A study into the mucosal absorption of isosorbide dinitrate at different intraoral sites

This study measured the absorption of isosorbide dinitrate (ISDN) into the systemic circulation after application of tablets to the buccal, palatal, or sublingual mucosa in six healthy subjects. After 1 minute serum levels were detectable by gas liquid chromatographic analysis from buccal and sublingual sites. Levels progressively increased, peaking at 5 minutes, and then progressively decreased during the 30-minute sampling period. At most of the time periods serum levels were greater from sublingual sites than from buccal sites. ISDN levels were not detected at any time in any subject after application to the palatal mucosa. As with the skin, the keratinized layer of the oral mucosa may be an important barrier to absorption. The findings appear relevant to the delivery of drugs via the oral mucosa for systemic effect.