The Organic Chemistry of Drug Design and Drug Action, Fourth Edition presents a unique approach to medicinal chemistry based on physical organic chemical principles and reaction mechanisms that rationalize drug action. The book's coverage allows readers to extrapolate core principles and mechanisms to many related classes of drug molecules. It reflects the significant changes in the process of drug design over the last decade and preserves the successful approach of the previous editions while also including significant changes in format and coverage. It is designed for undergraduate and graduate students in chemistry who are studying medicinal chemistry or pharmaceutical chemistry. Users, including research chemists and biochemists working in pharmaceutical and biotechnology industries will find this update to be useful in their daily work.