Different Types of Direct Compressible Excipients Affecting the Release Behavior of Theophylline Controlled-release Tablets Containing Eudragit Resins

Abstract

Theophylline released from direct-compressed tablets containing Eudragit RSPM/RLPM and different types of direct compressible excipients was investigated. The influences of the type of dissolution medium and stirring speed on the release behavior of theophylline were also studied. The results showed that the type of direct compressible excipients, dissolution medium and stirring conditions significantly influenced the dissolution rate. The tablet made by dicalcium phosphate or microcrystalline cellulose exhibited the most controlled-release behavior. Almost all the release kinetics of tablets followed a Fickian-transport model.     

Different Types of Direct Compressible Excipients Affecting the Release Behavior of Theophylline Controlled-release Tablets Containing Eudragit Resins

Theophylline released from direct-compressed tablets containing Eudragit RSPM/RLPM and different types of direct compressible excipients was investigated. The influences of the type of dissolution medium and stirring speed on the release behavior of theophylline were also studied. The results showed that the type of direct compressible excipients, dissolution medium and stirring conditions significantly influenced the dissolution rate. The tablet made by dicalcium phosphate or microcrystalline cellulose exhibited the most controlled-release behavior. Almost all the release kinetics of tablets followed a Fickian-transport model.     

Eudragit NE40-Drug Mixed Coating System for Controlling Drug Release of Core Pellets

This study was aimed at developing a controlled-release coating system around core pellets with aqueous dispersion, along with some water channeling agents. Core pellets of diltiazem were prepared using the extrusion-spheronization technique and subsequently coated with aqueous dispersion of Eudragit NE40 alone, or drug-polymer mixtures using bottom-spray fluidized bed coater. The lag time in drug release profiles increased as the coating levels of Eudragit NE40 were increased, whereas no lag time was observed in core pellets coated with drug-polymer mixtures. Mixed coating at the 7% level exhibited comparatively better release profiles and provided desirable release rates during the 12-hour testing interval. Diltiazem HCl release from mixed coating was fairly independent of pH and drug loading. Curing of coated pellets was found to be an essential step for stable drug release profiles. The selection of core size range had remarkable effect on drug release rate and was considerably reduced by using greater core size.     

A Mixture Experiment Approach for Controlling the Dissolution Rate of a Sustained-Release Tablet

Abstract

Several sustained-release tablet formulations with acceptable pharmacokinetic properties were found to be unstable because of the effects of lactose. Because the pharmacokinetic properties were acceptable, an attempt was made at developing stable formulations that reproduced the in vitro drug release characteristics of the unstable formulations. Through the use of a statistically designed mixture experiment, alternative formulations were generated and tested for dissolution. The dissolution data collected in the mixture experiment were used to develop a statistical regression model for identifying formulations with dissolution rates equal to those of the unstable formulations. The form of the regression model was based on the Higuchi equation. The data analysis indicated that it is possible to generate dissolution profiles that reproduce those of the original formulations by adjusting the ratios of Methocel® K4MCR Premium and Methocel KWOMCR Premium and by replacing the detrimental lactose with calcium phosphate dibasic anhydrous.     

A New Approach for Enhancing the Dissolution Rate of Phenacetin

Numerous attempts are conducted so as to develop a rapid dissolution rate for those poorly water-soluble drugs. A new approach for enhancing the intrinsic dissolution rate of phenacetin is ascribed. This technique is based on the concept of the recrystallization of phencetin from different surfactants concentrations. The observed enhancing effect in the dissolution rate of phenacetin, using this technique, may be cue to wetting and/or deaggregation effect. The dissolution rate study was investigated in 0.1 N HC1 at 37°C and 50 r.p.m. The experimental study showed that the dissolution rate, during the first few minutes, is markedly affected by this technique. The relative area under the curve from 0 to 30 minutes (R.A.U.C.) was used as a parameter to 0-30 compare the different dissolution rates of the drug after being recrystallized from 1% w/v of each surfactant solution. The extent, in the dissolution rate enhancing effect, was found to range from 2.66 to 3.25 times of that of the control. This technique is valuable as a preformulation phase of phenacetin in solid dosage forms.     

