海藻酸钠骨架材料中药物释放的影响因素

目的以海藻酸钠为亲水骨架材料，考察药物从海藻酸钠骨架片中释放的体外影响因素。方法以茶碱为模型药物，采用直接压片法制备了茶碱海藻酸钠亲水骨架片，通过对骨架片膨胀性、吸水性以及溶蚀性的考察，研究了影响药物从海藻酸钠骨架材料中释放的体外因素。结果茶碱海藻酸钠骨架片的释药速率和释药机理与骨架片中海藻酸钠粘度、释放介质pH值、离子强度以及转速均有关。结论海藻酸钠能有效地控制骨架片中药物的释放，是一种优良的亲水骨架材料。     

离子强度对丙基甲基纤维素骨架片释药的影响

目的：探讨溶出介质的离子强度对难溶性药物的丙基甲基纤维素（HPMC）骨架片释药的影响。方法：以甲氧苄胺嘧啶、卡马西平、磺胺甲恶唑和茶碱4种难溶性药物为模型药物，测定5种不同离子强度介质（水、0．20％氯化钠溶液、0．50％氯化钠溶液、0．90％氯化钠溶液和1．80％氯化钠溶液）下的药物释放度和溶出参数。结果：难溶性药物的HPMC骨架片释药随着其溶出介质离子强度的增加而减慢。结论：释药速率与离子强度之间存在较好的线性负相关关系。     

不同pH的溶出介质对HPMC骨架片释药的影响

目的探讨溶出介质的pH对难溶性药物的HPMC骨架片释药的影响.方法以甲氧苄胺嘧啶、卡马西平、磺胺甲恶唑和茶碱四种难溶型性药物为模型药物,测定四种pH缓冲溶液介质(pH1.0,pH4.0,pH6.0,pH7.5)下的药物的溶解度和释放度.结果难溶性药物的HPMC骨架片释药随着其溶解度的增加而加快.结论难溶性药物HPMC骨架片释药的差异主要与药物在不同pH的溶出介质中的溶解度有关.     

不同pH的溶出介质对HPMC骨架片释药的影响

目的　探讨溶出介质的pH对难溶性药物的HPMC骨架片释药的影响。方法　以甲氧苄胺嘧啶、卡马西平、磺胺甲恶唑和茶碱四种难溶型性药物为模型药物,测定四种pH缓冲溶液介质(pH1.0 ,pH4 .0 ,pH6 .0 ,pH7.5 )下的药物的溶解度和释放度。结果　难溶性药物的HPMC骨架片释药随着其溶解度的增加而加快。结论　难溶性药物HPMC骨架片释药的差异主要与药物在不同pH的溶出介质中的溶解度有关。     

尼莫地平缓释片制备及释药影响因素的考察

制备了尼莫地平缓释片.考察了影响尼莫地平亲水性骨架片体外释药的各种影响因素,如亲水性辅料的用量、制法、压片压力、片剂大小等.本文所制备的缓释片,在溶出介质为25%的乙醇溶液时,释药速度符合零级动力学方程(相关系数r＞0.99).     

影响魔芋胶骨架片释药体外释放因素的研究

目的 以魔芋胶为骨架材料,考察药物从魔芋胶骨架片中释放的体外释放因素.方法 以氨茶碱为模型药物,采取湿法制粒压片法制备了氨茶碱魔芋胶骨架片,通过对释放度实验研究了释放介质的离子强度,搅拌转速,不同测定方法,释放介质pH值对骨架片释药的影响.结果 桨法测得的平均释放时间(MDT值)和篮法无明显差别;在不同pH值释放介质中,药物的释放以在pH6.8 PBS中最快,蒸馏水中次之,0.1mol/L盐酸液中最慢;药物释放随释放介质离子强度增加而减慢;药物释放随搅拌转速增加而加快,药物释放机制为扩散和溶蚀机制协同作用.结论 魔芋胶能有效的控制骨架片中药物释放,是一种优良的亲水骨架材料.     

多索茶碱HP MC骨架片的药物释放影响因素研究

以HPMC为骨架材料 ,将多索茶碱制成缓释骨架片 ,考察HPMC种类、用量及粒径 ,填充剂种类及用量和制备工艺对多索茶碱缓释片体外释药速率的影响 .结果表明 :多索茶碱缓释骨架片的体外释药行为符合Higuchi方程 ,HPMC的种类、用量、粒度 ,填充剂的用量对多索茶碱的体外释药速率均有较明显的影响 ;亲水性填充剂的种类对释药速率影响不大 ;湿法制粒所得骨架片的释药速率比干法直接压片有所减慢 ;压片力的大小对释药速率也有一定的影响 .     

