Aspirin, Nitroglycerin, and Chest Pain: The EMT Playbook
When to give aspirin and nitroglycerin for chest pain, the contraindications the NREMT tests hardest, and why the 12-lead changes the plan.
October 2, 2026 · 6 min read
Chest pain is one of the most common EMS complaints and one of the most tested scenarios. The EMT workup is short: MONA has evolved to 'aspirin, nitro if appropriate, oxygen only if hypoxic, and rapid transport with a 12-lead when equipped.'
Aspirin
- Dose: 324 mg (four 81 mg chewables) or 325 mg tablet chewed.
- Indicated: suspected ACS in an adult without contraindication.
- Hold: true aspirin allergy, active GI bleed, recent hemorrhagic stroke.
Nitroglycerin
- Dose: 0.4 mg SL every 5 min up to 3 doses if BP stays adequate.
- Systolic BP > 100 mmHg required (many systems > 110).
- Hold: PDE-5 inhibitor within 24 h (48 h for tadalafil), right-sided MI (inferior STEMI with RV involvement), severe bradycardia or tachycardia.
Oxygen has changed
Routine high-flow O₂ for ACS is out. Titrate to SpO₂ ≥ 94%. Over-oxygenation can worsen ischemia.
The 12-lead decision
A 12-lead within 10 minutes of patient contact drives destination. STEMI = PCI-capable center. Transmit early. Right-sided leads (V4R) on any inferior STEMI to rule out RV infarct before nitro.
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