The coating is coated with a suitable material on the surface of the tablet.
Types of tablet coating:
Sugar coating and film coating. The film coating is divided into stomach-soluble, enteric-soluble and water-insoluble.
The purpose of tablet coating:
1. Control the release site of the drug in the gastrointestinal tract. For example, a drug that is unstable in gastric acid or stomach enzyme (or a drug that is highly irritating to the stomach) can be made into an enteric coated tablet, which is coated with an enteric coating. The membrane begins to dissolve in the small intestine, so that the drug is released in the small intestine, avoiding the damage of the stomach acid and stomach enzymes.
2. Control the release rate of the drug in the gastrointestinal tract. For example, a drug having a short half-life is formed into a core, and then coated with a suitable polymer film-forming material. By adjusting the thickness and permeability of the coating film, it can control the drug release rate to achieve sustained release, controlled release and long-term effects.
3. Cover up bitterness or bad smell. For example, berberine is bitter after the entrance. But after it is packaged into sugar-coated tablets, it can cover up its bitter taste, and it is convenient to take.
4. Protect the air from moisture and light to increase the stability of the drug. There are some drugs which are very easy to absorb moisture. After coating with a polymer material such as hydroxypropyl methylcellulose (HPMC), the tablet can effectively prevent moisture absorption and deterioration.
5. Prevent changes in the compatibility of drugs. For example, the operator can separately granulate, coat, and compress the two drugs to minimize direct contact between the two.
6. Improve the appearance of the tablet. Some drugs have a poor appearance when they are made into tablets (especially tablets of Chinese herbal medicine), and the appearance of the tablets can be significantly improved after coating.