A New Approach for Enhancing the Dissolution Rate of Phenacetin

Abstract

Numerous attempts are conducted so as to develop a rapid dissolution rate for those poorly water-soluble drugs. A new approach for enhancing the intrinsic dissolution rate of phenacetin is ascribed. This technique is based on the concept of the recrystallization of phencetin from different surfactants concentrations. The observed enhancing effect in the dissolution rate of phenacetin, using this technique, may be cue to wetting and/or deaggregation effect. The dissolution rate study was investigated in 0.1 N HC1 at 37°C and 50 r.p.m. The experimental study showed that the dissolution rate, during the first few minutes, is markedly affected by this technique. The relative area under the curve from 0 to 30 minutes (R.A.U.C.) was used as a parameter to 0–30 compare the different dissolution rates of the drug after being recrystallized from 1% w/v of each surfactant solution. The extent, in the dissolution rate enhancing effect, was found to range from 2.66 to 3.25 times of that of the control. This technique is valuable as a preformulation phase of phenacetin in solid dosage forms.     

Tableting of Eudragit RS and Propranolol Hydrochloride Solid Dispersion: Effect of Particle Size,Compaction Force,and Plasticizer Addition on Drug Release

The application of a solid dispersion (SD) system of propranolol HCl and Eudragit RS was evaluated in the preparation of prolonged release tablets. The effects of SD size fraction, compaction force, and inclusion of plasticizers [namely diethylphtalate (DEP) and triethylcitrate (TEC)] on crushing strengths of matrices and release profile of drug were also investigated. The results showed that when compressed as a tablet, the SD system was more efficient in prolonging drug release than physical mixture. This effect was due to formation of much harder tablets of the SD system (crushing strength 8.5 kg) compared with those of physical mixtures (crushing strength 2.7 kg). All matrices of the SD system showed release rate patterns that were best described by the Higuchi equation. It was also shown that the rate of drug release decreased from 19.8% to 9.13% min^??1/2 as the SD size fraction decreased from 300–350 to 125–250 µm. However, further reduction of size fraction did not significantly affect tablet crushing strength and drug release rate. Increase in compaction force from 5 to 30 kN increased the crushing strength of matrices from 2.9 to 13.6 kg. However, the rate of drug release remained nearly unchanged beyond compaction pressure of 10 kN, indicating that crushing strength of matrices in the range of 8.5–13.6 kg did not affect drug release rate. The addition of 5% or 10% of either plasticizer (DEP or TEC) led to an increase in crushing strength of matrices and more retardation of drug release. This effect was more pronounced for higher concentrations of plasticizers. This effect was probably due to more plastic deformation of matrices under the compaction force, which helped matrices to retain their shape throughout the dissolution test.     

基于LabVIEW的通过LXI接口控制33220A程序设计

本文针对GPIB/PXI/VXI总线仪器设备存在的问题,介绍了LXI联盟诞生及根据LXI仪器总线标准将仪器分为C类、B类、A类、并以图的形式给出了LXI标准物理结构,同时描述了LXI Class C Non Auto-MDIX接口含义,及在LabVIEW8.5开发环境下,以计算机为控制器实现与33220A函数/任意波形发生器的LXI接口进行通讯的控制方法和通过仪器网页控制仪器的方法,经应用证明这两种方法简单实用,可充分开发利用仪器本身的资源,灵活使用仪器程控功能,对从事自动测试程序设计者具有参考借鉴价值。     

Increasing the Dissolution Rate of some Benzothiadiazine Derivatives by Solid and Liquid Dispersion Techniques

Abstract

Dissolution rates of water-insoluble drugs such as Chlorothiazide, Hydrochlorothiazide, Flumethiazide and Cyclopenthiazide were markedly increased when dispersed in polyethylene glycol 6000. The increased dissolution rate was believed to be attributed to the molecular and for the colloidal dispersion of the drug in the matrix of PEG 6000. Bendroflumethiazide and Methylclothiazide were found to be decomposed by either of dispersion techniques.     

Increasing the Dissolution Rate of some Benzothiadiazine Derivatives by Solid and Liquid Dispersion Techniques

Dissolution rates of water-insoluble drugs such as Chlorothiazide, Hydrochlorothiazide, Flumethiazide and Cyclopenthiazide were markedly increased when dispersed in polyethylene glycol 6000. The increased dissolution rate was believed to be attributed to the molecular and for the colloidal dispersion of the drug in the matrix of PEG 6000. Bendroflumethiazide and Methylclothiazide were found to be decomposed by either of dispersion techniques.     

