What is the recommended dosage of Nitroglycerin (NTG) for acute angina or myocardial infarction?

Recommended Dosage of Nitroglycerin (NTG) for Acute Angina or Myocardial Infarction

For acute angina, the recommended dosage of sublingual nitroglycerin is one tablet (0.4 mg) dissolved under the tongue or in the buccal pouch at the first sign of an attack, which may be repeated approximately every 5 minutes until relief is obtained, for a maximum of 3 tablets in a 15-minute period. 1

Sublingual NTG Administration Protocol

For Patients Previously Prescribed NTG:

• Initial dose: One sublingual NTG tablet (0.4-0.6 mg)
• If symptoms persist after 5 minutes: Patient should call 9-1-1 immediately before taking additional NTG 2, 3
• While awaiting EMS: Patient may take additional NTG every 5 minutes up to a maximum of 3 doses total 2
• For chronic stable angina: If symptoms significantly improve after first dose, patient may repeat NTG every 5 minutes for maximum of 3 doses and call 9-1-1 if symptoms don't completely resolve 2

Administration Technique:

• Patient should sit down when taking NTG to prevent falls from potential lightheadedness 1
• Tablet should be dissolved under the tongue or in the buccal pouch, not swallowed 1
• NTG may produce a burning or tingling sensation when administered sublingually 1

Special Considerations and Contraindications

Contraindications:

• Systolic blood pressure <90 mmHg or 30 mmHg below baseline 3
• Concurrent use of phosphodiesterase-5 inhibitors within 24-48 hours 3
• Right ventricular infarction 3
• Severe aortic stenosis 3
• Concomitant use with soluble guanylate cyclase stimulators 1

Precautions:

• Use with caution in volume-depleted patients or those already hypotensive 1
• Hypotension induced by NTG may cause paradoxical bradycardia and increased angina 1
• Nitrate therapy may aggravate angina caused by hypertrophic cardiomyopathy 1
• Tolerance can develop with continuous nitrate exposure beyond 24 hours 3, 1

Intravenous NTG for Unstable Angina/Myocardial Infarction

For patients with unstable angina or myocardial infarction not responding to sublingual NTG:

• Starting dose: 5 mcg/min 3
• Titration: Increase by 5 mcg/min every 3-5 minutes 3
• Maximum recommended dose: 20 mcg/min 3
• Monitor: Blood pressure, heart rate, respiratory status, and clinical symptoms 3

Prophylactic Use

NTG may be used prophylactically 5-10 minutes prior to activities that might trigger an acute anginal attack 1.

When to Seek Emergency Care

Patients should seek immediate medical attention if:

• Pain persists after a total of 3 tablets in a 15-minute period 1
• Pain is different than typically experienced 1
• Symptoms are unimproved or worsening 5 minutes after the first NTG dose 2

Storage and Handling

NTG should be kept in the original glass container and tightly capped after each use to prevent loss of tablet potency 1.