Initial Pharmacotherapy for STEMI
The initial pharmacotherapy for STEMI should include immediate administration of aspirin 162-325 mg (chewed or IV) and a loading dose of a P2Y12 inhibitor, along with anticoagulation therapy appropriate for the planned reperfusion strategy. 1
Antiplatelet Therapy
Aspirin
- Initial dose: 162-325 mg loading dose (chewable/non-enteric coated or IV if oral ingestion not feasible) 1, 2
- Timing: Administer as soon as possible after STEMI diagnosis 1, 2
- Maintenance: Continue indefinitely at 81 mg daily (preferred maintenance dose) 1
P2Y12 Inhibitor
A loading dose should be given as early as possible or at the time of primary PCI 1:
- Clopidogrel: 600 mg loading dose, then 75 mg daily 1
- Prasugrel: 60 mg loading dose, then 10 mg daily 1
- Contraindicated in patients with prior stroke or TIA 1
- Ticagrelor: 180 mg loading dose, then 90 mg twice daily 1
For faster platelet inhibition in high-risk situations, crushing or chewing P2Y12 inhibitor tablets can improve absorption 3.
Anticoagulation Therapy
For Primary PCI
- Unfractionated heparin (UFH): Weight-adjusted IV bolus
- 50-70 U/kg when used with GP IIb/IIIa inhibitor
- 70-100 U/kg when used without GP IIb/IIIa inhibitor 2
- Bivalirudin: Can be used with or without prior UFH treatment 1
- Reasonable alternative to UFH + GP IIb/IIIa inhibitor in patients at high bleeding risk 1
- Fondaparinux: Should NOT be used as sole anticoagulant for PCI (risk of catheter thrombosis) 1
For Fibrinolytic Therapy
Anticoagulation should be administered for a minimum of 48 hours, and preferably for the duration of hospitalization (up to 8 days) 1:
- UFH: Weight-adjusted IV bolus and infusion to maintain aPTT 1.5-2.0 times control 1
- Enoxaparin: IV bolus followed by subcutaneous injection (dose adjusted for age, weight, and renal function) 1
- Fondaparinux: IV bolus followed by daily subcutaneous injections if creatinine clearance >30 mL/min 1
Fibrinolytic Therapy (if PCI not available within 120 minutes)
If primary PCI cannot be performed within 120 minutes of first medical contact, fibrinolytic therapy should be administered within 12 hours of symptom onset 1:
- Tenecteplase (TNK-tPA): Single IV bolus based on weight 4:
- <60 kg: 30 mg
- 60-70 kg: 35 mg
- 70-80 kg: 40 mg
- 80-90 kg: 45 mg
- ≥90 kg: 50 mg
Adjunctive Therapy
GP IIb/IIIa Inhibitors
- Consider in selected patients undergoing primary PCI 1:
ACE Inhibitors
- Should be administered orally within the first 24 hours to patients with:
- Anterior infarction
- Pulmonary congestion
- LVEF <0.40 1
- Avoid IV ACE inhibitors in the first 24 hours due to risk of hypotension 1
Important Considerations
- Time is myocardium: Initiate pharmacotherapy as soon as possible after STEMI diagnosis 1, 2
- Bleeding risk: Consider bivalirudin monotherapy in patients at high risk of bleeding 1
- Stent selection: Use bare-metal stents in patients with high bleeding risk or inability to comply with prolonged DAPT 1
- Prasugrel contraindication: Do not administer to patients with prior stroke or TIA 1
- Aspirin dose: While initial loading dose is 162-325 mg, a maintenance dose of 81 mg daily is preferred for long-term therapy 1
Common Pitfalls to Avoid
- Delayed antiplatelet administration: Administer aspirin and P2Y12 inhibitors as early as possible 2
- Using fondaparinux alone for PCI: Always add an anticoagulant with anti-IIa activity due to risk of catheter thrombosis 1
- Inappropriate P2Y12 inhibitor selection: Avoid prasugrel in patients with history of stroke/TIA 1
- IV ACE inhibitors: Avoid within first 24 hours due to hypotension risk 1
- Excessive aspirin dosing: Higher IV loading doses of aspirin (>400 mg) may increase in-hospital mortality compared to lower doses 5
Early and appropriate pharmacotherapy is critical in STEMI management to improve outcomes by reducing mortality, morbidity, and preserving quality of life.