Development and release mechanism of diltiazem HCl prolonged release matrix tablets

A coated matrix tablet formulation has been used to develop controlled release diltiazem HCl (DIL) tablets. The developed drug delivery system provided prolonged drug release rates over a defined period of time. DIL tablets prepared using dry mixing and direct compression and the core consisted of hydrophilic and hydrophobic polymers such as hydroxypropylmethylcellulose (HPMC), Eudragits RLPO/RSPO, microcrystalline cellulose, and lactose. Tablets were coated with Eudragit NE 30D, and the influence of varying the inert hydrophobic polymers and the amount of the coating polymer were investigated. The release profile of the developed formulation was described by the Higuchi model. Stability trials up to 6 months displayed excellent reproducibility.     

Design and evaluation of pH modulated controlled release matrix systems for colon specific delivery of indomethacin

Indomethacin, a potent non steroidal anti-inflammatory drug (NSAID), is indicated for the local treatment of colorectal carcinoma. The aim of the present study was to design and investigate various matrix systems for controlled and site specific delivery of indomethacin to the colon. Various pH sensitive and hydrophobic polymers were investigated for their effect on drug release and site specificity. Effect of proportion of Eudragit L100 and Eudragit S100 in matrix either alone or in combination was evaluated. Effect of hydrophobic non-swellable polymer ethyl cellulose on the release pattern of drug from the Eudragit bases was also investigated. Matrix tablets prepared with Eudragit showed pH dependent release profile with the formulations of Eudragit L100 showing faster rate of drug release than Eudragit S100 in alkaline pH. The release profile from matrix tablets containing Eudragit L100 and Eudragit S100 in combination or with ethyl cellulose correlated well with the relative proportion of the two polymer types in the matrix base. Selected formulations when evaluated in simulated gastric fluid pH without enzymes showed negligible to low drug release (less than 10%) in the first 4-6 h followed with controlled release for 14-16 h. It was concluded that pH sensitive matrix bases in combination with a hydrophobic polymer like ethyl cellulose canbe ideal for site specific delivery of drugs to colon with controlled release profile.     

Formulation optimization of solid dispersion of mosapride hydrochloride

Mosapride citrate (MSP) is a gastroprokinetic agent that acts as a selective 5-HT₄ agonist and accelerates the gastric emptying, and is used for the treatment of acid reflux, irritable bowel syndrome, and functional dyspepsia. The purpose of this study is to investigate the solid dispersion formulations of MSP with controlled release characteristic using various polymers, elucidate the release mechanism, and characterize the interaction patterns between MSP and polymers. Solid dispersions of MSP with different drug-to-polymer ratios were prepared by a solvent evaporation method and characterized in comparison with the simple physical mixtures. Eudragit RSPO, Eudragit RLPO, hydroxypropylmethylcellulose (HPMC) or Kollidon SR® was used as a controlled-release polymer along with polyvinylpyrrolidone (PVP) as a carrier. Characterization of MSP solid dispersion was performed using thermal analysis (DSC), powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, where the drug was converted from the crystalline state to amorphous state in all polymeric carriers used. In vitro dissolution studies showed that the drug release has been extended up to 24 h by using Eudragit RSPO or HPMC. Moreover, the formulations containing higher polymer content ratio showed better slow-release profile. These results indicate that the solid dispersion formulation containing PVP/Eudragit RSPO or HPMC mixture could serve as a good controlled-release system for MSP.     

4-氨基水杨酸钠结肠定位片的研究

目的制备一种新型口服结肠定位制剂，并考察其体外释药行为与犬体内的结肠定位特性。方法本试验选择4-氨基水杨酸钠作为模型药物，应用丙烯酸树脂Eudragit RL30D，RS30D和Eudragit FS30D分别作为缓释和肠溶层包衣材料，制得包衣片剂，使系统可依赖pH和时间双重机制释药。在体外释放试验中，系统在0.1 mol·L^-1盐酸溶液中运转2 h后，分别在pH为6.5，7.0或7.4的磷酸盐缓冲液中继续运转12 h。体内验证以放射性同位素锝（^99mTc）做标记，用γ-射线显影法来确定系统在胃肠道内的释药时间和位置。结果体外实验中，系统在0.1 mol·L^-1盐酸溶液中运转2 h后无药物释放，在pH高于6.5的介质中缓慢释药，介质的pH越高，药物释放越快。体内实验中， 包衣片在胃肠道上半部无药物释放， 到达结肠后开始释药； 而非包衣片在犬胃部即迅速崩解。结论本文采用的包衣材料使包衣片到达升结肠时开始释放药物，药物释放时间可达10 h以上。     

