Drug Release Properties of the Microcapsules of Adriamycin Hydrochloride with Ethylcellulose Prepared by a Phase Separation Technique

Abstract

Adriamycin hydrochloride was microencapsulated with ethylcellulose by a phase separation method to develop a prolonged release dosage form. Polyisobutylene (PIB) was used as a coacervation-inducing agent to control the particle size and drug release rate of the resultant microcapsules. With increasing the concentration of PIB (1 to 3 %) the average diameter of the microcapsules decreased, due to the fact that the microcapsules were discreted to a single microcapsule. At low concentration of PIB, the resultant microcapsules were agglomerated, which resulted in increasing the size. The microcapsules prepared with PIB 2 % prolonged desirably the drug release from the microcapsules. A little size effects of the microcapsules on the drug release rate was found for the microcapsules with PIB 2 % and 3 %.     

Mechanisms of Drug Release from Matrices Prepared with Aqueous Dispersion of Ethylcellulose

The objective of this study was to investigate the mechanism of acetaminophen (APAP) release from tablets prepared by the wet granulation method using an aqueous polymeric dispersion (Surelease) as a granulating agent. Tablets compressed from granules containing 10% w/w acetaminophen and 13.44% w/w total solids from Surelease released only 52.4% w/w drug after 120 min of dissolution testing, while controlled tablets without Surelease released 94.1% w/w drug. In order to prepare control tablets of 6.8 Kp hardness value, the upper compressional force recorded was 15.87 kN while tablets containing 13.44% w/w of total solids from Surelease had a recorded force of 6.28 kN. The drug release from tablets prepared with Surelease as a granulating liquid followed the diffusion-controlled model for an inert porous matrix     

Factors Influencing the Release of Aminophylline from Tableted Ethylcellulose Microcapsules

Microcapsules containing aminophylline cores in ethylcellulose walls have been prepared and tableted. The mechanical properties and the release characteristics of tablets obtained by direct compression at six different pressures (ranging from 265 to 1060 Kg.cm^-2) were studied. The release rate of the drug from tableted microcapsules increased with the increase of compression force and was higher than from uncompressed microcapsules, indicating that some damage of the polymeric wall occurred during the compression process. Among the various excipients tested as binding and protective agents, paraffined starch (a mixed system appositely set up) gave the best results, producing the slowest drug release rate. No important effect on drug release rate was found by changing the size of the microcapsules.     

Factors Influencing the Release of Aminophylline from Tableted Ethylcellulose Microcapsules

Abstract

Microcapsules containing aminophylline cores in ethylcellulose walls have been prepared and tableted. The mechanical properties and the release characteristics of tablets obtained by direct compression at six different pressures (ranging from 265 to 1060 Kg.cm^?2) were studied. The release rate of the drug from tableted microcapsules increased with the increase of compression force and was higher than from uncompressed microcapsules, indicating that some damage of the polymeric wall occurred during the compression process. Among the various excipients tested as binding and protective agents, paraffined starch (a mixed system appositely set up) gave the best results, producing the slowest drug release rate. No important effect on drug release rate was found by changing the size of the microcapsules.     

Effect of Drug Properties on Physical and Release Characteristics of Eudragit Microspheres Prepared by Spherical Crystallization Technique

Ten compounds having different solubilities and molecular weights were evaluated for incorporation into Eudragit microspheres using the spherical crystallization technique, and the effects of drug-related factors on the properties of Eudragit microspheres were investigated. The entrapment of the active compound within the microspheres was highly dependent on the acidic or basic characteristics of the drug. Structural changes were also observed on the microsphere surface prepared at different pH values. Microspheres prepared with slightly and very slightly soluble drugs such as salicylic acid, naproxen, piroxicam, indomethacin, and methylpred-nisolone indicated controlled-release properties. Generally, drug release from microspheres followed the Fickian diffusion model.     

