What is the appropriate dosage and administration of nitroglycerin (sublingual) for a patient with angina or acute chest pain and a history of cardiovascular disease?

How to Prescribe Sublingual Nitroglycerin

Prescribe sublingual nitroglycerin 0.3-0.4 mg tablets with instructions to take one tablet at the first sign of chest pain, and if pain is unimproved or worsening after 5 minutes, call 9-1-1 immediately while taking up to 2 additional doses (one every 5 minutes) for a maximum of 3 tablets total. 1, 2

Prescription Details

Standard dosing:

• Strength: 0.3-0.4 mg sublingual tablets 3, 2
• Quantity: Dispense #100 tablets (typical 3-month supply for prophylactic and acute use) 2
• Refills: 3-5 refills as appropriate 2

Critical Patient Instructions

For acute chest pain (suspected ACS or new/worsening symptoms):

• Take 1 tablet sublingually at first sign of chest pain 1, 2
• If pain is unimproved or worsening after 5 minutes, call 9-1-1 immediately 1, 3
• While waiting for EMS, may take up to 2 additional tablets (one every 5 minutes) for maximum of 3 total doses 1, 2
• This represents a critical update from older recommendations that advised taking 3 doses before calling for help—the new guideline prioritizes earlier EMS activation to reduce mortality 1

For chronic stable angina patients:

• If symptoms significantly improve after the first dose, may repeat every 5 minutes for maximum of 3 doses 1
• If pattern or severity of angina changes (more frequent, severe, or occurs at rest), contact physician immediately 1

Prophylactic use:

• May take 1 tablet 5-10 minutes before activities known to trigger angina 2, 4
• This prophylactic approach is under-utilized but can significantly improve quality of life 4

Administration Technique

Proper use:

• Dissolve tablet under tongue or in buccal pouch—do not chew, crush, or swallow 2
• Patient should sit down before taking to prevent falls from orthostatic hypotension 2
• Tablet may produce burning or tingling sensation, but this should not be used to assess potency 2

Safety Contraindications

Do not prescribe or use if:

• Systolic blood pressure <90 mmHg or ≥30 mmHg below baseline 3, 5, 2
• Heart rate <50 bpm or >100 bpm (in absence of heart failure) 5
• Recent phosphodiesterase-5 inhibitor use (sildenafil, tadalafil, vardenafil) within 24-48 hours—this is an absolute contraindication due to severe hypotension risk 3, 2
• Suspected right ventricular infarction (inferior wall MI on ECG) 3, 5
• Severe anemia or increased intracranial pressure 1
• Hypertrophic cardiomyopathy (may worsen angina) 2

Storage and Potency Instructions

Critical storage requirements:

• Keep tablets in original glass container 2
• Tightly cap after each use to prevent loss of potency 2
• Replace supply every 6 months even if not fully used, as tablets lose potency over time 2

Common Pitfalls to Avoid

Headache management:

• Headaches are common and may indicate drug activity 2
• Use smallest effective dose 1, 2
• Headaches typically diminish with continued use 2

Tolerance concerns:

• Long-acting nitrates may reduce effectiveness of sublingual nitroglycerin 1, 2
• Avoid continuous high-dose use (>10-12 hours daily) to prevent tolerance 2
• Sublingual use for acute episodes rarely causes tolerance 2

Drug interactions:

• Avoid concurrent use with soluble guanylate cyclase stimulators (riociguat) 2
• Caution with alcohol (may cause severe hypotension) 2
• Tricyclic antidepressants and anticholinergics may cause dry mouth, impairing tablet dissolution—consider artificial saliva products 2
• May reduce anticoagulant effect of heparin if used frequently 2

When to Escalate Care

Immediate 9-1-1 activation required if:

• Chest pain persists or worsens after 5 minutes and 1 nitroglycerin dose 1, 3
• Chest pain lasts >20 minutes 6
• Pain is different in character than typical angina 1, 2
• Do not take more than 3 doses (total 0.9-1.2 mg) in 15 minutes without medical evaluation 6, 2

Physician follow-up needed if:

• Pattern or severity of angina changes 1
• Increased frequency of nitroglycerin use 1
• Decreased effectiveness of medication 1

Concomitant Therapy

Always prescribe with:

• Aspirin 81-325 mg daily (unless contraindicated) for secondary prevention 5
• Instruct patient to chew 162-325 mg aspirin immediately if acute chest pain occurs 5