喷雾干燥法制备红霉素肠溶缓释微囊

目的：采用喷雾干燥法制备红霉素肠溶缓释微囊,并考察其释放特性。方法：以红毒素为囊心物,Eudragit S100为包衣材料,蓖麻油为增塑剂,乙醇为溶剂,将囊心物与囊材按1：2,1：3和1：4的比例喷雾干燥制备微囊。结果：经电镜扫描和X－射线衍射测定表明,囊心物：囊材按1：4比例制备的微囊外形圆整,包囊安全;体外释放度测定显示,微囊能稳定地在人工肠液中缓慢释放,药物1h释放量不超过30％,12h释放量不低于90％,与市售红霉素肠溶片相比,有明显缓释作用。结论：喷雾干燥法制备微囊,工艺稳定,可持续操作,可连续操作,制备的红霉素微囊有很好的肠溶行为缓释特征。     

Preparation of sustained release rifampicin microparticles for inhalation

Objectives The aim of this research was to develop a novel carrier‐free dry powder formulation of rifampicin for inhalation with controlled‐release properties. Methods Rifampicin dihydrate (RFDH) microcrystals were prepared by a polymorphic transformation of rifampicin. The prepared RFDH microcrystals were coated with poly (dl ‐lactide‐co‐glycolide) or poly (dl ‐lactide), using a spray‐dryer equipped with two different types of three‐fluid (3F) spray nozzles. The physicochemical and aerodynamic properties of the coated RFDH microcrystals were compared with those of conventional matrix microparticles. Key findings The coated RFDH powder, encapsulating 50% of rifampicin, was successfully prepared by simple in‐situ coating methods using two different types of 3F nozzles and had mass median aerodynamic diameter values of 3.5–4.5 µm . The thin flaky morphology of RFDH powders, providing good aerosolization properties, was maintained after coating. The coated RFDH formulations showed relatively low initial rifampicin release, compared with the uncoated RFDH crystals, followed by slow rifampicin release (about 70%) over 8 h in phosphate‐buffered saline media (pH 7.4). Significant chemical degradations were not observed from the crystalline‐structured RFDH formulations, while the amorphous‐structured matrix formulations showed chemical degradation in six months. Conclusions These polymer coated RFDH formulations may be a valuable alternative in the treatment of tuberculosis since the carrier‐free formulation offers the benefit of delivering a maximum‐potency formulation of the antibiotic directly to the site of infection, and long drug residence times may be achieved by the controlled release of the drug.     

Fast and pH-dependent release of domperidone from orally disintegrating tablets

There has been growing interest in orally disintegrating tablets (ODTs) during the last decade due to their better patient acceptance and compliance. Further, drug dissolution and absorption may be significantly improved. This work describes the preparation of fast and pH-dependent release ODTs for domperidone by direct compression using crospovidone as superdisintegrant. Solid dispersions of domperidone and Eudragit L100-55, at different weight ratios, were prepared and characterized by DSC, TGA, X-ray diffraction, and FTIR, which indicated the presence of drug–polymer interaction. Disintegration time, friability, and hardness of ODTs were evaluated. In vitro drug release in 0.1N HCl and in phosphate buffer (pH 5.8 and 6.8) was investigated. All domperidone ODTs had fast disintegration times (6 KP) and acceptable friability (<1%). Drug release from fast release ODTs was highly improved; reaching 97% after 10?min in 0.1N HCl, compared to the dissolution of the free drug. Drug release from solid dispersions was pH dependent; showing higher release rates at pH 6.8 than at lower pH values. The controlled-release ODT resulted in 47% drug release in 0.1N HCl, with the rest of drug released at pH 6.8. Domperidone ODTs were considered suitable for ODT formulation.     

Fluphenazine release from biodegradable microparticles: Characterization and modelling of release

Abstract

The release of actives encapsulated in biodegradable poly-lactide-co-glycolide (PLGA)-based microparticles may be diffusion controlled, dependent on polymer degradation, or may occur by a combination of drug diffusion and polymer degradation. This report applies a model, describing combined diffusional and polymer degradation-assisted drug release, to quantify the release of fluphenazine HCl (F-HCl) from PLGA microspheres. Parameters for the release process showed that both the initial drug release phase and the polymer controlled drug release phase were dependent on the F-HCl loading of the microspheres. The percentage drug released in the burst phase and the length of the lag phase were dependent on F-HCl loading. In the degradation controlled release phase, drug release was faster the higher the loading, as shown by the decrease in t_max from 27 to 10 days, as F-HCl loadings increased from 4.2 to 16.6%w/w. The presence of F-HCl was found to catalyse the degradation of PLGA polymer during particle manufacture and during dissolution. When compared to drug free microspheres, F-HCl accelerated PLGA degradation as shown by the ～5-fold increase in both PLGA degradation rate constant (k) and reduction in t_max.     

