Film Coating with Aqueous Latex Dispersions

Latex dispersions have proved to be very useful in aqueous-based film coating, especially in controlled-release applications. Film coatings commonly are colored with pigments to provide a means of product identification and to enable the manufacturer to distinguish similar products. Colored films allow the manufacturer to impart a distinct appearance to the dosage form, which is useful from a marketing standpoint. The use of pigments in film coatings also facilitates patient recognition and makes the product aesthetically appealing. Because both the latex polymer and pigment particles exist in the colloidal or near-colloidal state, interactions caused by surface properties may sometimes lead to unstable formulations. This article examines some of the issues that are important to consider when formulating latex dispersions with pigments.