Incomplete and delayed bioavailability of sublingual nitroglycerin.

Area of Science:

• Pharmacology
• Pharmacokinetics

Background:

• Sublingual nitroglycerin is commonly used for angina.
• Its absorption kinetics are not fully characterized.

Purpose of the Study:

• To quantify the absolute bioavailability of sublingual nitroglycerin.
• To determine the extent and rate of sublingual nitroglycerin absorption.

Main Methods:

• Eight healthy males received sublingual nitroglycerin (0.4 mg).
• Mouth rinses analyzed for residual drug after 8 minutes.
• Intravenous nitroglycerin infusions used for absolute bioavailability assessment.
• Plasma concentrations measured by capillary gas chromatography.

Main Results:

• Mean sublingual nitroglycerin bioavailability was 36.2% +/- 24.9%, with a wide range (2.6% to 113%).
• An average of 31.4% +/- 18.9% of the dose remained unabsorbed after 8 minutes.
• Peak plasma concentrations occurred at a mean of 5.3 +/- 2.3 minutes, with some up to 10 minutes.

Conclusions:

• Sublingual nitroglycerin absorption is neither instantaneous nor complete.
• Bioavailability is low and variable, with potentially long absorption times.
• Pharmacokinetic and pharmacodynamic assessments should account for these absorption characteristics.