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.     

Preparation and in vitro evaluation of sustained release tablet formulations of diclofenac sodium

The effects of formulation variables on the release profile of diclofenac sodium (DS) from hydroxypropylmethyl cellulose (HPMC) and chitosan matrix tablets were studied. DS tablets were prepared by wet granulation and direct compression methods and different ratios of HPMC and chitosan were used. Physical properties of the prepared tablets and targeted commercial sustained release (SR) tablet and the drug release were studied in tablets that were placed in 0.1 M HCl for 1 h and phosphate buffer solution was added to reach pH value of 7.5. In vitro studies showed that 20% HPMC contained SR formulation with direct (dry) compression method is the optimum formulation due to its better targeting profile in terms of release. This formulation also exhibited the best-fitted formulation into the zero order kinetics. The precision and accuracy of the analytical method were also checked. The repeatability and reproducibility of the method were also determined.     

Synthesis,characterization and evaluation of deacetylated xanthan derivatives as new excipients in the formulation of chitosan-based polyelectrolytes for the sustained release of tramadol

This paper addressed the application of deacetylated xanthan (XGDS) and chitosan (CTS) as a mixture blend forming hydrophilic matrices for Tramadol (TD) sustained release tablets. XGDSs derivatives were obtained by alkaline treatment of xanthan gum (XG) with various degrees of deacetylation (DD). The obtained products were characterized in terms of structural, thermal and physicochemical properties. Different tablet formulations containing CTS/XGDSs were prepared by direct compression method and compared to CTS/XG tablets. Flow properties of powder mixtures and pharmaceutical characteristics were evaluated. The dissolution test of TD was realized under simulated gastric and intestinal conditions to achieve drug release more than 24 h. All developed tablets were found conforming to standard evaluation tests. It was shown that CTS/XGDSs matrices ensure a slower release of TD in comparison with CTS/XG based formulations. Meanwhile, increasing DD resulted in a decrease of drug release. In addition, TD release from XGDS matrices was faster at pH (6.8) than at acidic pH (1.2). The matrix tablets based on CTS/XGDS4 (DD = 98.08%) were selected as the best candidates compared to the other systems in prolonging drug release. The optimal formulation was found to release 99.99% of TD after 24 h following a non-Fickian type.     

Structure and behaviour of hydrophilic matrix sustained release dosage forms: 1. The origin and mechanism of formation of gas bubbles in the hydrated surface layer

Gas bubbles are an important feature of the surface hydrated layer of hydrophilic matrix tablets in that they may significantly influence the performance of these dosage forms. Cryogenic SEM studies on the hydrated layer provide direct visual evidence for the origin and mechanism of formation of these bubbles. Air within the voids of the dry tablet core is observed to be progressively entrapped by swelling polymer particles within a partially hydrated region at the core/pseudogel interface, giving rise to discrete air pockets within the pseudogel layer.     

In vitro drug liberation and kinetics of sustained release indomethacin suppository

The aim of this study was to formulate sustained release (SR) suppositories containing indomethacin (IND) microspheres. In the first part of the study, IND microspheres were prepared by solvent evaporation method. Ethyl cellulose was used as polymer. Shape and surface characteristics, particle size and size distribution of microspheres were determined. The effect of drug: polymer ratio and stirring rate on microsphere formation, average particle size, drug loading capacity and in vitro IND release were investigated. The highest drug loading capacity was found with 1:1 drug-polymer ratio. Stirring rate caused insignificant effect on drug loading capacity but particle size. Increase in stirring rate resulted in a decrease in particle size. In the second part, SR suppositories were formulated by incorporating IND microspheres having the highest drug loaded. The bases used were PEG mixtures (400:1500:4000) and Witepsol H15. Qualitative controls and IND assay on the suppositories were carried out. The drugs released were evaluated by in vitro dissolution tests. Comparative results of SR suppositories containing IND microspheres with that of conventional ones showed that the former has sustained effect up to 480 min in vitro. Release results were evaluated kinetically and the data was fitted (Bt)(a) kinetics.     

