What is the equivalent dose of nitroglycerin patch for a patient taking 15mg of Imdur (isosorbide mononitrate) daily?

Equivalent Dose of 15mg Imdur to Nitroglycerin Patch

For a patient taking 15mg of Imdur (isosorbide mononitrate) daily, the equivalent dose of nitroglycerin patch is 0.2-0.4 mg/hour (5-10 mg/24h). 1

Dosing Conversion and Application

When converting from oral isosorbide mononitrate to transdermal nitroglycerin:

• Start with a nitroglycerin patch delivering 0.2-0.4 mg/hour (5-10 mg/24h) for patients previously on 15mg Imdur daily 1
• Apply the patch in the morning after discontinuing Imdur
• Remove the patch after 12-14 hours to provide a nitrate-free interval 1
• If angina is inadequately controlled, the dose can be increased to 0.4-0.6 mg/hour (10-15 mg/24h) 1
• Maximum recommended dose is 0.8 mg/hour (20 mg/24h) 1

Preventing Nitrate Tolerance

Nitrate tolerance is a significant clinical concern that requires specific management:

• Apply the patch in the morning and remove it after 12-14 hours to ensure a 10-12 hour nitrate-free interval 1
• Continuous 24-hour nitrate therapy leads to rapid development of tolerance within 24-48 hours 1, 2
• Intermittent patch therapy is superior to continuous therapy in maintaining anti-anginal efficacy 2
• The nitrate-free interval should occur during nighttime when most patients experience fewer angina attacks 3

Important Precautions

• Do not use nitroglycerin within 24 hours of sildenafil use or 48 hours of tadalafil use 4, 1
• Avoid use in patients with:
  • Systolic blood pressure <90 mmHg or >30 mmHg below baseline 4, 1
  • Marked bradycardia (<50 bpm) or tachycardia (>100 bpm) 4, 1
  • Suspected right ventricular infarction 4

Side Effects and Management

• Headache is the most common side effect but typically improves with continued use 1
• If nocturnal angina occurs during the nitrate-free interval, consider:
  • Adjusting the timing of the nitrate-free interval
  • Adding a beta-blocker during the nitrate-free period 1

Special Considerations

• Doses of 0.6-0.8 mg/hour (15-20 mg/24h) are usually optimal for most patients 2
• Abrupt discontinuation during long-term nitrate therapy may exacerbate anginal symptoms 5
• Patient compliance is typically better with once-daily administration of nitrates 5, 6

By following these guidelines, you can effectively transition a patient from 15mg of Imdur daily to an appropriate nitroglycerin patch regimen while maintaining efficacy and minimizing tolerance development.