Farmacja Polska (Dec 2021)
The formulation of mucoadhesive drug form for topical application in the oral cavity - application, manufacturing technology and testing methods
Abstract
There are over four hundred different diseases occurring within the oral cavity. These include, among others, mucositis, periodontitis, gingivitis, caries, oral infections, which are usually treated topically. Active substances for topical application in the oral cavity can be administered in the form of polymer films. Polymer films can ensure the delivery of the active substances directly to the affected area and a longer presence of the active substances in the oral cavity, which increases the effectiveness of the treatment. The film is easy to apply and the treatment can be discontinued immediately. The sustained-release systems can reduce the frequency of drug administration, the doses, and side effects. Infections can be caused by damage to the mucosa, and one of the benefits of buccal films is to create a protective barrier on the surface of the damaged tissue, which alleviates pain and increases effectiveness of the treatment. Depending on the active substance applied, the films may have antiseptic, antibacterial, antifungal, anti-inflammatory and analgesic effects. The paper describes the characteristics of the site of application of polymer films, i.e. the oral mucosa and the saliva environment. The advantages of a topical mucoadhesive drug form in comparison with tablets, liquid and semi-liquid formulations have been presented. Furthermore, characteristics of an ideal film for topical application in the oral cavity have been listed. Important factors which have influence on mucoadhesion are factors related to the properties of polymers as well as physical and physiological factors. Currently, there are six theories of mucoadhesion, such as: adsorption theory, diffusion theory, electrostatic theory, fracture theory, wettability theory and mechanical theory. The predominant methods of mucoadhesion testing are in vitro methods, which consist in testing the forces needed to break the connection between the mucoadhesive substance and the model membrane. The most important test methods include: tensile strength and percentage elongation, folding endurance. The polymers used to make the films are of the first and second generation. The first group includes anionic, cationic and non-ionic polymers. The second generation includes thiolated polymers, which can extend the residence time of the therapeutic substance at the site of application and allow for its controlled release. The methods of obtaining polymer films include: pouring method, hot melt extrusion method, semi-solid casting production method, pressing method, solid despersion extrusion method and methods using 3D printers. The film tests include the following: the study of the gel mass, measurement of the film thickness, pH, swelling index, moisture absorption, percentage of moisture, surface characteristics, organoleptic testing, chemical stability testing, disintegration time, drug content uniformity and in vitro drug release.
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