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Pharmacology is 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. In this book, these substances will usually be referred to as drugs. Medical pharmacology, or pharmacotherapeutics, is the use of drugs to achieve a beneficial therapeutic effect on some process within the patient or to promote toxic effects on the regulatory processes in organisms that are infecting the patient. Pharmacotherapeutics may be further subdivided into pharmacodynamics and pharmacokinetics. Pharmacodynamics (Chapter 2) evaluates the effect of the substance on biologic processes—or, the “effect of the drug on the body.” Pharmacokinetics (Chapter 3) examines the absorption, distribution, and elimination of substances—or, the “effect of the body on the drug.” Toxicology is the branch of pharmacology that deals with the undesirable effects of chemicals on individual cells and humans (medical toxicology) all the way up to their negative effects on complex ecosystems (environmental toxicology).

Humans have been using substances for their medicinal value throughout history. The earliest written records from China and Egypt list many remedies derived from plants and animals, including a few still recognized today as useful drugs. Most, however, were of limited clinical value or were actually harmful. Near the end of the 17th century, observation and experimentation began to replace theorizing in physiology and medicine. In the late 18th and early 19th centuries, experimental animal physiology and advances in chemistry further increased understanding of how chemical substances had their effects at the organ and tissue levels. Eventually, these discoveries led to the concept of drug selectivity in which a drug’s action is related to its structure because of how it specifically binds to a receptor. Also recognized at this time was that drugs could be grouped together into pharmacologic classes based on their chemical structure or physiologic effect. About 60 years ago, a major expansion of research efforts in all areas of biology began. This expansion coincided with the systematic development of controlled clinical trials that allow accurate evaluation of the therapeutic value of drugs. As new concepts and techniques have been introduced, information has accumulated about the action of drugs on their specific receptors. Many fundamentally new classes of drugs as well as new members of old classes have been introduced. Though still in its infancy, the field of pharmacogenomics will likely herald a new era of pharmaceutical intervention in which the knowledge of an individual’s response to drugs based on his or her genes will enable tailoring of medications and dosages to allow more effective medications with ever-safer profiles.

The extension of scientific principles into everyday pharmacotherapeutics is still ongoing. Unfortunately, the drug-consuming public is also exposed to vast amounts of inaccurate, incomplete, or unscientific information regarding the pharmacologic effects of drugs. This has resulted in the faddish use of innumerable expensive, ineffective, and sometimes harmful remedies and ...

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