Marc B. Brown, BSc (Hons), PhD, CChem FRSC, is the Chief Scientific Officer and Co-founder of MedPharm Ltd. He received his BSc (Hons) and PhD in Pharmaceutical Chemistry from Loughborough University. In 2006, after 14 years working as an academic at King's College London (KCL) and then as Director of Pharmaceutical Development at Hyal Pharmaceutical Corporation in Toronto, Canada, he took up a position as full-time and then part-time Chair of Pharmaceutics in the School of Pharmacy, University of Hertfordshire, where he remained until 2016. During this time, he was also awarded Honorary Professorial positions at the School of Pharmacy, University of Reading and the Institute of Pharmaceutical Science, King's College London. His research interests lie mainly in drug delivery to the skin, nail, and mucosal membranes and he has over 200 publications and 26 inventions describing his work. In 1999 whilst at KCL, Dr Brown co-founded MedPharm Ltd, a contract research organisation specialising in the development of topical and transdermal medicines. He acts as Chief Scientific Officer of MedPharm, which employs approximately 150 people in its GMP/GLP accredited facilities in the United Kingdom and the United States. He and MedPharm have been involved in the development of 50 topical and transdermal medicines and devices that have gained regulatory approval around the world. These include two generic topical products that were approved in the European Union based on bioequivalence testing alone. These submissions utilised MedPharm's validated in vitro and ex vivo performance testing models.

Adrian C. Williams, BSc (Hons), PhD, CChem FRSC, FAPS, FHEA, is Professor of Pharmaceutics and Research Dean (Health) at the University of Reading, UK. Dr Williams started working on transdermal and topical drug delivery for his PhD in 1987, under the supervision of Professor Brian Barry at the University of Bradford. Following his doctorate, he joined the academic staff in the Bradford School of Pharmacy and continued to research varied aspects of skin structure, function, and formulation design as he progressed to Professor of Biophysical Pharmaceutics. He relocated to the School of Pharmacy at the University of Reading in 2004 and established a research group working on novel topical and transdermal formulations, as well as other areas of formulation science. He has supervised over 50 postgraduate and postdoctoral researchers on projects funded by research councils, charities and industry. He has published over 200 articles, reviews, and book chapters which have been cited 14,000 times. Dr Williams sits on the editorial boards of the Journal of Pharmacy and Pharmacology and the Journal of Pharmaceutical Sciences, acts as a peer reviewer for national and international funding bodies and is also a member of advisory boards for international conferences and pharmaceutical companies. He is a Fellow of the Academy of Pharmaceutical Sciences and of the Royal Society of Chemistry.

Drs Brown and Williams have known each other for more than 30 years, and have worked together in supervising PhD student projects in the United Kingdom and United States.

Chapter 1: Structure and Function of Human Skin. Chapter 2: Theoretical Aspects of Transdermal and Topical Drug Delivery. Chapter 3: Chemical Modulation of Topical and Transdermal Permeation. Chapter 4: Physical and Technological Modulation of Topical and Transdermal Drug Delivery. Chapter 5: Topical and Transdermal Formulation Development.; Chapter 6: Performance Testing. Chapter 7: Process Development Considerations for Topical and Transdermal Formulations.