What are the current directions for using nitroglycerin (sublingual tablet) for acute angina pectoris or suspected myocardial infarction?

Directions for Using Nitroglycerin Sublingual Tablet

For acute angina or suspected myocardial infarction, one nitroglycerin tablet (0.4 mg) should be dissolved under the tongue or in the buccal pouch at the first sign of chest pain, and may be repeated approximately every 5 minutes for up to 3 tablets in a 15-minute period. If pain persists after 3 tablets, prompt medical attention is recommended. 1, 2

Proper Administration Technique

• Place the tablet under the tongue or in the buccal pouch - do not swallow, chew, or crush the tablet 1
• If possible, sit down when taking nitroglycerin to prevent falls from potential lightheadedness 1
• The tablet should dissolve completely under the tongue or in the buccal pouch
• A burning or tingling sensation may occur when administered sublingually, but this is not a reliable indicator of potency 1

Prophylactic Use

• Nitroglycerin may be used prophylactically 5-10 minutes before engaging in activities that might trigger an anginal attack 1, 3
• When used prophylactically, nitroglycerin can increase angina-free walking time, delay or abolish ST-segment depression, and increase exercise tolerance 3

Storage and Handling

• Keep nitroglycerin in the original glass container
• Tightly cap the container after each use to prevent loss of tablet potency 1

Important Precautions

• Use with caution in patients who may be volume-depleted or already hypotensive 1
• Do not administer additional nitroglycerin if systolic BP drops below 90 mmHg or 30 mmHg below baseline 2
• Do not administer nitroglycerin to patients who have taken PDE-5 inhibitors (e.g., sildenafil, tadalafil) within 24-48 hours 2
• Use with extreme caution in patients with suspected right ventricular infarction due to risk of profound hypotension 2
• Excessive use may lead to the development of tolerance 1

When to Seek Medical Attention

• If chest pain persists after a total of 3 tablets in a 15-minute period 1
• If the pain is different than typically experienced 1
• If symptoms are unimproved or worsening 5 minutes after taking 1 nitroglycerin dose, call 9-1-1 immediately 4
• For patients with chronic stable angina, if symptoms are significantly improved by 1 dose of nitroglycerin, it is appropriate to repeat nitroglycerin every 5 minutes for a maximum of 3 doses and call 9-1-1 if symptoms have not resolved completely 4

Special Considerations for Suspected Myocardial Infarction

• For patients with suspected acute myocardial infarction, immediately chew 162-325 mg of aspirin (unless contraindicated) in addition to nitroglycerin therapy 4
• Obtain a 12-lead ECG as soon as possible to assess for STEMI or other ischemic changes 2
• If nitroglycerin is ineffective, consider alternative analgesics such as IV morphine, especially if STEMI is diagnosed 2

By following these directions carefully, patients can maximize the effectiveness of sublingual nitroglycerin while minimizing potential adverse effects. Remember that nitroglycerin is a potent medication that requires proper administration and monitoring.