What are the recommended nitroglycerin (NTG) doses for an adult patient?

Nitroglycerin Dosing for Adults

Sublingual Nitroglycerin for Acute Angina

For acute angina, administer 0.4 mg sublingual nitroglycerin (tablet or spray), repeatable every 5 minutes up to a maximum of 3 doses (total ≤1.5 mg). 1

• The first dose may range from 0.3 mg to 0.6 mg, though 0.4 mg is most commonly used 1
• Onset of action occurs within 1–7 minutes, with hemodynamic effects persisting for at least 25 minutes 1
• Call emergency services if chest pain is unchanged or worsens 5 minutes after the first dose 1
• If symptoms persist after 3 sublingual doses, transition to intravenous nitroglycerin 1

Dose-Response Evidence

• Studies demonstrate a clear dose-response relationship: 0.4 mg and 0.8 mg sublingual spray produce significantly greater exercise time to angina onset compared to 0.2 mg 2, 3
• The 0.4 mg dose produces effects similar to 0.8 mg and is the standard recommended dose 1, 2

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Intravenous Nitroglycerin for Persistent Angina/ACS

Start IV nitroglycerin at 5–10 µg/min and titrate by 5–10 µg/min every 3–5 minutes until symptom relief or blood pressure response is achieved. 1, 4, 5

Titration Protocol

• Initial dose: 5–10 µg/min via continuous infusion through non-absorbing tubing 1, 5
• Titration increments: Increase by 5–10 µg/min every 3–5 minutes 1, 6
• If no response at 20 µg/min, switch to 10 µg/min increments, then 20 µg/min increments as needed 1, 4
• Maximum recommended rate: 200 µg/min, though doses up to 300–400 µg/min have been shown safe in select cases 1, 4, 6

Critical Monitoring Parameters

• Maintain systolic blood pressure (SBP) >110 mmHg in normotensive patients 4, 6
• In hypertensive patients, do not reduce SBP by more than 25% below baseline within the first hour 6
• Continuous blood pressure monitoring is mandatory; consider arterial line placement for higher doses or borderline BP 6

Common Pitfall: Tolerance Development

• Tolerance develops after 7–8 hours of continuous infusion and becomes significant after 24 hours 1, 4
• Patients requiring IV nitroglycerin beyond 24 hours may need periodic dose escalation to maintain efficacy 4
• Even at 300–400 µg/min, methemoglobin levels do not increase significantly during short-term use 4

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Transdermal Nitroglycerin for Chronic Stable Angina

Apply transdermal patches delivering 0.2–0.8 mg/hour for 12 hours daily, followed by a mandatory 12-hour nitrate-free interval to prevent tolerance. 1, 4

• Patches should be applied to clean, dry, hairless skin 1
• Remove after 12 hours and allow a 12-hour nitrate-free period before re-application 1, 4
• Maximum dose is 0.8 mg/hour every 12 hours 4
• Tolerance develops within 24–48 hours of continuous exposure without a nitrate-free interval 1, 7

Evidence on Tolerance

• High-dose transdermal nitroglycerin (30–60 mg/24 hours) produces significant antiischemic effects on day 1, but tolerance develops by day 2 even with intermittent (12-hour on/12-hour off) dosing 7
• The 10–12 hour nitrate-free interval is essential to prevent tolerance 1

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Oral Nitrates for Chronic Stable Angina

For chronic prophylaxis, use isosorbide mononitrate 20 mg twice daily with asymmetric dosing (e.g., 7 AM and 2 PM) to maintain a nitrate-free interval. 1

• Isosorbide dinitrate: 5–80 mg 2–3 times daily 1
• Isosorbide mononitrate: 10–20 mg twice daily with asymmetric dosing (7 AM and 7 hours later) to prevent tolerance 8
• Once-daily controlled-release isosorbide mononitrate (120–240 mg) does not produce tolerance and provides sustained daytime exercise duration 8

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Absolute Contraindications

Nitroglycerin is absolutely contraindicated within 24 hours of sildenafil or vardenafil, within 48 hours of tadalafil, and within 12 hours of avanafil due to risk of profound hypotension, MI, and death. 1, 4

Additional Contraindications

• SBP <90 mmHg or >30 mmHg below baseline 1, 4, 6
• Right ventricular infarction (obtain right-sided ECG leads [V4R] in all inferior STEMI patients before giving nitrates) 1, 4
• Marked bradycardia or tachycardia 4
• Advanced aortic stenosis 6

Critical Safety Point

• Query all patients for erectile dysfunction medication use before administering nitroglycerin 1
• Document PDE5-inhibitor use and timing in every chest pain evaluation 1
• Patients must be educated never to combine nitrates with PDE5 inhibitors 1

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Special Considerations for Hypertensive Emergencies

For hypertensive emergencies, initiate IV nitroglycerin at 5 µg/min and increase in 5 µg/min increments every 3–5 minutes. 6

• Do not reduce SBP by more than 25% within the first hour 6
• IV nitroglycerin is indicated for both blood pressure control and ischemia relief in hypertensive acute coronary syndrome 1

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Key Clinical Caveats

• Volume-depleted patients are at high risk for excessive hypotension with rapid titration 6
• Headache is a common side effect that may require symptomatic management 6
• Use extreme caution in right ventricular infarction due to preload dependence 1, 4, 6
• Non-absorbing tubing must be used for IV administration to prevent drug loss 1, 5