Can sublingual (under the tongue) nitroglycerin be used in a patient who is already on a nitroglycerin (nitroglycerin) drip?

Use of Sublingual Nitroglycerin While on Nitroglycerin Drip

Sublingual nitroglycerin can be used in patients already on a nitroglycerin drip when there is ongoing ischemic pain, but careful blood pressure monitoring is essential to avoid hypotension.

Rationale for Combined Use

Sublingual nitroglycerin provides rapid relief of acute ischemic symptoms while intravenous nitroglycerin offers more precise, continuous control. The American College of Cardiology/American Heart Association guidelines support this approach:

• Patients with ischemic discomfort should receive up to 3 doses of sublingual or aerosol nitroglycerin at 3-5 minute intervals until pain is relieved or low blood pressure limits its use 1
• Intravenous nitroglycerin can be titrated for more precise minute-to-minute control, but sublingual nitroglycerin can still be used for breakthrough symptoms 1

Protocol for Administration

When considering sublingual nitroglycerin in a patient already on a nitroglycerin drip:

1. Check blood pressure first:

   • Ensure systolic BP is >90 mmHg before administration 1
   • Avoid if systolic BP is <90 mmHg or ≥30 mmHg below baseline 1

2. Dosing:

   • Standard dose: 0.4 mg (1 tablet) sublingually
   • May repeat every 3-5 minutes for up to 3 doses if pain persists and BP remains stable 1

3. Monitoring:

   • Continuous vital sign monitoring is essential
   • Watch for hypotension for several minutes after each dose 1
   • Have IV access already established 1

Special Considerations and Contraindications

Avoid combined use in patients with:

• Hypotension (SBP <90 mmHg) 1
• Extreme bradycardia (<50 bpm) 1
• Tachycardia in absence of heart failure (>100 bpm) 1
• Right ventricular infarction 1
• Recent use of phosphodiesterase inhibitors (sildenafil within 24 hours, tadalafil within 48 hours) 1

Management of Adverse Effects

The most serious potential complication is hypotension, which can worsen myocardial ischemia 1. If hypotension occurs:

1. Discontinue nitroglycerin
2. Elevate legs
3. Administer rapid IV fluid bolus
4. Consider atropine if bradycardia is present 1

Evidence of Safety

Research suggests that high-dose sublingual nitroglycerin rarely causes significant hypotension, with an incidence of only 3.2% in one study 2. Even in patients with aortic stenosis (traditionally considered a contraindication), the risk of clinically relevant hypotension requiring intervention was not significantly increased when nitroglycerin was used for acute pulmonary edema 3.

Clinical Benefits

The combination approach allows for:

• Immediate relief of breakthrough pain with sublingual formulation
• Continuous background vasodilation with IV drip
• Potential reduction in infarct size when treatment begins early 1

Sublingual nitroglycerin spray may offer advantages over tablets, including faster onset of action and lower incidence of headache, particularly in patients with dry mouth 4.