Should I administer nitroglycerin (sublingual nitroglycerin) first to a patient with suspected acute coronary syndrome (ACS) or angina?

Should You Give Nitroglycerin First?

Yes, administer sublingual nitroglycerin immediately as first-line therapy for patients with suspected acute coronary syndrome or angina, provided there are no contraindications. 1, 2

Immediate Administration Protocol

Give one sublingual nitroglycerin tablet (0.3-0.4 mg) at the first sign of chest discomfort. 2, 1 The key steps are:

• Administer the first dose immediately when chest pain begins 1
• Patient should be sitting to minimize risk of hypotension-related falls 2
• Repeat every 5 minutes for up to 3 total doses if pain persists 1, 2
• If pain is unimproved or worsening after the first dose (5 minutes), call 9-1-1 immediately before taking additional nitroglycerin 1

Critical Contraindications - Check Before Administration

Do not give nitroglycerin if any of the following are present:

• Systolic blood pressure <90 mmHg or ≥30 mmHg below baseline 1
• Use of phosphodiesterase-5 inhibitors (sildenafil/vardenafil within 24 hours, tadalafil within 48 hours) 1, 3
• Suspected right ventricular infarction (especially with inferior wall MI) 1
• Severe bradycardia (<50 bpm) or tachycardia (>100 bpm) in absence of heart failure 1

What Comes After Nitroglycerin

While nitroglycerin is given first for symptom relief, aspirin 162-325 mg (chewed, non-enteric coated) should be administered simultaneously or immediately after unless contraindicated. 1 This is the only intervention with proven mortality benefit in ACS. 1

If chest pain persists after 3 sublingual doses (15 minutes total), transition to intravenous nitroglycerin starting at 10 μg/min and titrating upward by 10 μg/min every 3-5 minutes until pain relief or hemodynamic limits are reached. 1, 3

Common Pitfalls to Avoid

• Do not delay EMS activation waiting to see if nitroglycerin works - if pain persists or worsens after one dose at 5 minutes, call 9-1-1 immediately 1, 4
• Do not give more than 3 sublingual doses - this delays definitive care and increases risk of adverse effects 2, 4
• Do not use nitroglycerin as a diagnostic test - lack of response does not rule out ACS 1
• Do not forget to check for phosphodiesterase inhibitor use - this combination can cause life-threatening hypotension 1, 3, 2

Why Nitroglycerin First?

Nitroglycerin works through multiple mechanisms that directly address acute ischemia: it reduces preload through venodilation, modestly reduces afterload, dilates coronary arteries (including collaterals), and may inhibit platelet aggregation. 1 While randomized trials have not shown mortality reduction with nitrates alone, their rapid symptom relief and hemodynamic benefits make them appropriate first-line therapy. 1

The evidence supporting immediate nitroglycerin administration comes from multiple ACC/AHA guidelines (Class I recommendation, Level of Evidence B), which consistently recommend up to 3 doses at 5-minute intervals for acute chest pain. 1

Special Populations

For patients with chronic stable angina who experience complete symptom relief after one dose, they may continue with additional doses (up to 3 total) without immediately calling EMS. 1 However, any patient with suspected ACS (new onset, worsening pattern, or prolonged pain >20 minutes) requires immediate EMS activation. 1