What is the recommended dosing for nitroglycerin (NTG) in the management of angina or suspected myocardial infarction?

Nitroglycerin Dosing for Angina and Suspected Myocardial Infarction

For acute angina or suspected myocardial infarction, one sublingual nitroglycerin tablet (0.4-0.6 mg) should be dissolved under the tongue at the first sign of an attack, which may be repeated approximately every 5 minutes for a maximum of 3 tablets in a 15-minute period, with prompt medical attention recommended if pain persists. 1, 2

Sublingual Nitroglycerin for Acute Management

• Initial dosing: 0.4-0.6 mg sublingual tablet dissolved under the tongue or in the buccal pouch 1, 2
• Repeat dosing: May repeat every 5 minutes until relief is obtained 1
• Maximum dosing: No more than 3 tablets in a 15-minute period 2, 1
• Warning sign: If chest pain persists after 3 tablets in 15 minutes, or if pain is different than typically experienced, prompt medical attention is recommended (potential MI) 1

Patient Instructions for Sublingual NTG Use

• Patients should sit down when taking sublingual NTG to prevent falls due to potential lightheadedness 1
• The tablet should be dissolved under the tongue or in the buccal pouch, not chewed, crushed, or swallowed 1
• For patients with chronic stable angina who have been prescribed NTG previously:
  • If symptoms are significantly improved by 1 dose, they may repeat NTG every 5 minutes for a maximum of 3 doses 3
  • If chest discomfort/pain is unimproved or worsening 5 minutes after 1 NTG dose, the patient should call 9-1-1 immediately before taking additional NTG 3

Prophylactic Use

• NTG may be used prophylactically 5-10 minutes prior to engaging in activities that might precipitate an acute anginal attack 1

Intravenous Nitroglycerin for Acute Coronary Syndromes

For patients requiring IV nitroglycerin (e.g., in acute pulmonary edema or unstable angina):

• Initial dose: Start at 5 mcg/min 2
• Titration: Increase by 5 mcg/min every 3-5 minutes 2
• Alternative initial dosing: 15 μg bolus followed by 5-10 μg/min infusion, increased by 5-10 μg/min every 5-10 minutes 2
• Maximum recommended dose: 20 mcg/min (standard) or up to 200 μg/min in severe cases (with caution due to increased hypotension risk) 2

Long-term Nitrate Therapy Considerations

For patients requiring maintenance therapy:

• Transdermal patches: Initial dose of 0.2 mg/h, increased to 0.4 mg/h after 1-2 weeks, with further titration to 0.6 mg/h or 0.8 mg/h as needed (maximum 0.8 mg/h) 2
• Nitrate-free interval: To prevent tolerance, transdermal patches should be applied for 12-14 hours daily with a 10-12 hour nitrate-free interval (typically overnight) 2

Safety Considerations and Contraindications

• Monitor for hypotension, particularly with upright posture 1
• Contraindicated in patients with:
  • Systolic blood pressure <90 mmHg or ≥30 mmHg below baseline 2
  • Concurrent use of phosphodiesterase-5 inhibitors (within 24-48 hours) 2, 1
  • Right ventricular infarction 2
  • Severe aortic stenosis 2
• Common side effects include headache and hypotension 2
• Excessive use may lead to tolerance 1

Clinical Efficacy

• Field administration of NTG for suspected STEMI has been shown to provide clinically significant pain reduction without causing clinically significant decreases in blood pressure 4
• Intravenous NTG has demonstrated efficacy in reducing ischemic events in unstable angina pectoris 5

Common Pitfalls to Avoid

• Do not administer NTG to patients with systolic BP <90 mmHg as this can cause severe hypotension 2, 1
• Avoid concurrent use with phosphodiesterase inhibitors (e.g., sildenafil, tadalafil) due to risk of severe hypotension 2, 1
• Do not continue administering NTG if a patient develops blurred vision or dry mouth 1
• Ensure proper storage in original glass container, tightly capped after each use to prevent loss of tablet potency 1
• Remember that burning or tingling sensation during administration is not a reliable indicator of tablet potency 1