Biphasic release of indomethacin from HPMC/pectin/calcium matrix tablet: II. Influencing variables, stability and pharmacokinetics in dogs

The pectin/calcium interaction, which is the basis for biphasic release of indomethacin from the HPMC/pectin/calcium chloride matrix tablet, is susceptible to influence of a variety of variables that is supposed to be encountered by the oral route. In this study, the effect of influencing variables on biphasic release characteristics, the stability and the pharmacokinetics of the hybrid matrix tablet were investigated. An increasing tendency of the overall release rate was observed from pH 1.2 to 7.4. The power law correlation n values increased with pH, while the release lag time or 10% release time (T_0.1) decreased at pH 6.8 and 7.4. Ionic strength in the release media also influenced the biphasic release significantly at sodium chloride levels of over 0.5%. Obvious increase in overall release rate was observed at sodium chloride level of 0.9% with an n value of 1.20 and a T_0.1 of 3.4 h. At sodium chloride levels of over 2%, the pectin/calcium interaction was disrupted resulting in very fast release of indomethacin. Release in gradient pH media was similar to that in pH 6.8 citrate buffer. When pectinase (Pectinex Ultra SP-L) was added into the release medium in 22.2 pg/ml or over, obvious triggering on drug release was observed. The stress testing showed increased release at extreme relative humidity of 92.5%. Both accelerated testing for 6 m and long-term testing for 12 m affirmed fine stability, especially in release characteristics. Pharmacokinetic study in dogs gave T_max/C_max of 4 h/604 ng/ml and 3 h/1662 ng/ml for HPMC/pectin/calcium and HPMC/pectin tablet, respectively. The plasma indomethacin level of the calcium-containing tablet was maintained at a much lower level for 3 h with a MRT of 7.13 h, longer than 3.97 and 5.61 h for indomethacin crude drug and HPMC/pectin tablet, confirming delayed absorption. The AUC of the HPMC/pectin/calcium tablet was lower than that of the HPMC/pectin tablet and indomethacin crude drug showing incomplete absorption. It is concluded that the HPMC/pectin/calcium matrix tablet is potentially useful for colon-specific drug delivery.     

Sigmoidal release of indomethacin from pectin matrix tablets: effect of in situ crosslinking by calcium cations

Sigmoidal release pattern is therapeutically beneficial for timed release and colonic drug delivery, and is always observed in coated systems. In this study, sigmoidal release from pectin matrix tablets with indomethacin as a model drug was investigated. The underlying mechanisms are calcium cation-induced in situ crosslinking that retard the initial drug release to a limited percentage. Power law equation n values were estimated for sigmoidal release profiles. Results indicated that calcium chloride incorporated in pectin matrix functioned as retarding mechanisms on drug release. Larger amount of calcium chloride led to slower drug release and matrix erosion. Even at extremely high levels, retarding on drug release and matrix erosion rate was obvious, which highlighted the effect of calcium-induced in situ crosslinking as calcium chloride was a freely water-soluble salt. The sigmoidal release profiles were characterized by power law equation with high correlation coefficients of about 0.99 or over. Power law n values increased up to as high as 1.20 when calcium chloride content kept increasing. Erosion correlated well with release in almost all pectin matrix tablets indicating erosion-controlled mechanisms. It is concluded that large amount of calcium induces in situ crosslinking of pectin matrix and leads to sigmoidal release of indomethacin, and power law n values, sometimes larger than 1.0, are suitable to be used to describe sigmoidal release profiles.     