Damage Dependent Constitutive Behavior and Energy Release Rate for a Cohesive Zone in a Thermoviscoelastic Solid

In this paper a cohesive zone is introduced ahead of a crack tip in order to avoid the singularity at the crack tip. By applying thermodynamics to the cohesive zone and the surrounding body, a fracture criterion will be established so that the inelastic energy dissipation both in the cohesive zone and the surrounding bulk material can be distinguished from the energy released by fracture, and the propagation of crack can be predicted. In addition, the cohesive zone constitutive equation is constructed utilizing the Helmholtz free energy in the form of a single hereditary integral for a nonlinear viscoelastic material. The resulting constitutive model for the cohesive zone contains an internal state variable which represents the damage state within the cohesive zone. When the cohesive zone opening displacement is known, the energy release rate is thus history dependent, which is expressed in terms of the damage state, the length of separation in the cohesive zone and the geometric configuration of the cohesive zone opening displacement. Example results contained herein demonstrate this effect. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of Mucilage of Hibiscus rosasinensis Linn as Rate Controlling Matrix for Sustained Release of Diclofenac

This article reports the exploitation of novel hydrophilic excipient, that is, mucilage from Hibiscus rosasinensis Linn, for the development of sustained release tablet. Swelling ratio and flow properties analyses of dried mucilage powder were carried out. A 3² full factorial design was used. In factorial design, amounts of dried mucilage and dibasic calcium phosphate (DCP) were taken as independent factors and percentage drug release in 60 and 300 min and time for 80% drug release as dependent variables. Matrix tablet containing dried mucilage and diclofenac sodium (DS) was prepared through direct compression techniques. DS tablets were evaluated for hardness, friability, weight variation, in vitro drug release and water uptake, and mass loss study. The dried mucilage powder shows superior swelling capacity and excellent flow properties. Prepared tablets have acceptable hardness, friability, and uniformity in weight. It was found that batch HD8 fulfills all selected criteria. Drug release kinetics from these formulations corresponded best to the zero-order kinetics. Water uptake was independent whereas mass loss was dependent on agitation speed. The concept of similarity factor (f₂) was used to prove similarity of dissolution profile in distilled water and phosphate buffer and was found to be 90.68. It was concluded that mucilage can be used as release-retarding agent for 12 h when the drug–mucilage ratio was 1:1.5. So, matrix tablet containing dried mucilage is most suitable for sustained release of DS.     

Effect of Particle Size on the Dissolution Rate of Monophenylbutazone Solid Dispersion in Presence of Certain Additives

Abstract

Monophenylbutazone is a very sparingly soluble drug. The effect of particle size on the dissolution characteristics of monophenylbutazone in a dissolution medium of 0.1 N hydrochloric acid and 0.1 N hydrochloric acid to which was added 0.005% Tween 80, was carried out. The enhancement of the dissolution rate of the medicament was attained by formulating the drug in both solid dispersion and physical mixture using urea and polyethylene glycol 4000 as carriers. A comparative dissolution behaviour of the medicament in different solid dispersion and physical mixture ratios were investigated at particle, size of < 63 μ. Drug-urea solid dispersion of a ratio 5:95% produced the highest dissolution rate.     

A New Approach for Calculating the Mass Flow Rate of Entrained Air in a Freefalling Material Stream

This article presents the outcomes from a series of physical experiments to measure the air entrainment rates encountered within a stream of freefalling particles. The experimental work presented spans a range of particle parameters and hopper geometries. From these results a new theory for the prediction of air entrainment is developed and presented. This new method was developed specifically to facilitate a better understanding in the area of fugitive dust control associated with material handling systems, which are driven by the air entrainment during freefalling. From the work presented in this article, a better prediction capability of freefalling bulk materials in either constrained, or unconstrained systems, will allow for the optimization of either passive or active dust control strategies. This article presents several distinct sections that detail the experimental work used to determine the freefall stream parameters that were conducted to allow the development of the entrainment equations.     

Preparation of a Solid Dispersion by a Dropping Methodto Improve the Rate of Dissolution of Meloxicam

Application of a solid dispersion system is one of the methods used to increase the bioavailability of poorly water-soluble drugs. Adaptation of the dropping method from the chemical industry as a formulation procedure may help the scaling-up process and simplify the formulation of poorly water-soluble compounds. Meloxicam (ME), a nonsteroidal anti-inflammatory drug that is poorly soluble in water, and polyethylene glycol (PEG) 4000, a water-soluble carrier, were formulated by using a dropping method in an attempt to improve the dissolution of ME. Pure ME and physical mixtures and tablets of ME–PEG 4000 (1:3 ratio) were compared as regards their dissolution with samples formulated by the dropping method. The results revealed that the round particles (solid drops) exhibited a higher dissolution rate than those of the physical mixtures, tablets, and pure ME. Self-modeling curve resolution (SMCR) as a chemometric method was used to evaluate X-ray powder diffractometry (XRPD) data. The results demonstrated the presence of a new crystalline phase in the solid dispersion, which can help the fast and quantitative dissolution from the solid drops. The round particles can be adapted to individual therapy by using a distributor.     

