What is the recommended dosing for nitroglycerin in the treatment of angina pectoris?

Nitroglycerin Dosing for Angina Pectoris

Acute Anginal Attack (Sublingual/Buccal)

For acute angina relief, administer 0.3-0.6 mg sublingual nitroglycerin (or 0.4 mg spray) at the first sign of chest pain, repeating every 5 minutes for up to 3 doses over 15 minutes maximum. 1, 2, 3

• If pain persists after 3 tablets in 15 minutes, this is a medical emergency requiring immediate evaluation for possible myocardial infarction. 1, 2, 3
• The patient should rest in a sitting position during administration to minimize hypotension risk. 2, 3
• Onset of action occurs within 1-7 minutes with sublingual tablets or spray. 1

Prophylactic Use

• Administer 0.3-0.6 mg sublingually 5-10 minutes before activities that typically precipitate angina. 2, 3

Intravenous Nitroglycerin for Unstable Angina/Acute Coronary Syndromes

Start at 5-10 mcg/min via infusion pump and titrate upward by 10 mcg/min every 3-5 minutes until symptom relief or blood pressure response occurs. 1, 4

Titration Algorithm

• For the first 20 minutes: Increase by 10 mcg/min every 3-5 minutes. 1, 4
• If no response at 20 mcg/min: Use larger increments (10 mcg/min, then 20 mcg/min). 4
• Once partial response achieved: Reduce increment size and lengthen intervals between increases. 4
• Stop titrating once symptoms resolve—do not continue increasing for blood pressure effect alone. 4

Maximum Dosing

• The commonly used ceiling is 200 mcg/min, though not an absolute maximum. 1, 4
• Prolonged infusions at 300-400 mcg/min for 2-4 weeks have been safely administered without increasing methemoglobin levels. 1, 4
• If doses exceed 200 mcg/min, consider switching to alternative vasodilators. 4

Critical Safety Parameters

• Contraindicated if systolic BP <90 mmHg or >30 mmHg below baseline. 4
• Target systolic BP: Not less than 110 mmHg in normotensive patients. 4
• In hypertensive patients: Do not reduce mean arterial pressure by more than 25%. 4
• Absolutely contraindicated within 24 hours of sildenafil or 48 hours of tadalafil due to risk of profound hypotension and death. 1, 4
• Use with extreme caution or avoid entirely in right ventricular infarction, as these patients depend critically on preload. 4
• Marked bradycardia or tachycardia is a contraindication. 4

Tolerance Management

• Tolerance develops after 24 hours of continuous infusion and is dose and duration dependent. 4
• Increase infusion rate periodically if therapy extends beyond 24 hours. 4
• Transition to oral/topical nitrates within 24 hours once patient is stable and symptom-free for 12-24 hours. 4

Long-Acting Nitrates for Chronic Angina Management

Oral Isosorbide Dinitrate

• Standard formulation: 5-80 mg, 2-3 times daily. 1
• Slow-release formulation: 40 mg once or twice daily. 1

Oral Isosorbide Mononitrate

• Standard formulation: 20 mg twice daily. 1
• Slow-release formulation: 60-240 mg once daily. 1

Transdermal Nitroglycerin

• Dose: 0.2-0.8 mg/hour patch (≥10 mg per 24 hours for efficacy). 1, 5
• Apply for 12-14 hours, then remove for 10-12 hours to prevent tolerance—this nitrate-free interval is essential. 1, 5
• Continuous 24-hour application loses efficacy due to tolerance and offers little advantage over placebo with chronic dosing. 5

Vasospastic Angina Considerations

High-dose calcium channel blockers are primary therapy for vasospastic angina, not nitrates. 1, 6

• Verapamil: Up to 480 mg/day. 1
• Diltiazem: Up to 260 mg/day. 1
• Nifedipine: Up to 120 mg/day. 1
• Long-acting nitrates may be added in combination for additional symptom control. 1
• For acute vasospastic attacks resistant to sublingual nitrates, consider sublingual nifedipine 5-10 mg or intravenous nitrates/calcium antagonists. 6

Critical Pitfalls to Avoid

• Overdosing causes postural hypotension and reflex tachycardia, leading to "paradoxical" angina. 1
• Failure to incorporate nitrate-free intervals of 10-12 hours results in tolerance and loss of efficacy. 1, 5
• An anginal attack unresponsive to short-acting nitroglycerin should be treated as possible myocardial infarction. 1
• Optimize dosing of one anti-anginal drug before adding another. 1
• No dosage adjustment required in renal failure. 2, 3