Pharmacokinetic and Immunosuppressive Effects of Tacrolimus-Loaded Biodegradable Microspheres

目的：研究负载他克莫司的可生物降解微球（TLBM）在大鼠体内的药动学和免疫抑制作用。方法：制备TLBM。DA/Slc大鼠分别以1.6 mg/kg （n=9）、2.4 mg/kg （n=5）和7.2 mg/kg （n=7）的他克莫司含量皮下给药TLBM，达到长期缓释。DA/Slc大鼠以4.8 mg/kg （n=6）他克莫司含量单次皮下给药TLBM，以明确TLBM在器官摄取的主要部位。在大鼠肝移植模型中，受体术后第1天分别给予他克莫司含量0.16 mg/kg （n=5）、2.4 mg/kg （n=4）、4.8 mg/kg （n=3）的TLBM单次皮下给药。比较总生存天数。结果：TLBM颗粒的平均直径为87 ~ 90 μm。他克莫司在两批TLBM中的包封效率分别为6.48 w/w%和6.60 w/w%。从单次皮下给药后第1天开始，连续14天的平行浓度曲线具有显著性（p<0.01）。给药剂量与18 d内浓度-时间曲线下面积呈线性回归关系（p<0.01）。TLBM剂量与肝移植模型受者存活天数呈正相关。本研究的药代动力学研究显示，与除骨髓外的其他器官相比，TLBM在区域淋巴结中的他克莫司水平显著升高（p<0.01）。结论：TLBM可使他克莫司在14天内以非常稳定的方式逐渐释放，单次皮下给药后显示出剂量正比性和剂量依赖性免疫抑制。皮下给药后TLBM的主要摄取部位为给药途径的局部淋巴结。

Objective : To characterize the pharmacokinetics and immunosuppression of a tacrolimus loaded biodegradable microsphere (TLBM) in rats.Methods : We prepared TLBM. DA/Slc rats were given TLBM at a rate of 1.6 mg/kg (n=9), 2.4 mg/kg (n=5), and 7.2 mg/kg (n=7) tacrolimus contents, respectively, by a single subcutaneous administration to achieve sustained release over a long period. DA/Slc rats were given TLBM by a single subcutaneous administration at a rate of 4.8 mg/kg (n=6) tacrolimus contents to clarify the main site of TLBM uptake in the organs. In the rat liver transplantation model, the recipients were given TLBM at a rate of 0.16 mg/kg (n=5), 2.4 mg/kg (n=4), and 4.8 mg/kg (n=3) tacrolimus contents, respectively by a single subcutaneous administration on the first day postoperation. Overall survival days were compared.Results : The mean diameters of TLBM particles were 87-90 μm. The entrapping efficiencies of tacrolimus in two batches of TLBM were 6.48 w/w% and 6.60 w/w%. Continuous flat parallel concentration profiles were significant for 14 days from the first day after a single subcutaneous administration of TLBM (p<0.01). The relationship between the dosages of TLBM administration and area under the concentration-time curve (AUC) up to 18 days demonstrated a linear regression line (p<0.01). Also, the relationship between the dose of TLBM and the survival days of the recipients in the liver transplantation model showed a positive correlation. The present pharmacokinetic study of TLBM revealed significantly increased tacrolimus levels in the regional lymph nodes, compared with other organs except bone marrow (p<0.01).Conclusion : TLBM allowed tacrolimus to release gradually in a very stable manner for 14 days and revealed dose proportionality and dose-dependent immunosuppression after a single subcutaneous administration. The main site of TLBM uptake after subcutaneous administration was the regional lymph node of administration route.