Chapter 19 - Drug release: topical products

Abstract

In vitro release testing (IVRT) is a well-established analytical method used to measure the release rate of an active ingredient from a semisolid dosage form and to characterize the performance of topical drug products. First appearing in the literature more than fifty years ago, it has become a fundamental tool in the development and approval of topical drug products over the last 20 years. Despite the complexity associated with the release of active from a semisolid matrix, these methods have a number of applications and uses and have been primarily used to compare the underlying sameness in product quality characteristics. During the last two decades, various regulatory guidelines have been published, which have accelerated its use and significantly increased publications describing the methodology. This chapter will introduce the concepts, equipment, and theory behind IVRT, describe standard approaches to develop and validate appropriate methods, and discuss the critical parameters of the methods and potential sources of variability that must be well understood in order to implement highly effective methods.