI or NSTEMI | 162-325 mg | Chewed (non-enteric-coated), immediately |
| If not previously on aspirin | 325 mg preferred | Chewed as early as possible |
- Give to all patients with STEMI, NSTEMI, or unstable angina as soon as possible, unless contraindicated.
- The tablet must be chewed (not swallowed whole) to achieve rapid platelet inhibition - this ensures faster absorption and quicker onset of action (aspirin prevents thromboxane A2 formation, inhibiting platelet aggregation).
- This inhibition is irreversible and lasts for the 8-12 day lifespan of the platelet.
- Use non-enteric-coated aspirin only - enteric-coated formulations are absorbed too slowly for acute use.
"Give aspirin ≥162 milligrams and preferably 325 milligrams if naive of aspirin, as soon as possible to all patients with STEMI, NSTEMI, and unstable angina." - Tintinalli's Emergency Medicine
Maintenance Dose (Long-Term)
| Scenario | Dose |
|---|---|
| After acute MI, general maintenance | 81 mg/day (preferred) |
| With ticagrelor (dual antiplatelet) | ≤100 mg/day (higher doses reduce ticagrelor efficacy) |
| With clopidogrel or prasugrel | 81-325 mg/day |
- An 81 mg daily maintenance dose is required when aspirin is combined with ticagrelor (daily aspirin >100 mg actually reduces the effectiveness of ticagrelor).
- Dual antiplatelet therapy (aspirin + a P2Y12 inhibitor like clopidogrel, prasugrel, or ticagrelor) is continued for up to 1 year after ACS.
- After 1 year, aspirin 81 mg daily is continued indefinitely for secondary prevention, reducing subsequent MI risk by 20-25%.
Contraindications / Cautions
- True aspirin allergy
- Active bleeding or high bleeding risk
- In these cases, clopidogrel alone may be used as an alternative
Summary Table
| Phase | Dose |
|---|---|
| Acute (loading) | 162-325 mg chewed immediately |
| Maintenance (post-MI) | 81 mg/day indefinitely |
| With ticagrelor | ≤100 mg/day |
Sources: Goldman-Cecil Medicine, Tintinalli's Emergency Medicine, Braunwald's Heart Disease, Textbook of Family Medicine (ACC/AHA guidelines)
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