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A The Scope of Pharmacology 药理学范畴






A The Scope of Pharmacology


In its entirety, pharmacology embraces the knowledge of the history, source, physical and chemical properties, compounding, biochemical and physiological effects, mechanisms of action, absorption, distribution, biotransformation and excretion, and therapeutic and other uses of drugs. Since a drug is broadly defined as any chemical agent that affects living processes, the subject of pharmacology is obviously quite extensive.


For the physician and the medical student, however, the scope of pharmacology is less expansive than indicated by the above definitions. The clinician is interested primarily in drugs that are useful in the prevention, diagnosis, and treatment of human disease, or in the prevention of pregnancy. His study of the pharmacology of these drugs can be reasonably limited to those aspects that provide the basis for their rational clinical use. Secondarily, the physician is also concerned with chemical agents that are not used in therapy but are commonly responsible for household and industrial poisoning as well as environmental pollution. His study of these substances is justifiably restricted to the general principles of prevention, recognition, and treatment of such toxicity or pollution. Finally, all physicians share in the responsibility to help resolve the continuing sociological problem of the abuse of drugs.


A brief consideration of its major subject areas will further clarify how the study of pharmacology is best approached from the standpoint of the specific requirements and interests of the medical student and practitioner. At one time, it was essential for the physician to have a broad botanical knowledge, since he had to select the proper plants from which to prepare his own crude medicinal preparations. However, fewer drugs are now obtained from natural sources, and, more importantly, most of these are highly purified or standardized and differ little from synthetic chemicals. Hence, the interests of the clinician in pharmacognosy are correspondingly limited. Nevertheless, scientific curiosity should stimulate the physician to learn something of the sources of drugs, and this knowledge often proves practically useful as well as interesting. He will find the history of drugs of similar value.


The preparing, compounding, and dispensing of medicines at one time lay within the province of the physician, but this work is now delegated almost completely to the pharmacist1. However, to write intelligent prescription orders, the physician must have some knowledge of the physical and chemical properties of drugs and their available dosage forms, and he must have a basic familiarity with the practice of pharmacy. When the physician shirks his responsibility in this regard, he invariably fails to translate his knowledge of pharmacology and medicine into prescription orders and medication best suited for the individual patient.

药物的制备、合成与销售一度都是医生的职责,但这项工作现在几乎全归药师了。不过临床医师要想开出合理的处方,必须对药物的理化性质及其现有剂型有所了解,必须基本了解药房业务。若临床医师逃避这方面责任,他肯定用不好药理学及药物知识,从而难以开出适合每位患者的最佳医疗处方。 I

Pharmacokinetics deals with the absorption, distribution, biotransformation, and excretion of drugs. These factors, coupled with dosage, determine the concentration of a drug at its sites of action and, hence, the intensity of its effects as a function of time. Many basic principles of biochemistry and enzymology and the physical and chemical principles that govern the active and passive transfer and the distribution of substances across biological membranes are readily applied to the understanding of this important aspect of pharmacology2.


The study of the biochemical and physiological effects of drugs and their mechanisms of action is termed as pharmacodynamics. It is an experimental medical science that dates back only to the later half of the nineteenth century. As a border science, pharmacodynamics borrows freely from both the subject matter and the experimental techniques of physiology, biochemistry, microbiology, immunology, genetics, and pathology. It is unique mainly in that attention is focused on the characteristics of drugs. As the name implies, the subject is a dynamic one. The student who attempts merely to memorize the pharmacodynamic properties of drugs is foregoing one of the best opportunities for correlating the entire field of preclinical medicine. For example, the actions and effects of the saluretic agents can be fully understood only in terms of the basic principles of renal physiology and of the pathogenesis of edema. Conversely, no greater insight into normal and abnormal renal physiology can be gained than by the study of the pharmacodynamics of the saluretic agents.


Another ramification of pharmacodynamics is the correlation of the actions and effects of drugs with their chemical structures. Such structure-activity relationships are an integral link in the analysis of drug action, and exploitation of these relationships among established therapeutic agents has often led to the development of better drugs. However, the correlation of biological activity with chemical structure is usually of interest to the physician only when it provides the basis for summarizing other pharmacological information.


The physician is understandably interested mainly in the effects of drugs in man. This emphasis on clinical pharmacology is justified, since the effects of drugs are often characterized by significant interspecies variation, and since they may be further modified by disease. In addition, some drug effects, such as those on mood and behavior, can be adequately studied only in man. However, the pharmacological evaluation of drugs in man may be limited for technical, legal, and ethical reasons, and the choice of drugs must be based in part on their pharmacological evaluation in animals. Consequently, some knowledge of animal pharmacology and comparative pharmacology is helpful in deciding the extent to which claims for a drug based upon studies in animals can be reasonably extrapolated to man3.


Pharmacotherapeutics deals with the use of drugs in the prevention and treatment of disease. Many drugs stimulate or depress biochemical or physiological function in man in a sufficiently reproducible manner to provide relief of symptoms or, ideally, to alter favorably the course of disease. Conversely, chemicotherapeutic agents are useful in therapy because they have only minimal effects on man but can destroy or eliminate parasites. Whether a drug is useful for therapy is crucially dependent upon its ability to produce its desired effects with only tolerable undesired effects. Thus, from the standpoint of the physician interested in the therapeutic uses of a drug, the selectivity of its effects is one of its most important characteristics. Drug therapy is rationally based upon the correlation of the actions and effects of drugs with the physiological, biochemical, microbiological, immunological, and behavioral aspects of disease. Pharmacodynamics provides one of the best opportunities for this correlation during the study of both the preclinical and the clinical medical sciences.


Toxicology is that aspect of pharmacology that deals with the adverse effects of drugs. It is concerned not only with drugs used in therapy but also with the many other chemicals that may be responsible for household, environmental, or industrial intoxication. The adverse effects of the pharmacological agents employed in therapy are properly considered an integral part of their total pharmacology. The toxic effects of other chemicals are such an extensive subject that the physician must usually confine his attention to the general principles applicable to the prevention, recognition, and treatment of drug poisonings of any cause.



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