Buccal mucosa oral cavity

Buccal, sublingual, oral cavity Buccal mucosa gingival sulcus Bioadhesive patch biodegradable solution matrix, tablet... 

Oral. The oral route for dmg dehvery includes the gastrointestinal (GI) tract and the oral cavity including the buccal mucosa. The buccal mucosa is considered separately because of differences in the approach to dmg dehvery via this route. 

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. 

At present, despite the advantages offered by the buccal delivery route, such as the bypass of intestinal and hepatic first-pass metabolism for systemic delivery, very few pharmaceutical products employ this route of administration. The reasons that contribute to this situation include (1) high costs associated with development, (2) lack of standardized tests to identify drug candidates suitability for this route, (3) the limited understanding of the impact of metabolism and/or transporters found in the oral cavity mucosa on buccal delivery, and (4) the relatively small number of reports describing the usefulness and safety of excipients/permeation enhancers in humans [82, 83], Therefore, the... 

Excellent accessibility to the buccal mucosa makes application of the dosage form painless. It ean be preeisely loeated, and is easily removed without diseomfort at the end. The oral cavity consists of a pair of buccal mucosae. Hence, a drug delivery system can be applied at various sites, on the same mucosa or on the left or right buccal mucosa on different applications. This is particularly advantageous if the delivery system contains a drug or excipient whieh mildly and reversibly damages or irritates the mucosa. 

A buccal drug delivery system is applied to a specific area on the buccal membrane. Moreover, the delivery system ean be designed to be unidirectional in drug release so that it can be protected from the loeal environment of the oral cavity. It also permits the inclusion of a permeation enhancer/protease inhibitor or pH modifier in the formulation to modulate the membrane or the tablet-mucosal environment at that particular application site. While the irritation is limited to the well-defined area, the systemic toxicity of these enhancers/inhibitors and modifiers can be reduced. The buccal mucosa is well suited for this type of modification as it is less prone to irreversible damage [9]. In the event of drug toxicity, delivery can be terminated promptly by removal of the dosage form. 

The pertinent epithelia tissues of the oral cavity are the buccal and the sublingual ones. They are nonkeratinized tissues, both covered with a thin layer of mucus (Figure 1.8). The first is 500-800 pm thick, whereas the latter is 100-200 pm thick, and more vascularized than the former [121,122]. This difference in thickness may be a possible cause for the diversity in their permeabilities the sublingual is more permeable than the buccal mucosa, and the palatal mucosa is the least permeable. Permeability values of water and horseradish peroxidase (a 40-kDa heme protein commonly used as a permeation label) in the pig oral cavity are shown in Table 1.2. Blood vasculature in both epithelia of the oral cavity does not drain directly to... 

Keratinized epithelium is dehydrated, mechanically tough and chemically resistant. It is found in areas of the oral cavity subject to mechanical stress such as the mucosa of the gingiva (gums) and hard palate (roof of mouth). Non-keratinized epithelium is relatively flexible and is found in areas such as the soft palate, the floor of the mouth, the lips and the cheeks. Thus the regions of the oral cavity pertinent to drag delivery (i.e. the sublingual and buccal regions) have a non-keratinized epithelium. 

The process of maturation from basal cell through to desquamation (shedding) has been estimated at 13 days for the buccal epithelium and this process is probably representative of the oral mucosa as a whole. Thus the rate of cell turnover in the oral cavity is considerably faster than that of skin, which takes approximately 30 days (see Section 8.2.1). 

The permeability of the oral mucosal epithelium is intermediate between that of the skin epithelium, which is highly specialized for a barrier function (see Section 8.1) and the gut, which is highly specialized for an absorptive function. Within the oral cavity, the buccal mucosa is less permeable than the sublingual mucosa. 

A rich blood supply and lymphatic network in the lamina propria serve the oral cavity, thus drag moieties which traverse the oral epithelium are readily absorbed into the systemic circulation. The blood flow in the buccal mucosa is 2.4 mL min 1 cm 2 whereas that to the sublingual mucosa is 0.97 mL min-1 cm 2. 

Mouthwashes, toothpastes and other preparations are introduced into the oral cavity for local prophylactic and therapeutic reasons. It is not known to what extent components of these formulations are absorbed and give rise to systemic effects. The absorption of drugs through the oral mucosa, however, provides a route for systemic administration which avoids exposure to the gastrointestinal system. Dmgs absorbed in this way bypass the liver and have direct access to the systemic circulation. The sublingual, buccal and gingival... 

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