Methacrylate micro/nano particles prepared by spray drying: a preliminary in vitro/in vivo study

Delivery systems controlling drug release only in the colon holds great promises since they improve utilization of drug and decrease the dosing times comparison with conventional forms. The aim of the present study was to prepare polymeric microparticles on the basis of Ciprofloxacin via oral route for the treatment of inflammatory bowel disease. Ciprofloxacin was selected because of its extensive coverage for intestinal flora, relatively favorable side-effect profile and preliminary data suggesting its efficacy in the treatment of active Crohn's Disease. Microparticles were prepared using different acrylic compounds, namely Eudragit® RL (PO) and RS (PO) and a mixture of both. Spray-drying was used as a preparation method of Ciprofloxacin/Eudragit® microparticles using a Mini Spray Dryer B-290 (Büchi, Postfach, Switzerland). In vitro dissolution studies were performed to choose the best formulation and selected microparticles were characterized by size and morphology by environmental scanning electron microscopy. Yield and encapsulation efficiency were calculated and in vivo/ex vivo experiments were investigated both of which suggest that selected microparticles can be used for colon targeting of drugs increasing residence time of the drug in the affected area.     

Nano-scaled pH-responsive polymeric vesicles for intracellular release of doxorubicin

Polymeric vesicles produced by spontaneous self-association of poly(acrylic acid-co-distearin acrylate) (poly(AAc-co-DSA)) with varying ratios of AAc and DSA units in aqueous solution of pH 5.0 exhibit the pH-regulated drug release behavior. Through the electrostatic interaction with ionized AAc residues, doxorubicin (DOX) molecules can be highly accommodated onto either the inner or outer surfaces of vesicles when the pH is adjusted from 5.0 to 7.4. The extent of DOX encapsulation is dependent largely on the structural transition of vesicles in response to the pH change. While the pH-evolved drug release profile varies to some extent with the distribution of DOX molecules within vesicles, the drug release from vesicles is accelerated significantly via the disruption of the electrostatic interaction of DOX species with ionized AAc moieties at pH 5.0. The DOX-loaded polymeric vesicles show promoted cellular uptake and cytotoxicity comparable to free DOX for HeLa cells. This indicates that they are probably taken up by the cells via the lipid raft-mediated endocytosis.     

Formulation and pharmacodynamic evaluation of captopril sustained release microparticles

Cellulose propionate (CP) microparticles containing captopril (CAP) were prepared by solvent evaporation technique. The effects of polymer molecular weight, polymer composition and drug?:?polymer ratios on the particle size, flow properties, morphology, surface properties and release characteristics of the prepared captopril microparticles were examined. The anti-hypertensive effect of the selected CAP formulation in comparison with aqueous drug solution was also evaluated in vivo using hypertensive rats. The formulation containing drug?:?polymer blend ratio 1?:?1.5 (1?:?1 low?:?high molecular weight CP), namely F7, was chosen as the selected formulation with regard to the encapsulation efficiency (75.1%), flow properties (θ?=?24°, Carr index?=?5%, Hausner ratio?=?1.1, packing rate?=?0.535) and release characteristics. Initial burst effect was observed in the release profile of all examined formulations. DSC and SEM results indicated that the initial burst effect could be attributed to dissolution of CAP crystals present on the surface or embedded in the superficial layer of the matrix. The release kinetics of CAP from most microparticle formulations followed diffusion mechanism. After oral administration of the selected microparticle formulation (F7) to hypertensive rats, systolic blood pressure decreased gradually over 24?h compared to reference drug solution. These results may suggest the potential application of cellulose propionate microparticles as a suitable sustained release drug delivery system for captopril     

Reduction in burst release after coating poly(D,L-lactide-co-glycolide) (PLGA) microparticles with a drug-free PLGA layer

