Rational prescription of drugs based on 'Evidence-Based Medicine' determines the success of the therapy. Quick development of drug resistance necessitates the pragmatic use of drugs with the application of pharmacokinetic and pharmacodynamic principles. The drug chosen for the therapy should maximize the clinical benefits and minimize the unwanted side effects. An ideal prescription should focus on a patient's compliance and success rate of therapy. Rational prescription of drugs at right dose through optimal route of administration with required frequency and duration is the ultimate objective of this book. Hence, this book deals with the selection of a rational drug from the current list of approved drugs. This book emphasizes on the therapeutic approach with the basic input about the essential characteristics of drugs and provides an easy understanding to impart a better knowledge to the readers.