药物是如何到达人体内的目标部位的丨医学英语视听学习

How Medications Reach Their Target Sites Within Your Body

药物是如何到达人体内的目标部位的

Distribution is the process by which a medication is carried to its target tissue or site of action with the goal of causing a therapeutic response. 

分布是指药物被携带到目标组织或作用部位，引起治疗反应的过程。

This process follows medication absorption and precedes medication metabolism. Medication is first carried to highly vascularized tissues including the liver, heart, kidneys, and brain. 

药物分布是药物吸收和药物代谢之间的过程。药物先被携带到血管丰富的组织，如肝脏、心脏、肾脏和大脑。

Then medication is widely circulated within the body, reaching areas of less extensive blood supply such as skin, muscle, and fat. Medication then accumulates in the fat and in poorly vascularized tissues like bone, especially if the medication is lipophilic or strongly attracted to lipids. 

然后，药物在人体内广泛循环，到达血液供应不太丰富的区域，如皮肤、肌肉和脂肪。接下来，药物聚集在脂肪和血管不丰富的组织，如骨骼，特别是亲脂性或强脂溶性药物。

In the blood, some medication molecules bind to plasma proteins to which they are attracted. In this bound state, medication molecules are unable to produce a pharmacological effect. 

在血液中，有些药物分子被血浆蛋白吸引，与血浆蛋白结合。在这种结合状态下，药物分子不能发挥药理作用。

In bound and unbound form, the medication flows through the arteries and into capillaries. Capillaries carry the medication close to the tissue's cells, where hydrostatic pressure drives molecules between the capillary endothelial cells into the interstitial space. 

结合型和游离型药物通过动脉，进入毛细血管。毛细血管将药物携带到组织的细胞附近，该区域的静水压驱动毛细血管内皮细胞之间的分子进入细胞间隙。

Some protein-bound macromolecules are too large to pass through the vessel walls, so they never reach the target tissue.

一些蛋白结合大分子过大，不能通过血管壁，因此，它们永远无法到达目标组织。

Unbound or free molecules do reach the target tissue by exiting the bloodstream between the loose Junctions in the capillary endothelium into the interstitial space to interact with the tissue cells. 

未结合或游离分子通过毛细血管内皮细胞间的疏松连接离开血流，进入细胞间隙，到达目标组织，与组织细胞相互作用。

Some molecules bind to the cells while others remain in the extracellular fluid. The interaction of the unbound medication with the target tissue results in a therapeutic response.

一些分子与细胞结合，而另一些分子则仍留在细胞外液中。未结合药物与目标组织相互作用，发挥治疗效应。

There are many factors that affect distribution. For example, the effect of membrane permeability on distribution can be demonstrated in the brain. The brain's capillaries are impermeable to the majority of medications due to the blood-brain barrier, a membrane that blocks the entrance of both toxic and therapeutic substances into brain tissues. 

药物分布受许多因素影响。例如，大脑内的膜通透性影响药物的分布。大多数药物不能渗透到脑毛细血管中，因为大脑内存在阻止有毒物质和治疗物质进入脑组织的血脑屏障。

Some medications penetrate the blood-brain barrier based on features like low polarity and high solubility in lipids.

有些药物由于低级性和高脂溶性等特性，能够穿透血脑屏障。

Fat-soluble molecules cross cell membranes faster than water-soluble molecules due to the lipophilic nature and phospholipid composition of the cellular membrane. 

由于细胞膜的亲脂特性，及其磷脂组分，脂溶性分子比水溶性分子更快地穿过细胞膜。

Factors such as body fat percentage and disease also affect medication distribution. Fat deposits retain lipid-soluble unionized medication and release the molecules over time. Thus, obese patients may experience prolonged pharmacologic effects.

体脂率和疾病等因素也影响药物的分布。脂肪沉积影响脂溶性未电离药物，它将随着时间的推移逐渐释放分子。因此，肥胖患者的药物起效时间可能延长。

Inflammation, disease, and injuries such as burns can alter protein levels and thus medication binding, increasing capillary permeability and uptake in cells and tissues. 

炎症、疾病和烧伤等损伤会改变蛋白质的水平，从而改变药物的结合，增加毛细血管的通透性，促进细胞和组织的吸收速度。

As a complication of kidney disease, albumin cannot bind medications effectively, resulting in a low percentage of protein-bound medication. These shifts result in high levels of free medications circulating throughout the body.

作为肾脏疾病的一种并发症，白蛋白不能与药物有效结合，导致蛋白质结合药物的比例较低。这种转变将导致大量游离型药物在全身循环。