The high initial burst release of a highly water-soluble drug from poly (D,L-lactide-co-glycolide) (PLGA) microparticles prepared by the multiple emulsion (w/o/w) solvent extraction/evaporation method was reduced by coating with an additional polymeric PLGA layer. Coating with high encapsulation efficiency was performed by dispersing the core microparticles in peanut oil and subsequently in an organic polymer solution, followed by emulsification in the aqueous solution. Hardening of an additional polymeric layer occurred by oil/solvent extraction. Peanut oil was used to cover the surface of core microparticles and, therefore, reduced or prevented the rapid erosion of core microparticles surface. A low initial burst was obtained, accompanied by high encapsulation efficiency and continuous sustained release over several weeks. Reduction in burst release after coating was independent of the amount of oil. Either freshly prepared (wet) or dried (dry) core microparticles were used. A significant initial burst was reduced when ethyl acetate was used as a solvent instead of methylene chloride for polymer coating. Multiparticle encapsulation within the polymeric layer increased as the size of the core microparticles decreased (< 50 µm), resulting in lowest the initial burst. The initial burst could be controlled well by the coating level, which could be varied by varying the amount of polymer solution, used for coating.     

Production of BSA-loaded alginate microcapsules: Influence of spray dryer parameters on the microcapsule characteristics and BSA release

The aim of this study was to optimize the production of BSA-loaded alginate microcapsules by spray drying and to study the release of bovine serum albumin fraction V (BSA) under gastric simulated conditions. Microcapsule yield, BSA release, microcapsule size and size distribution were characterized following the application of different production parameters including inlet air temperature, inlet air pressure and liquid feed rate. The microcapsules were incubated in 0.1?N HCl and BSA release was quantified over time. The yields were higher with the pressure of 3?bar compared to 4?bar and with a feed rate of 0.45 vs. 0.2?ml?s^?1. A high feed rate (0.45 vs. 0.2?ml?s^?1) allows one to obtain microcapsules with a low BSA release (p?=?0.0327). The increase of the atomizer inlet temperature leads to microcapsules with a higher BSA release (p?=?0.0230). A higher air pressure of 4?bar compared to 3?bar resulted in a lower microcapsule size (2.55 vs. 2.80?µm) and led to a narrower size distribution (0.92 vs. 1.07). In conclusion, the spray dryer parameters influenced the alginate microcapsule characteristics as well as subsequent protein release into a simulated gastric medium.     

In vitro release kinetics of Tolmetin from tabletted Eudragit microparticles

In a previous paper the preparation has been described, by three different techniques, of microparticles made of Eudragit RS 100 and RL 100 containing a NSAI agent, Tolmetin. Freely flowing microparticles failed to affect significantly the in vitro drug release, which displayed a similar dissolution profile after micro-encapsulation to the free drug powder. Microparticles were then converted into tablets and the effect of compression on drug delivery, as well as that of the presence of co-additives, was studied in the present work. Furthermore, microparticles were also prepared by adding MgO to the polymer matrix, to reduce the sensitivity of the drug to pH changes during its dissolution. Similarly, magnesium stearate was also used for microparticle formation as a droplet stabilizer, in order to reduce particle size and hinder rapid drug release. A mathematical evaluation, by using two semi-empirical equations, was applied to evaluate the influence of dissolution and diffusion phenomena upon drug release from microparticle tablets.     

Interaction between nicardipine hydrochloride and polymeric microspheres for a controlled release system

The microspheres containing nicardipine hydrochloride (NCH) were prepared by the solvent evaporation method using acrylic polymers, Eudragit RS and L. The results of the release experiments with microspheres proposed that there should exist an interaction between NCH and the acrylic polymers. The mechanism of this interaction was investigated by differential scanning calorimetry (DSC) and powder X-ray diffractometry (XRD). These analysis indicated that NCH and polymers interact at the molecular level, possibly NCH forming a solid solution with polymers. Furthermore, the formulations ended with a solid solution between NCH and acrylic polymers and their blends made possible the preparation of controlled release microspheres to retard and to enhance drug release rate at pH 1.2 and 7.5, respectively.     

Effect of pH on diclofenac release from Eudragit RS100 microparticles. A kinetic study by DSC

The present work is aimed at investigating the release of Diclofenac (DCF) from Eudragit RS100T^® (RS) microparticles to a biological model membrane consisting of dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles (MLV). The microparticles were prepared by the Quasi-Emulsion Solvent Diffusion method (QESD). The drug release was monitored by Differential Scanning Calorimetry (DSC) technique, following the effects exerted by DCF on the thermotropic behaviour of DMPC multilamellar vesicles at different temperatures. DCF affects the transition temperature (T_m) of phospholipid vesicles, causing a m shift towards lower values, which is modulated by the drug fraction entering into the lipid bilayer. Calorimetric measurements were performed at two different pH (4.0 and 7.4) on suspensions of blank liposomes added to weighed amounts of unloaded and DCF-loaded microspheres, as well as to the powdered free drug, after incubation at 37°C. The T_m shifts, caused by the drug released from the polymeric system or by the free drug during incubation cycles, were compared to those caused by a chosen molar fractions of the free drug dispersed directly in the membrane. This in vitro study suggests as the kinetic process involved in drug release is influenced by the amount of drug loaded in the microspheres as well as by the pH value, acting on drug solubility and membrane disorder.     