效应面法优化吲哚美辛HPMC／果胶／氯化钙骨架片的双相释放

考察HPMC／果胶／氯化钙骨架片中两个自变量果胶／氯化钙重量比和骨架总重量对吲哚美辛释放的影响。采用二因素五水平星点设计，效应面法优化Peppas方程拟合参数n、K和T0.1（10％释放时间）。自变量对双相释放参数n和K值有显著影响，n、K和T0.1值可用二次多项式拟合，线性拟合效果不佳。数学模型拟合和效应面结果表明果胶／氯化钙重量比和骨架总重量两个因素间有显著交互作用。在具有较大n和T0.1值和较小K值的优化处方中，其果胶／氯化钙的比例约为1．0，骨架总重量处于中间值，约200mg。优化处方只有很好的预测性，n、K和T0.1值的预测偏差介于-7．33％和6．26％之间。星点设计可用于优化和预测药物从HPMC／果胶／氯化钙骨架片的释放。     

An in situ crosslinked compression coat comprised of pectin and calcium chloride for colon-specific delivery of indomethacin

Abstract

The use of pectin for colon-specific drug delivery has been extensively investigated; however, when used alone, pectin is often compromised due to its high solubility. This study explored the feasibility of using an in situ compression-coated crosslinking system, composed of pectin and calcium chloride, for colon-specific drug delivery. A pectin/calcium chloride (P/Ca) coating was compressed onto a core tablet. The colon specificity of the compression-coated tablet was verified by dissolution, pharmacokinetics and scintigraphy with ^99mTc labeling. The in situ pectin and calcium chloride gel slowed the release of indomethacin. The lag time varied between 3?h and 7?h depending on the amount of calcium chloride and the coating weight. Pectinase triggered the release of indomethacin from the compression-coated tablet, which was then accelerated by the calcium chloride in the coating layer. The compression-coated tablet had a prolonged t_max and apparent t_1/2, as well as a decreased C_max and AUC_0–t, compared with the core tablet counterpart. Evaluation with γ-scintigraphy verified colon-specific delivery of the compression-coated tablet. In conclusion, the P/Ca in situ crosslinking system worked well for colon-specific drug delivery.     

Colonic delivery of compression coated nisin tablets using pectin/HPMC polymer mixture.

Nisin containing pectin/HPMC compression coated tablets were prepared and their in vitro behavior tested for colonic delivery. Nisin is a 34-amino-acid residue long, heat stable peptide belonging to the group A lantibiotics with wide antimicrobial activity against Gram-positive bacteria. The invention can be useful for treating colonic infectious diseases such as by Clostridium difficile, and also by colonization of vancomycin-resistant enterococci. In this study, each 100mg core tablet of nisin was compression coated with 100% pectin, 90% pectin-10% HPMC, 85% pectin-15% HPMC, 80% pectin-20% HPMC, 75% pectin-25% HPMC, 100% HPMC at a coat weight of 400mg. The concentration and the activity of nisin were quantified using Well Diffusion Agar Assay. Drug release studies were carried out in pH 3.3 buffer solution. System degradation/erosion experiments were carried out in pH 1.2, 3.3, and 6.8 buffers using a pectinolytic enzyme. The biological activity and NMR studies were performed to assess the stability of nisin during the processing and after the in vitro tests. It was found that pectin alone was not sufficient to protect the nisin containing core tablets. At the end of the 6h 40% degradation was observed for 100% pectin tablets. HPMC addition required to control the solubility of pectin, a 5% increase in HPMC ratio in pectin/HPMC mixture provided a 2-h lag time for nisin release. Eighty percent pectin-20% HPMC appeared to be an optimum combination for further evaluation. Tablets maintained their integrity during the 6-h dissolution test, approximating the colon arrival times. Nisin was found to be active/stable during processing and after in vitro tests. Effect of polymer hydration on pectin degradation was found to be crucial for the enzyme activity. Sufficiently hydrated pectin degraded faster. The pectin/HPMC envelope was found to be a good delivery system for nisin to be delivered to the colon.     

