盐酸克林霉素微囊的体外释药及其影响因素的考察

目的 采用液中干燥法制备盐酸克林霉素微囊，并考察其体外释药特性。方法 以乙基纤维素为囊材制备微囊．用浆法研究其体外释药的影响因素。结果 药物释放速率随微囊粒径减小而增加；囊材粘度增加，药物释放速率降低；附加剂滑石粉对药物释放的影响较复杂，随着滑石粉比例增加．药物释放速率增加．但至一定比例后．速率降低。与市售胶囊相比．有明显缓释作用。结论 液中干燥法制备的盐酸克林霉素微囊有显著的缓释作用．有良好的开发应用前景。     

磺胺嘧啶微囊体外释药行为及影响因素考察

考察了用喷雾干燥法制备的磺胺嘧啶微囊的体外溶出过程。药物初期呈零级释放，后期释放呈指数关系。药物释放有明显的滞流层现象。释药初期累积溶出量对时间变化的斜率（ｋ）与搅拌速率的平方根的倒数呈直线关系。药物释放速率随微囊粒径减少而增加。囊材分子量和阻滞剂用量增加，使药物释放速率降低。附加剂滑石粉对药物释放的影响较复杂，随着滑石粉比例增加，药物释放速率增加，但至一定比例后，速率降低。     

吡哌酸缓释微囊的体外溶出特性考察

考察了不同主药含量、不同粒径的吡哌酸缓释微囊的药物溶出特性及在不同pH介质中的溶出行为,探讨了微囊中吡哌酸含量对微囊结构、半数测出时间T_(50)及药物渗透性的影响与因不同pH介质中由于药物溶解度不同而引起的溶出行为的改变。证实了微囊释药符合Higuchi方程,其结构与药物含量有关,药物渗透性及T_(50)~(1/2)与药物含量存在线性相关性,药物溶出因微囊粒径减小、药物于介质中溶解度增加而增加。     

吡哌酸微囊体外溶出及人体内生物利用度研究

<正> 吡哌酸(PPA)临床广泛用于治疗各种致病菌引起的呼吸道、胃肠道、泌尿道感染。用喷雾干燥法将其制备成微囊可掩盖药物本身味道从而进一步制备成适用于儿童的干糖浆等剂型。本文考察了吡哌酸微囊于蒸馏水及人工肠液中的溶出及人体内生物利用度。     

海藻酸钠-壳聚糖微囊成型机理及其对大分子药物的载药、释药研究海藻酸钠-壳聚糖微囊成型机理及其对大分子药物的载药、释药研究

目的考察海藻酸钠-壳聚糖微囊成型机理及其对大分子药物的载药及释药特性。方法采用乳化胶凝法制备海藻酸钠-壳聚糖微囊,通过差示扫描量热法(DSC)探讨其成型机理。以牛血清白蛋白(BSA)为模型药,研究微囊对大分子药物的包载能力及释药特性。结果DSC分析结果显示,组成微囊的各材料间发生静电相互作用而成型。随药载比增加,微囊中BSA的载药量由9.20％增至35.08％;随壳聚糖浓度升高,载药量由30.29％升至38.12％。载药微囊中BSA在PBS(pH 7.4)与0.1 mol·L^-1 HCl中均呈两相释放;随CTS浓度增大,BSA在0.1 mol·L^-1 HCl中的释放减慢。结论制备的微囊圆整且分散性好,微囊对BSA具较高包载能力,并具一定的缓释作用。     

海藻酸微囊的制备与评价

目的:探讨利用气体雾化技术(AAT)制备的脂溶性药物吲哚美辛和水溶性药物对乙酰氨基酚海藻酸微囊的理化特性.方法:采用筛分法测定微囊粒径,紫外分光光度法测定微囊的包封率及载药量,恒重法测定微囊中的含水量.结果:海藻酸钠浓度增加、输送速度增加和氮气压力增加与微囊粒径减小.微囊的包封率和载药量随着药物溶解度的增加而降低.微囊含水量最初随着冷冻干燥时间的延长急剧下降,当下降到一定程度后随着冷冻干燥时间的延长变化不大.结论:采用AAT方法制备海藻酸微囊方法简单,但是水溶性大的药物不宜用此法制备微囊.     