Reduction in burst release of PLGA microparticles by incorporation into cubic phase-forming systems

A high initial burst release of an phosphorothioate oligonucleotide drug from poly(lactide-co-glycolide) (PLGA) microparticles prepared by the w/o/w solvent extraction/evaporation was reduced by incorporating the microparticles into the following glycerol monooleate (GMO) formulations: 1) pure molten GMO, 2) preformed cubic phase (GMO + water) or 3) low viscosity in situ cubic phase-forming formulations (GMO + water + cosolvent). The in situ cubic phase-forming formulations had a low viscosity in contrast to the first two formulations resulting in good dispersability of the microparticles and good syringability/injectability. Upon contact with an aqueous phase, a highly viscous cubic phase formed immediately entrapping the microparticles. A low initial burst and a continuous extended release over several weeks was obtained with all investigated formulations. The drug release profile could be well controlled by the cosolvent composition with the in situ systems.     

Sustained release and pharmacologic evaluation of human glucagon-like peptide-1 and liraglutide from polymeric microparticles

Abstract

The GLP1-receptor agonists exert regulatory key roles in diabetes, obesity and related complications. Here we aimed to develop polymeric microparticles loaded with homologous human GLP1 (7-37) or the analogue liraglutide. Peptide-loaded microparticles were prepared by a double emulsion and solvent evaporation process with a set of eight polymers based on lactide (PLA) or lactide-glycolide (PLGA), and evaluated for particle-size distribution, morphology, in vitro release and pharmacologic activity in mice. The resulting microparticles showed size distribution of about 30–50?μm. The in vitro kinetic release assays showed a sustained release of the peptides extending up to 30–40?days. In vivo evaluation in Swiss male mice revealed a similar extension of glycemic and body weight gain modulation for up to 25?days after a single subcutaneous administration of either hGLP1-microparticles or liraglutide-microparticles. Microparticles-loaded hGLP1 shows equivalent in vivo pharmacologic activity to the microparticles-loaded liraglutide.     

Preparation of sustained release microparticles with improved initial release property

The objective of this study was to investigate the potential of various formulation strategies to achieve sustained release of the peptide, from injectable poly(D,L-lactide-co-glycolide) (PLGA) and d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) microparticles. The microparticles were prepared by a solvent evaporation method. Peptide loaded PLGA microparticles exhibited a pronounced initial burst release (22.3% in 1 day) and lag phase in phosphate buffer of pH 7.0. In contrast, blending of 5.0% TPGS (8.6% release in 1 day) or 10.0% TPGS (5.5% release in 1 day) in PLGA microparticles reduced initial burst release and the lag-phase time. Incorporation of TPGS in PLGA microparticles further increased drug release, attributable to improved drug encapsulation, increased particle size, and exempt of pores. PLGA+ 10.0% TPGS composite microparticles exhibited the most desirable drug release among all the formulations tested, and demonstrated triphasic release after minimal initial burst.     

薏苡仁酯两种微胶囊化方法的比较研究

目的：探讨意苡仁酯两种微胶囊化的方法及其工艺条件，选出能制备高质量微胶囊产品的较好方法，并确定其最佳工艺条件。方法：以丙酮为溶剂提取薏苡仁酯，分别采用锐孔凝固浴法和喷雾干燥法制备薏苡仁酯微胶囊。结果：锐孔一凝固浴法最佳工艺条件为壁材海藻酸钠初始溶液的质量浓度为10g／L，芯材薏苡仁酯与壁材海藻酸钠的质量之比为0．6：1，乳化剂在壁材与芯材乳化分散液中的质量浓度为单甘酯0．5g／L、蔗糖酯0．5g／L，乳化温度50～60℃，固化液CaCl2的质量浓度为10g／L。喷雾干燥法最佳工艺条件为海藻酸钠的质量浓度15g／L．薏苡仁酯与海藻酸钠的质量之比1：1，乳化剂的质量浓度为单甘酯0．5g／L，蔗糖酯0．5g／L，乳化温度60～70℃。结论：用喷雾干燥法制备得到的薏苡仁酯微胶囊包埋率较高，感官质量较好，保存效果较长。     

