What is the initial dose of medication for a patient presenting with Non-ST-Elevation Myocardial Infarction (NSTEMI) in the Emergency Room (ER)?

Initial Medication Dosing for NSTEMI in the Emergency Room

All NSTEMI patients presenting to the ER should immediately receive aspirin 162-325 mg orally (non-enteric coated, chewable for fastest absorption), followed by a P2Y12 inhibitor loading dose, with anticoagulation initiated concurrently. 1

Immediate Antiplatelet Therapy

Aspirin Administration

• Loading dose: 162-325 mg orally (non-enteric coated, chewable preferred) as soon as NSTEMI is suspected 1, 2
• Alternative route: 75-250 mg IV if oral administration is not feasible 3
• Maintenance dose: 75-100 mg daily (not 81-325 mg as previously recommended) starting after the loading dose 1
• The aspirin should be chewed when possible to achieve faster onset of antiplatelet action 1
• Continue indefinitely unless absolute contraindication exists 1, 4

Key caveat: When using ticagrelor specifically, aspirin maintenance must not exceed 100 mg daily, as higher doses reduce ticagrelor's efficacy 1

P2Y12 Inhibitor Selection and Dosing

For patients proceeding to PCI (invasive strategy):

• First-line: Ticagrelor 180 mg loading dose, then 90 mg twice daily maintenance 1, 2
• Alternative: Prasugrel 60 mg loading dose (if undergoing PCI and no contraindications), then 10 mg daily (or 5 mg daily if weight <60 kg or age ≥75 years) 1
• Third-line: Clopidogrel 600 mg loading dose (only when prasugrel/ticagrelor unavailable or contraindicated), then 75 mg daily 1, 2

For patients with conservative/delayed invasive strategy (>24 hours to angiography):

• Clopidogrel 300-600 mg loading dose or ticagrelor 180 mg may be considered upstream 1
• The 600 mg clopidogrel dose provides more rapid and reliable platelet inhibition than 300 mg 2

Prasugrel contraindications to avoid: Prior stroke/TIA, age ≥75 years (use cautiously with 5 mg maintenance if benefit outweighs risk), body weight <60 kg 1, 3

Anticoagulation Therapy

Initiate one of the following immediately (do not combine or switch between agents except UFH can be added to fondaparinux at PCI): 4

• Enoxaparin: IV bolus followed 15 minutes later by subcutaneous dosing; if age >75 years, omit IV bolus and use reduced subcutaneous dose 1
• Fondaparinux: IV bolus followed 24 hours later by subcutaneous dose 1
• Unfractionated heparin (UFH): Weight-adjusted IV infusion with aPTT monitoring after 3 hours 1

Anti-Ischemic Medications

Nitroglycerin

• Sublingual: 0.4 mg every 5 minutes for up to 3 doses for ongoing chest pain 4
• IV nitroglycerin: Initiate if chest pain persists after sublingual doses, or if heart failure/hypertension present 4
• Absolute contraindications: Systolic BP <90 mmHg (or >30 mmHg below baseline), heart rate <50 or >100 bpm without heart failure, right ventricular infarction, recent phosphodiesterase inhibitor use 1

Beta-Blockers

• Oral beta-blocker within 24 hours unless contraindicated 4
• Contraindications: Signs of heart failure, low-output state, increased cardiogenic shock risk, PR interval >0.24 seconds, second/third-degree heart block, active asthma/reactive airway disease 4
• Do not give if heart rate <60 bpm, systolic BP <100 mmHg, or moderate-severe LV dysfunction with signs of heart failure 1

Morphine

• Morphine sulfate IV for uncontrolled ischemic chest pain despite nitroglycerin 4
• Important caveat: Recent evidence suggests morphine may attenuate the protective effects of other cardioprotective agents, though it remains guideline-recommended for refractory pain 5

Oxygen

• Only administer if: Arterial oxygen saturation <90%, respiratory distress present, or signs of heart failure 4
• Routine oxygen in uncomplicated NSTEMI without hypoxemia is not recommended 1

Medications to AVOID

NSAIDs (except aspirin) are absolutely contraindicated - they increase mortality, reinfarction, hypertension, heart failure, and myocardial rupture risk 1, 4

Dosing Summary Table

Medication	Loading Dose	Maintenance Dose	Timing
Aspirin	162-325 mg PO (chewable)	75-100 mg daily	Immediately
Ticagrelor	180 mg PO	90 mg twice daily	Immediately or after angiography
Prasugrel	60 mg PO	10 mg daily (5 mg if <60 kg or ≥75 years)	After angiography, at PCI
Clopidogrel	600 mg PO	75 mg daily	Immediately or after angiography

Duration of dual antiplatelet therapy: Minimum 12 months unless bleeding risk outweighs benefit 1, 2