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Many tablets today are coated after pressing. Although sugar coating was popular in the past, the process has many drawbacks. Modern tablet coatings are based on polymers and polysaccharides, including plasticizers and pigments. Tablet coatings must be stable and strong enough to handle the tablet, not hold the tablets together during the coating process, and follow the fine contours of letters or logos embossed on the tablet. Coating is necessary for tablets with an unpleasant taste, and a smooth finish makes larger tablets easier to swallow. Tablet coatings are also useful for extending the shelf-life of ingredients sensitive to moisture or oxidation. Special coatings (for example with a pearlescent effect) can increase brand recognition.
If the active ingredient in the tablet is sensitive to acid, or irritating to the stomach lining, an enteric coating can be used, which is resistant to stomach acid, and dissolves in less acidic areas of the intestine. Enteric coatings are also used for drugs that may be negatively affected by taking longer to reach the small intestine, where they are absorbed. Coatings are often chosen to control the rate of drug dissolution in the gastrointestinal tract. Some drugs are better absorbed in certain parts of the digestive system. If this part is the stomach, then a coating is selected that quickly and easily dissolves in acid. If the absorption rate is best in the large intestine or colon, a coating that is acid resistant and dissolves slowly is used to ensure that the tablet reaches that point before disintegration. To measure the disintegration time of tablet coating and tablet core, automatic disintegration tester is used which is able to determine the complete disintegration process of a tablet by measuring the remaining height of thickness with each upward stroke of the disintegration tester basket.
There are two types of coating machines used in the pharmaceutical industry: coating pans and automatic coaters. Coating pans are mostly used to sugar coat pellets. Automatic coaters are used for all types of coating; They can be equipped with a remote control panel, a dehumidifier, and dust collector. Application of coatings containing alcohol requires an explosion-proof design.