A burst drug release caused by imperfection of polymeric film-coated microparticles prepared by a fluidized bed coater

The aim of this study was to investigate the drug release from microparticles coated with various polymeric films. Ibuprofen-loaded microparticles with diameter of 250 and 300 microm were prepared by a fluidized bed granulator. Five polymers were used as coating materials, i.e., ethylene vinyl acetate, ethyl cellulose, ethyl cellulose aqueous dispersion, polyethacrylate or Eudragit NE 30D, and carnauba wax. The coating was performed with a fluidized bed coater. Afterwards the coated microparticles were characterized in terms of particle size, morphology, and drug content. The drug dissolution was also investigated in pH 7.4 phosphate buffer. In our attempts for production of extended release ibuprofen microparticles coated with polymeric films, it was shown that the coating process had a significant effect on drug release. The undesired burst release of ibuprofen was observed in all film-coated microparticulate formulations, resulting from the imperfection of coating films.     

Design,in vitro and in vivo evaluation of glipizide Eudragit microparticles

Glipizide microparticles made with Eudragit (RS 100 and RL 100), prepared by emulsion solvent evaporation technique were evaluated for various in-vitro properties viz. encapsulation efficiency, particle size and surface morphology, drug release pattern and in-vivo hypoglycaemic activity. The optimized formulation parameters were used to prepare smooth and spherical microparticles (2–32 µm) with higher entrapment efficiency (67–89%). Drug release patterns of glipizide microparticles of Eudragit RS 100 and Eudragit RL 100 with drug-to-polymer ratio of 1 : 4 (i.e. EGM14 and ELGM14) have shown gradual and extended release for 24 h with cumulative release of glipizide to the extent of 72.3% and 83.9%, respectively. However, EGM14 showed a significant in-vivo hypoglycaemic effect up to 12 h in rabbits while ELGM14 showed for 9 h. Hence, glipizide microparticles of Eudragit RS 100 (glipizide: polymer 1 : 4) is better suited for oral sustained release formulation.     

胸腺肽α1结肠释放片的制备及其体外释药研究

目的:制备胸腺肽α1结肠释放片(Tα1片),评价其体外释药性能。方法:将Tα1制成片芯,2次包衣,内层为壳聚糖盐酸盐,外层为尤特奇L100-55。高效液相色谱(HPLC)法进行含量及含量均匀度测定,扫描电镜法评价壳聚糖盐酸盐包衣膜在模拟大肠液中的降解作用。以荧光剂FD-4为模型化合物,同法制备模拟结肠片,荧光分光光度法检测其在pH 1.2盐酸溶液,pH 6.8磷酸盐缓冲液及模拟大肠液中的体外释放性能。结果:Tα1片的含量及含量均匀度符合《中国药典》相关规定;电镜扫描结果表明,壳聚糖盐酸盐包衣膜在模拟大肠液中具有显著降解作用;模拟结肠片在pH 1.2盐酸溶液和pH 6.8磷酸盐缓冲液中的累积释药量6 h内小于23％,而在模拟大肠液中4 h基本释药完全。结论:本研究所制备的Tα1结肠释放片具有潜在的结肠靶向释药效果。     

Properties of theophylline tablets dry powder coated with Eudragit® E PO and Eudragit® L 100-55

The aim of the present study was to investigate the influence of Eudragit^® E PO on the drug release mechanism of Eudragit^® L 100-55 film coatings applied to theophylline tablets by a dry powder coating technique. The process was entirely liquid-free. Calculation of the Flory-Huggins interaction parameter based on solubility parameters suggested immiscibility of the two copolymers. MDSC thermograms were characterized by two glass transitions for the investigated Eudragit^® E PO/Eudragit^® L 100-55 ratios and confirmed incomplete miscibility of the copolymers at processing conditions. FT-IR analysis was employed to study binding interactions of the polymers. Due to the higher affinity of the plasticizer, triethyl citrate, for Eudragit^® E PO compared to Eudragit^® L 100-55, redistribution of the plasticizer was observed during the curing phase of the process. Plasticizer migration also affected the initial phase of drug release from powder-coated theophylline tablets that were stored for four weeks. Drug release from powder-coated tablets was dependent on the polymer blend ratio, coating thickness, and the pH of the dissolution medium. A broad range of pH dependent theophylline release profiles were obtained as a function of the polymer blend ratio. The particle size of the coating powder influenced the microstructure of the film coating.