药学英语Unit7 Text A 注释及译文

Unit Seven

Text A Biopharmaceutics

Before the reader can appreciate the meaning and clinical significance of

biopharmaceutics, it is necessary to introduce the concept of drug bioavailability.

1. appreciate [ə'pri: ʃ ieit] vt. 欣赏；感激；领会；鉴别

vi. 增值；涨价

2. bioavailability ['baiəuə,veilə'biləti] n. 生物利用度；生物药效率

为了使读者能够理解生物药剂学的含义和其对于药物临床应用的重要意义，有必要先给大家介绍一下药物生物利用度的概念。

Bioavailability

The therapeutic response 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 case of systemically acting drugs ( i. e. drugs that reach these

sites via the systemic circulation) it is generally accepted for clinical purposes 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 consequence 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. 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. However, to measure the concentration of an unbound drug in plasma water

requires more complex and sensitive assay methods than to measure the total

concentration of both unbound and bound drug in total plasma. Thus, for clinical

purposes, drug concentration 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. It has been assumed that the plasma drug concentration is

directly proportional to the clinical effect of that drug.

1. systemically [ sistə'mætikəli ] adv. 有系统地，有组织地，有条理地，全身地

systemic [si'stemik; -'sti:-] adj.系统的；体系的；全身的

2. purpose ['pə:pəs] n. 目的；用途；意志 vt. 决心；企图；打算

3. dynamic equilibrium [dai'næmik] [,i:kwi'libriəm] 动态平衡；动力平衡

4. plasma ['plæzmə] n. 等离子体；血浆

5. reversible [ri'və:səbl] adj. 可逆的；可撤消的；可反转的n. 双面布料

6. capillary endothelium [kə'piləri, 'kæpi-] [,endəu'θi:liəm] 毛细血管内皮

7. assay [ə'sei] n. 化验；试验vt. 分析；化验；尝试vi. 鉴定；经检验证明内含成分

8. simplification [,sɪmpləfə'keʃən] n. 简单化；单纯化

9. valid ['vælid] adj. 有效的，有根据的；正当的

10. draw inferences ['infərəns] 作出推论

11. consistently [kən'sistəntli] adv. 一贯地；一致地；坚实地

12. proportional to [prə'pɔ:ʃənəl] 与……相称，与……成比例

通常情况下，药物达到其作用部位、并维持足够的药物浓度，才能发挥疗效。对于发挥全身作用的药物（即通过体循环到达其作用部位的药物），人们通常认为药物在作用部位的浓度与血浆药物浓度之间保持动态平衡。这种动态平衡的重要意义在于通过调整血浆药物浓度可以使药物在其作用部位维持有效的浓度。严格来讲，因为药物经常与血浆蛋白发生可逆结合，所以与药物在血浆中的浓度相比，药物在血浆中所含的水中的浓度是指示其在作用部位浓度的更准确的指标。只有游离的药物（溶解在血浆中所含的水中的药物）才能透过毛细血管内皮细胞进入其他体液中，到达各个组织、器官，再到达其作用部位。因为药物可以血细胞相结合或者进入血细胞，所以药物在全血中的浓度也不是指示其在作用部位浓度的准确的指标。但是，与测定血浆中药物总浓度相比（与蛋白结合的药物浓度与游离药物浓度之和），测定血浆中游离药物的浓度需要更复杂、更灵敏的检测方法。因而，通常将血浆中药物的总浓度作为衡

量其在作用部位的浓度和评价其疗效的指标。但是我们应该意识到这种简化的做法有时会引起很大的偏差。事实也是如此，只有在依据充分时，即已证实血药浓度与药物的临床疗效密切相关时，我们才能依据血药浓度推测其临床疗效。

The concentration of drug in blood plasma depends on numerous factors. These

include the relative amount of an administered dose that enters the systemic

circulation, the 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.

1. numerous ['nju:mərəs] adj. 许多的，很多的

2. administer [əd'ministə] vt. 管理；执行；给予

vi. 给予帮助；执行遗产管理人的职责；担当管理人

血浆药物浓度受到许多因素的影响。其中包括药物吸收的速度和程度，药物在体循环和各组织、器官中分布的速度和程度，以及药物在体内的清除速率。

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. 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,