The coating is commonly used in solid form preparation, according to the coating material can be divided into powder coating, coating, coating, coating tablet, capsule, granule coating; divided into sugar coated, film coating, film coating according to different coating materials (with a wide variety of polymer materials as the foundation, including enteric coating, special coating material) (such as stearic acid, paraffin, chitosan); according to different coating technology into spray coating, dip coating, dry pressure coating, electrostatic coating, laminated coating, spray coating which is most widely used, its principle is the coating liquid atomized droplet covered in the material (powder, granules, the tablet surface, and quickly drying) to form coating; coating according to the objective divided into water soluble coating, gastric soluble coating, insoluble coating, sustained-release coating, enteric coating.
Coating effects include:
1.Dampproof, avoiding light and isolating air to increase the stability of the medicine;
Cover up bad smells and reduce irritation;
2.Improve appearance, easy to identify;
3.Control the release part of a drug, such as in gastric juice, easily destroyed by a destroyer and release it in the intestine;
4.Control the rate of drug diffusion and release;
5.To overcome incompatibility. The coating material should have the following requirements: non-toxic, chemically inert, stable in heat, light, water, air, do not react with drug coated; it can dissolve into evenly dispersed in a dispersion medium suitable for coating; the coating layer can form a continuous, firm and smooth, with crack resistance and good water, wet insulation, shading, airtight effect; the solubility should meet certain requirements, sometimes not affected by PH, sometimes can only be dissolved in a specific range of PH.
At the same time, a material with the above characteristics is not common, so it is more inclined to use mixed coating materials to learn from each other.
Tablet coating is the most widely used. It often uses pan coating and buried tube coating (efficient coating machine coating). The latter is better for film coating. The coating with smaller size, such as pellets and powders, is suitable for coating in fluidized beds.
Film coating has many advantages over sugar coating:
1.Shorten the time and reduce the material cost;
2.No significant increase in weight;
3.The bottom coat is not needed;
4.Strong, resistant to crushing and cracking;
5.It can print, and does not affect the engraving of the core;
6.It can affect the effective protection of products from light, air and water;
7.We have no adverse effect on the disintegration time;
8.The product is beautiful;
To provide opportunities for the use of non aqueous coating;
The process and materials can be standardized. Preparation of new product R & D is now generally used in coating film coating, the basic composition of film coating prescription including film-forming agent (coating material), solvent, plasticizer, colorant, can also add porogen and insoluble filler etc.. The formulation of film coating is critical to coating success. The film coating material used in water soluble - hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC) and polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), enteric materials including enteric acrylic resin, hydroxypropyl methyl cellulose phthalate ester two (HPMCP), cellulose acetate phthalate two formic acid ester (CAP), shellac, insoluble materials including ethyl cellulose (EC), maize.