FILM-COATING OF TABLETS

Film coatings of tablets

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A film coating is a thin shell formed on the surface of a microsphere (pellets). Tablets or granules after drying of the film-forming substance solution applied to their surface. The thickness of the film coating layer is approximately from 5 to 50 microns. The droplets of the coating liquid are sprayed onto the initial particles. The supplied process air evaporates the liquid and dries the film layer on the surface of the particles. The small droplet size and low viscosity ensure uniform distribution of the film on the particle surface. An important point when applying the coating is a very uniform application of the coating material. The coatings must be dense, without mechanical damage and cracks. Film coating is an effective way of applying protective...

Film coatings for modified-release applications

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Modified release film coatings can be applied to pharmaceutical products to achieve modification, control the release of a medicinal substance. All coatings on the kinetics of drug release can be divided into the following four types: Coatings that provide periodic release of LV (intermittent release). This type includes coatings resistant to the effects of gastric juice — intestinal soluble coatings. Coatings that provide instant release of LV. Coatings that provide a steady (continuous) release of LV. Coatings that provide delayed (delayed) release of LV. Let's look at each type of coatings in more detail. Coatings that provide periodic release of the medicinal substance. This type of coating provides a prolonged effect of the dosage form, when injected into the body, LV is released in portions,...

Coatings that provide medicine substance release

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With this type of coating, the medicinal substance from the tablets can be released instantly. These types of coatings include polymers developed by BASF: polyvinyl alcohol (PVA), Kollicoat IR white and Kollicoat Protect. PVS-based films are very elastic, but the coating process is possible only in a narrow range of varying technological parameters. This polymer is rapidly dispersed in water during the preparation of the dispersion for the film coating, forms shiny, non-sticky and very flexible films that do not crack during storage. The addition of a plasticizer is not required to create a coating. Kollicoat IR can be replaced by GPMC and other coatings with immediate release of LV in new tablet preparations. The use of Kollicoat IR increases the cost-effectiveness of the coating...

Problems encountered during coating application

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As in the case of sugar coatings, problems may arise after or during the application of the film coating. Tablets, Pellets and granules on which the coating is applied may not be strong enough or delaminate during the coating process. Due to the fact that film coatings are relatively thin, their ability to hide defects is significantly lower than that of sugar coating. When using a film coating, various problems may arise. One example is sticking, which occurs when the fluid flow rate exceeds the drying rate, which causes the gluing of tablets, pellets and granules and their further destruction.

Fluidized bed coating application

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The application of film coatings is carried out in apparatuses for combined granulation, drying and coating processes. A distinctive feature is the lower location of the nozzle. There are two possible ways of organizing the process: applying a film coating directly to crystals or granules containing a medicinal substance; conducting a preliminary stage — layering the medicinal substance on inert particles (pellets are most often used), after which a film coating is applied. During the coating process, a layer of particles is placed in a fluidized bed apparatus.

Coating methods and equipment

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In modern pharmaceutical production, the following methods of applying film coatings are used.Coating in drums; coating in a fluidized bed (spraying from above, spraying from below, coating tangentially); technology of jet fluidization. Coating in drums has already been discussed in the section "Methods and equipment for coating".The technological parameters of the film coating process are: temperature, quantity and humidity of incoming and outgoing air, spray rate and pressure from the nozzle, layer temperature. At the same time, the technological parameters can be adjustable (temperature and amount of incoming air), unregulated (humidity at the inlet) and fixed (spray rate and duration of the process. DIOSNA has developed a vertical centrifugal coater VCC (from the English coater — coating plant). Unlike conventional drum-type coating systems, the VCC...

Coating of pellets, pellets and tablets

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After the tableting process, the finished tablet most often needs to be coated. In the modern pharmaceutical industry, the importance of tablet coating is increasing.

Encapsulation by fluidized bed coating method

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Application of coatings in a fluidized bed of fine particles under supercritical conditions is a new developing technology designed for encapsulation of thermolabile products. Supercritical liquids are unique solvents because their density is similar to the densities of liquids, while the viscosity and diffusion coefficient are close to these indicators for gases. Spraying of supercritical solutions makes it possible to obtain droplets and particles of submicron size, as well as to spray on other particles. Since the cohesive and adhesive forces for supercritical solutions are small compared to these indicators for organic solvents, the capillary compression force is insignificant.

Dredge coating for tablets

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The term “coated coating” comes from the French word “dragee” and means “applying a sugar coating”. A drained tablet consists of a core tablet containing a medicinal substance (substance) and a coating containing several excipients. The core tablet must be mechanically strong. Tablets to be drained should not have a flat shape to avoid sticking together. Let’s consider one of the old methods of coating — sugar coating. Sugar coating is an effective way of applying large layers of coatings, primarily to mask the taste. This type of coating is used for temperature-sensitive and brittle solid dosage forms. The first stage of this technology is the spraying of a solution for spraying onto a particle (tablet, pellet). The air supplied to the device evaporates the…

Substances for film coating of tablets

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The main components in most finished dosage forms with a film coating are polymers, plasticizers, dyes and solvents (or the liquid phase). Polymers. Ideal properties for the polymer are solubility in a wide range of solvents for the variation of the composition of the finished dosage form, the possibility of creating a coating with suitable mechanical properties, and the corresponding solubility in gastrointestinal fluids - such as not to reduce the bioavailability of medicinal substances. The most suitable polymers for film coatings are cellulose esters, especially hydroxypropylmethylcellulose (HPC), hydroxypropylcellulose (HPC), with which slightly sticky coatings are obtained, and methylcellulose (MC), although this polymer can slow down the dissolution of the medicinal substance. Alternatives to cellulose esters are acrylic copolymers (such as methacrylic and methyl methacrylic...