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器官移植中霉酚酸的药代动力学 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
作者:佚名 论文来源:本站原创 点击数: 更新时间:2008-10-3 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
摘要:霉酚酸酯作为主要的免疫抑制剂已被国内外广泛应用于预防、治疗移植器官急性排异反应。霉酚酸酯在体内通过转化为霉酚酸而发挥免疫抑制活性。在不同的移植群体中,均可发现个体之间霉酚酸药代动力学的巨大差异,并且体内、外因素会影响其药代动力学。
2. 肝移植受者的药代动力学 肝移植受者MPA药代动力学个体之间亦存在很大的差异。Shaw等(11)总结了22例肝脏移植患者口服1g Bid MMF时MPA-AUC范围为5-160 mg.h/L。另一些研究(16-19)也证实了这种巨大的差异(表2)。 肝移植术后MPA药代动力学变化趋势与肾移植基本一致。Pisupati等(17)报道了10例肝移植患者的试验,他们的平均MPA Cmax在移植后1周至1月之间达到了4倍的增长(p < 0.05),同样MPA-AUC12h亦随时间增加(p < 0.05)。Brunet等(18)亦报道了肝移植术后6月的MPA-AUC12h比早期有显著增长(p < 0.05)。 表2 肝移植受者MPA药代动力学参数
三. 影响霉酚酸药代动力学的因素 1. 联合应用其它免疫抑制剂 有多项临床及基础研究表明联合应用CsA会降低MPA的暴露(1,20-22)。一项关于CsA对MPA浓度影响的研究(20)显示,在联合应用CsA治疗期间,MPA谷浓度显著降低。而伴随使用他克莫司(TAC)时的MPA暴露高于联合CsA,这在一项42例小儿肾移植的试验(21)中得到证实,那些伴随使用TAC的患者MPA-AUC比伴随使用CsA的患者平均高出82 %。Hesselink等(22)证实CsA会阻碍MRP2介导的MPAG转运,即阻止MPAG从胆管上皮细胞进入胆汁从而影响MPA-EHC,最终导致MPA暴露度下降,在药时曲线上反映出服药后6-12 h降低的MPA浓度。伴随使用西罗莫司的移植受者MPA药代动力学表现与合用TAC者相似(23)。 2. 严重肾脏病损 随着GFR的下降,MPAG清除率随之下降,血浆浓度明显提升。肾移植术后严重肾脏病损受者、GFR异常者血浆MPAG浓度较GFR正常者高2-3倍,MPAG-AUC也高出3-6倍(11)。Shah等(24)测定19例非血透患者和6例健康志愿者的MPA和MPAG血浆清除率发现,MPA血浆清除率随GFR下降而轻微下降,提示肾功能损害对MPA-AUC影响甚微,而MPAG血浆清除率随GFR的下降而显著下降。严重肾功能损害患者的MPAG-AUC96h是轻度肾功能损害者或健康者的3至6倍。 Shah等(24)研究了单次口服1 g MMF后患者的血浆样本,认为肾功能不全甚至严重肾功能损害对MMF的脱脂化作用影响甚微。Bullingham等(1)亦认为,肾脏病损时多剂量MMF的药代动力学与单一剂量相一致,其对MPA影响很小,而MPAG清除率与肌酐清除率呈线性相关;另外,MPA和MPAG的蛋白结合率高,血液透析对血浆MPA或MPAG浓度无显著影响。当血浆MPAG处于高浓度(> 100 mg/L)时,MPAG将和MPA竞争白蛋白结合位点,导致MPA游离度上升(3,11)。尿毒症亦使MPA的白蛋白结合率降低,导致药物的清除率上升,以及fMPA暴露增加,这种影响在低蛋白血症中尤其明显,因此,在严重肾损的情况下,fMPA暴露不能由总MPA水平预测(11)。 3. 血清白蛋白 Nowak等(9)发现血清白蛋白浓度显著影响MPA的暴露。中重度肝硬化代偿期的患者,当其血浆MPA浓度为40 mg/L时,游离度为2.80 %,约为正常血浆的2倍(1)。肝移植术后早期,白蛋白水平向正常值靠近,同时胆红素水平下降,Pisupati等(17)的试验显示,这段时间内患者MPA的血浆蛋白结合率增加而游离度下降。在移植术后一周和移植术后一月之间,游离度有2.5倍的差异,这可能促使了不同的试验或者个体之间 MPA药代动力学的差异,其中肝移植受者的变异最大(11)。 Jain等(16)认为,MPA谷浓度和血清白蛋白浓度之间显著相关,MPA谷浓度的增加平行于血清白蛋白浓度的增加。我们移植中心(19)在肝移植受者中观察到血清白蛋白浓度小于35 g/L时MPA-AUC12h显著下降(p = 0.009)。 参 考 文 献 1. 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Cyclosporin A, but not Tacrolimus, inhibits the biliary excretion of mycophenolic acid glucuronide possibly mediated by multidrug resistance-associated protein 2 in rats. J Pharmacol Exp Ther 2004; 309: 1029-35 7. Roberts MS, Magnusson BM. Enterohepatic circulation:physiological,pharmacokinetic and clinical implications.Clin Pharmacokinet 2002; 41: 751-90 8. Shaw LM, Nawrocki A. Using Established Immunosuppressant Therapy Effectively: Lessons from the Measurement of Mycophenolic Acid Plasma Concentrations. Ther Drug Monit 2004; 26: 347-51 9. Nowak I, Shaw LM. Mycophenolic acid binding to human serum albumin: characterization and relation to pharmacodynamics. Clin Chem 1995; 41: 1011-7 10. Weber LT, Shipkova M, Armstrong VW. The pharmacokinetic- pharmacodynamic relationship for total and free mycophenolic acid in pediatric renal transplant recipients: a report of the