穿心莲内酯微囊的制备及溶出度考察

目的:研究以丙烯酸树脂Ⅳ号为囊材的穿心莲内酯微囊的制备方法及其体外溶出特点.方法:采用液中干燥法制备穿心莲内酯微囊,并按<中国药典>方法测定体外溶出度.结果:该法制备的穿心莲内酯微囊,在水中药物几乎没有溶出,而在酸性溶出介质中则可快速释放.结论:该方法所制备微囊不仅可以有效掩盖穿心莲内酯的苦味,而且在胃液中能够快速释放.     

分子筛效应对氟尿嘧啶白蛋白毫微囊释药速率的影响

目的：用分子筛理论和方法研究不同制备条件对白蛋白微囊内部孔径及释药速度的影响。方法：利用低压色谱仪采用分子筛层析的方法测定不同量的固化剂对化学交联固化法制备的白蛋白毫微囊药物释放速度的关系。结果：实验表明,在相同条件下制成 乳后以不同交联剂量制备的毫微囊药物释放速率不同。结论：交联剂的用量越大,毫微囊的内部孔径越小,药物的释放速度越慢。但是药物的性质也有一定的影响。     

尼群地平缓释微球的制备及其体内外相关性的研究

目的制备具有固体分散体结构的尼群地平缓释微球 ,并筛选具有良好体内外相关性的释放介质。方法采用球晶造粒法制备尼群地平缓释微球 ,考察微球的粒径、载药量、包封率及释放行为 ,并根据 6只试验犬体内药物动力学试验结果 ,将不同时间的吸收分数与不同释放介质的相应时间点的体外累积释放百分数作线性回归 ,筛选具有良好体内外相关性的释放介质。结果制备的微球的粒径随搅拌速度的增加而减少 ,包封率均在 96 80 %以上 ,药物从微球中的释放速度随处方中固体分散体载体量的增加而增加 ,随阻滞剂量的增加而减小。以 1 7 4mmol L十二烷基硫酸钠为释放介质时 ,体外累积释放百分数与体内吸收分数相关系数较好 (r =0 985 1 ) ,方程为Fa =1 64 5 8ft-2 7 64 2。结论该方法较适用于难溶性药物制备缓释微球。以 1 7 4mmol L十二烷基硫酸钠水溶液为释放介质可作为控制微球内在质量的标准     

内含脂质体的聚电解质微囊作为药物载体的制备与表征

目的:通过层层自组装技术(LBL)制备内含有脂质体的聚电解质微囊,并对其结构及其对药物的自沉积作用和释放性能进行研究.方法:利用共沉淀法制备碳酸钙模板,在其表面层层组装可生物降解的壳聚糖和海藻酸钠,去除碳酸钙模板后,得到内含脂质体的聚电解质微囊.通过透射电镜(TEM),扫描电镜(SEM)等对微囊的结构、自沉积作用及释放性能进行表征.结果:TEM和SEM显示本实验成功得到了内含脂质体的聚电解质微囊;随着多柔比星给药浓度的增高,载体的囊内药物浓度呈非线性增加,在给药浓度为1 mg·ml-1的条件下,微囊内的最高药物浓度达520.1 mg·ml-1;48 h内,微囊在不同pH(5.0,6.5,7.4)的PBS中的累积释放百分率分别达到59.2%,54.3%,44.8%.结论:内含脂质体的聚电解质微囊具有良好的自沉积作用和释放能力,作为新型的药物载体具有较好的应用前景.     

The study of drug release from microspheres adhered on pig vesical mucosa

The object of our work is the preparation of a mucoadhesive drug delivery system intended for intravesical application. In the present work, microspheres with Eudragit RS matrix polymer and different mucoadhesive polymers, i.e. chitosan hydrochloride (Ch), sodium salt of carboxymethyl cellulose (CMC) and polycarbophil (PC) were prepared to evaluate their influence on the mucoadhesive properties of microspheres. Different parameters were determined and their influence on pipemidic acid release from microspheres adhered on intact and damaged pig vesical mucosa was evaluated: swelling of polymers, mucoadhesion strength of polymeric films and drug dissolution according to USP XXIV method. The dissolution rate from microspheres containing different mucoadhesive polymers decreases as follows: PC>Ch>CMC. PC swelled to the largest volume among all polymers and as a result the fastest release of the drug from PC microspheres was obtained. The release rate of pipemidic acid from microspheres adhered on intact mucosa followed the order PC>CMC>Ch. These results show that both drug dissolution and mucoadhesion strength strongly influence drug release from adhered microspheres. The slowest release from Ch microspheres could be interpreted by the largest mucoadhesion strength of Ch polymeric films. The release rate of pipemidic acid from microspheres adhered on damaged mucosa followed the order PC=Ch>CMC. The results obtained on pathologically changed mucosa model support the indication of the role of glycosaminoglycans and polymer charge in the mucoadhesion process on vesical mucosa. Analysis of release data shows that the drug dissolution profiles follow the Higuchi kinetics better than the release profiles from adhered microspheres and different kinetics might be a consequence of different release mechanisms.     

