This book delves into the complexities of transdermal patches, addressing the pivotal role of adhesion in ensuring optimal drug delivery. It provides a comprehensive overview of the factors influencing adhesion, materials used in patch formulation, and innovative testing methods. It explores the latest advancements in materials, testing techniques, the impact of environmental factors on patch performance, and FDA regulatory expectations for adhesion testing of transdermal products. This book is intended for researchers, pharmaceutical scientists, regulatory professionals, and healthcare professionals involved in drug delivery systems.