The Effect of Curing on Drug Release and Morphological Properties of Ethylcellulose Pseudolatex-Coated Beads

Abstract

Drug-containing nonpareil beads were coated in a fluidized bed with a commercial ethylcellulose pseudolatex, Aquacoat. The drug release was investigated as a function of curing conditions (curing time and temperature) for a hydrophilic and lipophilic drug (chlorpheniramine maleate and ibuprofen) at different levels of plasticizer (triethyl citrate). Curing of coated beads at elevated temperatures immediately after the coating process significantly changed the drug release pattern. Both a retardation and an enhancement in drug release were seen, with the extent being dependent on the type of drug and curing conditions. With chlorpheniramine maleate, a drug with low affinity for the ethylcellulose coating, a curing step was necessary at intermediate plasticizer levels to obtain good film formation and a limiting drug release pattern, while the use of higher plasticizer levels eliminated the need for a curing step. With ibuprofen, a lipophilic drug with high solubility in the ethylcellulose coating, drug crystals were apparent on the bead surface after curing. Curing of ibuprofen beads as a function of time initially decreased but then substantially increased the drug release as a result of drug diffusion across the ethylcellulose membrane with subsequent crystallization on the bead surface. An intermediate seal coat reduced the diffusion of the drug into the ethylcellulose coating.     

The Effect of Curing on Drug Release and Morphological Properties of Ethylcellulose Pseudolatex-Coated Beads

Drug-containing nonpareil beads were coated in a fluidized bed with a commercial ethylcellulose pseudolatex, Aquacoat. The drug release was investigated as a function of curing conditions (curing time and temperature) for a hydrophilic and lipophilic drug (chlorpheniramine maleate and ibuprofen) at different levels of plasticizer (triethyl citrate). Curing of coated beads at elevated temperatures immediately after the coating process significantly changed the drug release pattern. Both a retardation and an enhancement in drug release were seen, with the extent being dependent on the type of drug and curing conditions. With chlorpheniramine maleate, a drug with low affinity for the ethylcellulose coating, a curing step was necessary at intermediate plasticizer levels to obtain good film formation and a limiting drug release pattern, while the use of higher plasticizer levels eliminated the need for a curing step. With ibuprofen, a lipophilic drug with high solubility in the ethylcellulose coating, drug crystals were apparent on the bead surface after curing. Curing of ibuprofen beads as a function of time initially decreased but then substantially increased the drug release as a result of drug diffusion across the ethylcellulose membrane with subsequent crystallization on the bead surface. An intermediate seal coat reduced the diffusion of the drug into the ethylcellulose coating.     

The Kinetics of Drug Release from Ethylcellulose Solid Dispersions

Abstract

Sulphadiazine - ethylcellulose (EC) solid dispersions with different drug: carrier ratios were prepared and fractionated. In vitro drug release followed an apparent zero-order kinetics rate constant being dependent on the thickness of the coat which was the rate controlling step in the process. Drug release was found to increase as the granule size was decreased. The amount of drug released was found to be pH dependent thus showing the existence of pores in the coat surrounding the drug particles. Inclusion of polyethylene glycol or sodium lauryl sulphate in the coat material or dissolution medium resulted in increased dissolution, an effect which was attributed to increase in porosity, reduction of interfacial tension and increase in wettability which was associated with the presence of these compounds.     

Effects of Surfactant on Release Characteristics of Clonidine Hydrochloride from Ethylcellulose Film

The effects of Tween 80 (polysorbate 80) and Span 80 (sorbitan monooleate) surfactants on release characteristics of clonidine hydrochloride from ethylcellulose 10 and 20 cps matrix films containing castor oil as a plasticizer were investigated. The release rates of drug from these films in water at 37°C were found to increase with the addition of surfactant, which was highest for the film prepared from ethylcellulose 20 cps with Tween 80. The experimental values of the cumulative amount of drug released were found to conform to the solution matrix model. The calculated values of the cumulative amount of clonidine hydrochloride released using the experimentally determined diffusion coefficients were also found to be in good agreement with the observed values.     

Effect of the Drying Method on the Mechanical and Drug Release Properties of Pellets Prepared by Extrusion-Spheronization

Many pelletization processing variables are capable of influencing the fundamental properties of pellets. This study was designed to elucidate the effect of the drying technique on the mechanical and skeletal properties of spheronized particles. Although much has been reported on the effect of the formulation and processing variables associated with extrusion and spheronization, little attention has been paid to the nature and length of the subsequent drying process. Pellets were prepared containing either 80%w/w ibuprofen or 80%w/w lactose with 20%w/w microcrystalline cellulose. The resulting spherical pellets were dried either by tray drying or fluidized-bed drying. This work has revealed that the drying technique has a quantifiable effect on the diametral crushing strength and elasticity of the pellets, their in-vitro drug release and a qualitative effect on the surface characteristics of ibuprofen pellets.     