吲达帕胺缓释片的研制及释药机理考察

目的：研制吲达帕胺缓释片，并考察其释药机理。方法：以HPMC为骨架材料，以微晶纤维素、乳糖和可压性淀粉调节释放度，对吲达帕胺缓释片的影响因素进行了考察，并采用正交试验设计筛选处方。结果：吲达帕胺缓释片的组成为：HPMC K4M 37．5mg，HPMC K15M7．5mg，乳糖45．0mg，可压性淀粉37．5mg，微晶纤维素21．0mg，硬脂酸镁1．5mg，药物的释放符合零级动力学方程，释放机制为骨架溶蚀机制；释药速率受介质pH值的影响，几乎不受压片压力的影响。结论：研制的吲达帕胺缓释片体外释放符合国外同类产品的释药特性。     

In vitro evaluation of pectin-HPMC compression coated 5-aminosalicylic acid tablets for colonic delivery.

In this study, we report pectin-HPMC compression coated core tablets of 5-aminosalicylic acid (5-ASA) for colonic delivery. Each 100 mg core tablet contained 5-ASA and was compression coated at 20 kN or 30 kN using 100% pectin, 80% pectin-20% HPMC, or 60% pectin-40% HPMC, at two different coat weights as 400 or 500 mg. Drug dissolution/system erosion/degradation studies were carried out in pH 1.2 and 6.8 buffers using a pectinolytic enzyme. The system was designed based on the gastrointestinal transit time concept, under the assumption of colon arrival times of 6 h. It was found that pectin alone was not sufficient to protect the core tablets and HPMC addition was required to control the solubility of pectin. The optimum HPMC concentration was 20% and such system would protect the cores up to 6 h that corresponded to 25-35% erosion and after that under the influence of pectinase the system would degrade faster and delivering 5-ASA to the colon. The pectin-HPMC envelope was found to be a promising drug delivery system for those drugs to be delivered to the colon.     

吲哚拉辛HPMC骨架片药物释放因素研究

目的 考察影响吲哚拉辛亲水性骨架片体外释药的各种因素。方法 以羟丙基甲基纤维素（HPMC）为骨架材料,用湿法制粒和粉末直接压片法制备缓释骨架片,并考察HPMC用量、粒度、制备方法、片子大小及其它辅料对吲哚拉辛HPMC骨架片的体外释药的影响。结果 吲哚拉辛HPMC骨架片的体外释药均符合Higuchi方程。HPMC的用量,粒度和制法,片子大小对吲哚拉辛的释放速率随HPMC粒度和片子的减小而减慢。淀粉、PVP、MCC的加入（每片HPMC的含量不变）均加快吲哚拉辛释药速率,且加入量不同,其释药速率问具有显著性差异。随着EC加入量的增加（≥40mg。片^-1）．吲哚拉辛释放速率显著加快。结论 HPMC用量和粒度、制备方法、片子大小及其它辅料为影响吲哚拉辛骨架片释放速率主要因素。     

布洛芬HPMC骨架片药物释放因素研究

目的 考察影响布洛芬亲水性骨架片体外释药的各种因素。方法 以羟丙基甲基纤维素（HPMC）为骨架材料，用湿法制粒和粉末直接压片法制备缓释骨架片，并考察HPMC用量，粒度，制备方法，片子大小及其它辅料对布洛芬HPMC骨架片的体外释药的影响。结果 布洛芬HPMC骨架片的体外释药均符合Higuchi方程。HPMC的用量，粒度和制法，片子大小对布洛芬的释放速率均有显著影响。湿法制片的释药速率比干法慢。布洛共姝释药速率随HPMC粒度的减小和片子的增大而减慢。淀粉，PVP、MCC、EC的加入（每片HPMC的含量不变）均减慢布洛芬释药速率。结论 HPMC用量、粒度、制备方法、片子大小及其它辅料为布洛芬骨架片释放速率的主要因素。     

Swelling and erosion of pectin matrix tablets and their impact on drug release behavior.

The aim of this study was to investigate swelling and erosion behaviors of hydrophilic matrix tablets using pectin and their impact on drug release. The matrix tablets were prepared by direct compression using different types of pectin. Swelling and erosion studies of pectin matrix tablets were carried out in various media. The pectin matrix tablets formed a continuous gel layer while in contact with the aqueous medium undergoing a combination of swelling and erosion. The swelling action of pectin matrices was controlled by the rate of its hydration in the medium. Release studies showed that the swelling and erosion of matrices influenced the drug release. The extent of matrix swelling, erosion and diffusion of drug determined the kinetics as well as mechanism of drug release from pectin-based matrix tablets. The release data showed a good fit into the power law or the Korsmeyer-Peppas equation indicating the combined effect of diffusion and erosion mechanisms of drug release.     

