释 义 adj. 肠肝的
例 句 Hypercholic acidemia is caused by the interruption of enterohepatic circulation and deterioration of hepatic function after portasystemic shunt. 高胆酸血症主要为门体分流术后肝肠循环阻断和肝功能恶化所致。
circulation 英/sɜːkjʊ'leɪʃ(ə)n/ 美/,sɝkjə'leʃən/
释 义 n. 流通，传播；循环；发行量；（图书的）借出
例 句 Hemoglobin was the carrier of oxygen in blood circulation. 血红蛋白是血液循环中输送氧的载体。
作者： Gary Eichenbaum
期刊：J Pharm Sci
Strategies for increasing the bioavailability of compounds that undergo extensive first-pass metabolism have generally fallen into two categories: chemical and drug delivery based. Chemical-based approaches include structural modification of the parent compound, coadministration of an enzyme inhibitor, inhibition of efflux transporters such as p-glycoprotein, or coadministration of a buffering agent such as sodium bicarbonate. Structural modification is a common approach used prior to candidate selection and in the development of backup compounds. For example, nitrofenac, a structural analog of diclofenac, does not produce the intestinal toxicities (e.g., ulcerations) that are observed with diclofenac.An example of coadministration of an inhibitor is methoxaslen, which is a CYP2A6 inhibitor that blocks the metabolism of nicotine and has been shown to decrease nicotine clearance, increase nicotine bioavail- ability, and decrease smoking behaviors.Inhibitors such as ketoconazole have been used to reduce the extent of metabolism of cytotoxic and antiviral drugs, thereby improving the bioavailability and efficacy of these agents.Drug delivery approaches include bypassing duodenal or gastric metabolism and delivering a compound to the colon through the use of a controlled-release delivery system or bypassing the first pass to liver through transdermal, oral cavity, or parenteral routes.Although both chemical- and drug delivery-based approaches can be effective for overcoming extensive first-pass metabolism, they can also have limitations. For example, structural modification of acompound that is in clinical trials generates a com- pletely new chemical entity that requires a new development program, including nonclinical toxicology, resulting in increased time, cost, and risk. Furthermore, chemical modification may not be feasible in cases wherein the site of metabolism is essential for the biological activity of the chemical series. In cases wherein multiple enzymes form a toxic metabolite, the use of enzyme inhibitors may be of limited value. If there are no regional differences in gut metabolism or there is poor colonic absorption, it is unlikely that an oral controlled-release delivery approach would deliver adequate drug levels.