Effect of the Drying Method on the Mechanical and Drug Release Properties of Pellets Prepared by Extrusion-Spheronization

Abstract

Many pelletization processing variables are capable of influencing the fundamental properties of pellets. This study was designed to elucidate the effect of the drying technique on the mechanical and skeletal properties of spheronized particles. Although much has been reported on the effect of the formulation and processing variables associated with extrusion and spheronization, little attention has been paid to the nature and length of the subsequent drying process. Pellets were prepared containing either 80%w/w ibuprofen or 80%w/w lactose with 20%w/w microcrystalline cellulose. The resulting spherical pellets were dried either by tray drying or fluidized-bed drying. This work has revealed that the drying technique has a quantifiable effect on the diametral crushing strength and elasticity of the pellets, their in-vitro drug release and a qualitative effect on the surface characteristics of ibuprofen pellets.     

溶剂蒸发法制备油核/聚合物壳微胶囊

通过溶剂蒸发法制备了十六烷/聚甲基丙烯酸甲酯核/壳结构微胶囊。SEM和光学显微镜照片显示,微胶囊呈球形,囊壁透明,表面光滑。系统研究表明,在相同条件下,随着PMMA用量的增加,微胶囊粒径增大,粒径分布变宽;随着搅拌速度的增加或/和稳定剂PVA量的增大,微胶囊的粒径减小,粒径分布变窄。     

时间控制/pH依赖型盐酸黄连素结肠给药系统的控释性能

以全硅MCM-41介孔分子筛为主体,以盐酸黄连素(BH)药物分子为客体,利用天然高分子海藻酸钠(SA)和壳聚糖(CS)为包覆材料,通过振荡吸附-浸提法制备了时间控制/pH依赖型BH/MCM-41/CS-SA结肠给药系统。利用XRD、SEM、BET、FTIR等技术对其理化性质进行了表征,并采用分光光度法对其载药和体外释药性能进行了评价。结果表明,BH/MCM-41/CS-SA的载药率为23.5%,载药后未破坏MCM-41的介孔结构。体外释放结果表明,相较BH/MCM-41,BH/MCM-41/CS-SA具有显著的时滞/pH依赖敏感释药特征,具备较好的结肠靶向给药性能,还具有长效控缓释放效果。     

Shape‐Memory Properties of Polyetherurethane Foams Prepared by Thermally Induced Phase Separation

In this study, we report the preparation of two structurally different shape‐memory polymer foams by thermally induced phase separation (TIPS) from amorphous polyetherurethanes. Foams with either a homogeneous, monomodal, or with a hierarchically structured, bimodal, pore size distribution are obtained by adoption of the cooling protocol. The shape‐memory properties have been investigated for both foam structures by cyclic, thermomechanical experiments, while the morphological changes on the micro scale (pore level) have been compared to the macro scale by an in situ micro compression device experiment. The results show that the hierarchically structured foam achieves higher shape‐recovery rates and a higher total recovery as compared to the homogeneous foam, which is due to an increased energy storage capability by micro scale bending of the hierarchically structured foam compared to pure compression of the homogeneous foam.     

Compressibility Characteristics of Matrices Prepared with Ethylcellulose Aqueous Dispersion

Granules of acetaminophen (APAP) and Lactose Fast Flo were prepared by wet granulation method using Surelease aqueous dispersion as a granulating liquid. Acetaminophen granules containing different total solids (from Surelease) were compacted into tablets using instrumented tablet press to investigate the effect of the levels of Surelease (total solids) on the compressional properties of various formulations. Measurements were made of their compressibility, force displacement, works and forces analysis during compaction. All formulations containing Surelease utilized the compaction energy better than formulations of the same composition prepared without Surelease. As the level of total solids from Surelease was increased in the formula, the compressibility characteristic was enhanced. Granules with Surelease exhibited better deformation and densification behaviors and gave tablets of better mechanical strength compared to control tablets.     