Calcium pectinate gel beads for controlled release drug delivery:: I. Preparation and in vitro release studies

Calcium pectinate gel (CPG) beads of indomethacin, a poorly soluble drug, were prepared by dispersing indomethacin in a solution of pectin and then dropping the dispersion into calcium chloride solution. The droplets instantaneously formed gelled spheres by ionotropic gelation. The effect of several factors such as pectin type, the presence of a hardening agent and the drug loading were investigated on the percentage of drug entrapped, size distribution and drug release from the CPG beads. The release characteristics were studied using the rotating basket dissolution method. Strong spherical beads with narrow size distributions, high yields and good entrapment efficiencies could be prepared. All factors investigated have significantly affected the release of indomethacin from CPG beads. The mechanism of drug release from CPG beads followed the diffusion controlled model for an inert porous matrix. Therefore, calcium pectinate gel could be a useful carrier for controlled release drug delivery of poorly soluble drugs.     

乙肝清HPMC K4M/PVP K30骨架缓释片的研制与体外评价

目的进行乙肝清HPMC K4M/PVP K30骨架缓释片的研制与体外评价。方法以中药赶黄草和贯叶连翘的提取物为原料药,以HPMC K4M和PVP K30两种粘度不同,水合行为差异较大的亲水高分子材料联合使用作为骨架材料,制备缓释12 h的"乙肝清骨架缓释片"。以"HPMC+PVP K30"总量在处方中的百分量和HPMC在"HPMC+PVP K30"总量中的百分量为考察因素,通过处方单因素考察和星点设计—效应面法进行优化,得到最佳的制剂处方。并通过均一性实验和体外释药行为研究进行体外评价。结果本片剂优化处方中最低HPMC K4M与PVP K30用量不得低于20%。最佳制剂处方为骨架材料HPMC+PVP K30总量占片剂质量的27.03%,HPMC占HPMC+PVP K30总量的49.04%。本处方具有良好的重现性与稳定性;片剂药物释放符合一级释放模型。结论制备了载药量40%的乙肝清提取物缓释片,并优化得到了其最佳的制剂处方。     

Controlled release of dual drug-loaded hydroxypropyl methylcellulose matrix tablet using drug-containing polymeric coatings.

A dual drug-loaded hydroxypropylmethylcellulose (HPMC) matrix tablet simultaneously containing drug in inner tablet core and outer coated layer was formulated using drug-containing aqueous-based polymeric Eudragit RS30D dispersions. Effects of coating levels, drug loadings in outer layers, amount and type of five plasticizers and talc concentration on the release characteristics were evaluated on the characteristics in simulated gastric fluid for 2 h followed by a study in intestinal fluids. Melatonin (MT) was selected as a model drug. The surface morphology of dual drug-loaded HPMC tablets using scanning electron microscope (SEM) was smooth, showing the distinct coated layer with about 75-microm coating thickness at the 15% coating level. Unlike the uncoated and conventionally coated HPMC tablet, the dual drug-loaded HPMC matrix tablet gave a biphasic linear release, showing a zero-order for 4 h (first) followed by another zero-order release when fitted using linear regression (r(2) = 0.99). As the coating levels (15, 25%) increased, the release rate was further decreased. The biphasic release profiles of dual drug-loaded HPMC matrix tablet was unchanged except when 25% coating level containing 0.5% drug concentration was applied. As the drug concentration in polymeric coating dispersion increased (0.25-1.0%), the amount of drug released increased. The time for the first linear release was also advanced. However, the biphasic release pattern was not changed. The biphasic release profiles of dual drug-loaded HPMC matrix tablet were highly modified, depending on the amount and type of five plasticizers. Talc (10-30%) in coating dispersion as an anti-sticking material did not affect the release profiles. The current dual drug-loaded HPMC matrix tablet, showing biphasic release profiles may provide an alternative to deliver drugs with circadian rhythmic behaviors in the body but needs to be further validated in future in human studies. The dual drug-loaded coating method is also interesting for the modified release of poorly water-soluble drugs because solubilizers and other additives can be added in drug-containing polymeric coating dispersions.     

