How do I order nitroglycerin for an adult with suspected or known angina after confirming there are no contraindications such as severe hypotension, recent phosphodiesterase‑5 inhibitor use, severe anemia, elevated intracranial pressure, or nitrate allergy?

How to Order Nitroglycerin for Angina

For acute angina, administer sublingual nitroglycerin 0.4 mg (or 0.3-0.6 mg) every 5 minutes for up to 3 doses while the patient is sitting; if chest pain persists after 3 doses over 15 minutes, seek immediate medical attention as this may represent acute coronary syndrome requiring emergency intervention. 1, 2

Sublingual Nitroglycerin for Acute Angina Relief

Immediate administration protocol:

• Place one 0.4 mg tablet under the tongue at the first sign of anginal chest pain 1, 2
• Patient must be sitting during administration to prevent orthostatic hypotension and syncope 1, 3
• Repeat dosing: If pain persists after 5 minutes, give a second tablet 2
• Third dose: If pain continues after another 5 minutes, give a third tablet 2
• Critical decision point: If chest pain persists 5 minutes after the third tablet (total 15 minutes), this represents treatment failure requiring immediate emergency medical attention 1, 2

Prophylactic use before anticipated angina:

• Administer 5-10 minutes before activities known to precipitate angina (exercise, sexual activity, cold exposure) 1, 2

Intravenous Nitroglycerin for Refractory or High-Risk Angina

When to escalate to IV nitroglycerin:

• Ongoing ischemic chest pain unrelieved by 3 sublingual doses 1
• Hypertension with angina 1
• Heart failure or pulmonary congestion with angina 1
• High-risk unstable angina or non-ST elevation MI 1

IV nitroglycerin dosing protocol:

• Starting dose: 10 mcg/min via continuous infusion using non-absorbing tubing 1
• Titration: Increase by 10 mcg/min every 3-5 minutes until symptom relief or blood pressure response 1
• If no response at 20 mcg/min, increase increments to 10-20 mcg/min 1
• Practical ceiling: 200 mcg/min is commonly used as maximum dose 1
• Goal: Titrate to symptom relief; blood pressure reduction is not required if symptoms resolve 1

Important tolerance considerations:

• Tolerance develops after 24 hours of continuous IV therapy 1
• May require periodic dose increases to maintain efficacy beyond 24 hours 1
• Avoid abrupt discontinuation; taper gradually to prevent rebound ischemia 1

Absolute Contraindications (Class III - Do Not Give)

Check these before ANY nitroglycerin administration:

• Hypotension: Systolic BP <90 mm Hg OR ≥30 mm Hg below baseline 1, 4, 5
• Phosphodiesterase-5 inhibitor use: 1, 4, 5
  • Sildenafil (Viagra) or vardenafil within 24 hours
  • Tadalafil (Cialis) within 48 hours
  • Avanafil within 12 hours
  • Risk: Profound, potentially fatal hypotension 1, 4
• Right ventricular infarction: Patients are preload-dependent; nitrates cause catastrophic hemodynamic collapse 1, 4, 5
• Severe bradycardia: Heart rate <50 bpm 1, 4, 5
• Tachycardia without heart failure: Heart rate >100-110 bpm in absence of HF 1, 4, 5
• Severe anemia 1, 3
• Elevated intracranial pressure 1, 3

Critical Clinical Pitfalls to Avoid

Always obtain right-sided ECG in inferior STEMI before giving nitroglycerin:

• Up to 50% of inferior MIs involve the right ventricle 4
• RV infarction requires adequate preload; nitrates are potentially lethal in this setting 4

Specifically ask about erectile dysfunction medications:

• Patients may not volunteer this information 4
• Must inquire about sildenafil, tadalafil, vardenafil, and avanafil use in preceding 24-48 hours 4, 5

Monitor blood pressure closely:

• Recheck BP before each sublingual dose if patient appears symptomatic 1
• Continuous BP monitoring required during IV infusion 1

Long-Acting Nitrates for Chronic Angina Prophylaxis

Alternative formulations when appropriate:

• Transdermal nitroglycerin patches: 0.2-0.8 mg/hour for 12 hours daily (remove for 12-hour nitrate-free interval to prevent tolerance) 1
• Isosorbide mononitrate: 60-240 mg once daily (extended release) 1
• Isosorbide dinitrate: 5-80 mg 2-3 times daily 1

Tolerance prevention is mandatory:

• Provide 10-12 hour nitrate-free interval daily to maintain efficacy 1, 6
• Continuous dosing (≥3 times daily or 24-hour patches) causes complete tolerance 6

Common Side Effects

• Headache: Occurs in up to 82% of patients; usually diminishes with continued use 7
• Orthostatic hypotension: Common but often asymptomatic; may cause dizziness, weakness, or syncope 3, 7
• Nearly 10% of patients cannot tolerate nitrates due to disabling headaches or dizziness 7