阿昔洛韦药物树脂复合物体外释药动力学的研究

目的:制备阿昔洛韦药物树脂复合物并对其体外释药动力学进行考察。方法:以静态交换法制备了阿昔洛韦药物树脂复合物并对阿昔洛韦药物树脂在不同溶出介质中的释药动力学进行了考察。结果:体外释药动力学研究表明,阿昔洛韦药物树脂的释药速率随着溶出介质中离子强度的增大、温度的升高而加快,且释药速率与反离子种类有关。结论:阿昔洛韦药物树脂的释药速率与溶出介质的离子强度、反离子种类和温度有关。     

茶碱缓释片的制备及其初步稳定性考察

目的：考察茶碱羟丙基甲基纤维素（HPMC）骨架片的制备方法及其初步稳定性。方法：以HPMC为骨架材料,采用湿颗粒法制备茶碱缓释片,考察了HPMC用量、HPMC黏度及释放介质pH值对药物体外释放行为的影响,以及光照、高温及高湿度对茶碱缓释片稳定性的影响。结果：HPMC用量和黏度显著影响茶碱释药速率,释放介质pH值对茶碱释药速率影响较小。光照、高温及高湿度不影响茶碱缓释片的含量及释放度。结论：通过使用合适黏度的HPMC及调节HPMC用量可获得具有理想释药行为的茶碱缓释片,且其稳定性良好。     

左羟丙哌嗪缓释骨架片的制备及体外释药行为评价

［摘要］　目的：制备左羟丙哌嗪缓释骨架片,考察其体外释放度,探讨其释药机制。方法：以亲水性高分子材料HPMC为骨架,采用湿法制粒,制备左羟丙哌嗪缓释骨架片,评价不同pH值条件下的释放度,并将释放数据拟合方程。结果：HPMC用量增加,左羟丙哌嗪释放速度下降;溶出介质pH对药物的释放特性有一定影响。在本实验条件下,HPMC用量对水溶液中药物的释放机制无明显影响,释药过程符合Higuchi方程(R2=0.988 9~0.990 4)或一级方程(R2=0.987 5~0.990 2),释药机制为非Fickian扩散(n=0.615 3~0.633 9)。结论：左羟丙哌嗪缓释骨架片的体外释放符合缓释要求,释放表现为药物扩散和凝胶溶蚀的协同作用。     

Xanthan gum to tailor drug release of sustained-release ethylcellulose mini-matrices prepared via hot-melt extrusion: in vitro and in vivo evaluation.

Mini-matrices (multiple-unit dosage form) with release-sustaining properties were developed by means of hot-melt extrusion using ibuprofen as the model drug and ethylcellulose as sustained-release agent. Xanthan gum, a hydrophilic polymer, was added to the formulation to increase the drug release since ibuprofen release from the ibuprofen/ethylcellulose matrices (60/40, w/w) was too slow (20% in 24 h). Changing the xanthan gum concentration as well as its particle size modified the in vitro drug release. Increasing xanthan gum concentrations yielded a faster drug release due to a higher liquid uptake, swelling and erosion rate. Regarding the effect of the xanthan gum particle size, no difference was observed for formulations containing 10% and 20% xanthan gum. However, using 30% xanthan gum, drug release was influenced by the particle size of the hydrophilic polymer due to the susceptibility of the coarser xanthan gum particles to erosion. Drug release from the mini-matrices was mainly diffusion controlled, but swelling played an important role to obtain complete drug release within 24 h. Drug release was influenced by the ionic strength of the medium as the conformation of xanthan gum molecules is determined by the salt concentration. An oral dose of 300 mg ibuprofen was administered to dogs (n=6) in a cross-over study design either as an immediate-release preparation (Junifen), as a sustained-release formulation (Ibu-Slow 600 mg (1/2 tablet)) or as the experimental mini-matrices (varying in xanthan gum concentration). Administration of the experimental formulations sustained the ibuprofen release. Although a significant difference in dissolution rate of the 20% and 30% xanthan gum mini-matrices was detected in vitro, the difference in relative bioavailability was limited (70.6% and 73.8%, respectively).     

