Excipients functionality: Importance and compendial status

Abstract

Traditional understanding of excipients as simple, inert and inactive ingredients of pharmaceutical preparations was changed when it became clear that they may significantly affect quality, safety and efficacy of pharmaceutical preparations. Excipients variability caused by differences in raw materials and production process may affect their performance in the final formulation. In order to manufacture/compound drug of acceptable quality it is necessary to identify those characteristics of excipients that are important for their intended function, assess mechanism and extent of their influence on the intended function, and define the acceptable range of their values. These characteristics are known as functionality-related characteristics of excipients, and the way and the extent by which excipients fulfill their intended function in final formulation is defined as their functionality. Having in mind that functionality depends on the final formulation and manufacturing/compounding process, it cannot be generalized, but it can be defined in context of certain pharmaceutical preparation, obtained by certain compounding/manufacturing process. This paper discusses definition, importance and compendial status of functionality and functionality-related characteristics of excipients, as well as functionality-related characteristics as critical quality attributes, from the perspective of QbD concept of drug development.