Effect of anionic polymers on the release of propranolol hydrochloride from matrix tablets.

Anionic polymers, namely Eudragit S, Eudragit L 100-55, and sodium carboxymethylcellulose, were incorporated into hydroxypropylmethylcellulose (HPMC K100M) to modify the drug release from HPMC matrices. The effects of changing the ratio of HPMC to anionic polymers were examined in water and in media with different pH. The dissolution profiles were compared according to release rates. The interaction between propranolol hydrochloride and anionic polymers was confirmed using the UV difference spectra method. The drug release was controlled with the type of anionic polymer and the interaction between propranolol hydrochloride and anionic polymers. The HPMC-anionic polymer ratio also influenced the drug release. The matrix containing HPMC-Eudragit L 100-55 (1:1 ratio) produced pH-independent extended-release tablets in water, 0.1 N HCl, and pH 6.8 phosphate buffer.     

Novel sustained-release fast-disintegrating multi-unit compressed tablets of lornoxicam containing Eudragit RS coated chitosan-alginate beads

Novel fast-disintegrating multi-unit tablets (FDMUTs) were prepared to modify the release of lornoxicam (a potent non-steroidal anti-inflammatory drug with a short half-life) as well as to combine the advantages of multi-unit systems with the cost-effectiveness of compressed tablets. The proposed FDMUTs consisted of sustained-release lornoxicam beads directly compressed with fast-disintegrating component, containing amorphous solid dispersion of lornoxicam, anticipating rapid drug release that starts in the stomach to rapidly alleviate the painful symptoms and continues in the intestine to maintain extended analgesic effect. Initially, calcium-alginate and chitosan-alginate beads containing lornoxicam were prepared. Then, the erosion of selected beads formulation was suppressed by treatment with Eudragit RS either through polymer-reinforcement or beads coating. The beads, which elicited appropriate sustainment of lornoxicam release, were directly compressed with fast-disintegrating components to form FDMUTs. The release characteristics of the original beads were maintained after compression which indicates that the adopted compression process did not induce mechanical damage to the beads or coating. All of the prepared FDMUTs demonstrated acceptable physical properties that complied with compendial requirements. Release studies, performed in simulated gastric and intestinal fluids used in sequence to mimic the gastrointestinal transit, illustrate that the FDMUTs containing 8?mg lornoxicam equally distributed between the sustained-release beads and the fast-release component, showed the desired release profile.     

Once daily sustained release tablets of venlafaxine, a novel antidepressant.

Venlafaxine is a unique antidepressant that differs structurally from other currently available antidepressants. Sustained release tablets of venlafaxine to be taken once daily were formulated with venlafaxine hydrochloride equivalent to 75 mg of venlafaxine base. Matrix system based on swellable as well as non-swellable polymers was selected for sustaining the drug release. Different polymers viz. hydroxypropylmethylcellulose (HPMC), cellulose acetate, Eudragit RSPO, ethylcellulose etc. were studied. Combinations of non-swellable polymers with HPMC were also tried in order to get the desired sustained release profile over a period of 16 h. The effect of drug to polymer ratio on in vitro release was studied. The marketed formulation was evaluated for different parameters such as appearance, weight variation, drug content and in vitro drug release. The optimized formulation was subjected to stability studies at different temperature and humidity conditions as per ICH guidelines. These were evaluated for appearance, weight variation, thickness, hardness, friability, drug content and in vitro drug release at selected time intervals. In vivo studies were carried out for the optimized formulation in 12 healthy human volunteers and the pharmacokinetic parameters were compared with the marketed one.     

