载环孢素纳米球的制备及释放特性*

目的：制备一种环孢素A（CsA）缓释纳米体系。方法：以PLA-co-PEG共聚物材料作为环孢素药物的释放载体；采用超声振荡技术制备载环孢素的PLA—PEG—PLA纳米球；分析纳米球的粒径与分布以及纳米球降解过程中的形貌变化；体外释放试验探讨制备的纳米球的降解特性以及与载体材料、介质pH值之间的影响关系；小鼠灌胃后HPLC法测定血药浓度。结果：采用PLA—PEG—PLA共聚材料装载CsA，药物包封率达到89．2％。纳米球平均粒径为242．3nm，载药后平均粒径增大到320．2nm。扫描电镜分析发现纳米球在磷酸缓冲液中溶胀程度与降解速率依赖于介质pH值。体外模拟释放表明载药纳米球的药物释放速率与载体降解速率一致，持续稳定释药时间〉7d。动物模型也证实该载CsA纳米球可维持血液中稳定的药物浓度5d以上。结论：利用本方法制备的载CsA纳米球是一种较理想的环孢素药物剂型，具有临床应用价值。     

环孢素A-Eudragit S100纳米粒冻干粉制剂在犬体内的药动学

目的:研究环孢素A-Eudragit S100纳米粒冻干粉制剂(freeze-dried cyclosporine A-Eudragit S100 nanoparticles,CyA-S100-NP)在家犬体内药动学及相对生物利用度。方法:以双周期交叉随机试验设计法,高效液相色谱法测定6只家犬口服给予环孢素A-Eudragit S100纳米粒冻干粉硬胶囊和新山地明微乳软胶囊(Neoral)后环孢素A的血药浓度,采用3P97软件计算药动学参数。结果:经3P97软件拟合,环孢素A的药动学过程符合二室模型。与Neoral相比,CyA-S100-NP的AUC显著增大(P<0.05),CL显著降低(P<0.05),相对生物利用度为135.9%。结论:CyA-S100-NP可促进药物口服吸收,显著提高环孢素A的生物利用度,有望开发成为一种新型口服环孢素A纳米粒固体制剂。     

环孢素A栓剂的相对生物利用度

目的 :研究环孢素A栓剂与环孢素A口服液的相对生物利用度。方法 :利用荧光偏振免疫分析仪测定家兔直肠给予环孢素A栓剂 2 5mg·kg-1(n =4)与口服环孢素A口服液 2 5mg·kg-1(n =4)后血药浓度 ,计算两者的药物动力学参数和相对生物利用度 ,并进行统计学分析。结果 :环孢素A栓剂的相对生物利用度为 ( 12 2 .4± 2 9.3) % ,两者的动力学参数间差异无显著性 (P >0 .0 5 )。结论 :环孢素A栓剂与环孢素A口服液具有生物等效性 ,可以通过对环孢素A栓剂的进一步改进 ,提高其生物利用度。     

环孢素A pH敏感性纳米粒的制备与大鼠口服药代动力学

目的研究环孢素A(CyA) pH敏感性纳米粒的制备工艺与口服药代动力学性质。方法采用改良的乳化-溶剂扩散技术(QESD)制备CyA pH敏感性纳米粒；经大鼠灌胃给药，HPLC法测定全血药物浓度，计算口服相对生物利用度。结果经3P87程序拟合，确定CyA在大鼠体内的药代动力学过程为二室模型；与Neoral微乳相比，CyA-E100，CyA-L100，CyA-L100-55和CyA-S100纳米粒的相对生物利用度分别为94.8%，115.2%，113.6%和132.5%。结论经统计分析，CyA-S100纳米粒可以显著改善CyA的生物利用度(P<0.05)，而CyA-L100-55纳米粒，CyA-L100纳米粒和CyA-E100纳米粒与Neoral微乳相比无显著性差异。实验结果表明,pH敏感性纳米粒有望成为促进蛋白、多肽类药物及难溶性药物口服吸收的有效载体。     

环孢素A自微乳软胶囊的制备及质量控制

目的：制备环孢素A自微乳软胶囊,确定纳米粒径测定方法,控制产品质量。方法：通过测定环孢素A溶解度,以及以自微乳化后的粒径、自乳化时间和色泽为指标,对油相、潜溶剂、乳化剂、助乳化剂进行筛选,制备环孢素A自微乳软胶囊;通过稳定性、精密度等方法学试验,确定自微乳化后乳滴直径测定方法,控制产品质量。结果与结论：油相、潜溶剂、乳化剂、助乳化剂比例为1∶2∶2∶2时可获得优良的自乳化效果,软胶囊平均自微乳粒径为25 nm,因此提高了环孢素生物利用度,减少了服用量。     