The use of response surface methodology for the formulation and optimization of salbutamol sulfate hydrophilic matrix sustained release tablets

The objective of this study was to develop a hydrophilic matrix formulation with in vitro release characteristics similar to Asthalin^® tablets and that would sustain the release of salbutamol sulfate over a 12-h period. A central composite design was used as the framework for manufacturing formulations that may be used to understand the relationships between polymer levels and in vitro release characteristics. Tablets were manufactured using wet granulation with Surelease^® as the granulating fluid and different levels of Methocel^® K100M, xanthan gum, and Carbopol^® 974P as matrix-forming materials. In vitro dissolution testing was conducted using USP Apparatus 3 and samples were analyzed using a validated reversed-phase HPLC method. The results revealed that the levels and types of polymers had a significant impact on the rate of drug release from these formulations and that it was possible to optimize the levels of matrix-forming polymers to achieve the desired release characteristics. Statistical design and response surface methodology have been successfully used to understand and optimize formulation factors and interactions that impact the in vitro release characteristics of salbutamol sulfate from a potential multisource sustained release dosage form.     

Formulation and evaluation of a sustained-release tablets of metformin hydrochloride using hydrophilic synthetic and hydrophobic natural polymers

Metformin hydrochloride has relatively short plasma half-life, low absolute bioavailability. The need for the administration two to three times a day when larger doses are required can decrease patient compliance. Sustained release formulation that would maintain plasma level for 8-12 h might be sufficient for daily dosing of metformin. Sustained release products are needed for metformin to prolong its duration of action and to improve patient compliances. The overall objective of this study was to develop an oral sustained release metformin hydrochloride tablet by using hydrophilic Eudragit RSPO alone or its combination with hydrophobic natural polymers Gum copal and gum damar as rate controlling factor. The tablets were prepared by wet granulation method. The in vitro dissolution study was carried out using USP 22 apparatus I, paddle method and the data was analysed using zero order, first order, Higuchi, Korsmeyer and Hixson-Crowell equations. The drug release study revealed that Eudragit RSPO alone was unable to sustain the drug release. Combining Eudragit with gum Copal and gum Damar sustained the drug release for more than 12 h. Kinetic modeling of in vitro dissolution profiles revealed the drug release mechanism ranges from diffusion controlled or Fickian transport to anomalous type or non-Fickian transport. Fitting the in vitro drug release data to Korsmeyer equation indicated that diffusion along with erosion could be the mechanism of drug release.     

Sustained release of hydrophobic and hydrophilic drugs from a floating dosage form

Floating dosage forms enable the sustained delivery of drugs in the gastro-intestinal tract. In this study, a type of multi-unit floating gel bead was synthesized with calcium alginate, sunflower oil, and a drug of interest through an emulsification/gelation process. The alginate beads with oil addition were able to continuously float over the medium for 24h under constant agitation while the non-oily beads could not. Three kinds of drugs with different hydrophilicities, ibuprofen, niacinamide and metoclopramide HCl, were tested in the study. The hydrophobic drug ibuprofen was released in a sustained manner for 24h, due to the oil partitioning. With suitable modification, the beads were able to also release the hydrophilic drugs, niacinamide and metoclopramide HCl, for a similar duration. Therefore a floating dosage form that is able to sustain release both hydrophobic and hydrophilic drugs within its extended gastric retention time has been developed.     

Drug release from silicone elastomer through controlled polymer cracking: an extension to macromolecular drugs

An attempt to promote macromolecule release at controlled rates from a polydimethylsiloxane elastomer (Silastic Q7-4840) through osmotically induced osmotically active granules in the 40–106,106–150 or 150–212 μm size range, composed of bovine serum albumin (BSA) and sodium chloride in a 35:65 or 70:30 w/w ratio. The latter granule composition was found to be unsuitable, due to an inadequate level of osmotic agent. With the 35:65 w/w BSA-NaCl ratio in granules protein release to normal saline is of zero-order in the matrix swelling stage. The stationary release rate and time scale are modulated through matrix geometry and granule load and size. With disk-shaped devices and 106–150 or 150–212 μm granule size the release rate and granule load are linked by a log-log correlation. The release pattern is determined by the rate of polymer cracking. The solutes are carried through cracks by a composite convective-diffusive flux.     

