代谢
头孢他啶是一种碳青霉烯类抗生素,在大鼠、猴和人身上的代谢和分布进行了研究。斯普拉格-道莱大鼠和恒河猴通过静脉给药给予放射性标记的头孢他啶(分别为60和30 mg kg(-1)),健康的正常志愿者接受单一固定剂量1000 mg。收集尿液和粪便以确定总放射性。在健康志愿者中,(14)C-头孢他啶通过水解代谢到β-内酰胺环开环衍生物和未改变药物的肾排泄而消除。大约相等的量被排泄为β-内酰胺环开环代谢物和未改变的药物(分别为剂量的36.7%和37.5%)。在人体中,次要酰胺水解产物约占剂量的1%。大约10%的给药放射性在粪便中回收,这表明有一小部分通过胆汁和/或肠道排泄。在动物中,更大比例的剂量通过代谢消除;未改变药物的排泄在大鼠和猴中分别占剂量的17%和5%。在猴中,β-内酰胺环开环和酰胺水解代谢物分别占剂量的74.8%和7.59%,而在大鼠中,这些代谢物分别占剂量的31.9%和20%。用新鲜大鼠组织匀浆的体外研究表明,肺和肾是介导β-内酰胺环开环代谢物形成的主要器官。脱氢肽酶-I的特异性抑制剂西拉司丁在大鼠中抑制了头孢他啶的体内和体外代谢,这强烈表明肺和肾中头孢他啶的水解是由这种酶介导的。
The disposition and metabolism of ertapenem, a carbapenem antibiotic, was examined in rat, monkey and man. Sprague-Dawley rats and Rhesus monkeys were given, by intravenous administration, radiolabelled doses of ertapenem (60 and 30 mg kg(-1), respectively), and healthy normal volunteers received a single fixed dose of 1000 mg. Urine and feces were collected for determination of total radioactivity. In healthy volunteers, (14)C-ertapenem was eliminated by a combination of hydrolytic metabolism to a beta-lactam ring-opened derivative and renal excretion of unchanged drug. Approximately equal amounts were excreted as a beta-lactam ring-opened metabolite and unchanged drug (36.7 and 37.5% of dose, respectively). A secondary amide hydrolysis product accounted for about 1% of the dose in man. About 10% of the administered radioactivity was recovered in feces, which suggested that a minor fraction underwent biliary and/or intestinal excretion. In animals, a greater fraction of the dose was eliminated via metabolism; excretion of unchanged drug accounted for 17 and 5% of dose in rats and monkeys, respectively. In monkeys, the beta-lactam ring-opened and amide hydrolysis metabolites accounted for 74.8 and 7.59% of the dose, respectively, whereas in rats, these metabolites accounted for 31.9 and 20% of dose, respectively. In vitro studies with fresh rat tissue homogenates indicated that lung and kidney were the primary organs involved in mediating formation of the beta-lactam ring-opened metabolite. The specific inhibitor of dehydropeptidase-I, cilastatin, inhibited the in vivo and in vitro metabolism of ertapenem in rats, which suggested strongly that the hydrolysis of ertapenem in lung and kidney was mediated by this enzyme.
来源:Hazardous Substances Data Bank (HSDB)