Dosage forms adhesivity

A pulsed system, called Time-Clock System, has been developed. It comprises a solid dosage form coated with a hydrophobie surfactant layer to which a water-soluble polymer is attached to improve adhesion to the core [66]. The thickness of the outer layer determines the time required to disperse in an aqueous environment. Following the dispersion of the outer layer, the eore becomes available for dispersion. An advantage is that eommon pharmaceutical excipients can be used to manufacture this system. Studies performed on human volunteers showed that the lag time was not affeeted by gastrie residence time. Furthermore, the dispersion of the hydrophobic film was not influenced by the presence of intestinal digestive enzymes or by the mechanieal aetion of the stomach. 

The adsorption theory states that the bioadhesive bond formed between an adhesive substrate and tissue or mucosae is due to van der Waals interactions, hydrogen bonds, and related forces. Alternatively, when mucus or saliva are interacting with a solid dosage form, the molecules of the liquid are adsorbed on the solid surface. This is an exothermic process. The free energy of adsorption is given by Eq. (1). 

Adhesive ointments have not been investigated as extensively as have adhesive tablets or adhesive patches. Nevertheless, attempts have been made to utilize this dosage form primarily for local therapy [56]. 

Buccal dosage forms can be of the tablet, patch, gel, or ointment type and can be employed for local or systemic delivery. For local deliveiy, conventional dosage forms such as solutions and various types of tablets (immediate release, effervescent, etc.) are more suitable. These forms generally have uncontrolled drug release with subsequent variable absorption and short residence times, and may not provide sufficient bioavailability. Novel dosage forms such as adhesive tablets, patches, gels, and... 

For liquid (e.g., solution, suspension, elixir) and semisolid (e.g., creams, ointments) dosage forms in permeable or semipermeable container closure systems, a change to an ink and/or adhesive used on the permeable or semipermeable packaging component to one that has never been used in a CDER-approved product of the same dosage form, same route of administration, and same type of permeable or semipermeable packaging component (e.g., low density polyethylene, polyvinyl chloride). 

Sustained adhesion of the dosage form (tablet, patch) to the mucosa is an important first step to successful buccal delivery. The mucus plays an important role during this mucoadhe-sive process by buccal drug delivery systems. The interaction between the mucus and mucoadhesive polymers generally used in most dosage forms can be explained by theories summarized in Table 9.1. 

The buccal mucosa comprises an expanse of smooth and relatively immobile surface and thus is ideally suited to the use of retentive delivery systems. In contrast, the sublingual mucosa is unsuitable for adhesive dosage forms for a number of reasons, including ... 

The sealing agent contacts the dosage form and the forming film. The forming film may be a single film, a coated film, or a laminate. A pouch typically consists of film or laminate which is sealed at the edges by heat or adhesive. 

A pulsed system, called the Time-Clock System, has been developed. The system comprises a solid dosage form coated with a hydrophobic surfactant layer to which a water-soluble polymer is attached to improve adhesion to the core. The thickness of the outer layer determines the time required to disperse in an aqueous environment. After the dispersion of the outer... 

A polymeric film that possesses inherent bioadhesive properties has the added benefit of simplifying the dosage form design and reducing the preparation cost, due to the elimination of the adhesive layer in... 

Bioadhesive polymers are used mainly to overcome the short residence time of drug and the dosage form to improve localization of the drug and to achieve controlled or sustained release of the drug. Bioadhesive polymers can be divided into three broad categories 1) wet adhesives, i.e., polymers that become sticky on hydration 2) polymers that are electrostatic in nature and adhere primarily owing to non-specific and non-covalent interactions and 3) polymers that can bind to a specific site on the cell surface. ... 

Novel dosage forms such as adhesive tablets, patches, gels, and ointments have been developed primarily... 

Smart, J.D. An in vitro assessment of some mucosa adhesive dosage forms. Int. J. Pharm. 1991, 73, 69-74. 

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