What is the recommended dosing for nitroglycerin (sublingual tablets) in acute angina attacks?

Nitroglycerin Dosing for Acute Angina

For acute angina attacks, take one 0.3-0.4 mg sublingual nitroglycerin tablet at the first sign of chest pain, and if pain is unimproved or worsening after 5 minutes, call 9-1-1 immediately before taking additional doses. 1, 2

Sublingual Tablet Dosing Protocol

Initial Dose and Emergency Response

• Take 1 tablet (0.3 or 0.4 mg) sublingually at the first sign of anginal chest pain 2
• If chest pain is unimproved or worsening after 5 minutes following the first dose, call 9-1-1 immediately to access emergency medical services BEFORE taking additional nitroglycerin 1
• This represents a critical change from older protocols—the emphasis is now on early activation of emergency services rather than completing a full course of nitroglycerin first 1

Dosing for Chronic Stable Angina (Different Protocol)

• In patients with chronic stable angina whose symptoms are significantly improved by the first dose, repeat nitroglycerin every 5 minutes for a maximum of 3 doses 1, 2
• Call 9-1-1 if symptoms have not resolved completely after 3 doses in 15 minutes 2
• The distinction here is important: if the first dose provides significant relief, you can continue; if not, activate emergency services immediately 1

Administration Technique

• Dissolve the tablet under the tongue or in the buccal pouch—do not chew, crush, or swallow 2
• Patient should sit down during administration to prevent falls from lightheadedness or dizziness 2
• Use caution when returning to standing position 2

Prophylactic Use

• Take nitroglycerin 5-10 minutes before activities that might precipitate an acute anginal attack 2
• This is appropriate for patients who can predict their angina triggers 2

Intravenous Nitroglycerin Dosing (Hospital Setting)

When to Use IV Nitroglycerin

• Consider IV nitroglycerin for persistent anginal pain after sublingual nitrate therapy, or if acute coronary syndrome is accompanied by hypertension or pulmonary edema 1
• Use only in hemodynamically stable patients with systolic blood pressure ≥90 mm Hg 1

IV Dosing Protocol

• Start at 10 mcg/min and titrate upward by 10 mcg/min every 3-5 minutes until pain relief or hemodynamic response occurs 1, 3, 4
• Commonly used ceiling dose is 200 mcg/min, though doses up to 300-400 mcg/min have been safely administered 3
• After reaching 20 mcg/min without response, use larger increments (10-20 mcg/min) 3

Critical Safety Parameters for IV Use

• Do not initiate if systolic BP <90 mm Hg or >30 mm Hg below baseline 3
• Avoid in suspected right ventricular infarction 1
• Absolute contraindication: phosphodiesterase-5 inhibitor use within 24 hours (sildenafil/vardenafil) or 48 hours (tadalafil) due to risk of profound hypotension, MI, and death 1, 3
• Tachyphylaxis develops after approximately 24 hours of continuous infusion 1, 3

Important Caveats and Pitfalls

Tolerance Development

• Use only the smallest effective dose to prevent tolerance development 2
• Excessive sublingual use (scores of tablets daily for >10-12 hours) can lead to tolerance, though this is uncommon with appropriate use 2
• With IV infusions, tolerance is dose and duration dependent, typically developing after 24 hours 3

Hemodynamic Concerns

• Severe hypotension can occur, particularly in volume-depleted patients or those already hypotensive 2
• Hypotension may be accompanied by paradoxical bradycardia and increased angina 2
• Monitor blood pressure closely, especially in elderly patients 1

Drug Interactions

• Absolute contraindication with recent PDE5 inhibitor use (within 12-48 hours depending on agent) 1
• Concomitant alcohol use may cause hypotension 2
• Nitrate therapy may aggravate angina caused by hypertrophic cardiomyopathy 2

Storage and Potency

• Keep nitroglycerin in the original glass container, tightly capped after each use to prevent loss of potency 2
• The burning or tingling sensation under the tongue should NOT be used as a reliable indicator of tablet potency 2

When Nitroglycerin Fails

• If pain persists after 3 tablets in 15 minutes, or if the pain is different than typically experienced, seek prompt medical attention 2
• This may indicate acute myocardial infarction rather than stable angina 1