Suger coating tablate
- 1. COATING OF TABLET By, Samir vekariya
- 2. DEFINITION • A tablet coating is a covering over a tablet, used to mask the taste, make it easier to swallow, or protect the active medication inside. A tablet coating is applied to make the tablet smoother and easier to swallow. A tablet coating colors and protects the tablet, and masks a bad taste.
- 3. PURPOSE OF TABLET COATING • Cover the unpleasant taste, odor and color. • Physical and chemical protection in medicine from environment (light, moisture, and air). • Control of drug release as in enteric coating or sustained release or more usually to coated multi particulates. • To protect drug from the gastric environment of the stomach with an acid-resistant enteric coating. • Improve the appearance of tablets. • Assist and facilitate the identification of drug. • Easing the process of blistering.
- 4. TYPES OF TABLET COATING Various kinds of tablet coating Sugar coating Film coating Enteric coating Press coating
- 5. SUGER COATING • Sugar coating is still a widely used coating process because it gives the excellent tablet appearance. • The sugar coating process involves different steps, the duration of which ranges from a few hours to a few days. • A successful product greatly depends on the expertise of the coating operator. • This is especially right in the case of the pan-ladling method, in which the coating solutions are poured over the tablet cores. • The coating operator determines the quantity of solution to add, the rate and method of pouring, when to apply drying air, and how fast or long the tablets should be tumbled in the pan. • Newer techniques utilize spraying systems and varying degrees of automation to improve the coating efficiency and product uniformity. • Regardless of the methods used, a successful sugar coating process yields elegant and highly glossed tablets.
- 6. The basic sugar coating process includes the following steps. Sealing Sub-coating Syruping Finishing Polishing The tablet cores preferably have deep convex surfaces with thin rounded edges to facilitate the sugar coating. Since sugar coating tends to be long and vigorous, the cores should be relatively resistant to breakage, chipping, and abrasion.
- 7. Seal Coating • A seal coat is applied to prevent the moisture penetration into the tablet core. This is especially needed in pan-ladling processes, in which localized over-wetting of a portion of the tablet bed occurs. • The over-wetted tablets would absorb excess moisture without a seal coat, and leads to tablet softening or disintegration and affect the physical and chemical stability of the finished product. • In spray processes, it is possible to adjust the application of the sub-coats and further coats so that localized over-wetting does not occur.
- 8. • This adjustment thus eliminates the seal coating step. Shellac is an effective sealant, but tablet disintegration and dissolution times tend to lengthen on ageing because of the polymerization of the shellac. • Zein is an alcohol-soluble protein derivative from corn. It has also been used as an effective sealant. Lengthening dissolution times have not been reported on the ageing of zein seal coated tablets.
- 9. Subcoating • The sub coating is applied to round the edges of tablets and build up the tablet size. • Sugar coating can enhance the tablet weight by 50-100 percent. • The sub-coating step consists of alternately applying a sticky binder solution to the tablets followed by a dusting of sub-coating powders and then drying. • Consequent sub coats are employed in the same manner until the tablet edges have been covered and the desired thickness is obtained.
- 10. • For spray processes, a sub-coating suspension containing both the binder and the insoluble powder is sprayed intermittently on the moving tablet bed. • With both methods of application, control of the drying rate is critical to obtaining a rapid application of the sub-coat.
- 11. Syrup (Smoothing or Color) Coating • This step is used to cover and fill the imperfections of the tablet surface that is caused by the sub-coating step and to impart the desired colour to the tablet. • This step perhaps needs the most skill. Generally, the first syrup coats that are applied, it contains some suspended powders. It is called as “grossing syrups”. • Dilute colourants can be added to this phase to provide a tinted base that facilitates uniform colouring in later steps. • In general, no colour is added until the tablets are quite smooth; premature application to rough tablets can produce a mottled appearance in the final coated tablets. • In subsequent syruping steps, syrup solutions containing the dye are applied until the final size and colour are achieved. In the final syruping or finishing step, a few clear coats of syrup may be applied.
- 12. Polishing • The desired lustre is obtained in this final step of the sugar coating process. • The coated tablets can be polished in clean and standard coating pans, or in a canvas lined polishing pans. • The tablets can be polished by carefully applying powdered wax (carnauba or beeswax) or warm solutions of these waxes in naphtha or other suited volatile solvents.