Overview, Advantage And Disadvantage Of Buccal Tablet

Buccal tablet are drugs intended to be dissolved in buccal pouches. Tablets are designed not to disintegrate. It is placed near the opening of the parotid duct to provide the medium to dissolve the tablet.

Buccal tablet

Owing to the ease of the administration, the oral cavity is an attractive site for the delivery of drugs. Through this route it is possible to realize mucosal (local effect) and transmucosal (systemic effect) drug administration.

Advantages Of Buccal Tablet

Buccal mucosa has an excellent accessibility, an expanse of smooth muscle and relatively immobile mucosa, hence suitable for administration of controlled release dosage tablets. Additionally, buccal tablets have a high patient acceptability compared to other non-oral transmucosal routes of drug administration.

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Direct access to the systemic circulation through the internal jugular vein avoids acid hydrolysis in the gastrointestinal (GI) tract and bypasses drugs from the hepatic first pass metabolism leading to high bioavailability. Moreover, rapid cellular recovery of the buccal mucosa is another advantage of this route.

Disadvantages Of Buccal Tablet

Disadvantages of drug delivery by this route are the low permeability of the buccal membrane, specifically when compared to the sublingual membrane, and a smaller surface area. The total surface area of the membranes of the oral cavity available for drug absorption is 170 cm² of which ∼50 cm² represents non-keratinized tissues, including the buccal membrane.

Continuous secretion of saliva (0.5–2 l/day) leads to subsequent dilution of the drug. Swallowing of saliva can also potentially lead to the loss of dissolved or suspended drug and, ultimately, the involuntary removal of the dosage form.

There are some problems associated with buccal drug delivery of which hazard of choking by involuntarily swallowing the tablets is a concern. Additionally, such a dosage form is inconvenient when the patient is eating or drinking or unconscious.

Anatomy Of Buccal Route

The buccal mucosa consists of a surface layer of stratified squamous epithelium linked to the underlying connective tissue (lamina propria and submucosa) by a basal lamina. In the connective tissue a network of blood capillaries is present where drugs that have permeated through the epithelium can enter the systemic circulation. The surface layers of the epithelium (approximately the uppermost 25–30%) are reported to be the main barrier to the penetration of substances.

The drug transport pathways across buccal mucosa can be both transcellular and paracellular, but for many hydrophilic drugs the permeation is mainly due to passive diffusion via the paracellular route.

Design Of Formulations For Buccal Tablet

Buccal adhesive tablets with the size 1–3 cm and a daily dose of 25 mg or less are preferable. The maximal duration of buccal delivery is approximately 4–6 h.

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Ideally pharmaceutical buccal adhesive tablets should contain mucoadhesive agents, penetration enhancers and enzyme inhibitors. Mucoadhesive agents are used to maintain an intimate and prolonged contact of the formulation with the absorption site while penetration enhancers improve the drug permeation across mucosa (trans-mucosal delivery) or into deepest layers of the epithelium (mucosal delivery). The enzyme inhibitors ideally protect the drug from the degradation by means of mucosal enzyme.

Although saliva secretion facilitates the dissolution of drug, involuntary swallowing of saliva also affects its bioavailability. These disadvantages can be avoided by developing unidirectional release systems with backing layer. This concept may also results in high drug bioavailability.

Types Of Buccal Tablet

Two types of tablets i.e. monolithic and double-layered matrix tablets have been investigated for buccal delivery of drugs.

Monolithic Tablets

Monolithic tablets consist of a mixture that contains drug and swelling bioadhesive/sustained release polymer. These tablets exhibit a bidirectional release. They can be coated on the outer or on all sides but one face with water impermeable hydrophobic substances to allow a unidirectional drug release for systemic delivery. They include use of viscous natural or synthetic gums or mixtures of gums can be compressed to form a hydrated surface layer from which the medicament slowly diffuses and is available for absorption through buccal mucosa.

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Double Layered Tablets

Double layered tablets comprise an inner layer based on a bioadhesive polymer and an outer non-bioadhesive layer containing the drug for a bi-directional release but mainly a local action. In the case of systemic action, the drug is loaded into the inner bioadhesive layer whereas the outer layer is inert and acts as a protective layer. Alternatively, the drug is loaded into a controlled release layer and diffuses towards the absorbing mucosa through the bioadhesive layer, whereas a water impermeable layer assures the mono-directional release.