Swelling and drug release behaviour of xanthan gum matrix tablets

The swelling and drug release behaviour of xanthan gum matrix tablets were studied using three drugs having different properties, i.e., caffeine as a soluble neutral drug, indomethacin as an insoluble acidic drug, and the sodium salt of indomethacin as a soluble acidic drug. Swelling was ascertained by measuring the axial and the radial expansion of matrix tablets following exposure to media of physiological ionic strength. The mean drug dissolution time and swelling rate were calculated from dissolution and swelling experiments, respectively, and were used as responses for comparison under different experimental conditions. The dependence of drug release on the swelling of the polymer matrix and on the type of the drugs added was established. The former is mainly influenced by the ionic strength and buffer concentrations. The latter is affected by the solubility of the drug. The mechanism of matrix swelling follows Case I diffusion, whereas drug release from this polymer matrix conforms to Case II diffusion.     

Effect of calcium ions on the gelling and drug release characteristics of xanthan matrix tablets

Xanthan is a well-known biopolymer. It is an anionic polysaccharide, whose primary structure depends on the bacterial strain and fermentation conditions. Xanthan was extensively studied in combination with galactomannans, and over 90 patents cover the technology of this preparation. Our aim was to investigate the relation between the physical properties of a xanthan matrix in the absence or presence of calcium ions and its influence on the release of pentoxifylline. The release of pentoxifylline from xanthan tablets in purified water was shown to be very slow and governed by the process of polymer relaxation. The presence of calcium ions significantly increased the drug release, changing the release mechanism into a more diffusion controlled one. Xanthan matrices showed substantially faster and more extensive swelling in water than in the presence of Ca2+ ions. Surprisingly, negative correlation between drug release and degree of swelling was obtained for xanthan: the higher the swelling, the slower the drug release. Higher ionic strength led to lower erosion of xanthan tablets, and the gel layers formed were more rigid and of firmer texture, as shown by rheological experiments and textural profiling. The results indicate that the presence of Ca2+ ions in the solution or in matrices does not cause crosslinking of xanthan polymers, but causes charge screening of ionized groups on the trisaccharide side chains of xanthan, leading to lower inter-molecular repulsion and changing water arrangement. The understanding of the parameters influencing drug release leads to the conclusion that xanthan is suitable for controlled release formulations, especially with the incorporation of certain small counterions.     

Effects of the method of preparation on the compression, mechanical, and release properties of khaya gum matrices

A study has been made of the compression properties of khaya gum matrices and the effects of drug concentration and method of preparation of the material on the compression, mechanical and the drug release characteristics of the matrices. Khaya gum matrix tablets were prepared by direct compression and wet granulation methods. The compression properties of the formulations were assessed using the equations of Heckel and Kawakita. The mechanical properties of the tablets were evaluated using crushing strength and friability of the tablets, whereas the release properties of the tablets were evaluated by using the disintegration and dissolution times. The results obtained show that khaya gum deformed mainly by plastic deformation. The compression properties of the formulations were affected by the concentration of the drug and the method of preparation of the materials for compression. Tablets prepared by wet granulation showed faster onset and higher amount of plastic deformation during compression than those prepared by direct compression. Tablets containing dicalcium phosphate showed higher mechanical strength and disintegration and dissolution times. Wet granulation also increased the mechanical strength of the tablet without significantly affecting the drug release characteristics from the matrix tablets. Thus, the wet granulation method could be useful in the preparation of khaya gum matrix tablet with acceptable mechanical properties and drug release properties.     

Effects of the Method of Preparation on the Compression,Mechanical, and Release Properties of Khaya Gum Matrices

A study has been made of the compression properties of khaya gum matrices and the effects of drug concentration and method of preparation of the material on the compression, mechanical and the drug release characteristics of the matrices. Khaya gum matrix tablets were prepared by direct compression and wet granulation methods. The compression properties of the formulations were assessed using the equations of Heckel and Kawakita. The mechanical properties of the tablets were evaluated using crushing strength and friability of the tablets, whereas the release properties of the tablets were evaluated by using the disintegration and dissolution times. The results obtained show that khaya gum deformed mainly by plastic deformation. The compression properties of the formulations were affected by the concentration of the drug and the method of preparation of the materials for compression. Tablets prepared by wet granulation showed faster onset and higher amount of plastic deformation during compression than those prepared by direct compression. Tablets containing dicalcium phosphate showed higher mechanical strength and disintegration and dissolution times. Wet granulation also increased the mechanical strength of the tablet without significantly affecting the drug release characteristics from the matrix tablets. Thus, the wet granulation method could be useful in the preparation of khaya gum matrix tablet with acceptable mechanical properties and drug release properties.     

