Tablets — Texture Application Note

Tablet coating has numerous functionalities including tablet strengthening, controlled release, ease of handling and packaging, protect the tablet from moisture, improve taste, facilitate swallowing, and provide tablet identity. The film coating often contains polymers, plasticisers, water-soluble dyes, pacifiers (such as titanium dioxide), various inorganic materials (such as iron oxides), and talc. Plasticisers improve flexibility and reduce brittleness otherwise caused by polymers. The titanium dioxide serves to increase adhesion and the talc minimises tackiness between coated tablets. These compounds service to improve tablet appearance (e.g., colour and opacity), film coating and barrier properties.

The adhesion of a coating to a tablet is influenced by the strength of interfacial bonds between film and tablet surface and the internal stresses within the coating. Poor adhesion results in peeling, markedly reducing film functionality. The mechanical protection provided by the coating can also be compromised by loss of adhesion, leading to the accumulation of moisture at the film-tablet interface. This can have profound effects on the stability of moisture-labile drugs.