This book casts new light on the field of oral drug absorption. It outlines both the concept of the past and the novel concept of Finite Absorption Time (FAT). In addition, the authors explore the correlated need for re-definition of bioavailability, bioequivalence providing a plethora of experimental data. Accordingly, this book is intended for academics/students or scientists working in pharmaceutical industries, regulatory agencies, and contract research organizations. It can be used for teaching purposes in under- and post-graduate courses dealing with biopharmaceutics, pharmacokinetics and biomedical engineering.