阿昔洛韦胃漂浮缓释片的制备及体外释放

目的制备阿昔洛韦胃漂浮缓释片,并通过紫外分光光度法考察其体外释放影响因素。方法以阿昔洛韦为模型药物,分别以壳聚糖、羟丙基甲基纤维素K15M(HPMC K15M)、Eudragit S100和碳酸钙为基质制备胃漂浮缓释片,用释放度测定法考察影响药物释放的因素。结果随着HPMC K15M用量增加,药物的释放显著减慢,碳酸钙用量增加,药物释放加快。结论制备的阿昔洛韦胃漂浮缓释片漂浮性良好,且能够达到缓释的目的。     

Preparation and in vitro/in vivo evaluation of sustained-release metformin hydrochloride pellets.

In this study, metformin hydrochloride (MH) sustained-release pellets were successfully prepared by centrifugal granulation. Seed cores preparation, drug layering, talc modification and coating of polymeric suspensions were carried out in a centrifugal granulator. Talc modification was performed before coating in order to overcome the high water solubility of metformin. The influence of surface modification by talc, the effects of Eudragit types and ratios, as well as the correlation between in vitro release and in vivo absorption were investigated in detail. Experimental results indicated that talc modification made a decisive contribution to controlling the drug release by avoiding drug dumping. Three dissolution media: 0.1 M HCl, distilled water and pH 6.8 phosphate buffer were employed to determine the in vitro release behaviors of the above metformin hydrochloride pellets. The relative bioavailability of the sustained-release pellets was studied in 12 healthy volunteers after oral administration in a fast state using a commercially available immediate release tablet (Glucophage) as a reference. Following coating with a blend of Eudragit L30D-55 and Eudragit NE30D (1:20), at 7% or 10% coating level, respectively (referred to as F-2, F-3), the pellets acquired perfect sustained-release properties and good relative bioavailability. The Cmax, Tmax and relative bioavailability for F-2 and F-3 coated pellets were 1.21 microg/ml, 6 h, 97.6% and 1.65 microg/ml, 8 h, 165%, respectively. Combined use of two Eudragit polymers with different features as coating materials produced the desired results. Restricted delivery of metformin hydrochloride to the small intestine from differently coated pellets resulted in increased relative bioavailability and a sustained release effect. The adoption of several different pH dissolution media established a better relationship between the in vitro release and in vivo absorption of the sustained-release pellets.     

包衣技术在盐酸二甲双胍缓释片制备中的应用

目的：研究3种不同包衣技术对盐酸二甲双胍缓释片体外释药的影响。方法：在固定片芯处方的基础上，分别采用压制包衣技术、有机溶剂包衣技术和水性包衣技术，结合骨架缓释技术，对体外释放12h的盐酸二甲双胍缓释片进行研究。结果：采用水性包衣技术结合骨架缓释技术，盐酸二甲双胍的体外释放可达12h以上。结论：可采用水性包衣技术结合骨架缓释技术制备水溶性极强的药物的缓释片，药物在体外释放时，通过包衣膜的机制主要以扩散机制为主。     

尼莫地平缓释片制备

目的尼莫地平缓释片制备。方法通过比较体外释放度筛选处方。将尼莫地平微粉化与羟丙甲纤维素等混合,湿法制粒后制备缓释片,测定其释药度。结果羟丙甲纤维素、乳糖等对释放度均有影响。结论试制的与已经上市的尼莫地平缓释片释放行为基本一致。     

血塞通脉冲控释片的处方优化

目的:优化血塞通脉冲控释片的处方。方法:采用单因素试验考察片芯崩解剂种类、片芯崩解剂用量、包衣液组成和包衣增重百分率对药物累积释放率的影响;采用正交试验考察片芯崩解剂用量、包衣液组成、包衣增重百分率对释药时滞时间的影响,优化血塞通脉冲控释片的处方。结果:最佳处方为片芯崩解剂用量为15%,包衣增重百分率为9%,包衣液组成为Eudragit L100∶EC=1.5∶1(m/m);在该处方条件下,血塞通脉冲片的体外释药时滞为6 h左右,然后迅速脉冲式释药。结论:所选处方合理,制备的血塞通脉冲控释片能达到设计要求,体外试验可达到脉冲释药时滞效果。     

