Buccal absorption measurement

Although the undissociated (un-ionized) form of a drug has the higher lipid solubility, the un-ionized moieties themselves have differing lipid solubilities. A common way of assessing the lipid solubility of a drug is to measure its oil-water partition coefficient. As with pH, buccal absorption has been shown to be positively correlated with a drug s oil-water partition coefficient. 

Buccal Absorption of Acids. When a data set contains high log D values, quadratic terms in log D enter in to regression analyses just as with high log P s. Beckett and Moffat (6) measured the buccal absorption rates for a range of carboxylic acids (Table III). Again we find the rates are correlated well with an equation in log D terms alone (eq 7). An optimum log D of 3.28 can be calculated. The best alternative analysis is eq 8 7). 

Buccal Absorption at Various pH s. I would like to show you one additional example that supports the premise that log D correlations relate to the amount of a compound at a site, that I find very impressive. Not only can one combine data for the absorption of acids and bases, but the regression results hold for any pH (any pH not affecting the system itself). Schurman and Turner (8) measured the buccal absorption rate of propranolol and n-hexylphenylacetic acid from pH 4 to pH 9. (Table IV). The absorption rate for these compounds is well described by the simple equation 9. A quadratic equation (10) provides an even better fit. 

Methods for studying the permeability of intact mucosa comprise of techniques that exploit the biological response of the organism locally or systemically and those that involve direct local measurement of uptake or accumulation of penetrate at the surface. The most widely used methods include in vivo studies using animal models, buccal absorption tests, and perfusion chambers for studying drug permeability. 

Drug transport and availability have also been measured for routes of administration other than oral. Rectal absorption of acetaminophen and salicylate , buccal absorption of barbituates and a series of n-alka-noic acids , peritoneal dialysis " , penetration across the vitreous barrier of the eye , and the significance of vehicle composition in the skin penetration of fluocinolone acetonide were all studied. 

This is usually done by gavage, (direct intubation into the stomach) or by administration of encapsulated material. This allows accurate measurement of the amount administered and an accurate time of administraton. It is not usually done by mixing with the feed or drinking water, as the material would frequently not be acceptable to the animal and the amount consiuned would not be known. This method of administration omits one area of exposure which is important in human accidental exposure, emd that is absorption in the mouth or buccal area however, there is no reasonable way to overcome this. 

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