药学学报  2015, Vol. 50 Issue (6): 775-782   PDF    
基于双重扩散机制的利培酮骨架微球/乙酸异丁酸蔗糖酯复合型原位贮库的制备与评价
林霞1,2 , 唐星3 , 徐宇虹1, 张宇3, 张岩3, 何海冰3    
1. 上海交通大学药学院, 上海 200240;
2. 江南大学药学院, 江苏 无锡 214122;
3. 沈阳药科大学药学院, 辽宁 沈阳 110016
摘要:针对乙酸异丁酸蔗糖酯 (sucrose acetate isobutyrate, SAIB) 原位贮库前期药物突释问题, 本文以利培酮为模型药物, 将其预先包载于骨架微球中再分散至SAIB贮库系统中, 制备利培酮骨架微球/SAIB复合型原位贮库.考察不同载体包括壳聚糖和聚乳酸-羟基乙酸共聚物 [poly(lactide-coglycolide), PLGA]、载体/药物比例及骨架微球形态对复合型贮库药物释放的影响.结果表明, 与壳聚糖微球/SAIB贮库和单独SAIB贮库相比, PLGA 骨架微球/SAIB复合型贮库 (Ris-Pm-SAIB) 可显著降低体外药物突释 (0.64%), 体内药物突释也显著降低, 0~4天药时曲线下面积 (AUC0-4d) 仅为 (105.2 ± 24.4) ng·mL-1·d; 此外, 通过调节微球形态控制贮库释药速度, 多孔性PLGA微球/SAIB复合型贮库 (Ris-PPm-SAIB) 肌肉注射大鼠后AUC0-4d增至 (194.6 ± 15.8) ng·mL-1·d, 突释略有增加, 但78天时血药浓度仍为 (9.0 ± 2.5) ng·mL-1, 4~78天AUC4–78d由 (379.0 ± 114.3) ng·mL-1·d增至 (465.0 ± 149.2) ng·mL-1·d, 可保证药物充分释放.研究表明, 多孔性PLGA骨架微球/SAIB复合型原位贮库在降低利培酮体内外药物突释的同时, 可保证后期药物充分释放, 实现体内持续释药78天.
关键词利培酮     乙酸异丁酸蔗糖酯     聚乳酸-羟基乙酸共聚物微球     原位贮库     控制释放     药动学    
Preparation and evaluation of risperidone-loadedmicrosphere/sucrose acetate isobutyrate in situ forming complex depot with double diffusion barriers
LIN Xia1,2 , TANG Xing3 , XU Yu-hong1, ZHANG Yu3, ZHANG Yan3, HE Hai-bing3    
1. School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China;
2. School of Pharmacy, JiangnanUniversity, Wuxi 214122, China;
3. School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
Abstract: In the present study, a risperidone loaded microsphere/sucrose acetate isobutyrate (SAIB) in situ forming complex depot was designed to reduce the burst release of SAIB in situ forming depot and to continuously release risperidone for a long-term period without lag-time. The model drug risperidone (Ris) was first encapsulated into microspheres and then the Ris-microspheres were embedded into SAIB depot to reduce the amount of dissolved drug in the depot. The effects of different types of microsphere matrix, including chitosan and poly(lactide-coglycolide) (PLGA), matrix/Ris ratios in microspheres and morphology of microspheres on the drug release behavior of complex depot were investigated. In comparison with the Ris- loaded SAIB depot (Ris-SAIB), the complex depot containing chitosan microspheres (in which chitosan/Ris = 1:1, w/w) (Ris-Cm-SAIB) decreased the burst release from 12.16% to 5.80%. However, increased drug release rate after 4 days was observed in Ris-Cm-SAIB, which was caused by the high penetration of the medium to Ris-Cm-SAIB due to the hydrophilie of chitosan. By encapsulation of risperidone in PLGA microspheres, most drugs can be prevented from dissolving in the depot and meanwhile the hydrophobic PLGA can reduce the media penetration effect on the depot. The complex depot containing PLGA microspheres (in which PLGA/ drug = 4:2, w/w) (Ris-Pm-SAIB) showed a significant effectiveness on reducing the burst release both in vitro and in vivo whereby only 0.64% drug was released on the first day in vitro and a low AUC0-4d value [(105.2 ± 24.4) ng·mL-1·d] was detected over the first 4 days in vivo. In addition, drug release from Ris-Pm-SAIB can be modified by varying the morphology of microspheres. The porous PLGA microspheres could be prepared by adding medium chain triglyceride (MCT) in the organic phase which served as pore agents during the preparation of PLGA microspheres. The complex depot containing porous PLGA microspheres (which were prepared by co-encapsulation of 20% MCT) (Ris-PPm-SAIB) exhibited a slightly increased AUC0-4d of (194.6 ± 15.8) ng·mL-1·d and high plasma concentration levels from 4 to 78 days [Cs(4-78d) = (7.8 ± 1.2) ng·mL-1]. The plasma concentration on 78 day C78d was (9.0 ± 2.5) ng·mL-1 which was higher than that of Ris-Pm-SAIB [C78d = (1.6 ± 0.6) ng·mL-1]. In comparison with Ris-Pm-SAIB, the AUC4-78d of Ris-PPm-SAIB increased from (379.0 ± 114.3) ng·mL-1·d to (465.0 ± 149.2) ng·mL-1·d, indicating sufficient drug release from the Ris-PPm- SAIB. These results demonstrate that the risperidone loaded porous PLGA microsphere/SAIB in situ forming complex depot could not only efficiently reduce the burst release of SAIB depot both in vitro and in vivo, but also release the drug sufficiently in vivo, and be capable to continuously release the drug for 78 days.
Key words: risperidone     sucrose acetate isobutyrate     poly(lactide-coglycolide) microsphere     in situ forming depot     controlled release     pharmacokinetics    