Formulation and Optimization of a Sustained-Release Tablet of Ketorolac Tromethamine

The objective of our study was to formulate a sustained-release tablet of Ketorolac tromethamine, which is a nonsteroidal anti-inflammatory agent. A 2 3 full factorial design (8 runs) was selected. The variables studied were the amount of drug (30 and 40 mg), ratio of hydroxypropyl methylcellulose (HPMC)/sodium carboxymethylcellulose (NaCMC) (240/40 and 140/140 mg), and amount of ethylcellulose (140 and 180 mg). Swelling-controlled matrix tablets were manufactured by direct compression of formulation ingredients using a Stokes single punch tablet press. Dissolution tests were performed using USP apparatus 3 (Bio-Dis II), at various pHs to mimic the conditions that exist in the gastrointestinal tract. Responses studied included time for 50% of the drug to dissolve (T 50), diffusional exponent (n) that characterizes the release mechanism, and percent friability of the tablets. Analysis of variance indicated that the release rate (T 50) was affected by the HPMC/NaCMC ratio, amount of drug, and two-way and three-way interactions; whereas the amount of drug, HPMC/NaCMC ratio, ethylcellulose, and the interaction between drug and HPMC/NaCMC and HPMC/NaCMC and ethylcellulose and also three-way interactions were significantly affecting the diffusional exponent (n) . The release mechanism was found to be super-case II transport. The friability of the tablets was significantly affected by all three factors: amount of drug, HPMC/NaCMC ratio, and amount of ethylcellulose. The formulation giving the best release characteristics was identified.     

Formulation and optimization of a sustained-release tablet of ketorolac tromethamine

The objective of our study was to formulate a sustained-release tablet of Ketorolac tromethamine, which is a nonsteroidal anti-inflammatory agent. A 2 3 full factorial design (8 runs) was selected. The variables studied were the amount of drug (30 and 40 mg), ratio of hydroxypropyl methylcellulose (HPMC)/sodium carboxymethylcellulose (NaCMC) (240/40 and 140/140 mg), and amount of ethylcellulose (140 and 180 mg). Swelling-controlled matrix tablets were manufactured by direct compression of formulation ingredients using a Stokes single punch tablet press. Dissolution tests were performed using USP apparatus 3 (Bio-Dis II), at various pHs to mimic the conditions that exist in the gastrointestinal tract. Responses studied included time for 50% of the drug to dissolve ( T 50 ), diffusional exponent ( n ) that characterizes the release mechanism, and percent friability of the tablets. Analysis of variance indicated that the release rate ( T 50 ) was affected by the HPMC/NaCMC ratio, amount of drug, and two-way and three-way interactions; whereas the amount of drug, HPMC/NaCMC ratio, ethylcellulose, and the interaction between drug and HPMC/NaCMC and HPMC/NaCMC and ethylcellulose and also three-way interactions were significantly affecting the diffusional exponent ( n ). The release mechanism was found to be super-case II transport. The friability of the tablets was significantly affected by all three factors: amount of drug, HPMC/NaCMC ratio, and amount of ethylcellulose. The formulation giving the best release characteristics was identified.     

