Bai J P, Chang L L, Guo J H
College of Pharmacy, University of Minnesota, Minneapolis 55455, USA.
Crit Rev Ther Drug Carrier Syst. 1995;12(4):339-71. doi: 10.1615/critrevtherdrugcarriersyst.v12.i4.30.
Although the distal small intestine has less lumenal and apical proteolytic activities, it has high activities of some apical peptidases. Colonic proteolytic activities are substantial, but their nature is less understood. The small intestine has di- and tripeptide transporter, facilitating absorption, and P-glycoprotein, an efflux pump suggested to limit absorption of small peptides. Several peptide and nonpeptide drugs have higher absorption in the ileum; however, enhancement on their absorption by enhancers varies from site to site. Specific delivery systems can target drugs to the distal intestine utilizing distinct regional pHs and specific microbial enzymes, but the key is how to achieve a reliable release.
虽然远端小肠的肠腔和顶端蛋白水解活性较低，但它具有一些顶端肽酶的高活性。结肠的蛋白水解活性很高，但其性质尚不太清楚。小肠有二肽和三肽转运体促进吸收，还有P-糖蛋白，一种被认为会限制小肽吸收的外排泵。几种肽类和非肽类药物在回肠的吸收较高；然而，增强剂对它们吸收的促进作用因部位而异。特定的给药系统可以利用不同区域的pH值和特定的微生物酶将药物靶向输送到远端肠道，但关键是如何实现可靠的释放。
