SECTION I-BASIC PRINCIPLES 1.Introduction-Bertram G.Katzung,MD,PhD INTRODUCTION Pharmacology can be defined as the study of substances that interact with living systems through chemical processes,especially by binding to regulatory molecules and activating or inhibiting normal body processes.These substances may be chemicals administered to achieve a beneficial therapeutic effect on some process within the patient or for their toxic effects on regulatory processes in parasites infecting the patient.Such deliberate therapeutic applications may be considered the proper role of medical pharmacology,which is often defined as the science of substances used to prevent,diagnose,and treat disease.Toxicology is that branch of pharmacology which deals with the undesirable effects of chemicals on living systems,from individual cells to complex ecosystems. THE HISTORY OF PHARMACOLOGY Prehistoric people undoubtedly recognized the beneficial or toxic effects of many plant and animal materials.Early written records from China and from Egypt list remedies of many types,including a few still recognized as useful drugs today.Most,however,were worthless or actually harmful.In the 1500 years or so preceding the present,there were sporadic attempts to introduce rational methods into medicine,but none was successful owing to the dominance of systems of thought that purported to explain all of biology and disease without the need for experimentation and observation.These schools promulgated bizarre notions such as the idea that disease was caused by excesses of bile or blood in the body,that wounds could be healed by applying a salve to the weapon that caused the wound,and so on. Around the end of the 17th century,reliance on observation and experimentation began to replace theorizing in medicine,following the example of the physical sciences.As the value of these methods in the study of disease became clear,physicians in Great Britain and on the Continent began to apply them to the effects of traditional drugs used in their own practices.Thus,materia medica-the science of drug preparation and the medical use of drugs-began to develop as the precursor to pharmacology.However,any real understanding of the mechanisms of action of drugs was prevented by the absence of methods for purifying active agents from the crude materials that were available and-even more-by the lack of methods for testing hypotheses about the nature of drug actions. In the late 18th and early 19th centuries,Francois Magendie,and later his student Claude Bernard. began to develop the methods of experimental animal physiology and pharmacology.Advances in chemistry and the further development of physiology in the 18th,19th,and early 20th centuries laid the foundation needed for understanding how drugs work at the organ and tissue levels. Paradoxically,real advances in basic pharmacology during this time were accompanied by an outburst of unscientific promotion by manufacturers and marketers of worthless "patentSECTION I - BASIC PRINCIPLES 1. Introduction  Bertram G. Katzung, MD, PhD INTRODUCTION Pharmacology can be defined as the study of substances that interact with living systems through chemical processes, especially by binding to regulatory molecules and activating or inhibiting normal body processes. These substances may be chemicals administered to achieve a beneficial therapeutic effect on some process within the patient or for their toxic effects on regulatory processes in parasites infecting the patient. Such deliberate therapeutic applications may be considered the proper role of medical pharmacology, which is often defined as the science of substances used to prevent, diagnose, and treat disease. Toxicology is that branch of pharmacology which deals with the undesirable effects of chemicals on living systems, from individual cells to complex ecosystems. THE HISTORY OF PHARMACOLOGY Prehistoric people undoubtedly recognized the beneficial or toxic effects of many plant and animal materials. Early written records from China and from Egypt list remedies of many types, including a few still recognized as useful drugs today. Most, however, were worthless or actually harmful. In the 1500 years or so preceding the present, there were sporadic attempts to introduce rational methods into medicine, but none was successful owing to the dominance of systems of thought that purported to explain all of biology and disease without the need for experimentation and observation. These schools promulgated bizarre notions such as the idea that disease was caused by excesses of bile or blood in the body, that wounds could be healed by applying a salve to the weapon that caused the wound, and so on. Around the end of the 17th century, reliance on observation and experimentation began to replace theorizing in medicine, following the example of the physical sciences. As the value of these methods in the study of disease became clear, physicians in Great Britain and on the Continent began to apply them to the effects of traditional drugs used in their own practices. Thus, materia medicathe science of drug preparation and the medical use of drugsbegan to develop as the precursor to pharmacology. However, any real understanding of the mechanisms of action of drugs was prevented by the absence of methods for purifying active agents from the crude materials that were available andeven moreby the lack of methods for testing hypotheses about the nature of drug actions. In the late 18th and early 19th centuries, Francois Magendie, and later his student Claude Bernard, began to develop the methods of experimental animal physiology and pharmacology. Advances in chemistry and the further development of physiology in the 18th, 19th, and early 20th centuries laid the foundation needed for understanding how drugs work at the organ and tissue levels. Paradoxically, real advances in basic pharmacology during this time were accompanied by an outburst of unscientific promotion by manufacturers and marketers of worthless "patent