利培酮 (risperidone,Ris) 作为第二代非典型抗精神病药物,主要用于治疗急性和慢性精神分裂症。精神分裂症患者需长期用药,以降低复发率。因此,将利培酮制备成长期持续释药的缓释制剂,对提高患者顺应性、避免口服给药所致的血药浓度波动具有重要的意义。

2008年,由美国Johnson & Johnson公司开发的 利培酮长效注射剂 (Risperdal® Consta®) 获FDA批准上市,为聚乳酸-羟基乙酸共聚物 [poly (lactide- coglycolide),PLGA] 缓释微球。临床研究表明,该长效注射剂疗效好[1],但其在体内外均存在2~3周的药物释放延滞期[2, 3]。初次使用后,前三周药物释放不足1%,需口服抗精神病药物来维持治疗效果,连续给予4个剂量 (历时8周) 后才可达到稳态血药浓度[4],为临床给药带来不便。近年来很多关于利培酮缓释微球的研究多集中于如何消除药物释放延滞期实现持续释药,如加入无机碱加速药物释放[5]、改变制备工艺[6, 7]等,上述方法所制备微球可基本消除药物释放延滞期,但第1天药物释放量高达20%,存在明显的药物突释,且体外释放周期仅为15天。因此,开发可在体内长期持续释放药物且无突释的利培酮长效制剂具有重要意义。

基于小分子基质——乙酸异丁酸蔗糖酯 (sucrose acetate isobutyrate,SAIB) 的原位贮库系统是近年来极具潜在应用优势的沉淀型有机原位贮库系统。其与基于聚合物基质 (PLGA) 的原位贮库相比,具有以下优势: ① 无药物释放延滞期; ② 缓释时间可调控性强,药物释放时间由数小时延长至数月; ③ 有机溶剂含量低,通常< 20%,即可使SAIB的黏度降低到0.05~0.2 Pa·s,可通过普通注射器和针头注射到体内[8]; 较已上市Eligard® (PLGA为基质) 的有机溶剂含量 (N-甲基吡咯烷酮 > 50%) 明显降低; ④ 可选择溶剂系统广泛,且可以无水乙醇为溶剂,具有更好的生物相容性。目前,SAIB原位贮库系统已广泛应用于多种性质不同的药物,包括小分子化合物[9]、蛋白及多肽类药物[10, 11, 12],其中Durect公司开发的布比卡因-SAIB原位贮库系统 (缓释72 h) 已完成Ⅲ期临床试验[13]。本研究选择SAIB作为载体,旨在制备一种体内无延滞、低突释并可长期持续释药的利培酮长效注射剂。

