What is the recommended dose of nitroglycerin for treating angina pectoris?

Nitroglycerin Dosing for Angina Pectoris

For acute anginal attacks, administer sublingual nitroglycerin 0.3-0.6 mg (up to 1.5 mg) at the first sign of chest pain, repeating every 5 minutes for up to 3 doses over 15 minutes; if pain persists after 3 tablets, seek immediate medical attention as this may represent myocardial infarction. 1, 2

Acute Symptom Relief (Short-Acting Nitroglycerin)

Sublingual Administration

• Dose: 0.3-0.6 mg sublingual tablet dissolved under the tongue at first sign of angina 3, 1, 2
• Repeat dosing: May repeat approximately every 5 minutes until relief is obtained 1, 2
• Maximum acute dosing: Up to 3 tablets over 15 minutes 1, 2
• Critical safety point: If pain persists after 3 tablets in 15 minutes, this constitutes a medical emergency requiring immediate evaluation for possible myocardial infarction 3, 1, 2

Sublingual Spray Alternative

• Dose: 0.4 mg spray as needed 3
• Duration of effect: Similar to sublingual tablets (1-7 minutes onset) 3

Prophylactic Use

• Timing: Administer 5-10 minutes before activities that may precipitate angina 1, 2
• Patient positioning: Patient should rest in sitting position during administration to minimize risk of postural hypotension 1, 2

Intravenous Nitroglycerin for Unstable Angina/Acute Coronary Syndromes

Initial Dosing and Titration

• Starting dose: 5-10 mcg/min via infusion pump 4
• Titration schedule: Increase by 10 mcg/min every 3-5 minutes for the first 20 minutes until symptom relief or blood pressure response 4
• After 20 mcg/min: Use larger increments (10-20 mcg/min) if no response 4
• Commonly used ceiling: 200 mcg/min, though not an absolute maximum 3, 4
• Extended dosing: Prolonged infusions at 300-400 mcg/min for 2-4 weeks have been safely administered without increasing methemoglobin levels 3, 4

Critical Contraindications and Safety Parameters

• Absolute contraindications:

  • Systolic blood pressure <90 mmHg or >30 mmHg below baseline 3, 4
  • Phosphodiesterase inhibitor use within 24 hours (sildenafil) or 48 hours (tadalafil) due to risk of fatal hypotension 4
  • Marked bradycardia or tachycardia 3, 4
  • Right ventricular infarction (extreme caution or avoid entirely as these patients are preload-dependent) 4

• Blood pressure targets:

  • Maintain systolic BP ≥110 mmHg in normotensive patients 4
  • In hypertensive patients, do not reduce mean arterial pressure by more than 25% 4

Tolerance Management

• Onset of tolerance: Develops after 24 hours of continuous infusion 3, 4
• Management strategy: Increase infusion rate periodically if therapy extends beyond 24 hours 3, 4
• Transition timing: Convert to oral/topical nitrates within 24 hours once patient is stable and symptom-free for 12-24 hours 3, 4
• Gradual discontinuation: Taper dose gradually rather than abrupt cessation to avoid rebound ischemia 3

Long-Acting Nitrate Formulations for Chronic Management

Oral Isosorbide Dinitrate

• Dose: 5-80 mg, 2-3 times daily 3
• Slow-release formulation: 40 mg once or twice daily 3
• Duration of effect: Up to 8 hours 3

Oral Isosorbide Mononitrate

• Standard formulation: 20 mg twice daily 3
• Slow-release formulation: 60-240 mg once daily 3
• Duration of effect: 12-24 hours 3

Transdermal Nitroglycerin

• Dose: 0.2-0.8 mg/hour patch 3
• Application schedule: Apply for 12-14 hours, then remove for 10-12 hours to prevent tolerance 3, 5
• Duration of effect: 8-12 hours during intermittent therapy 3
• Tolerance prevention: Patches lose efficacy by 24 hours with continuous use; intermittent dosing is essential 5

Special Considerations for Vasospastic Angina

Acute Attack Management

• First-line: Sublingual nitroglycerin 0.3-0.4 mg, repeat after 3-5 minutes if needed 6
• Alternative for resistant cases: Sublingual nifedipine 5-10 mg 6
• Intravenous options: Nitroglycerin or isosorbide dinitrate 2-10 mg IV 6

Chronic Prevention

• High-dose calcium channel blockers are primary therapy: Verapamil up to 480 mg/day, diltiazem up to 260 mg/day, or nifedipine up to 120 mg/day 3
• Combination therapy: Most patients require long-acting nitrates combined with high-dose calcium antagonists for symptom control 3

Common Pitfalls to Avoid

• Overdosing: Excessive nitroglycerin causes postural hypotension and reflex tachycardia, leading to "paradoxical" angina 3
• Continuous nitrate exposure: Results in tolerance within 24 hours; always incorporate nitrate-free intervals of 10-12 hours 3, 5
• Ignoring non-response: An anginal attack unresponsive to short-acting nitroglycerin should be treated as possible myocardial infarction 3
• Polypharmacy without optimization: Optimize dosing of one anti-anginal drug before adding another; three-drug regimens may provide less protection than two drugs 3