基于自增强型互穿聚合物网络凝胶的中药缓释体系的构建与表征

目的 构建并表征用于中药缓释的自增强互穿聚合物网络水凝胶(SR-IPNH)体系。方法 基于洛沙姆网络和甘草酸(GA)网络,构建SR-IPNH体系。得益于GA自组装纤维网络与泊洛沙姆网络的相互渗透交联,水凝胶的机械强度得到显著提高。在本体系中,GA既是OA的治疗成分又是水凝胶的强化剂,使体系的机械强度不需借助化学交联剂就能得到强化。本工作考察了所制备凝胶的流变性、成胶性、体外可注射性、载药性能、体外释放行为及初步稳定性。结果 所制备的SR-IPNH在室温下具有良好的流动性,在35.1 ℃下能2.5 min内快速凝胶,证明本体系具有良好的热敏成胶性能。胶凝实验表明体系具有良好的可注射性和成胶性能,这为关节腔内原位注射治疗提供了必要条件。含量分析结果表明,体系中芍药苷和甘草酸的含量分别为1.88 %和0.86 %。流变学考察结果显示,甘草酸能使凝胶的储能模量G′显著上升,且损耗因子tan δ显著降低,这说明体系的弹性性能得到加强,机械强度得到提升。药物体外释放研究结果显示本体系具备显著的缓释性能,揭示GA的释放受到自扩散和凝胶溶解的双重影响。此外,稳定性实验结果显示室温、密闭和黑暗环境更适合SR-IPNH的贮藏。结论 本研究成功制备了SR-IPNH体系,表征结果展示出良好的机械强度和缓释性能。本工作为中医药治疗OA提供新的思路和技术支持。     

Characterization and superficial transformations on mini-matrices made of interpolymer complexes of chitosan and carboxymethylcellulose during in vitro clarithromycin release

Different interpolymer complexes (IPCs) of chitosan (CS) and carboxymethylcellulose sodium salt (CMC) were used to elaborate mini-matrices containing clarithromycin (CAM). IPCs were characterized by FTIR, DSC and powder X-ray (XRD).Compression processes did not modify the physical state of CAM which was in its polymorph Form II. However, during tableting, polymer/polymer interactions occurred to form matrix systems that were confirmed by DSC.When mini-matrices were placed in acetate buffer (pH 4.2), the formation of a CAM solvate was determined by XRD, FTIR and DSC, showing the presence of incorporated crystallizing solvent molecules. Grazing incidence X-ray diffraction (GID) enabled us to profile transformations of CAM on surfaces of mini-matrices when it is in intimate contact with dissolution medium, and its conversion to a solvate form prior to its dissolution process. Besides, FTIR and DSC revealed polymer–polymer electrostatic interactions during dissolution process.Furthermore, swelling and eroding studies and in vitro drug release exhibited that when increasing the amount of CS within IPCs, swelling and erosion rates were greater and CAM release was faster. Zero-order kinetics from drug release profiles were related to linear erosion kinetics, and highlighted that erosion played an important role in drug release due to CAM poor solubility at this pH.     

