ABSTRACT
The∗ optimization of pharmaceutical formulations with regard to one or more attributes has always been a subject of importance and attention for those engaged in formulation research. Product formulation is often considered an art, the formulator’s experience and creativity providing the “raw material” for the creation of a new product. Given the same active ingredient and a description of the final marketed product, two different scientists will very likely concoct different formulations. Certainly, human input is an essential ingredient of the creative process. In addition to the art of formulation, techniques are available that can aid the scientist’s choice of formulation components that will optimize one or more product attributes. These techniques have been traditionally applied in the chemical and food industries, for example, and in recent years have been applied successfully to pharmaceutical formulations. In this chapter, we describe the application of factorial designs (and modified factorials) and simplex lattice designs to formulation optimization. When the effects of factors on a pharmaceutical process or response are unknown, the use of screening designs to estimate factor effects may be indicated.
16.1 INTRODUCTION The pharmaceutical scientist has the responsibility to choose and combine ingredients that will result in a formulation whose attributes conform with certain prerequisite requirements. Often, the choice of the nature and quantities of additives (excipients) to be used in a new formulation is based on experience, for example, similar products previously prepared by the scientist or his or her colleagues. To break habits based on experience and tradition is difficult. Although there is much to be said for the practical experience of many years, we often become caught in the web of the past. The application of formulation optimization techniques is relatively new to the practice of pharmacy. When used intelligently, with common sense, these “statistical” methods will broaden the perspective of the formulation process.