由于SAIB原位贮库给药系统在体外条件下为溶液形式,注射后溶剂需从贮库中扩散至注射部位,同时水渗入到贮库中,使SAIB沉淀形成高黏度的原位贮库,在贮库形成过程中大量药物随有机溶剂扩散而迁移到周围组织液中造成药物突释[14],这是SAIB原位贮库系统所面临的最大难点。有人向SAIB溶液中加入聚乳酸 (polylactic acid,PLA) 作为释放调节剂,可显著降低重组人生长激素 (rhGH) 在体内的突释[15]。在前期工作中,作者尝试向SAIB系统中加入

PLA和PLGA,通过降低传质速率 (药物扩散速率和溶剂扩散速率) 来控制药物突释和后期药物释放速度,在体外取得了较好释放行为,但体内仍存在一定的突释[16, 17, 18]。可能的原因包括: ① 在体内条件下,SAIB贮库形态不固定,可以单一贮库单元存在,也可以多单元形式存在,此种情况的比表面积显著增加,导致药物体内释放速度明显加快; ② 在体内条件下,肌肉组织中血流等体液处于流动状态,扩散释放的药物被体液带走,导致药物扩散速度变快。因此,降低贮库与介质中浓度差可调控药物突释。

本研究拟设计一种游离药物浓度低的利培酮骨架微球/SAIB复合型原位贮库系统 (图 1A),以降低贮库与介质中浓度差,其中药物包载于骨架微球中,使SAIB基质中溶解的游离药物浓度接近于零,从而有效降低贮库形成过程中的药物突释; 贮库形成后药物扩散受双重骨架控制,从而实现缓慢释药。鉴于颗粒/骨架型缓释给药系统的药物释放通常受混悬在贮库中颗粒性质的影响[19],因此本研究拟通过调节骨架材料性质,使用疏水性不同的载体材料 (如壳聚糖、PLGA),考察骨架载体材料对复合型贮库释药行为的影响; 在此基础上,设计一种多孔性骨架微球/SAIB复合型贮库 (图 1B),以期通过孔道扩散结合骨架扩散,在降低药物突释的同时,保证后期药物释放速度。

Figure 1 The structures of risperidone-loaded microsphere/SAIB complex depot (A) and risperidone-loaded porous microsphere/ SAIB complex depot (B). SAIB: Sucrose acetate isobutyrate
材料与方法

试药 利培酮 (济南汇丰达化工有限公司); 9-羟基利培酮对照品 (加拿大Toronto Research Chemicals公司); SAIB (美国Sigma Aldrich公司); 壳聚糖 (脱乙酰度> 83%,Mw 6 kDa,大连鑫蝶祥瑞甲壳素有限公司); PLGA 75:25 (Mw 28 kDa,长春应用化学研究所赠送); 聚乙烯醇 (polyvinyl alcohol,PVA,水解度87%~89%,Mw 72.6~81.4 kDa,日本可乐丽株式会社); 无水乙醇 (分析纯)、甲醇、乙腈 (色谱纯,天津康科德科技有限公司); 其他试剂均为分析纯。

仪器 EYELA SD 1000型喷雾干燥机 (日本Tokyo Rikakikai公司); IKA®T18高速分散匀质机 (德国IKA公司); 膜乳化器、Shirasu porous glass (SPG) 膜 (孔径10 μm,日本SPG Technology CO.,Ltd); VirTis advantage ES-53冷冻干燥机 (美国SP Industries,Inc.); ZHWY-110X30往复式水浴恒温摇床 (上海智诚分析仪器制造有限公司); ZRS-8G 药物溶出度仪 (天大天发科技有限公司); LS230型激光粒度仪 (美国贝克曼公司); HITACHI高效液相色谱仪 (日本日立公司); Waters超高效液相-串联质谱仪 [配有Waters ACQUITYTM超高效液相 (自动进样器、二 元溶剂管理器、Waters三重四级杆检测器 (TQD) 和Masslynx色谱工作站),美国Waters公司]; Barnstead EASY pure®ⅡRF/UV超纯水机 (美国Lowa公司)。

