The goal of this book is to provide a comprehensive view of the scientific bases on issues surrounding the importance of drug-enzyme and drug-transporter interactions and the quantitative predictions of clinically relevant transporter and enzyme based interactions. Although much progress has been made in predicting in vivo metabolic drug interactions based on in vitro studies, the quantitative prediction of clinically relevant transporter-and enzyme based drug interactions remains to be a challenge. The more complex metabolic drug interactions such as inductive, mechanism-based and allosteric drug interactions render difficulty for prediction in vivo. This book will further assess the progress made in quantitatively predicting metabolic and transporter-based drug interactions as well as highlight areas where such predictions are poor or not possible.