Film coatingMastering formulation and the coating process
Tablets are the most widely used oral dosage form, a large proportion of which are coated with a film-forming composition. Seppic develops effective and easy-to-use film coating agents for medications and dietary supplements, thanks to its expertise in film coating, and in selecting compositions based on a tablet’s type and desired functionality.
The tablet coating process
The coating process results in the formation of a thin layer of polymer around the tablet. This layer, 20 to 100 µm thick, represents approximately 1 to 10% of the tablet’s initial weight. During coating, the formulation is applied to the tablet core in a coating turbine.
A complex step in tablet production
Coating technology involves having an expansive knowledge of ingredients and their interactions, expertise in formulation and in the various coating processes, in order to produce a smooth, regular and homogeneous film that completely covers the surface of the tablet. This requires the interaction between three elements:
- The tablet core, designed to withstand the mechanical stresses applied during the coating process and to facilitate the adhesion of the film to the tablet’s surface. The tablet’s shape strongly influences the mixing characteristics in the film-coating turbine and the uniformity of the final film on the tablets.
- Formulation of the coating, with its composition and viscosity.
- The coating process, and equipment, which strikes a delicate balance between atomization of the coating dispersion, and drying. The final quality of the film-coated tablets relies on critical process parameters.
Expertise in coating formulation
The film-coating formulation combines four key ingredients:
- A film-forming polymer, which provides the mechanical strength of the film. The most widely used polymers in non-functional film coating are cellulose derivatives such as hypromellose.
- Plasticizers, used to improve the flexibility of the film formed and prevent it from cracking or breaking. They work by weakening the attraction between the polymer molecules to make the film more malleable.
- Coloring agents, which increase opacity, protect from light, and color the film.
- Fillers, which can be added to reduce tack and improve slip, or to adjust the content of insoluble materials in the coating composition.
Seppic draws on in-depth knowledge of these different parameters of the coating stage and their interconnections, and its expertise in formulation, to develop robust, efficient, and ready-to-use formulations to facilitate the coating process by its customers. These formulations combine a film-forming polymer, plasticizer, and fillers, either with or without coloring agents, with appropriate grades selected and optimized proportions.
The many benefits of film coating
Beyond the aesthetic dimension, the coating film plays a major role in the therapeutic adherence and functional properties of tablets:
- It prolongs the shelf life of the tablets by protecting them from light, moisture and oxidation. For instance, Seppic has developed Sepifilm™ LP for the protection of active ingredients sensitive to humidity.
- It improves the appearance of the tablets, especially when the active pharmaceutical ingredient, or the nutraceutical active ingredient, is colored or produces an inhomogeneous color. Coating films can be colored, which can serve as brand recognition or to differentiate different medications taken by the patient.
- It facilitates the patient’s ingestion by smoothing the surface of the tablet.
- It improves the taste and masks the odors associated with the active pharmaceutical ingredients and the nutraceutical active ingredients.
- It controls the release of the active ingredient. The use of specific polymers can delay the release of the active ingredient, or target different sites of the gastrointestinal tract, depending on the pH.
Know-how in natural coloring
Natural coloring is a growing trend. Different natural dyes exist such as beta-carotene or curcumin. However, designing film-coating agents based on natural dyes remains a challenge, especially to obtain a color that is stable over time.
By combining its coloring know-how and expertise in film-coating formulation, Seppic has developed ready-to-use colored film-coating agents Sepifilm™ Naturally Colored for dietary supplements. These film-coating agents are formulated with coloring foodstuffs obtained from fruits, vegetables and edible plants, by a simple physical process in water. They demonstrate remarkable color fastness when the tablets are exposed to light.