Particulates in semi-solid pharmaceutical products

Abstract

Particles may be found in a wide range of topical pharmaceutical products, whether as active substances, as functional excipients, or as a constituent part of the drug product, as in the case of emulsion droplets. Formulation of a drug substance as solid particulates introduces a dependence on the dissolution of the drug substance to exert its therapeutic benefit, but at the same time offers the possibility of more sustained drug delivery to the target tissue than may be obtained from a solution formulation. Particles may be employed as emulsifiers (Pickering emulsions) and as thickening agents in gel formulations. Finally, particles may be emulsion droplets in cream or lotion formulations, which usually contain one or more active ingredients dissolved in the dispersed phase. In all of these applications, various attributes of the solid particles may be critical to the functionality of the formulation. These attributes, and the principal techniques used for characterizing particulates for these purposes, are described in this chapter. Also reviewed are the unit operations particularly associated with the manufacture of such products, including mixing, material incorporation and size reduction.