Kinetics of drug release from polylactic acid-hydrocortisone microcapsules

Polylactic acid microcapsules of similar particle size distribution containing various drug loadings of hydrocortisone were prepared. The microcapsules, which contained randomly dispensed drug particles, showed a dissolution pattern which consists of a fast first-stage and a slow second-stage drug release. Our studies showed that the kinetics of drug release from the microcapsules can be adequately described by a spherical matrix model based on a flux mechanism involving the diffusion of dissolved drug at the penetrating front of the dissolution medium. Drug loading played an important role in the control of drug release rate. An empirical relationship between drug loading and drug diffusibility through the polymeric matrix was developed and showed that the rate of drug release increased exponentially with the increase in drug loading. The microcapsules were further shown to exhibit increased rate of drug release in dissolution medium containing either cetylpyridium chloride or aerosol OT. The effect of the surfactants was attributed to surface tension lowering and improved wetting of the microcapsule particles.     

Kinetics of drug release from polylactic acid—hydrocortisone microcapsules

Abstract

Polylactic acid microcapsules of similar particle size distribution containing various drug loadings of hydrocortisone were prepared. The microcapsules, which contained randomly dispensed drug particles, showed a dissolution pattern which consists of a fast first-stage and a slow second-stage drug release. Our studies showed that the kinetics of drug release from the microcapsules can be adequately described by a spherical matrix model based on a flux mechanism involving the diffusion of dissolved drug at the penetrating front of the dissolution medium. Drug loading played an important role in the control of drug release rate. An empirical relationship between drug loading and drug diffusi-bility through the polymeric matrix was developed and showed that the rate of drug release increased exponentially with the increase in drug loading. The microcapsules were further shown to exhibit increased rate of drug release in dissolution medium containing either cetylpyridium chloride or aerosol OT. The effect of the surfactants was attributed to surface tension lowering and improved wetting of the microcapsule particles.     

The influence of magnesium stearate on the characteristics of mucoadhesive microspheres

Microspheres containing the mucoadhesive polymer chitosan hydrochloride, with matrix polymer Eudragit RS, pipemidic acid as a model drug and agglomeration preventing agent magnesium stearate were prepared by the solvent evaporation method. The amount of magnesium stearate was varied and the following methods were used for microsphere evaluation: sieve analysis, drug content and dissolution determination, scanning electron microscopy, xray diffractometry, DSC and FTIR spectroscopy. The results showed that average particle size decreased with increasing amount of magnesium stearate used for microsphere preparation. This is probably a consequence of stabilization of the emulsion droplets with magnesium stearate. Higher pipemidic acid content in the microspheres was observed in larger particle size fractions and when higher amounts of magnesium stearate were used. It was also found that these two parameters significantly influenced the dissolution rate. The important reason for the differences in drug content in microspheres of different particle sizes is the diffusion of pipemidic acid from the acetone droplets in liquid paraffin during the preparation procedure. The physical state of pipemidic acid changed from crystalline to mostly amorphous with its incorporation in microspheres, as shown by x-ray diffractometry and differential     

The influence of magnesium stearate on the characteristics of mucoadhesive microspheres