喷雾干燥法制备利培酮颗粒和壳聚糖骨架微球 按表 1称取适量利培酮,并加入处方量骨架材 料,用0.1% 醋酸水溶液溶解,0.45 μm滤膜滤过,参照文献[16]喷雾干燥条件: 进口温度: 130 ℃; 供液速度: 7 mL·min-1; 雾化压力: 190 kPa; 干燥风速: 0.64 m3·min-1,溶液喷干后,调节进口温度使出口温度保持在80 ℃并维持15 min,使所得粉末通过二次干燥进一步降低残留水分,即得。

Table 1 Formulations of risperidone in 1% acetic acid solution

膜乳化法制备PLGA骨架微球 采用快速膜乳化法[20, 21]制备PLGA骨架微球,具体制备方法如下: 称取处方量的利培酮、PLGA和适量添加剂,加入到有机相 (二氯甲烷-苯甲醇,4∶1,v/v) 中,其中PLGA质量浓度为200 mg·mL-1,待全部溶解后,缓慢滴入到10倍体积的1% PVA水溶液中,3 000 r·min-1预乳化30 s。迅速转移至膜乳化装置中,以0.05 MPa氮 气压力通过孔径为10 μm的SPG膜(预先用连续相充分浸润) 1次,将所得乳液分散至10倍体积的1% PVA水溶液中,40 ℃旋转蒸发15 min,挥散有机溶剂使微球固化,将收集的微球用蒸馏水洗涤3次,冷冻干燥即得到PLGA骨架微球。

利培酮骨架微球/SAIB复合型原位贮库系统的制备 利培酮骨架微球/SAIB复合型原位贮库系统均在临用前制备。具体制备方法如下: 称取SAIB适量,配制85% (w/w) SAIB/无水乙醇溶液。临用前,分别称取处方量利培酮颗粒、壳聚糖骨架微球和PLGA骨架微球,与上述SAIB溶液涡旋充分混合,得均一混悬液,使最终载药量为25 mg·g-1,即得利培酮/SAIB原位贮库系统 (Ris-SAIB)、利培酮壳聚糖骨架微球/SAIB复合型原位贮库系统(Ris-Cm-SAIB) 和利培酮PLGA骨架微球/SAIB复合型原位贮库系统 (Ris-Pm-SAIB)。

骨架微球形态观察 将双面导电胶带黏附于铜锭上,取利培酮骨架微球适量均匀涂布在导电胶上,喷金后用扫描电子显微镜观察。

骨架微球粒径及粒度分布 PLGA骨架微球采用LS230型激光粒度仪湿法测定模式,将适量PLGA骨架微球加入到0.1% PVA水溶液中制成混悬液,控制遮光比大于8% 并保持稳定时,开始测定,测定时间持续60 s。

体外药物释放测定 精密称取适量利培酮喷干粉末及壳聚糖微球 (相当于利培酮25 mg),加入明胶囊壳中,参照中国药典2010年版二部附录ⅩC第一法,以含0.02% NaN3的10 mmol·L-1磷酸盐缓冲溶液 (pH 7.4) 900 mL为溶出介质,转速为50 r·min-1,依此法操作,分别于1、2、4、6、8、12、24和36 h取溶液5 mL,滤过,续滤液以HPLC法测定药物含量。

精密称取适量PLGA微球或原位贮库 (相当于利培酮2.5 mg),分别加入到装有3 mL释放介质 (含0.02% NaN3的10 mmol·L-1磷酸盐缓冲溶液,pH 7.4) 的Eppendorf试管中,于37 ℃恒温水浴摇床中振摇 (100 r·min-1)。分别在规定的时间内取出全部释放介质 (其中PLGA微球体外释放样品先以5 000 r·min-1离心10 min后,再取出全部释放介质),同时补充3 mL新鲜的释放介质。以HPLC法测定药物浓度。

利培酮骨架微球/SAIB复合型原位贮库系统的药动学研究 24只Wistar雄性大鼠,体重 (200 ± 20) g,随机分成4组,每组6只,实验前禁食,分别于大鼠右后腿注射12.5 mg·kg-1利培酮骨架微球/SAIB复合型原位贮库系统,于给药后0.042、0.083、0.17、0.33、0.5、1、2、4、6、8、10、14、18、22、26、30、34、38、42、46、50、54、65和78天由眼眶后静脉丛取血约0.3 mL,置预先肝素化的1.5 mL尖底离心试管中,4 000 r·min-1离心10 min,吸取上层血浆于 -80 ℃保存。测定时吸取血浆100 μL,参照文献[16]采用液液萃取法处理血浆样品,超高效液相色谱-质谱联用法分析测定,以当日的标准曲线计算各时间点样品中利培酮和9-羟基利培酮的浓度。

