Following the Semi-solid Microstructure Workshop sponsored by BASF and hosted by the Rutgers Center for Dermal Research, a pharmaceutical product development working group was formed. The group, known as the Q3 Working Group, selected the following five areas of focus: Particle/Globule Size and Distribution, Viscosity/Rheology/Spreadability, In Vitro Testing, State of API, State of Excipients. A committee was appointed for each of these five areas. The committees were tasked to review the literature, identify best practices, list experimental details required for an independent lab to duplicate the test, and propose scientific studies that may meaningfully advance this specific area of focus. Each committee has a chair (or co-chairs) that are the lead author(s) of the chapter. The Q3 Working Group members serve as the critical reviewers of each chapter, making suggestions thatimprove the quality of the document and that make each of the five chapters uniform in scope and content.

Part I - Critical Quality Attributes: 1. Rheological Characterization in the Development of Topical Drug Products.- 2. In Vitro Release & Permeation Tests as Critical Quality Attributes in Topical Product Development.- 3. Determination of Particle Size and Microstructure in Topical Pharmaceuticals.- Part II - Role of API and Excipients: 4. Quality Assessment of API in Semisolid Topical Drug Products.- 5. The Role of Excipients in the Microstructure of Topical Semi-solid Drug Products.