Microspheres containing the mucoadhesive polymer chitosan hydrochloride, with matrix polymer Eudragit RS, pipemidic acid as a model drug and agglomeration preventing agent magnesium stearate were prepared by the solvent evaporation method. The amount of magnesium stearate was varied and the following methods were used for microsphere evaluation: sieve analysis, drug content and dissolution determination, scanning electron microscopy, x-ray diffractometry, DSC and FTIR spectroscopy. The results showed that average particle size decreased with increasing amount of magnesium stearate used for microsphere preparation. This is probably a consequence of stabilization of the emulsion droplets with magnesium stearate. Higher pipemidic acid content in the microspheres was observed in larger particle size fractions and when higher amounts of magnesium stearate were used. It was also found that these two parameters significantly influenced the dissolution rate. The important reason for the differences in drug content in microspheres of different particle sizes is the diffusion of pipemidic acid from the acetone droplets in liquid paraffin during the preparation procedure. The physical state of pipemidic acid changed from crystalline to mostly amorphous with its incorporation in microspheres, as shown by x-ray diffractometry and differential scanning calorimetry. No differences were observed in the physical state of pipemidic acid and in microsphere shape and surface between different size fractions of microspheres, prepared with different amounts of magnesium stearate. Additionally, no correlation between the physical state of the drug in different microspheres and their biopharmaceutical properties was found.     

Effect of ethylene-vinyl acetate concentration on ethylcellulose-walled microcapsules: preparation and release kinetics of theophylline microcapsules

The effect of concentration of ethylene-vinyl acetate (EVA) copolymer, used as a coacervation-inducing agent, on the preparation of ethylcellulose microcapsules was studied with theophylline as the core material. The influence of EVA concentration on the micromeritic properties of the microcapsules and their drug release behaviour were investigated. Particle size distribution of the microcapsules obtained was dependent on the amount of EVA copolymer. As the EVA concentration increased the quantity of larger particles was reduced and that of the smaller particles was increased. Thus EVA might be used as a protective colloid to prevent aggregation of the microcapsules. The porosity of the microcapsules decreased with respect to EVA concentration, but the wall thickness of the microcapsules showed a corresponding increase. Zero-order release kinetics, from the resulting microcapsules in the initial dissolution phase was obtained. The apparent zero-order release rate in the initial steady-state decreased with the increase of EVA concentration, but T50 increased. The higher concentration of EVA causing a thick, compact wall lead to an effective prolongation of drug release.     

Suspensions of prolonged-release diclofenac-Eudragit and ion-exchange resin microcapsules: II. Improved dissolution stability

PURPOSE: The stability of prolonged release 100 microm -size ion-exchange resin (IER) diclofenac microcapsules (prepared by the Wurster process) and coated with Eudragit RS30D was evaluated using dissolution analysis. METHODS: The IER microcapsules were suspended in 0.1% methylcellulose and stored at 23 and 37 degrees C and the dissolution study conducted over a 6-month period. The surface morphology of the microcapsules was examined using scanning electron microscopy (SEM). RESULTS: The dissolution of the suspensions stored at 23 degrees C on day 1 or 7 and was similar to that of day 30 with slightly faster dissolution on day 60. In contrast, release from suspensions stored at 37 degrees C decreased with storage. The decrease in dissolution with increased temperature was possibly due to the polymer relaxation (micromelting) that was enough to seal the drug within the matrix, resulting in slow dissolution. SEM of the suspended microcapsules correlated with the dissolution data, i.e. the surfaces of microcapsule stored at 37 degrees C showed decreased roughness or smoothening and closing of pores with time and, hence, retardation of drug release, compared with samples stored at 23 degrees C. The dissolution kinetics (shown by the linearity of Bt vs. time profiles) indicated that release mechanism was diffusion. CONCLUSIONS: The suspensions of diclofenac IER microcapsules were stable up to 30 days at ambient temperature, which makes the formulation potentially useful as reconstitutable product.     

Preparation and evaluation of ethylcellulose microcapsules of indomethacin

Indomethacin was microencapsulated with ethylcellulose using a modified spherical agglomeration process, aiming at a sustained release preparation without side effects on the stomach. The surface morphology of the microcapsules was examined using scanning electron microscopy. The microcapsules were porous and spherical, and their porosity increased with increasing the viscosity of ethylcellulose.In vitro dissolution process followed Higuchi’s diffusion model for first 3 hr. Release rate of the drug from microcapsules decreased as the viscosity of ethylcellulose or the weight ratio of indomethacin to ethylcellulose was decreased. The release rate also decreased with increasing the microcapsule size. The microcapsules induced less gastric ulcer in rats than raw drug.