环孢素A新制剂研究进展

<正> 环孢素 A 为第3代选择性免疫抑制剂,由于其口服制剂生物利用度低、个体差异大、外用制剂则存在经皮转运困难问题,加之环孢素 A 较严重的肾毒性及中枢神经系统毒性、肝毒性、消化道反应等,使其应用受限。本文对近年来环孢素 A 新制剂的研究进展进行综述。环孢素 A 微乳剂可增加亲脂性药物和难溶性药物的溶解度和溶出性能,从而改善其体内吸收,提高口服生物利用度。环孢素 A 纳米粒不仅可以提高物体内靶向性,还可改变药物的药动力学,并在一定程度上改善药物的生物膜穿透能力。环孢素 A 乳酸-羟乙酸共聚物纳米粒能使血药浓度更高,保持时间更久;环孢素 A 聚乙酸丙酯纳米粒能明显提高其角膜穿透能力,提高生物利用度;环孢     

环孢素A混合胶团的制备及质量评价

目的：筛选环孢素A（cyclosporine A，CYA）脱氧胆酸钠/磷脂混合胶团的制备工艺，并初步考察其性质。方法：利用正交试验设计考察了制备所需的载体质量比、温度及水合介质对载药量、包封率的影响。结果：在胆酸钠与磷脂的质量比为1：1，反应温度为60℃和以水为水合介质的条件下，所得到的包封率可达90％以上，载药量达到4％以上，平均粒径约为180nm。结论：通过正交设计得到了高包封率和高载药率的环孢素A混合胶团。     

非诺贝特胶囊剂及家犬体内生物利用度

目的采用纳米分散技术制备非诺贝特胶囊剂,以提高其溶出度及生物利用度。方法用反溶剂沉淀法和高压匀质法制备非诺贝特纳米混悬剂,并通过喷雾干燥将其固化以制备胶囊剂,用差示扫描量热法(differential scanning calorimetry,DSC)和X-射线粉末衍射分析表征药物在胶囊剂中的存在状态,并测定药物的溶出度及家犬体内的生物利用度。结果非诺贝特以纳米晶体状态分散于胶囊剂中,自制胶囊溶出度为国产胶囊的3倍,相对生物利用度为国产胶囊的(274.5±15.6)%。结论自制非诺贝特胶囊剂可以通过增加非诺贝特的分散度来提高药物的溶出度与生物利用度。     

基于甘草酸为载体的紫杉醇-甘草酸纳米胶束的构建和口服生物利用度的评价

目的：构建紫杉醇-甘草酸纳米胶束（paclitaxel-loaded glycyrrhizic acid micelles）并对其理化性质及口服生物利用度进行考察。方法：所制备纳米胶束的包封率和载药量通过高效液相色谱法检测并计算;采用动态光散射仪测定其粒径分布;以紫杉醇溶液作为对照组,考察纳米胶束口服给药后药动学的变化;采用在体in-situ肠封闭法考察不同肠道对紫杉醇的吸收差异。结果：采用超声分散法制备载紫杉醇-甘草酸纳米胶束大小均匀,平均粒径为（245.42±5.62） nm;药物胶束的包封率为90.22%±0.27% （n=3）,载药量为7.90%±0.10%（n=3）;与对照组相比,纳米胶束口服生物利用度提高约6倍,很大程度上是由于紫杉醇在空肠以及结肠上吸收的增加引起。结论：该方法所制备的纳米胶束制剂能有效提高紫杉醇口服生物利用度,发挥甘草酸药物载体的特点以及药用安全性的优点,该纳米胶束可作为紫杉醇新的药物传递系统,具有临床应用前景。     

