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【生化和药理】体内合成糖类皮质激素,是胆固醇通过一系列反应,经孕烯醇酮和孕酮转化为皮质醇的过程。循环中内源性皮质醇约95％都与血浆蛋白结合,特别是一种特异性皮质激素结合蛋白(CBG或皮质激素传递蛋白),还有少量是与白蛋白结合的。皮质醇很快即由循环清除,血浆半寿期约90分钟。皮质醇在很多组织特别是肝中迅速代谢,以原形由尿中排出的,不到2％。皮质醇的活性部分是11β羟基,外源性药物如可的松和强的松,都是11-酮基化合物,要在体内转化为相应的11—β羟基化合物皮质醇和强的松龙,才能具有皮质激素的作用。这项反应主要在肝内进行。故肝功能严重障碍的病人,应直接采用强的松龙代替强的松,以确保活性化合物的取得无误。
[Biochemical and pharmacological] In vivo synthesis of glucocorticoids, cholesterol is through a series of reactions, pregnenolone and progesterone into cortisol process. Approximately 95% of circulating endogenous cortisol binds to plasma proteins, specifically a specific corticosteroid-binding protein (CBG or corticosteroid) and a small amount to albumin. Cortisol is quickly cleared by circulation, and the plasma half-life is about 90 minutes. Cortisol rapidly metabolizes in many tissues, especially the liver, and excretes less than 2% from the urine. The active portion of cortisol is the 11β hydroxyl group. Extrinsic drugs such as cortisone and prednisone are both 11-keto compounds that are converted in vivo to the corresponding 11-β hydroxy cortisol and prednisolone With the role of corticosteroids. This reaction is mainly in the liver. Therefore, patients with severe liver dysfunction, prednisolone should be used directly instead of prednisone to ensure that the active compound is made.