Penetration of nicotine and nitrosonornicotine across porcine oral mucosa.

The use of smokeless tobacco (chewing tobacco or snuff) results in contact between this material and the lining of the mouth over relatively long periods of time. As tobacco contains nicotine and a carcinogen, nitrosonornicotine (NNN) there is a likelihood of systemic absorption of both these compounds under these conditions. This study measured the penetration of nicotine and NNN across skin and various regions of oral mucosa. Specimens of porcine skin, keratinized gingiva and non-keratinized floor of mouth and cheek mucosa were placed in perfusion chambers and the flux across these tissues of isotopically labeled water, nicotine and NNN was determined; permeability constants were calculated for each compound and for each region and the values compared statistically. Skin showed a lower permeability than the oral regions to all compounds and floor of mouth was generally the most permeable site. Nicotine passed across oral mucosa almost as rapidly as water, the most permeable region being floor of mouth, whereas gingiva and buccal mucosa showed a similar, but lower, permeability. The non-keratinized oral regions were most permeable to NNN and this can be related to the known distribution of oral carcinomas, regions with the higher permeability being sites that show the greatest tendency to develop such lesions.