The science and techniques of restoring patients to health. The United States Pharmacopoeia is a reference volume, published every five years by the U.S. Pharmacopoeial Convention, which describes and defines approved therapeutic agents, as well as sets standards for purity, assay, etc. Suppose a drug has been completely absorbed from its site of application, has reached an equilibrium in its distribution among the several tissues of the body, and that no biotransformation or excretion of the drug has occurred. The capacity of a drug to manifest only one kind of action. Cf. Cf. Drugs are commonly considered capable of participating in one or more of the following general kinds of therapy: A single drug may have two or more therapeutic effects in the same patient at the same or different times, or in different patients. Clinically, the standardized safety margin probably has greater practical meaning than does the therapeutic index, and, unlike the therapeutic index, the meaningfulness of the standardized safety margin does not depend on the parallelism of the dose effect curves from which the LD1 and ED99 are inferred. Drugs that obey first-order kinetics with low doses may obey zero-order kinetics with large doses. A decline in the response to repeated applications of agonist, typically occurring over a relatively short time scale (seconds to hours). In addition to pharmacotherapeutics or drug therapy, there exist coordinate fields of therapeutics such as surgical therapy, psychotherapy, physical therapy, occupational therapy, dietotherapy, etc. Whether or not a system has spare receptors depends upon the nature of the receptor and its coupling to the measured response, the number of receptors, and the intrinsic activity of the agonist. To serve as a basis for quantitative estimation of the effects of the independent variable in excess of those effects produced by non-specific changes in the environment or the experimental system. Cf. The pharmacodynamicist, or pharmacologist, identifies the effects produced by drugs, and determines the sites and mechanisms of their action in the body. In biological experiments, particularly, variability and instability of the biological test system can markedly influence the apparent effects and effectiveness of substances being tested. The definition of a specific T or τ may be explicit or may be inferred from the context in which it is found. If, with increasing doses of material, a time-concentration curve and a dose-effect curve cannot be demonstrated, one cannot conclude that the material is responsible for the effects observed. Selectivity is concerned with site of action; specificity, with the kinds of action at a site. Parameters in one experiment (stimulus strength, for example) might well be independent variables in another. physical dependence: Condition in which the body requires a substance (drug) not normally found in the body in order to avoid symptoms associated with withdrawal, or the abstinence syndrome. In practice, it is useful to know how long it takes for Cmaxto reach some specified level with respect to Css,max, i.e., how long it takes for Cmax/Css,max to reach, say, 0.95. The idea of half-life is legitimately applied only to the case of a drug eliminated from body fluid according to the laws of first-order reaction kinetics. The science and study of the factors which determine the amount of chemical agents at their sites of biological effect at various times after the application of an agent or drug to biological systems. Cf. Half-Life, b, kel, First-Order Kinetics. CI. Confidence Interval. Tolerance typically develops over days to weeks, and is distinguished from tachyphylaxis, a more rapid decline in the effect of a drug. D/Vd = C, when the Vdand F of the drug are known. t½ = 0.301/b = 0.693/kel, where 0.301 and 0.693 are the logarithms of 2 to the bases 10 and e, respectively. One of the elements of an experiment which can be varied, but which the experimenter tries to control or maintain constant during the course of a specific experiment, while intentionally altering the independent variable and observing changes in the dependent variable. It is characteristic of true drug effects that a generally hyperbolic relationship exists between dose and latency. except that the negative control drug lacks the ingredient that is expected to be responsible for the biological effect of the test preparation. Terms of Use. The curves are continuous, i.e. A patient would be considered abnormally sensitive to aspirin if a small fraction of the normal analgesic dose gave adequate pain relief; or, were an abnormally large dose of aspirin required to afford pain relief, the subject would be said to be “insensitive” to aspirin. If a patient manifested an allergic response after raking aspirin, he would be considered hypersensitive to aspirin, regardless of whether the aspirin afforded him relief from pain, and regardless of the size of the dose required to elicit the allergic response. Agents are included on the basis of their therapeutic value. Toxic effects may be idiosyncratic or allergic in nature, may be pharmacologic side effects, or may be an extension of therapeutic effect produced by overdosage. A reference volume published formerly by the American Pharmaceutical Association containing standards of purity and methods of assay for some drugs, and formulae and methods of manufacture for a variety of pharmaceutical preparations. Knowing the expected value of Css,max and the fractional achievement desired, e.g. See also Desensitization, Tolerance. Usually a high degree of sensitivity induced by some specific procedure such as denervation, administration of another drug, etc. The purpose of such a comparison is to express the amount or degree of the designated property in the “other “material as a fraction or multiple of the amount or degree of the property contained in the standard. When monotonicity of a dose-effect curve does not obtain, one may infer that the system under study is not unique or singular: either more than one active agent or more than one effect is under study. 1. ), and the approximate locus of drug distribution may be inferable. 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