结果与讨论 1 骨架载体材料对利培酮骨架微球/SAIB复合型原位贮库系统体外药物释放的影响 1.1 壳聚糖骨架微球对复合型原位贮库体外药物释放的影响

以壳聚糖为骨架材料,制备Ris-Cm-SAIB,与Ris-SAIB进行体外释放比较,考察壳聚糖及壳聚糖/利培酮比例对Ris-Cm-SAIB药物释放的影响,结果见图 2。由图可知,与单独药物喷干颗粒相比,壳聚糖骨架微球可显著降低药物释放速度,壳聚糖用量越高,药物释放速度越慢。同样,与Ris-SAIB相 比,Ris-Cm-SAIB (C1-SAIB和C2-SAIB) 的药物突释降低,并且壳聚糖用量越高,药物突释越小。此外,将药物释放曲线用Higuchi方程 (公式1) 进行拟合,均具有较好的相关系数,如表 2所示。其中斜率代表药物释放速度,随壳聚糖比例增加,1~4天药物释放速度逐渐减小,4~30天药物释放速度逐渐增加。

$Q = 2{C_0}\sqrt {\frac{{Dt}}{\pi }} $ (1)


Figure 2 Effect of different chitosan/drug ratios on the in vitro drug release of chitosan microspheres (A) and risperidone-loaded chitosan microsphere/SAIB complex depot (Ris-Cm-SAIB,B) in release medium (10 mmol·L-1 phosphate buffered saline solution,pH 7.4,0.02% NaN3) at 37 ℃ (x± s,n = 3). Ris: Bare drug particles; C1: Chitosan/drug (w/w) = 1∶5; C2: Chitosan/drug = 1∶1; Ris-SAIB: Risperidone-loaded SAIB depot; C1-SAIB: Ris-Cm-SAIB (chitosan/drug = 1∶5); C2-SAIB: Ris-Cm-SAIB (chitosan/drug = 1∶1)

Table 2 Evaluation of drug release kinetics of different depots according to the Higuchi equation. BR: Burst release; R: Regression coefficient
1.2 PLGA骨架微球对复合型原位贮库体外药物释放的影响

以疏水性材料PLGA为骨架材料,制备利培酮PLGA骨架微球/SAIB复合型原位贮库 (Ris- Pm-SAIB),考察PLGA骨架微球及PLGA/药物比例对Ris-Pm-SAIB药物释放的影响,结果见图 3。将药物释放曲线用Higuchi方程 (公式1) 进行拟合,见表 3。PLGA微球释放结果显示 (图 3A),3种PLGA骨架微球药物释放速度显著低于药物颗粒 (Ris) 和壳聚糖骨架微球,随着PLGA/药物比例的增加,药物释放速度显著降低。

Figure 3 Effect of different PLGA/drug ratios on the in vitro drug release of PLGA microspheres (A) and risperidone-loaded PLGA microsphere/SAIB complex depot (Ris-Pm-SAIB,B) in pH 7.4 PBS at 37 ℃ (x± s,n = 3). PLGA microspheres: P1,PLGA/drug (w/w) = 4∶1; P2,PLGA/drug = 2∶1; P3,PLGA/drug = 4∶3; P1-SAIB: Ris-Pm-SAIB (PLGA/drug = 4∶1); P2-SAIB: Ris-Pm-SAIB (PLGA/drug = 2∶1); P3-SAIB: Ris-Pm-SAIB (PLGA/drug = 4∶3)

与Ris-SAIB和Ris-Cm-SAIB相比,Ris-Pm-SAIB可显著降低药物突释 (0.64%~2.16%)。当PLGA/药物比例为4∶1和2∶1时,所制备复合型贮库P1- SAIB与P2-SAIB药物释放速度均显著降低 (图 3B)。当PLGA与药物比例降低为4∶3时,药物突释增加至2.16%,且药物释放速度显著高于P1-SAIB和P2- SAIB (表 3显示斜率增加)。可能与PLGA微球 (P3) 载药量过高,药物主要吸附于微球表面,而导致药物释放增加有关。