卡托普利缓释片的实验研究

采用羟丙基甲基纤维素(HPMC)凝胶制备的巯甲丙脯酸(卡托普利)缓释片,其体外释放曲线符合 Higuchi 动力学。HPMC 在片剂中含量达到30%以上才能控制巯甲丙脯酸的释放。HPMCK_4M、K_(15)M和 K100M 的粘度差异对凝胶片释放并无影响,释放介质的 pH 及压片压力对该制剂的药物释放影响不大。     

Chronopharmaceutical drug delivery from a pulsatile capsule device based on programmable erosion

We report the development of a chronopharmaceutical capsule drug delivery system capable of releasing drug after pre-determined time delays. The drug formulation is sealed inside the insoluble capsule body by an erodible tablet (ET). The release time is determined by ET erosion rate and increases as the content of an insoluble excipient (dibasic calcium phosphate) and of gel-forming excipient (hydroxypropylmethylcellulose; HPMC) increases. The time-delayed release of a model drug (propranolol HCI) was investigated by dissolution testing (USP XXIII paddle method). Both composition and weight of ET influence the time of drug release. Moreover it was found that drug release was controlled by the quantity of HPMC, irrespective of lactose content within the tablet weight range 80-160 mg, when above a threshold concentration of 20% HPMC. Programmable pulsatile release has been achieved from a capsule device over a 2-12-h period, consistent with the demands of chronotherapeutic drug delivery. The time of drug release can be controlled by manipulation of tablet formulation.     

Calcium pectinate gel beads for controlled release drug delivery:: I. Preparation and in vitro release studies

Calcium pectinate gel (CPG) beads of indomethacin, a poorly soluble drug, were prepared by dispersing indomethacin in a solution of pectin and then dropping the dispersion into calcium chloride solution. The droplets instantaneously formed gelled spheres by ionotropic gelation. The effect of several factors such as pectin type, the presence of a hardening agent and the drug loading were investigated on the percentage of drug entrapped, size distribution and drug release from the CPG beads. The release characteristics were studied using the rotating basket dissolution method. Strong spherical beads with narrow size distributions, high yields and good entrapment efficiencies could be prepared. All factors investigated have significantly affected the release of indomethacin from CPG beads. The mechanism of drug release from CPG beads followed the diffusion controlled model for an inert porous matrix. Therefore, calcium pectinate gel could be a useful carrier for controlled release drug delivery of poorly soluble drugs.     

Correlation between the viscoelastic properties of the gel layer of swollen HPMC matrix tablets and their in vitro drug release

Abstract

Drug release from hydroxypropyl methylcellulose (HPMC) hydrophilic matrix tablets is controlled by drug diffusion through the gel layer of the matrix-forming polymer upon hydration, matrix erosion or combination of diffusion and erosion mechanisms. In this study, the relationship between viscoelastic properties of the gel layer of swollen intact matrix tablets and drug release was investigated. Two sets of quetiapine fumarate (QF) matrix tablets were prepared using the high viscosity grade HPMC K4M at low (70?mg/tablet) and high (170?mg/tablet) polymer concentrations. Viscoelastic studies using a controlled stress rheometer were performed on swollen matrices following hydration in the dissolution medium for predetermined time intervals. The gel layer of swollen tablets exhibited predominantly elastic behavior. Results from the in vitro release study showed that drug release was strongly influenced by the viscoelastic properties of the gel layer of K4M tablets, which was further corroborated by results from water uptake studies conducted on intact tablets. The results provide evidence that the viscoelastic properties of the gel layer can be exploited to guide the selection of an appropriate matrix-forming polymer, to better understand the rate of drug release from matrix tablets in vitro and to develop hydrophilic controlled-release formulations.     

吡嘧司特钾水凝胶骨架缓释片的研究

目的研制吡嘧司特钾(TBX)水凝胶缓释骨架片.方法以羟丙甲基纤维素(HPMC)为骨架材料,考察HPMC用量、黏度及压片压力等对主药体外释放速度的影响,优化处方工艺.结果所得片剂体外释放实验表明10h累积释放度＞75%,其释放行为符合Hguchi方程.HPMC的用量、黏度、制备方法及压片片力的大小等对TBX的释放速率均有显著影响.结论用高黏度的HPMC作为亲水凝胶骨架片的基质能达到较好的缓释作用.