What is the recommended loading dose for ST-Elevation Myocardial Infarction (STEMI)?

Loading Dose Recommendations for STEMI

For patients with ST-Elevation Myocardial Infarction (STEMI), the recommended loading dose is aspirin 162-325 mg (chewable or non-enteric coated) plus a P2Y12 inhibitor loading dose (clopidogrel 600 mg, prasugrel 60 mg, or ticagrelor 180 mg) as early as possible or at the time of primary PCI. 1, 2

Antiplatelet Loading Doses

Aspirin Loading

• Aspirin: 162-325 mg orally (chewable/non-enteric coated form) or 250-500 mg IV if oral ingestion is not possible 1
• Should be administered as soon as possible after STEMI diagnosis
• Chewable or non-enteric coated forms are preferred for faster absorption

P2Y12 Inhibitor Loading (to be given with aspirin)

• Clopidogrel: 600 mg loading dose 1
• Prasugrel: 60 mg loading dose 1
  • Contraindication: Do not use in patients with prior stroke or TIA 1
• Ticagrelor: 180 mg loading dose 1

Anticoagulant Loading Doses for Primary PCI

Unfractionated Heparin (UFH)

• With planned GP IIb/IIIa inhibitor: 50-70 U/kg IV bolus 1
• Without planned GP IIb/IIIa inhibitor: 70-100 U/kg IV bolus 1

Bivalirudin

• 0.75 mg/kg IV bolus, followed immediately by 1.75 mg/kg/h infusion 1, 3
• Additional 0.3 mg/kg bolus may be given if needed based on ACT at 5 minutes 3
• Preferred over UFH with GP IIb/IIIa inhibitors in patients at high risk of bleeding 1
• For patients with creatinine clearance <30 mL/min, reduce infusion to 1 mg/kg/h 3

GP IIb/IIIa Inhibitor Loading (if used)

• Abciximab: 0.25 mg/kg IV bolus, then 0.125 mcg/kg/min (maximum 10 mcg/min) 1
• Tirofiban (high-bolus dose): 25 mcg/kg IV bolus, then 0.15 mcg/kg/min 1
• Eptifibatide (double bolus): 180 mcg/kg IV bolus, then 2 mcg/kg/min; second 180 mcg/kg bolus 10 min after first 1

Important Considerations

Timing of Administration

• Loading doses should be given as early as possible after STEMI diagnosis 1, 2
• Ideally administered before or at the time of primary PCI 1

Contraindications and Precautions

• Avoid prasugrel in patients with history of stroke or TIA 1
• Avoid fondaparinux as sole anticoagulant for PCI due to risk of catheter thrombosis 1, 2
• Adjust bivalirudin dosing in renal impairment 3
• Consider bleeding risk when selecting anticoagulant strategy 1

Common Pitfalls

1. Delayed administration: Antiplatelet loading should not be delayed; administer as soon as STEMI is diagnosed
2. Using enteric-coated aspirin: This formulation has slower onset of action and should be avoided for loading dose 1
3. Inappropriate P2Y12 inhibitor selection: Prasugrel should be avoided in patients with prior stroke/TIA 1
4. Inadequate anticoagulation: Ensure proper dosing based on patient weight and renal function
5. Failure to recognize aspirin resistance: Some patients on chronic aspirin therapy may still benefit from additional loading dose 4

Post-Loading Maintenance Therapy

After loading doses, transition to maintenance therapy:

• Aspirin: 81 mg daily (preferred maintenance dose) 1
• P2Y12 inhibitor: Continue for at least 1 year after DES placement or at least 30 days (up to 1 year) after BMS placement 1

The evidence strongly supports early and appropriate loading doses of antiplatelet and anticoagulant medications to improve outcomes in STEMI patients undergoing primary PCI, with careful consideration of bleeding risk and contraindications.