胰岛素聚酯微粒的制备及大鼠体内药效学研究

目的　探讨利用一种新型聚酯材料—ε-己内酯-D,L-丙交酯嵌段共聚物(PCLA)制备微粒型药物载体的可能性。方法　通过双乳化溶剂蒸发技术制备ε-己内酯-D,L-丙交酯嵌段共聚物微粒(PCLA-MP),用扫描电镜观察其形态,粒径分析仪(particle analyser)测定粒径;以胰岛素(INS)为模型药物,制备胰岛素聚酯微粒(INS-PCLA-MP);建立了测定INS包封率的HPLC方法;INS抗体捕捉实验考察PCLA-MP载药机理;以pH 7.4的磷酸盐缓冲液为介质,探讨INS-PCLA-MP体外释药特性;建立了药物致大鼠糖尿病模型,通过葡萄糖氧化酶法(GOD-PAP)测定血糖值来评价INS-PCLA-MP经皮下给药后的降血糖作用;以INS-SOL为对照,计算药理相对生物利用度。结果　制备的微粒大小均匀,表面光滑圆整,平均粒径1.9 μm;INS的包封率为76.46%;抗体捕捉实验证实,被包封的INS中只有小部分(18.25%)分布在MP的表面;INS-PCLA-MP的体外释放曲线包括突释相及随后的缓慢释放相;药效学研究表明,12 u.kg^-1的INS-PCLA-MP经糖尿病大鼠皮下给药后具有明显的降血糖作用,药理相对生物利用度为132.95%。结论　PCLA嵌段共聚物作为药物输送系统的载体材料有着良好的前景,PCLA-MP有可能成为一种新型的药物载体。     

Studies on the cyclosporin A loaded stearic acid nanoparticles

Stearic acid nanoparticles were prepared in this study by melt-homogenization to investigate the possibility of them as a new kind of drug carrier system. Some physicochemical properties of stearic acid nanoparticles were studied and morphology examined by transmission electron microscope. Cyclosporin A as a model drug was then encapsulated into stearic acid nanoparticles. Following the establishment of high performance liquid chromatography assay for cyclosporin A analysis in stearic acid nanoparticles or blood samples, the encapsulation ratio of cyclosporin A to stearic acid nanoparticles was estimated and pharmacokinetics as well as bioavailability of cyclosporin A stearic acid nanoparticles after oral administration to Wistar rats were studied, using the Sandimmun Neoral® (an available microemulsion system of cyclosporin A) as a reference. The mean diameter of cyclosporin A stearic acid nanoparticles was 316.1 nm, while the encapsulation ratio of cyclosporin A to stearic acid nanoparticles reached to 88.36%. It was demonstrated by IR spectra and differential scanning calorimetry that there was no chemical reaction occurred between the cyclosporin A and stearic acid. The relative bioavailability of cyclosporin A stearic acid nanoparticles over reference was nearly 80%, and the time to reach maximum concentration (T_max) of cyclosporin A after oral administration of cyclosporin A stearic acid nanoparticles was delayed significantly than the reference, suggesting an obvious sustained release effect. The stearic acid nanoparticles might be a very potential drug carrier.     

Biodegradable nanoparticles as a delivery system for cyclosporine: preparation and characterization

Cyclosporine (CyA) was incorporated into polycaprolactone nanoparticles (PCL-NP) in order to increase its oral bioavailability and to control drug distribution, thereby potentially reducing its toxicity. Prior to in vivo studies, the carrier was optimized and characterized by using different techniques. Light scattering (LS) and transmission and scanning electron microscopy (TEM and SEM) indicated the NP were spherical in shape with a mean size of approximately 100 nm. The influence of the solvent evaporation conditions and the polymer and drug amounts on CyA incorporation was established in order to optimize drug loading. When acetone and excess water were removed at constant temperature, no aggregation phenomena were observed. A value of 180 mg PCL was the minimum polymer amount necessary to encapsulate 95% of the drug initially added to the preparation. Under these conditions, HPLC analysis revealed that approximately 130 microg CyA per mg PCL were incorporated for a total CyA concentration of 2.5 mg/ml, being part of the drug adsorbed onto the particle surface. No structural changes or instability of the components during NP preparation were detected by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). However, GPC studies showed a competition between poloxamer and CyA for adsorption onto the carrier. In addition, DSC results suggested that at least part of the drug associated to NP remained in its crystal form. Therefore, CyA-loaded NP were easily manufactured and characterized and allow for the administration of therapeutic drug doses to experimental animals.     

Biodegradable nanoparticles as a delivery system for cyclosporine: preparation and characterization

Cyclosporine (CyA) was incorporated into polycaprolactone nanoparticles (PCL-NP) in order to increase its oral bioavailability and to control drug distribution, thereby potentially reducing its toxicity. Prior to in vivo studies, the carrier was optimized and characterized by using different techniques. Light scattering (LS) and transmission and scanning electron microscopy (TEM and SEM) indicated the NP were spherical in shape with a mean size of 100nm. The influence of the solvent evaporation conditions and the polymer and drug amounts on CyA incorporation was established in order to optimize drug loading. When acetone and excess water were removed at constant temperature, no aggregation phenomena were observed. A value of 180mg PCL was the minimum polymer amount necessary to encapsulate 95%of the drug initially added to the preparation. Under these conditions, HPLC analysis revealed that 130mug CyA per mg PCL were incorporated for a total CyA concentration of 2.5mg/ml, being part of the drug adsorbed onto the particle surface. No structural changes or instability of the components during NP preparation were detected by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). However, GPC studies showed a competition between poloxamer and CyA for adsorption onto the carrier. In addition, DSC results suggested that at least part of the drug associated to NP remained in its crystal form. Therefore, CyA-loaded NP were easily manufactured and characterized and allow for the administration of therapeutic drug doses to experimental animals.     