Chemiadsorbates of Drugs on Silica: A New Approach to Drug Release Modification

The preparation, characterization and in-vitro release of 2-phenylethylal-cohol and thymol chemiadsorbates on a porous silica support of mean pore size of 10 nm are described. Drug molecules are linked to the silica surface by =Si-O-C= bonds via their alcoholic or their phenolic group, respectively. UV and IR spectroscopy were used to identify the chemiadsorbates and to characterize the adsorbed state of the drug molecules. The in-vitro release of the active component from this type of immobilized drug was found to be dependent on drug structure, the preparation technique (surface coverage of the chemiadsorbate) and the pH of the dissolution fluid. In the latter case increasing rates of release occured by increasing the pH. The release profiles are discussed here, considering the possible use of these chemiadsorbates in drug release modification.     

Chemiadsorbates of Drugs on Silica: A New Approach to Drug Release Modification

Abstract

The preparation, characterization and in-vitro release of 2-phenylethylal-cohol and thymol chemiadsorbates on a porous silica support of mean pore size of 10 nm are described. Drug molecules are linked to the silica surface by =Si-O-C= bonds via their alcoholic or their phenolic group, respectively. UV and IR spectroscopy were used to identify the chemiadsorbates and to characterize the adsorbed state of the drug molecules. The in-vitro release of the active component from this type of immobilized drug was found to be dependent on drug structure, the preparation technique (surface coverage of the chemiadsorbate) and the pH of the dissolution fluid. In the latter case increasing rates of release occured by increasing the pH. The release profiles are discussed here, considering the possible use of these chemiadsorbates in drug release modification.     

Nanoarchitectonics for Controlling the Number of Dopant Atoms in Solid Electrolyte Nanodots

Controlling movements of electrons and holes is the key task in developing today's highly sophisticated information society. As transistors reach their physical limits, the semiconductor industry is seeking the next alternative to sustain its economy and to unfold a new era of human civilization. In this context, a completely new information token, i.e., ions instead of electrons, is promising. The current trend in solid‐state nanoionics for applications in energy storage, sensing, and brain‐type information processing, requires the ability to control the properties of matter at the ultimate atomic scale. Here, a conceptually novel nanoarchitectonic strategy is proposed for controlling the number of dopant atoms in a solid electrolyte to obtain discrete electrical properties. Using α‐Ag_2+δS nanodots with a finite number of nonstoichiometry excess dopants as a model system, a theory matched with experiments is presented that reveals the role of physical parameters, namely, the separation between electrochemical energy levels and the cohesive energy, underlying atomic‐scale manipulation of dopants in nanodots. This strategy can be applied to different nanoscale materials as their properties strongly depend on the number of doping atoms/ions, and has the potential to create a new paradigm based on controlled single atom/ion transfer.     

A Shrinkage Approach for Failure Rate Estimation of Rare Events

Systems have become more and more reliable due to technological advancement. For highly reliable systems, there are usually very few or even no failures during the testing and operation. On the other hand, given a short operating or testing time, the failure of the system is also rare even the failure rate is relatively high. The classical maximum likelihood estimation approach results in degenerated estimates zero when no failure occurs and hence meaningless. To overcome this problem, we investigate a shrinkage approach for the estimation of the failure rate of rare events from multiple heterogeneous systems provided that some of them have failures. The shrinkage estimator shrinks the MLE toward a predetermined data‐dependent point in the parameter space and could be expressed as a weighted average of MLE and the data‐dependent point. Examples are shown how the procedure can be implemented. Simulation studies show that our approach performs better than the other approaches in most cases. Copyright © 2014 John Wiley & Sons, Ltd.     

合金产品中镍释放率的检测方法

本文叙述了一个白K金合金的镍释放率检测方法。配制一种人工汗液，将含镍的合金样品浸入一个星期后用火焰原子吸收光谱仪检测溶液中的浸出镍的含量，单位为μg/cm^2/week。使用合理的调整系数，得出该合金样品的镍释放率。通过比对实验，证明该方法现实可行。