Table 3 Evaluation of drug release kinetics of Ris-Pm-SAIB according to the Higuchi equation

上述结果表明,与Ris-SAIB和Ris-Cm-SAIB相比,Ris-Pm-SAIB可显著降低药物突释,且药物释放行为符合Higuchi方程,表明Ris-Pm-SAIB药物释放仍为扩散机制。Ris-Pm-SAIB中大部分药物被包载于PLGA骨架微球内部,贮库中溶解游离药物显著降低,仅有少量药物在贮库形成过程中扩散至释放介质中,从而显著降低药物突释; 贮库形成后,药物需先由PLGA骨架微球扩散至SAIB基质中,再扩散至释放介质中,由于受双重骨架扩散控制,药物释放速度显著低于Ris-SAIB; 此外,与壳聚糖相比,PLGA疏水性较强,可有效避免释放介质渗入贮库内部,因此Ris-Pm-SAIB整体药物释放速度低于Ris-Cm-SAIB。

2 骨架微球形态对Ris-Pm-SAIB体外药物释放的影响

P2-SAIB虽可降低药物突释量,但其30天药物释放量仅为14.54% (图 3B)。为避免Ris-Pm-SAIB后期药物释放不完全,在微球制备过程中,固定PLGA/药物比例为2∶1,向有机相中分别加入5%、10%、20%的中链甘油三酯 (medium chain triglyceride,MCT),制备多孔性微球,以加速药物释放。MCT用量对微球性质和表面形态的影响结果分别见表 4图 4。结果显示,MCT对微球粒径分布及大小无显著性影响,对微球表面形态影响较大。加入MCT后,微球表面呈多孔状,且随着MCT用量的增加,孔洞显著增多。微球结构形态与聚合物沉淀动力学密切相关[22],在溶剂挥发过程中,MCT对PLGA溶解性能很差或不溶解,可在聚合物基质中产生MCT富集相,由于MCT与水不相溶,而与二氯甲烷可互溶,二氯甲烷可快速扩散至MCT富集相,从内部加速PLGA沉淀,形成内部多孔结构,而这部分二氯甲烷在冻干过程中可以除去,并在微球表面产生大量孔洞[23]

Figure 4 Scanning electron microscope (SEM) micrograms of PLGA microspheres prepared by separately adding 0% (P2),5% (PP1),10% (PP2) and 20% (PP3) MCT in the organic phase (×8k)

Table 4 The effects of medium chain triglyceride (MCT) content in the organic phase on the properties of PLGA microspheres. SD: Standard deviation; EE: Encapsulation efficiency of microspheres

多孔性微球孔洞结构可导致大量释放介质进入微球内部,药物扩散路径缩短,从而加速药物释放 (图 5A)。随着微球孔洞增多,药物释放速度也随之增加,当MCT用量达到20% 时,骨架微球可在30天时达到完全释放。同样,将多孔性微球分散于SAIB/无水乙醇溶液中制备Ris-PPm-SAIB后,SAIB/溶剂系统迅速经微球孔洞扩散至微球内部,药物经孔道快速扩散至SAIB基质中,导致Ris-PPm-SAIB药物释放速度加快 (表 5)。当加入20% MCT时,PP3-SAIB药物突释增加至2.69%,前期药物释放速度明显变快; 14天时累积药物释放量为20.76% (图 5B),约相当于P2-SAIB的两倍,可保证后期药物有效释放。

Table 5 Evaluation of drug release kinetics of Ris-Pm-SAIB and Ris-PPm-SAIB according to the Higuchi equation

Figure 5 The effects of morphology of microspheres on the in vitro drug release of PLGA microspheres (A) and risperidone- loaded porous PLGA microsphere/SAIB complex depot (Ris- PPm-SAIB) (B) in pH 7.4 PBS at 37 ℃ (x± s,n = 3). P2-SAIB: Ris-Pm-SAIB (0% MCT); PP1-SAIB: Ris-PPm-SAIB (5% MCT); PP2-SAIB: Ris-PPm-SAIB (10% MCT); PP3-SAIB: Ris-PPm- SAIB (20% MCT)