Encapsulation of hydrophobic drugs in polymeric micelles through co-solvent evaporation: the effect of solvent composition on micellar properties and drug loading

This study was designed to develop an optimized co-solvent evaporation procedure for the efficient encapsulation of hydrophobic drugs in polymeric micelles of methoxy poly(ethylene oxide)-block-poly(epsilon-caprolactone) (MePEO-b-PCL). MePEO-b-PCL block copolymers having varied MePEO and PCL molecular weights were synthesized, assembled to polymeric micelles, and used for the encapsulation of cyclosporine A (CyA) by a co-solvent evaporation method. The co-solvent composition was varied by changing the type of organic co-solvent (using acetone, acetonitrile and tetrahydrofuran), the ratio of organic to aqueous phase, and their order of addition. Carrier size, morphology and encapsulated CyA levels were defined by dynamic light scattering (DLS), transmission electron microscopy (TEM) and HPLC, respectively, and the effect of co-solvent composition on micellar properties and loaded CyA levels was evaluated. Application of acetone and acetonitrile as the selective co-solvent for the core-forming block led to a decrease in the average diameter of self-assembled structures. When acetone was added to water, a decrease in the ratio of organic to aqueous phase led to an increase in the loading efficiency of CyA in MePEO-b-PCL micelles. A similar trend in CyA loading was observed for MePEO-b-PCL micelles of varied MePEO and PCL block lengths. The ratio of organic to aqueous phase did not affect CyA loading when water was added to acetone. Irrespective of the order of addition, the decrease in the organic to aqueous phase ratio caused a reduction in the average diameter of the empty and CyA loaded micelles. We conclude that the co-solvent evaporation method may be optimized to improve the efficiency of drug encapsulation in polymeric micelles. For CyA encapsulation in MePEO-b-PCL micelles, addition of acetone to water at lower organic to aqueous phase ratio is shown to be the optimum procedure leading to higher drug encapsulation and smaller average diameter for the self-assembled structures.     

Oral evaluation in rabbits of cyclosporin-loaded Eudragit RS or RL nanoparticles

The hydrophobic cyclic undecapeptide cyclosporin A (CyA) used in the prevention of graft rejection and in the treatment of autoimmune diseases was encapsulated by nanoprecipitation within non-biodegradable polymeric nanoparticles. The effect of polymers (Eudragit RS or RL) and additives within the alcoholic phase (fatty acid esters and polyoxyethylated castor oil) on the size, zeta potential and the encapsulation efficiency of the nanoparticles was investigated. The mean diameter of the various CyA nanoparticles ranged from 170 to 310 nm. The size as well as the zeta potential increased by adding fatty acid ester and polyoxyethylated castor oil within the organic phase. No significant differences in surface potential were observed for all formulations tested. Probably due to the very low water solubility of the drug, high encapsulation efficiencies were observed in a range from 70 to 85%. The oral absorption of CyA from these polymeric nanoparticles was studied in rabbits and compared to that of Neoral capsule. Based on comparison of the area under the blood concentration-time curve values, the relative bioavailability of CyA from each nanoparticulate formulation ranged from 20 to 35%.     

Modulation of mdr1a and CYP3A gene expression in the intestine and liver as possible cause of changes in the cyclosporin A disposition kinetics by dexamethasone