国产布洛芬缓释片的体内外相关性

目的对国产布洛芬缓释片的体内外相关性进行研究。方法体外释放度采用中国药典1995年版二部的转篮法,体内血药浓度用HPLC法和3P97程序计算药动学参数。结果在7h时平均累积释放77.44%;10名男性健康志愿者口服单剂量600mg布洛芬缓释片的体内过程符合开放一室模型,AUC,C     

盐酸维拉帕米脉冲释放片体内外释药特性

目的：研究盐酸维拉帕米脉冲释放片体内外释药特性。方法：用干法压制包衣技术制备盐酸维拉帕米脉冲释放片，调整包衣中致孔剂用量，通过体外释放度试验考查时滞，并用HPLC法测定家兔血药浓度，考查体内外时滞的相关性。结果：体内外时滞基本相符。结论：可用体外时滞预测体内的时滞。     

Development of sustained release antipsychotic tablets using novel polysaccharide isolated from Delonix regia seeds and its pharmacokinetic studies

A natural polysaccharide was isolated from the seeds of Delonix regia. The isolated polysaccharide could maintain aqueous equilibrium between the dosage form and the surrounding medium due to its massive competence of water absorption (80.72%) and swelling index (266.7%). The Scanning Electron Micrograph of a polysaccharide exhibits rough surface with pores and crevices, hence, the drug release will be retarded because of the drug particles entrapment in the pores and crevices. Further, the surface tension of polysaccharide is higher than that of water, which may facilitate sustained release of drugs from dosage forms. An antipsychotic drug, quetiapine fumarate has a short half-life of 6 h and administered multiple times per day. Hence the quetiapine fumarate oral sustained release tablets were formulated using this polysaccharide in the concentration of 5–30% to avoid the side effects and increase patient compliance. Dissolution of the developed tablets with 25% polysaccharide content showed a better release profile than the other batches (5–20%) at the end of 12 h. The strong matrix complex has low solubility in water, it does not dissolve rapidly and the drug continues to diffuse through the gel layer at a consistent rate. Drug release from the matrix tablets follows matrix type except F-4 and F-5 which follow first order and Hix.crow type. The bioavailability study was carried out using healthy male New Zealand white rabbits that show the AUC_(0–inf) value for developed SR tablets is 1.44 times higher than the reference thus, indicating more efficient and sustained drug delivery capable of maintaining plasma drug levels better.     

对乙酰氨基酚/MCM-41载药体系的制备及其缓释性能的研究

目的制备对乙酰氨基酚/MCM-41缓释体系,并考察其体外释放行为。方法在碱性和室温条件下制备MCM-41介孔材料;采用浸渍法将解热镇痛药物对乙酰氨基酚组装到MCM-41的孔道中,通过XRD、IR、低温N2吸附对MCM-41介孔材料及药物组装体进行表征;测定组装体的载药量、载药时间以及在人工胃液中的释放行为。结果介孔材料MCM-41作为药物载体具有较短的载药时间(7 h)、较大的载药量(46.65%)、较低的释放速率(6 h仅释放35.6%)。结论通过测定组装体在体外模拟人工胃液和人工肠液中的释放速率,结果表明制得了对乙酰氨基酚/MCM-41缓释释放体系。     

In vitro and in vivo assessment of polymer microneedles for controlled transdermal drug delivery

Microneedles (MNs) system for transdermal drug delivery has the potential to improve therapeutic efficacy, proving an approach that is more convenient and acceptable than traditional medication systems. This study systematically researched dissolving polymer MNs fabricated from various common FDA-approved biocompatible materials, including gelatine, chitosan, hyaluronic acid (HA) and polyvinyl alcohol (PVA). Upon application of MN patches to the porcine cadaver skin, the MNs effectively perforated the skin and delivered drugs to subcutaneous tissue on contact with the interstitial fluid. Both the in vitro and in vivo drug release tests showed the similar trends but different release rates among the prepared MNs. Interestingly, the drug-release kinetics of PVA MNs were able to be altered by changing the molecular weight. To evaluate the feasibility using the proposed MNs for treating diabetes, an in vivo insulin absorption study in diabetic mice was performed. The results showed different insulin release properties of MNs fabricated from various kinds of polymer, leading to different decrease in blood glucose levels. We made a systematic and comprehensive study of some drug-loaded polymer MNs, and anticipated that dissolving polymer MNs have potential to improve therapeutic efficacy through controlled drug release.     

