Buccal cavity, absorption

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. 

Manning AS, Evered DF (1976) The absorption of sugars from the human buccal cavity. Clin Sci Mol Med 51 127-132... 

Sadoogh-Abasian F, Evered DF (1979) Absorption of vitamin C from the human buccal cavity. Br J Nutr 42 15-20... 

The ergot alkaloids are variably absorbed from the gastrointestinal tract. The oral dose of ergotamine is about 10 times larger than the intramuscular dose, but the speed of absorption and peak blood levels after oral administration can be improved by administration with caffeine (see below). The amine alkaloids are also absorbed from the rectum and the buccal cavity and after administration by aerosol inhaler. Absorption after intramuscular injection is slow but usually reliable. Bromocriptine and cabergoline are well absorbed from the gastrointestinal tract. 

The oral cavity offers a relatively large surface area (the total area of the buccal cavity is approximately 100 cm2) for drag absorption. 

The highly vascular surface of the oral mucosa ensures rapid absorption and onset of action, as well as the maintenance of sink conditions. In particular, the sublingual route is characterized by a rapid onset of action. The buccal cavity offers the combined advantages of a relatively rapid onset of action, with the potential for sustained delivery over several hours. 

The buccal cavity is a useful alternative to the intestinal route for drag absorption in situations where the gastrointestinal route is unfeasible. Examples include ... 

Fig. 3 The influence of pH on the absorption of the weak acid phenobarbitone and the weak base chloroquine from the buccal cavity in three healthy volunteer subjects. (Redrawn from Ref. l)...

Orally administered drugs are mainly absorbed in the small intestine (duodenum, jejunum, and ileum) and in the large intestine (colon) however, other regions, such as buccal cavity, stomach, and rectum, also can be considered potential sites for drug absorption. The various anatomical and physiological characteristics of each segment are briefly described in Table 1. 

Experiments with some analgesics showed that the highly lipid-soluble etorphine was absorbed several times more rapidly from the buccal cavity than the less lipid-soluble morphine. Impressive absorption has been... 

Tarazska MJ, Absorption of clindamycin from the buccal cavity,... 

When dealing with oral dosage forms, it is important to study the various changes occurring within the oral cavity, particularly if a buccal or sublingual formulation is being considered. Table 7 lists the changes within the oral cavity that have thus far been elucidated [124,127,138-144], It is very important to note that there is a decrease in the capillary blood supply to the oral mucosa. This may make it difficult to predict accurately the absorption rates that will occur when... 

One of the most common in vivo methods used to assess the permeability of the buccal mucosa is the buccal absorption test of Beckett and Triggs [13]. In this test, a known volume of a drug solution is introduced into the oral cavity of a subject, who swirls it around for a specified period of time and then expels it. The subject then rinses his or her mouth with an aliquot of distilled water or buffer solution, and the expelled drug solution and rinse are combined and analyzed for drug content. The difference between the initial and final drug concentration in the solution is assumed to be the amount of drug taken up into the oral mucosa. 

Currently, most strategies for buccal delivery of peptide drugs have focused on the application of excipients that would shorten the time of absorption and adhere drugs to a local site on the mucosa, thus decreasing exposure to proteolytic degradation and possible release of drug back into the mouth cavity. This strategy has been utilized in the buccal delivery of insulin, enkephalin, and testosterone [37, 70]. 

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