Bases buccal absorption

Wagner, J. G. Sedman, A. J., Quantitation of rate of gastrointestinal and buccal absorption of acidic and basic drugs based on extraction theory, J. Pharmacokinet. Biopharm. 1, 23-50 (1973). 

The importance of pH on drug absorption from the mouth has been extensively studied using the buccal absorption model, in which loss of drug from buffered drug solutions placed in the mouth is monitored. The influence of pH on the absorption of the weak base chloroquine and of the weak acid phenobarbitone is shown in Fig. 

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. 

Buccal Absorption of an Acid and a Base at Six pH Values and Physicochemical Constants Used for Eq 9, 10... 

Eq. Ill [345] correlates the buccal absorption rate constants of an acid (p-hexylphenylacetic acid, pK = 4.36) and a base (propranolol, pK = 9.45) at different pH values with log Papp values (Table 16) [345, 470]. 

Absorption from the buccal cavity has been shown to follow exactly the same principles as those described for absorption from the stomach and intestine. The pH of human and canine saliva is usually about 6. Bases in people are absorbed only on the alkaline side of their pK, that is, only in the nonionized form. At normal saliva pH, only weak bases are absorbed to a significant extent. 

A request for a waiver of in vivo B A/BE studies based on the BCS is not appropriate for dosage forms intended for absorption in the oral cavity (e.g., sublingual or buccal tablets). 

Rgure 9.15 Relationship between the log P of solute and the percentage absorption through the buccal mucosa of human subjects for bases (O) and acids ( )... 

Tissue-based systems evaluation of transport mechanism segmental absorption evaluation evaluation of absorption enhancing strategies other tissues (nasal, buccal) comparison between species possible presence of nerves (e.g., local control, crypt-villus axis) transporters and enzymes as in vivo limited database viability of tissue low throughput limited access to (human) tissue... 

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