求翻译：这主要是由于体内对药物存在很多种巨大的屏障。如口服给药受胃肠道上 皮细胞中酶系及肝中酶系的降解与代谢；静脉注射给药要经过同 血浆蛋白结合、代谢、分解等作用，最后通常也仅有很少部分到达靶位，其浓度达不到有效的血药浓度。是什么意思？

This is mainly due to the body there is a variety of huge barrier to drugs. By the degradation and metabolism of the enzymes in the gastrointestinal tract epithelial cells and liver enzymes, such as oral administration; intravenous administration to go through the same plasma protein binding, metabo

This is mainly due to the drug in the body there is a lot of great barrier. Such as oral medication the gastrointestinal tract epithelial cells in liver enzymes, and enzymes, and metabolic degradation of; intravenous medication to the plasma protein, and metabolite, disintegration, and are usually i

This mainly is because in vivo are very many to the medicine existence a kind of giant barrier.If takes orally gives the medicine the gastro-intestinal tract epithelial cell in the enzymatic system and the liver the enzymatic system degeneration and metabolism; The intravenous injection must pass th

This is mainly due to the huge body on drugs there are many kinds of barriers. Oral epithelial cells of the gastrointestinal tract enzymes and degradation in liver enzymes and metabolic; intravenous administration to go through with the plasma protein binding, metabolism, digestion, last part is usu

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