Properties of Nanostructured Hydroxyapatite Prepared by a Spray Drying Technique

In previous studies nano sized hydroxyapatite (HA) particles were prepared by solgel or precipitation methods, in which the products were washed by aqueous or non-aqueous liquids to remove impurities or undesired components. The washing is know to modify the surfaces of the cystalline particles. This study evaluated properties of nano HA materials prepared by a spray drying method in which the HA product was not exposed to any liquid after its formation. The spray drying apparatus consisted of a nozzle that sprayed an acidic calcium phosphate solution in the form of a fine mist into a stream of filtered air flowing through a heated glass column. The water and volatile acid were evaporated by the time the mist reached the end of the column, and the fine particles were collected by an electrostatic precipitator. Powder x ray diffraction patterns suggested the material was amorphous, exhibiting a single broad peak at 30.5° 2θ. However, high resolution transmission electron microscopic analysis showed that the particles, some of which were 5 nm in size, exhibited well ordered HA lattice fringes. Small area diffraction patterns were indicative of HA. Fourier transfer infrared spectroscopy showed patterns of typical of HA with small amounts of HPO₄²⁻. The thermodynamic solubility product of the nano HA was 3.3 × 10⁻⁹⁴ compared to 1 × 10⁻¹¹⁷ for macro scale crystalline HA. These results showed that a spray drying technique can be used to prepare nanometer sized crystalline HA that have significantly different physicochemical properties than those of its bulk-scale counterpart.     

Compressibility Characteristics of Matrices Prepared with Ethylcellulose Aqueous Dispersion

Abstract

Granules of acetaminophen (APAP) and Lactose Fast Flo were prepared by wet granulation method using Surelease aqueous dispersion as a granulating liquid. Acetaminophen granules containing different total solids (from Surelease) were compacted into tablets using instrumented tablet press to investigate the effect of the levels of Surelease (total solids) on the compressional properties of various formulations. Measurements were made of their compressibility, force displacement, works and forces analysis during compaction. All formulations containing Surelease utilized the compaction energy better than formulations of the same composition prepared without Surelease. As the level of total solids from Surelease was increased in the formula, the compressibility characteristic was enhanced. Granules with Surelease exhibited better deformation and densification behaviors and gave tablets of better mechanical strength compared to control tablets.     

相分离法构建聚乳酸/纳米羟基磷灰石复合纳米纤维支架及性能

通过液.液相分离法构建纳米纤维聚左旋乳酸/蚋米羟基磷灰石(NF-PLLA/nHA)仿生复合支架,利用扫描电镜、压缩测试、微量二喹啉甲酸(BCA)法、X射线衍射及差示扫描量热等手段对其进行表征.结果显示,nHA均匀馕嵌在PLLA纳米纤维间隙中,不影响其纳米纤维结构且明显提高力学性能.同时,nHA的引入还能增加对牛血清白蛋...     

Controlled Release Theophylline Tablet with Acrylic Polymers Prepared by Spray-Drying Technique in Aqueous System

Abstract

Sustained release and enteric theophylline tablets were prepared by directly compressing spray-dried microsphers with Eudragits L30D, L100-55 and E30D. The spray-drying process was free from using organic solvent. Drug dissolution of the enteric tablet in an acidic solution (pH 1.2) was highly dependent on the polymer content of the microsphere. Completely enteric function was observed with drug-to-polymer ratio of 1:3 using Eudragit L30D or L100-55. Tablet with Eudragit E30D formulated at the 2–40% level showed good sustained drug release which was throughly independent of the pH of dissolution media. The dissolution pattern was similar to that of Theo-dur and gave a straight line in Higuchi plot. In each tablet, the controlled drug release was attributed to continuous and well-dispersed polymer matrix formed by spray-drying and subsequent compressing process     

Controlled Release Theophylline Tablet with Acrylic Polymers Prepared by Spray-Drying Technique in Aqueous System

Sustained release and enteric theophylline tablets were prepared by directly compressing spray-dried microsphers with Eudragits L30D, L100-55 and E30D. The spray-drying process was free from using organic solvent. Drug dissolution of the enteric tablet in an acidic solution (pH 1.2) was highly dependent on the polymer content of the microsphere. Completely enteric function was observed with drug-to-polymer ratio of 1:3 using Eudragit L30D or L100-55. Tablet with Eudragit E30D formulated at the 2-40% level showed good sustained drug release which was throughly independent of the pH of dissolution media. The dissolution pattern was similar to that of Theo-dur and gave a straight line in Higuchi plot. In each tablet, the controlled drug release was attributed to continuous and well-dispersed polymer matrix formed by spray-drying and subsequent compressing process