星点设计-效应面法优化五酯缓释片处方

目的:优化五酯缓释片的处方。方法:以羟丙甲基纤维素、磷酸氢钙的用量为考察因素,分别以3、8、14、22h取样时间点的体外累积释放度为考察指标,选用星点设计-效应面法优化处方,并对该结果进行验证。结果:优化的处方为羟丙甲基纤维素、磷酸氢钙的用量分别为13.30%～30.00%、14.14%～17.07%。结论:通过星点设计-效应面法建立的模型可用于五酯缓释片处方的优化,所建立的数学模型具有准确的预测性。     

盐酸二甲双胍缓释微丸的制备及体外释放度考察

目的:制备盐酸二甲双胍(metformin hydrochloride,MH)缓释微丸,并考察其体外释药行为。方法:通过离心造粒法制得MH微丸,以乙基纤维素水分散体(Surelease),丙烯酸树脂水分散体(EudragitNE30D,RS30D)作为膜控释包衣材料,通过流化床包衣制备MH缓释微丸,并考察不同包衣材料、包衣增重、固化时间、释放介质对释放度的影响。结果:离心造粒制得微丸圆整度好,有一定强度,适合包衣,Surelease包衣增重11%时所得的缓释微丸在12 h具有明显的缓释效果,不受释放介质的影响,为零级释放,且12 h释放可以达到85%以上。释放机制主要是通过无孔膜扩散作用。结论:通过离心造粒并用Surelease包衣的MH缓释微丸缓释效果明显,且为零级释放。     

Chitosan dispersed system for colon-specific drug delivery

A chitosan dispersed system (CDS), which was composed of active ingredient reservoir and the outer drug release-regulating layer dispersing chitosan powder in hydrophobic polymer, was newly developed for colon-specific drug delivery. An aminoalkyl methacrylate copolymer RS (Eudragit) RS) was selected as a hydrophobic polymer because it is hardly dissolved in acidic medium in which easily dissolves chitosan. In order to obtain the bi-functional releasing characteristics, i.e. time dependent and site specific, capsules containing the active ingredient (Drug Capsules) were coated by the chitosan dispersed hydrophobic polymer, resulting in CDS Capsules. The release rate could be controlled by changing the thickness of the layer. Furthermore, for colon-specific drug delivery, an additional outer enteric coating was necessary to prevent the drug release from CDS Capsules in the stomach, since chitosan dispersed in the layer dissolves easily under acidic conditions. Resultant enteric-coated CDS Capsules reached the large intestine within 1-3 h after oral administration and they were degraded at the colon in beagle dogs.     

Citric acid monohydrate as a release-modifying agent in melt extruded matrix tablets

Incomplete drug release and particle size-dependent dissolution performance can compromise the quality of controlled release matrix systems. The objective of the current study was to investigate the ability of citric acid monohydrate (CA MH) to enhance the release of diltiazem hydrochloride from melt extruded Eudragit((R)) RS PO tablets and to eliminate drug particle size effects. Preformulation studies demonstrated the thermal stability of all components, drug insolubility in the polymer but miscibility with the CA MH. Tablets with either constant polymer levels or constant drug-to-polymer ratios and containing different drug particle size fractions and increasing amounts of CA MH were manufactured by melt extrusion and characterized by dissolution testing, powder X-ray diffraction and scanning electron microscopy. The addition of CA MH to the formulation promoted the thermal processibility and matrix integrity by plasticization of the polymer. The drug release from systems with constant drug-to-polymer ratio was significantly increased when CA MH was added as a result of enhanced pore formation. Particle size effects were eliminated when large amounts of CA MH were used due to the loss of drug crystallinity. Matrix tablets with CA MH furthermore showed a faster and more complete drug release compared to systems with drug only or alternative pore formers (sucrose, NaCl, or PEG 3350). The enhanced drug release was attributed to the amorphous character of the soluble components, improved drug dispersion in the plasticized polymer along with increased polymer permeability. In summary, CA MH promoted the miscibility between the drug and Eudragit((R)) RS PO during hot-melt extrusion, resulting in the extrusion of an amorphous system with improved dissolution characteristics.     

