Solid layers based typically on cellulose derivatives and may include plasticizers and pigments. They are usually employed for one or more of the following reasons:

1. Protection of the ingredients (from light or moisture).

2. Masking the bad taste of the drug.

3. Masking possible batchwise differences in the appearance of raw materials and hence allaying possible patient concern over tablets of differing appearance.

4. Coating confers mechanical strength and facilitates handling.

5. Colored coating aids in the rapid identification of a product.

6. Functional film coating is used to impart enteric or controlled-release properties to the tablet.