We investigated the effect of dexamethasone (DEX) on the disposition kinetics of cyclosporin A (CyA) and the mechanism of this drug interaction. Rats were treated with DEX (1 or 75mg/kg per day, i.p.) once a day for 1-7 days, and the blood concentration of CyA was measured after an i.v. or p.o. dose of CyA (10mg/kg) at 1.5hr after the last DEX treatment. In rats treated with a low dose of DEX (1mg/kg), the blood concentration of CyA after i.v. administration was unchanged compared with that of untreated rats, whereas the blood concentration after oral administration was significantly decreased, and this decrease was dependent on the duration of DEX administration. The total clearance (CL(tot)) of CyA was unchanged, but the bioavailability was significantly decreased to about one-third of that in DEX-untreated rats after 7 days of DEX treatment. At this time, the expression of mdr1a mRNA and P-gp in the liver and intestine was increased, whereas CYP3A2 was unaffected at both the mRNA and protein levels. In rats treated with a high dose of DEX (75mg/kg), the blood concentration of CyA was significantly decreased after both i.v. and p.o. administrations compared with those of untreated rats. The bioavailability of CyA was decreased, and the CL(tot) was significantly increased. The P-gp and CYP3A2 in the liver and intestine were increased at both the mRNA and protein levels. Our results indicate that the drug interaction between CyA and DEX is a consequence of modulation of P-gp and CYP3A2 gene expression by DEX, with differential dose-dependence.     

Mechanism of decrease of oral bioavailability of cyclosporin A during immunotherapy upon coadministration of amphotericin B

The trough level of blood concentration of cyclosporin A (CyA) in a patient receiving immunotherapy was observed to decrease following coadministration of amphotericin B (AMB). This clinical observation was confirmed experimentally in Wistar rats intravenously given AMB (1.5 or 3.0 mg/kg) or saline (control) for 4 days, followed by CyA (10 mg/kg). The blood concentration of CyA after i.v. or p.o. administration in both AMB groups was significantly decreased compared with the control. The oral bioavailability of CyA after 1.5 or 3.0 mg/kg AMB treatment was decreased to 67% or 46%, respectively, of that of the control group. AMB treatment increased the expression levels of mdr1a and mdr1b mRNAs in the duodenum to about three times the control, and expression of CYP3A2 mRNA in the liver was increased to about twice the control. The P-gp and CYP3A2 proteins were increased significantly. These findings suggest that the oral bioavailability of CyA is reduced as a result of both increased efflux transport via P-glycoprotein in the duodenum and an increased first-pass effect of CYP3A2-mediated hepatic metabolic activity, induced by AMB. It is suggested that careful monitoring of CyA levels is necessary in the event of AMB administration to patients receiving immunotherapy with CyA.     

Saturable Binding of Cyclosporin A to Erythrocytes: Estimation of Binding Parameters in Renal Transplant Patients and Implications for Bioavailability Assessment

Cyclosporin (CyA) exhibits saturable binding to erythrocytes. A one-site binding model was fitted to data from renal transplant patients receiving CyA therapy. The average maximum binding capacity is 2560 µg CyA/liter of packed erythrocytes; the unbound CyA concentration associated with 50% saturation of the binding site is 67 µg/liter. Analysis indicates that whole-blood CyA measurement to monitor drug therapy should be viewed cautiously, particularly when the hematocrit varies considerably. The error in estimating absolute bioavailability at steady state from whole-blood measurements, resulting as a consequence of the saturable binding, has been explored. Although extrapolation to the therapeutic situation, which involves transient drug administration, is difficult, errors of up to 25% are anticipated. When an accurate estimate of bioavailability is required, analysis based on plasma data is proposed. For bioequivalence testing, both blood and plasma CyA data are equally acceptable.     

Spray-dried redispersible oil-in-water emulsion to improve oral bioavailability of poorly soluble drugs.

A physically stabilized dry emulsion dosage form reforming the original emulsion after rehydration was developed by spray-drying a liquid oil-in-water emulsion containing maltodextrin as carrier and sodium caseinate as emulsifying agent. Several oil:water as well as maltodextrin:water ratios were tested, the homogenization and spray-drying processes and the reconstitution properties were investigated and an optimum formulation was selected for poorly soluble drug incorporation, having an identical oil:water and carrier:water ratio of 10% (w/w) and a load of solid material of 20% (w/w). Lipophilic 5-phenyl-1,2-dithiole-3-thione (5-PDTT) was selected as a model drug. 5-PDTT release from the solid state emulsion was studied using an in vitro two-phase stirred model and the relative bioavailability of 5-PDTT in the dry emulsion was obtained in the rabbit after oral administration of the reconstituted emulsion, compared to a 5-PDTT-sulfobutyl ether 7 beta-cyclodextrin complex in solution. Incorporation of 5-PDTT in the oil phase neither affects the surface morphology of the powder nor the reconstitution, the droplet size or the drug releasing properties and, furthermore, allows a 3-fold improvement of 5-PDTT relative bioavailability in rabbit after oral administration. These results indicate that dry emulsions may be considered as relevant dosage forms to improve bioavailability of poorly absorbable lipophilic drugs.