German study group on mycophenolate mofetil therapy. J Am Soc Nephrol 2002; 13: 759-68 11. Shaw LM, Korecka M, Venkataramanan R, et al. Mycophenolic acid pharmacodynamics and pharmacokinetics provide a basis for rational monitoring strategies. Am J Transplant 2003; 3: 534-42 12. Pawinski T, Hale M, Korecka M, et al. Limited sampling strategy for the estimation of mycophenolic acid area under the curve in adult renal transplant patients treated with concomitant Tacrolimus. Clin Chem 2002; 48: 1497-504 13. Yu Zicheng, Zhou Peijun, Xu Da, et al. Investigation on pharmacokinetics of mycophenolic acid in Chinese adult renal transplant patients. Br J Clin Pharmacol 2006; 62: 446-52 14. Yeung S, Tong KL. Pharmacokinetic study of mycophenolate mofetil in asian renal transplant recipients. Transplant Proc 2000; 2001: 1753-4 15. Shum B, Duffull SB. Population pharmacokinetic analysis of mycophenolic acid in renal transplant recipients following oral administration of mycophenolate mofetil. Br J Clin Pharmacol 2003; 56: 188-97 16. Jain A, Venkataramanan R, et al. Pharmacokinetics of mycophenolic acid after mycophenolate mofetil administration in liver transplant patients treated with tacrolimus. J Clin Pharmacol 2001; 41: 268-76 17. Pisupati J, Jain A, Burckart G, et al. Intraindividual and interindividual variations in the pharmacokinetics of mycophenolic acid in liver transplant patients. J Clin Pharmacol 2005; 45: 34-41 18. Brunet M, Cirera I, Martorell J, et al. Sequential determination of pharmacokinetics and pharmacodynamics of mycophenolic acid in liver transplant patients treated with mycophenolat mofetil. Transplantation 2006; 81: 541-6 19. Chen H, Peng CH, Yu ZZ, et al. Pharmacokinetics of mycophenolic acid and determination of area under the curve by abbreviated sampling strategy in chinese liver transplant recipients. Clin Pharmacokinet 2007; 46: 175-85 20. Smak Gregoor PJ, de Sevaux RG, Hene RJ, et al. Effect of cyclosporine on mycophenolic acid trough levels in kidney transplant recipients. Transplantation 1999; 68: 1603-6 21. Filler G, Zimmering M, Mai I. Pharmacokinetics of mycophenolate mofetil are influenced by concomitant immunosuppression. Pediatric Nephrol 2000; 14: 100-4 22. Hesselink DA, van Hest RM. Cyclosporine interacts with mycophenolic acid by inhibiting the multidrug resistance-associated protein 2. Am J Transplant 2005; 5: 987-94 23. Flechner SM, Goldfarb D, Modlin C, et al. Kidney transplantation without calcineurin inhibitor drugs: a prospective, randomized trial of sirolimus versus cyclosporine. Transplantation 2002; 74: 1070-6 24. Shah J, Bullingham R, Rice P, et al. Pharmacokinetics of oral mycophenolate mofetil (MMF) and metabolites in renally impaired patients [abstract]. Clin Pharmacol Ther 1995; 57: 149 上海交通大学医学院瑞金临床医学院 费悦 上海交通大学医学院附属瑞金医院移植科 陈皓 上海交通大学医学院附属瑞金医院普外科 杨卫平 |
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