Properties of sustained release hot-melt extruded tablets containing chitosan and xanthan gum

The aim of this study was to investigate the influence of pH, buffer species and ionic strength on the release mechanism of chlorpheniramine maleate (CPM) from matrix tablets containing chitosan and xanthan gum prepared by a hot-melt extrusion process. Drug release from hot-melt extruded (HME) tablets containing either chitosan or xanthan gum was pH and buffer species dependent and the release mechanisms were controlled by the solubility and ionic properties of the polymers. All directly compressed (DC) tablets prepared in this study also exhibited pH and buffer species dependent release. In contrast, the HME tablets containing both chitosan and xanthan gum exhibited pH and buffer species independent sustained release. When placed in 0.1N HCl, the HME tablets formed a hydrogel that functioned to retard drug release in subsequent pH 6.8 and 7.4 phosphate buffers even when media contained high ionic strength, whereas tablets without chitosan did not form a hydrogel to retard drug release in 0.1N HCl. The HME tablets containing both chitosan and xanthan gum showed no significant change in drug release rate when stored at 40 °C for 1 month, 40 °C and 75% relative humidity (40 °C/75% RH) for 1 month, and 60 °C for 15 days.     

Development and evaluation of natural gum-based extended release matrix tablets of two model drugs of different water solubilities by direct compression

The study was aimed at developing extended release matrix tablets of poorly water-soluble diclofenac sodium and highly water-soluble metformin hydrochloride by direct compression using cashew gum, xanthan gum and hydroxypropylmethylcellulose (HPMC) as release retardants. The suitability of light grade cashew gum as a direct compression excipient was studied using the SeDeM Diagram Expert System. Thirteen tablet formulations of diclofenac sodium (∼100 mg) and metformin hydrochloride (∼200 mg) were prepared with varying amounts of cashew gum, xanthan gum and HPMC by direct compression. The flow properties of blended powders and the uniformity of weight, crushing strength, friability, swelling index and drug content of compressed tablets were determined. In vitro drug release studies of the matrix tablets were conducted in phosphate buffer (diclofenac: pH 7.4; metformin: pH 6.8) and the kinetics of drug release was determined by fitting the release data to five kinetic models. Cashew gum was found to be suitable for direct compression, having a good compressibility index (ICG) value of 5.173. The diclofenac and metformin matrix tablets produced generally possessed fairly good physical properties. Tablet swelling and drug release in aqueous medium were dependent on the type and amount of release retarding polymer and the solubility of drug used. Extended release of diclofenac (∼24 h) and metformin (∼8–12 h) from the matrix tablets in aqueous medium was achieved using various blends of the polymers. Drug release from diclofenac tablets fitted zero order, first order or Higuchi model while release from metformin tablets followed Higuchi or Hixson-Crowell model. The mechanism of release of the two drugs was mostly through Fickian diffusion and anomalous non-Fickian diffusion. The study has demonstrated the potential of blended hydrophilic polymers in the design and optimization of extended release matrix tablets for soluble and poorly soluble drugs by direct compression.     

Controlled-release tablets from carrageenans: effect of formulation, storage and dissolution factors.

The purpose of this study was to investigate the potential of two carrageenans, iota-carrageenan and lambda-carrageenan for the preparation of controlled-release tablets. Tablets were compressed on a Carver press and the effect of formulation factors, moisture, and storage on the release of theophylline was studied. The effect of sodium chloride in the tablet formulation and a change in the ionic strength of the dissolution media was studied on the release of three model drugs. The release rate increased both with an increase in tablet diameter and increase in drug to carrageenan ratio in the tablets. The two lubricants studied had a negligible effect on the rate of drug release at their commonly used concentrations. Moisture content of carrageenans, storage of tablets at 37 degrees C/75% RH for 3 months, and incorporation of 10% sodium chloride in the tablets did not have any significant effect on the release rate. The change in ionic strength of simulated gastric fluid altered the release rate whereas the ionic strength of simulated intestinal fluid did not have a significant effect on the release rate. Carrageenan tablets were relatively insensitive to small changes in formulation parameters and dissolution conditions.     

盐酸丁螺环酮缓释片的制备及体外释放研究

目的 :为了减少给药次数和减小药物的毒副作用 ,制备盐酸丁螺环酮缓释片。方法 :采用亲水凝胶骨架材料 (HPMC)制备该缓释片 ,并考察药物与HPMC不同比例组成、HPMC不同粘度等对该水溶性药物释放的影响。结果 :药物 /HPMC之比为影响释放过程的主要因素 ,HPMC(高粘度 )的粘度与药物释放无关 ,且该骨架片的释药与释放介质的 pH无关。 结论 :该缓释片制备工艺简单 ,缓释速率可控。