Leaky enteric coating on ranitidine hydrochloride beads: Dissolution and prediction of plasma data.

The present research is based on the hypothesis that leaky enteric-coated pellets formulations are able to provide sustained input for drugs that have an absorption window, such as ranitidine hydrochloride, without jeopardizing their bioavailability. Leaky enteric-coated pellets formulations are defined as enteric-coated pellets that allow some of the drug to be released from the formulation in gastric fluid. Different approaches to making leaky enteric-coated pellets were investigated using extrusion-spheronization followed by spray coating. Leaky enteric coats were formulated using a commonly used enteric polymer, Eudragit((R)) L 30 D-55, combined with soluble compounds including lactose, PEG 8000 and surfactants (Span 60 (hydrophobic) or Tween 80 (hydrophilic)). The rate of drug release from the formulations in simulated gastric fluid can be tailored by varying the additive's amount or type. All leaky enteric-coated formulations studied completely released the drugs within 30min after changing dissolution medium to phosphate buffer, pH 6. Predictions of plasma concentration-time profiles of the model drug ranitidine hydrochloride from leaky enteric-coated pellets in fasted conditions and from immediate-release formulations were performed using computer simulations. Simulation results are consistent with a hypothesis that leaky enteric-coated pellets formulations provide sustained input for drugs shown to have an absorption window without decreasing bioavailability. The sustained input results from the combined effects of the formulation and GI transit effects on pellets. The present research demonstrates a new application of knowledge about gastrointestinal transit effects on drug formulations. It also shows that enteric-coating polymers have new applications in areas other than the usual enteric-coated formulations. The hypothesis that a leaky enteric-coated pellets formulation may maintain or increase the bioavailability of drugs that have a window of absorption is still to be confirmed by further in vivo studies.     

丙烯酸树脂水性包衣工艺制备氯化钾缓释片的研究

目的:研究氯化钾缓释片的优化工艺.方法:采用丙烯酸树脂水性包衣工艺,通过体外溶出试验对工艺参数进行筛选.结果:包衣后热处理、包衣处方因数(聚合物配比、增塑剂、包衣增重等)都对缓释片释放度有影响,而浆法转速和介质渗透压对缓释片释放度几乎无影响.结论:本研究缓释片的体外释放按零级模式释药.     

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。     

Effect of Different Polymer Concentration on Drug Release Rate and Physicochemical Properties of Mucoadhesive Gastroretentive Tablets

Mucoadhesive tablets have emerged as potential candidates for gastroretentive drug delivery providing controlled release along with prolonged gastric residence time. Gastroretentive mucoadhesive tablets could result in increased bioavailability due to prolonged gastric residence time. A hydrophilic matrix system was developed as mucoadhesion is achievable on appropriate wetting and swelling of the polymers used. The polymers were so chosen so as to provide a balance between swelling, mucoadhesion and drug release. The polymers chosen were hydroxypropyl methylcellulose K4M, chitosan, and Carbopol 934. The concentrations of these polymers used has a great impact on the physicochemical properties of the resulting formulation. The tablets were formulated using wet granulation method and tranexamic acid was used as the model drug. The prepared tablets were characterized for size, shape, appearance, hardness, friability, weight variation, swelling, mucoadhesion and in vitro drug release. Several batches of tablets were prepared by varying the ratio of hydroxypropyl methylcellulose K4M and Chitosan. The batches having a greater ratio of chitosan showed higher rate of swelling, greater erosion, less mucoadhesion and faster release rate of the drug whereas the batches having greater ratio of hydroxypropyl methylcellulose K4M showed lesser rate of swelling, less erosion, better mucoadhesion and a smaller drug release rate. The level of carbopol was kept constant in all the batches.