体外结果显示,与Ris-SAIB相比,Ris-Pm-SAIB可显著降低药物突释; 通过调节微球形态,制备的多孔性微球/SAIB复合型贮库 (Ris-PPm-SAIB) 在降低突释的同时,可加速后期药物释放速度。此外,与市售利培酮长效注射剂 (Risperdal® Consta®) 相比,无药物释放延滞期。Risperdal® Consta®第1天释放1.6%药物后,2~24天几乎无药物释放,随后药物快速释放,40天药物释放完全,存在22天释放延滞期,在体外可缓释16天[2, 3]。而Ris-Pm-SAIB和Ris-PPm-SAIB均无药物释放延滞期,体外条件下可持续释放药物60天以上。

3 骨架微球形态对复合型贮库体内药动学的影响

12.5 mg·kg-1剂量的Ris-Pm-SAIB及Ris-PPm- SAIB给予大鼠肌肉注射后,活性成分 (利培酮与9-羟基利培酮之和) 的平均血药浓度-时间曲线如图 6所示,主要药动学参数见表 6。结果显示,随着MCT用量的增加,Cmax逐渐增加。与P2-SAIB相比,当MCT用量达到20% 时,AUC0-4d由 (105.2 ± 24.4) ng·mL-1·d增加至 (194.6 ± 15.8) ng·mL-1·d; 而在4~78天药物依然能够维持较快的释放速度,78天时血药浓度C78d仍可达 (9.0 ± 2.5) ng·mL-1,平均血药浓度Cs (4-78d) 为(7.8± 1.2) ng·mL-1,AUC4-78d由(385.3 ± 126.6) ng·mL-1·d增加到 (465.0 ± 149.2) ng·mL-1·d,保证了药物充分释放。

Figure 6 The plasma concentration-time profiles of active components (risperidone plus 9-OH-risperidone) after i.m. administration of Ris-Pm-SAIB and Ris-PPm-SAIB to rats at dose of 12.5 mg·kg-1 (x± s,n = 6). Each concentration-time profile from 0 to 2 days was scaled up and inserted in the right top of the corresponding figure

Table 6 The non-compartmental model pharmacokinetic parameters of the active component (risperidone plus 9-OH-risperidone) after i.m. administration of Ris-Pm-SAIB and Ris-PPm-SAIB to rats at dose of 12.5 mg·kg-1( x ± s,n = 6)

与Ris-Pm-SAIB相比,Ris-PPm-SAIB中微球呈多孔性结构,使药物经微球孔道快速扩散至SAIB基质中,前期药物释放速度增加; 随着MCT用量的增加,微球孔洞增多,前期 (0~4天) 药物释放速度变快,后期 (4~78天) 释放速度略有增加。当MCT用量为20% (PP3-SAIB),与其他组相比仍能维持在较高的血药浓度水平。

基于PLGA骨架微球的Ris-Pm-SAIB及Ris-PPm- SAIB与前期报道[18]的单独SAIB贮库相比,前期药物突释显著降低,Cmax由 (1 950.8 ± 268.4) ng·mL-1降至 (73.9 ± 30.6)~(226.6 ± 154.4) ng·mL-1,Cmax/Cs由415.8 ± 175.5降至10.8 ± 4.8~31.0 ± 13.6,突释程度约降低了93%~97%; 缓释时间由25天延长至78天。本研究所制备的基于PLGA骨架微球的Ris-Pm-SAIB和Ris-PPm-SAIB主要是通过降低原位贮库系统中溶解的游离药物量来降低前期药物突释。其药物释放速度主要受药物由微球扩散至SAIB基质中的速度控 制,因此整体释药速度较低。其中,基于多孔性骨架微球的Ris-PPm-SAIB,药物受孔道扩散和骨架扩散双重控制,即可降低药物突释,又可保证后期药物充分释放,使血药浓度长期维持在较高的水平。

结论

与Ris-SAIB相比,本研究设计的Ris-Pm-SAIB可显著降低药物前期突释量和药物整体释放速度。在此基础上,可通过改变PLGA骨架微球结构制备Ris- PPm-SAIB,药物释放由双重骨架控制调节为孔道-骨架控制,在降低SAIB贮库药物突释的同时,可保证后期药物充分释放,使血药浓度在78天内维持在较高的水平。

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