Oral drugs enter the stomach, where they either dissolve and pass through the cell membranes of epithelial cells lining the stomach or travel, undissolved, through the stomach to the small intestine, which is the most common site of absorption.

口服藥物進入胃部後，要麼溶解並通過胃黏膜上皮細胞的細胞膜，要麼在未溶解的情況下通過胃部進入小腸，而小腸是最常見的吸收部位。

Here, drugs dissolve and pass through the intestinal wall.

在這裡，藥物溶解並通過腸壁。

Oral drugs then travel through the portal venous system to the liver, where they undergo the first pass effect.

然後，口服藥物通過門靜脈系統進入肝臟，在肝臟中產生首過效應。

During this process, the liver metabolizes some of the drug, either inactivating it or excreting it into bile for elimination from the body.

在此過程中，肝臟會對部分藥物進行代謝，使其失活或排入膽汁排出體外。

The remaining amount of active drug leaves the liver and reaches general circulation and target organs.

剩餘的活性藥物離開肝臟，進入血液循環和目標器官。

If a drug is administered via intravenous injection, it passes directly into the bloodstream, thus bypassing absorption in the GI tract.

如果通過靜脈注射給藥，藥物會直接進入血液，從而繞過消化道的吸收。

If administered through intramuscular or subcutaneous injection, the drug enters either muscle or subcutaneous tissue, where it passes through gaps between cells into capillary walls and then into general circulation or target organs, also bypassing absorption in the GI tract.

如果通過肌肉注射或皮下注射給藥，藥物會進入肌肉或皮下組織，通過細胞間隙進入毛細血管壁，然後進入血液循環或目標器官，也會繞過消化道吸收。

Bioavailability is the net amount of a dose of a drug that is actually absorbed into the bloodstream.

生物利用度是指藥物實際被血液吸收的淨劑量。

The bioavailability of oral drugs is less than 100% because of the first pass effect of the liver.

由於肝臟的首過效應，口服藥物的生物利用度低於 100%。

In contrast, the bioavailability of IV drugs is 100% because they are not exposed to the first pass effect of the liver.

相比之下，靜脈注射藥物的生物利用度為 100%，因為它們不會受到肝臟首過效應的影響。

Different drug formulations alter bioavailability because they are not absorbed at the same rate or to the same extent.

不同的藥物配方會改變生物利用度，因為它們的吸收率或吸收程度並不相同。

For example, tablets dissolve at varying rates.

例如，藥片的溶解速度各不相同。

Enterocotid drugs dissolve in the small intestine, not the stomach.

腸溶藥物在小腸而非胃中溶解。

Because gastric emptying time differs between individuals, absorption times also vary.

由於每個人的胃排空時間不同，吸收時間也不同。

Sustained release formulas contain tiny spheres that dissolve at different rates, resulting in a steady drug release throughout the day, but also resulting in variable absorption.

緩釋配方含有以不同速度溶解的微小球體，可在一天中穩定釋放藥物，但也會導致藥物吸收率的變化。

Some factors affecting drug absorption are The rate of dissolution Drugs that dissolve faster are absorbed faster Surface area Since the lining of the small intestine has more surface area than the lining of the stomach, most drugs are absorbed faster in the small intestine.

影響藥物吸收的一些因素包括 溶解速度 溶解快的藥物吸收也快 表面積 由於小腸黏膜的表面積大於胃黏膜，是以大多數藥物在小腸中吸收更快。

Blood flow The greater the concentration gradient between the drug-filled stomach and the rapidly flowing drug-free blood, the faster the absorption.

血流 充滿藥物的胃與快速流動的不含藥物的血液之間的濃度梯度越大，吸收越快。

Lipid solubility Highly lipid-soluble drugs pass through the phospholipids in the cell membrane more easily than drugs of low lipid solubility.

脂溶性 脂溶性高的藥物比脂溶性低的藥物更容易通過細胞膜上的磷脂。

And pH partitioning Absorption is faster when the difference between the pH at the site of administration and the pH of the plasma attracts more drug molecules to ionize in the plasma.

當用藥部位的 pH 值與血漿 pH 值之間的差異吸引更多的藥物分子在血漿中電離時，藥物的吸收就會更快。