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Pharmacology may 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. In this book, these substances will be referred to as
drugs. Drugs are administered to achieve a beneficial therapeutic
effect on some process within the patient or for their toxic effects
on regulatory processes in organisms infecting the patient. Such
deliberate therapeutic applications may be considered the proper
role of pharmacotherapeutics, which is often defined as medical
pharmacology (i.e., drugs used to prevent, diagnose, and treat diseases).
Pharmacotherapeutics may be further subdivided into pharmacodynamics
and pharmacokinetics. Pharmacodynamics evaluates the effect of
the substance on biologic processes, and will be discussed in Chapter 2. Pharmacokinetics examines the absorption, distribution, and elimination
of substances, and will be discussed in Chapter 3. Toxicology is
the branch of pharmacology that deals with the undesirable effects
of chemicals on living systems, from individual cells to complex
ecosystems.
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The use of substances for their medicinal value has occurred
throughout history. Prehistoric people undoubtedly recognized the
beneficial or toxic effects of many plant and animal materials. The
earliest written records from China and Egypt list remedies of many
types, including a few still recognized today as useful drugs. Most,
however, were of limited clinical value or were actually harmful.
Around the end of the 17th century, reliance on observation and
experimentation began to replace theorizing in medicine. In the
late 18th and early 19th centuries, methods for experimental animal
physiology and advances in chemistry further increased the understanding
of these chemical substances. This understanding resulted in the
concept of drug selectivity, and that drugs may be grouped together
into pharmacologic classes based on their physiologic effect or chemical
structure. About 50 years ago, there began a major expansion of
research efforts in all areas of biology. This expansion coincided
with the development of controlled clinical trials that allowed
accurate evaluation of the therapeutic value of drugs. As new concepts
and new techniques were introduced, information accumulated about
the action of drugs on the biologic substrate. During the last half
century, many fundamentally new pharmacologic classes and new members
of old classes were introduced.
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The extension of scientific principles into everyday pharmacotherapeutics
is still ongoing. Unfortunately, the drug-consuming public is still
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 the growth of a huge “alternative
health-care” industry. Conversely, lack of understanding
of basic scientific principles and the investigative process has
led to rejection of medical science by a segment of the public,
and a common tendency to assume that all adverse drug effects are
the result of malpractice. Two general principles should form the
basis of understanding for the evidence-based use of drugs. First, all substances may, under certain
circumstances, be toxic. ...