The therapeutic respon of a drug is normally dependent on an adequate concentration of the drug being achieved and then maintained at the site or sites of action of the drug. In the ca of systemically acting drugs (i.e. drugs that reach the sites via the systemic circulation), it is generally accepted for clinical purpos that a dynamic equilibrium exists between the concentration of drug at its site(s) of action and the concentration of drug in blood plasma. An important conquence of this dynamic equilibrium is that it permits a therapeutically effective concentration of drug to be achieved at its site(s) of action by adjustment of the concentration of drug in blood plasma. 一件难忘的事开头
药物的治疗反应通常是依赖于适当的药物达到并保持在该位点或药物的作用部位的浓度。在全身作用药物的情况下（即药物通过全身血液循环达到这些位点），它是公认的临床用途，在其部位的药物浓度之间存在一种动态平衡的作用和血浆中的药物浓度。这种动态平衡的一个重要后果是，它允许一个治疗有效药物浓度保持在其位点实现的血药浓度的调节作用。
Strictly speaking, the concentration of drug in plasma water (i.e. protein-free plasma) is a more accurate index of drug concentration at the site(s) of action than the concentration of
drug in whole plasma since a drug may often bind in a reversible manner to plasma protein. Only drug which is unbound (i.e. dissolved in plasma water) can pass out of the plasma through the capillary endothelium and reach other body fluids and tissues and hence its site(s) of action. Drug concentration in whole blood is also not considered to be an accurate indirect index of the concentration of drug at its site(s) of action since drug can bind to and enter blood cells.
严格地说，血浆（即水无蛋白血浆）中的药物浓度是药物浓度更准确的指标对比于当药物往往结合在一个可逆的血浆蛋白在血浆药物时的浓度。只有药物是未结合（即溶解在血浆中的水）可以从血浆通过毛细血管内皮细胞渗透到其他体液和组织中，在它的位点起作用。由于药物可以结合并进入细胞，所以血液中的药物浓度也不被认为是在其作用部位的药物浓度准确的间接指标。
However, to measure the concentration of an unbound drug in plasma water requires more complex and nsitive assay methods than to measure the total concentration of both unbound and bound drug in total plasma. Thus, for clinical purpos, drug concentra
大鼓和小鼓tion in blood plasma is usually measured and is regarded as an index of drug concentration at the site(s) of action of the drug and of the clinical effects of the drug. However, it should be realized that this is a simplification and may not always be valid. Indeed one should not draw inferences about the clinical effects of a drug from its plasma concentration until it has been established that the two are consistently correlated.
手抄报读书然而，衡量一个非结合药物在血浆中的浓度比测量未结合的和总血浆结合药物的总浓度需要更复杂的和敏感的检测方法。因此，临床用途，血药浓度的测量通常是被认为是在作用部位的药物浓度指数以此来衡量药物的作用和药物的临床疗效。然而，应该认识到，这是一个简化和可能并不总是有效的。我们的确不应该从药物的血浆浓度的临床效果来推论，除非两者已建立了相关关系。
It has been assumed that the plasma drug concentration is directly proportional to the clinical effect of that drug.
The concentration of drug in blood plasma depends on numerous factors. The include the relative amount of an administered do that enters the systemic circulation, t
he rate at which this occurs, the rate and extent of distribution of the drug between the systemic circulation and other tissues and fluids and the rate of elimination of the drug from the body.
血浆药物浓度已被假定为与该药物的临床效果成正比。
血浆中药物的浓度取决于许多因素。这些包括一个剂量进入体循环的相对量，该反应发生的速率，药物分布在循环系统的速率和程度和其他组织和体液和体内的药物消除率。
Apart from the intravenous route of drug administration, where a drug is introduced directly into the blood circulation, all other routes of administering systemically acting drugs involve the absorption of drug from the place of administration into the blood.电脑检测不到硬盘1 Drug must be absorbed in a sufficient quantity and at a sufficient rate in order to achieve a certain blood plasma concentration which, in turn, will produce an appropriate concentration of drug at its site(s) of action to elicit the desired therapeutic respon.
长沟
除了药物静脉给药，当药品被直接进入血液循环系统作用的时候，所有其他方式的全身作
用的给药都涉及药物如何从给药位置到达血液。药物必须吸收足够量和有足够的速度才能达到一定的血浆浓度，反过来，通过在其位点上产生一个适当的药物浓度的行为来得到想要的治疗作用。
It follows that there are two aspects of drug absorption which are important in clinical practice, namely, the rate and the extent to which the administered do is absorbed. Simply becau a certain do of a drug is administered to a patient，there is no guarantee (except for intravenous administration) that all of that do will reach the systemic circulation. The fraction of an administered do of drug that reaches the systemic circulation in unchanged form is known as the bioavailable do.
絮乱
因此，药物的吸收在临床实践中有很重要的两个方面，即吸收剂量的速率和程度。因为给病人服用一定剂量的药物，不能保证（除静脉给药）所有的剂量都达到全身血液循环。药物到达体循环而不发生变性的剂量被称为生物有效剂量。hp进bios
The relative amount of an administered do of a particular drug which reaches the systemic circulation intact and the rate at which this occurs is known as the bioavailability
of that drug. Bioavailability is thus concerned with the quantity and the rate at which the intact form of a particular drug appears in the systemic circulation following administration of that drug. The bioavailability exhibited by a drug is thus very important in determining whether a therapeutically effective concentration is achieved at the site(s) of action of the drug.
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