During formulation of solid dosage forms, film coating is used to improve the appearance and stability of tablets, make them easier to swallow, mask the taste, modify or sustain release, protect the drug from the harsh gastric environment, protect from moisture and/or oxidation and, as a result, to improve the stability and overall therapeutic effect of the final drug product. Depending on the individual needs, a polymer with appropriate properties is chosen during formulation development to serve as film-coating matrix. In addition to the polymer which is solubilized in a solvent, the coating formulation typically includes additives such as plasticizers, anti-tacking agents and pigments. This solution is sprayed onto a rotating or fluidized tablet bed and subsequent drying leads to removal of the solvent, resulting in a deposition of coating material around each tablet core.
Pre-mixed solutions are commonly used for tablet film coating. These solutions offer ease-of-use as no additional formulation is required and can reduce the time needed for designing compounds and sourcing ingredients. While a pre-mixed solution can offer greater convenience, they increase dependence on an individual supplier and reduce flexibility in the formulation which can prolong the response time to regulatory requests if an ingredient needs to be changed. In addition, there will be limited ability to adapt the formulation if incompatibilities arise. Instead, many formulators prefer to design the coating composition themselves to tailor it to their specific needs.