Effect of different polymers and their combinations on the release of metoclopramide HCl from sustained-release hydrophilic matrix tablets

Metoclopramide HCl (MTC) is commonly used for the management of gastrointestinal disorders. It has a short biological half-life and is usually administered four times daily to maintain effective concentrations throughout the day. The aim of this study is to develop sustained-release hydrophilic matrix tablet formulations of drug to achieve reproducible and predictable release rates, extended duration of activity, decreased toxicity, reduction of required dose, optimized therapy, and improved patient compliance. Hydroxypropylmethyl cellulose (HPMC), carboxymethylcellulose sodium (NaCMC), chitosan and Carbopol 981 were incorporated in the matrix system separately or in combinations as release controlling factor by direct compression technique. Compatibility among the formulation components was assessed by DSC and FTIR analysis. MTC release from matrix was evaluated by using the US Pharmacopeia dissolution apparatus II. All formulations met the criteria of pharmacopeial requirements. Dissolution studies show that polymer type and concentration are important parameters on drug release. Chitosan, carbopol and NaCMC formulations exhibited pH-dependent drug release profile whereas HPMC did not. All the formulations containing 1:1 ratio of HPMC and chitosan exhibited desired drug release showing that all active substance releases progressively in a period of whole dissolution time and therefore it can be regarded as worthy of consideration for the manufacture of sustained-release MTC product.     

Enhanced delivery efficiency and sustained release of biopharmaceuticals by complexation-based gel encapsulated coated microneedles: rhIFNα-1b example

Coated microneedles (MNs) are widely used for delivering biopharmaceuticals. In this study, a novel gel encapsulated coated MNs (GEC-MNs) was developed. The water-soluble drug coating was encapsulated with sodium alginate (SA) in situ complexation gel. The manufacturing process of GEC-MNs was optimized for mass production. Compared to the water-soluble coated MNs (72.02% ± 11.49%), the drug delivery efficiency of the optimized GEC-MNs (88.42% ± 6.72%) was steadily increased, and this improvement was investigated through in vitro drug release. The sustained-release of BSA was observed in vitro permeation through the skin. The rhIFNα-1b GEC-MNs was confirmed to achieve biosafety and 6-month storage stability. Pharmacokinetics of rhIFNα-1b in GEC-MNs showed a linearly dose-dependent relationship. The AUC of rhIFNα-1b in GEC-MNs (4.51 ng/ml·h) was bioequivalent to the intradermal (ID) injection (5.36 ng/ml·h) and significantly higher than water-soluble coated MNs (3.12 ng/ml·h). The rhIFNα-1b elimination half-life of GEC-MNs, soluble coated MNs, and ID injection was 18.16, 1.44, and 2.53 h, respectively. The complexation-based GEC-MNs have proved to be more efficient, stable, and achieve the sustained-release of water-soluble drug in coating MNs, constituting a high value to biopharmaceutical.     

Importance of drug type, tablet shape and added diluents on drug release kinetics from hydroxypropylmethylcellulose matrix tablets

The dissolution of 7 drugs from hydroxypropylmethylcellulose (HPMC) matrices have been examined to determine the time exponent (tⁿ) required to produce linear dissolution profiles. A value of n = ˜ 0.67 was obtained for time-dependent release for soluble drugs, the precise values being 0.71, 0.65, 0.67 and 0.64 for promethazine hydrochloride, aminophylline, propranolol hydrochloride and theophylline, respectively. The insoluble drugs, indomethacin and diazepam, displayed values of n = 0.90 and 0.82 indicating a near zero-order release. Matrices containing tetracycline hydrochloride, however, showed a value of n = 0.45 and displayed complex release patterns and lower release rates than anticipated on the basis of solubility. Replacement of HPMC by calcium phosphate or lactose increased the dissolution rates of promethazine hydrochloride although the values of n were unchanged. Differences in release rates between lactose and calcium phosphate replacement occurred only when matrices contained high levels of the diluents. A straight line relationship existed between release rates and tablet surface area for HPMC tablets containing promethazine hydrochloride.