Characterization of 5-Fluorouracil Release from Hydroxypropylmethylcellulose Compression-Coated Tablets

Hydrogel compression-coated tablets are able to release the core drug after a period of lag time and have potential for colon-specific drug delivery based on gastrointestinal transit time concept. This study investigated the factors influencing in vitro release characteristics of a model drug 5-fluorouracil from hydroxypropylmethycellulose (HPMC) compression-coated tablets. The core tablet, prepared by a wet granulation compression method, was designed to disintegrate and dissolute quickly. To prepare the compression-coated tablets, 50% of the HPMC/lactose coat powder was precompressed first, followed by centering the core tablet and compressing with the other 50% of the coat powder. Release characteristics were evaluated in distilled water by using a Chinese Pharmacopoeia rotatable basket method. Effect of HPMC viscosity, lactose content in outer shell, and overall coating weight of outer shell on release lag time (T_lag), and zero-order release rate (k) were studied. Release of drug from compression-coated tablets began after a time delay as a result of hydrogel swelling/retarding effect, followed by zero-order release for most of the formulations studied. HPMC of higher viscosity (K4M and K15M) provided better protection of the drug-containing core, showing increased release lag time and slower release rate. Incorporating lactose in outer shell led to decrease of T_lag and increase of k. T_lag and k are exponentially and linearly correlated to lactose content, expressed as weight percentage of the outer shell. Larger coating weight (W) of outer shell produced larger coating thickness (D) around core tablet, which resulted in increase in T_lag and decrease in k. There was good fitting of a linear model for each of the four variables W, D, T_lag, and k. Hardness of the compression-coated tablets and pHs of the release media had little effect on drug release profile. It is concluded that the release lag time and release rate are able to be tailored through adjusting the formulation variables to achieve colon-specific drug delivery of 5-fluorouracil.     

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.     

Biphasic release of indomethacin from HPMC/pectin/calcium matrix tablet: I. Characterization and mechanistic study.

Calcium-induced crosslinking of pectin acts as the dominating factor controlling drug release from pectin-based matrices. The same interaction was employed to modify indomethacin release from HPMC/pectin/calcium matrix in this study. The aim was to characterize the release profiles, and to study the formulation variables and the underlying mechanisms. The matrix tablet was made up of pectin HM 70, calcium chloride and HPMC K4M, and prepared by the wet granulation method. In vitro release was performed in water and characterized by the power law. Matrix erosion was evaluated by studying the weight loss and pectin release. Biphasic release of indomethacin from the HPMC/pectin/calcium matrix tablet was observed, and extraordinary power law exponent n values of over 1.0 were observed. Increase in calcium amount led to more significant retardation on drug release. The two power law parameters, n and K, correlated to the amount of calcium in the matrix. A lag time of over 4 h can be achieved at HPMC/pectin/calcium chloride amount of 100 mg/100 mg/100 mg. Both matrix weight loss and pectin release were linearly correlated to indomethacin release, indicating erosion-controlled drug release mechanisms. The hybrid matrix showed retarded erosion and hydration rate, which served as the basis for retarded indomethacin release. It is concluded that the pectin/calcium interaction can be employed to modify drug release from HPMC/pectin/calcium matrix tablet with biphasic release patterns for potential timed or site-specific drug delivery.     

Preparation and evaluation of pectin-based colon-specific pulsatile capsule in vitro and in vivo

The purpose of this study was to develop and evaluate a colon-specific, pulsatile drug delivery system, which consists of an impermeable capsule body filled with a 5-aminosalicylic acid rapid-disintegrating tablet and a pectin-based erodible plug placed in the opening of the capsule body. To obtain an appropriate gel-forming ability and suitable lag time for the colon-specific drug delivery, high-methoxy pectin (HM-pectin) was formulated with lactose and lowmethoxy pectin (LM-pectin) with HPMC to prepare the plug tablet. In order to evaluate the lag time, prior to the rapid drug release, both the formulation of the plug tablet and in vitro release medium were studied. The lag time prior to the rapid drug release was mainly determined by the HM-pectin/lactose or LM-pectin/HPMC ratio. The addition of pectinase or rat cecal content into the release medium shortened the lag time significantly, which predicted the probable enzyme sensitivity of pectin plug tablet. In vivo studies showed that the plasma concentration of drug can only be detected 6h after oral administration of the pulsatile capsule, which indirectly proved the colon-specific characteristics. These results show that the pulsatile capsule may have the therapeutic action for colon-specific drug delivery.     

Factors Effecting the Morphology of Eudragit S-100 Based Microsponges Bearing Dicyclomine for Colonic Delivery

The purpose of this study was to design microsponge-based novel colon-specific drug delivery system bearing dicyclomine. Eudragit S-100-based microsponges containing the drug in varying amount were prepared using quasi-emulsion solvent diffusion method. The microsponges were prepared by optimizing various process parameters. Differential scanning calorimetry and Fourier transform infrared studies indicated compatibility and stability of the drug in various formulations. Shape and surface morphology of the microsponges were examined using scanning electron microscopy. The formulations were subjected to in vitro release studies, and the results were evaluated kinetically and statistically. In vitro release data showed a biphasic pattern with an initial burst effect. In the first hour, drug release from microsponges was found to be between 17% and 31%. The cumulative percent release at the end of eighth hour was noted to be between 53% and 83%. The release kinetics showed that the data followed Higuchi model and the main mechanism of drug release was diffusion. The colon-specific tablets were prepared by compressing the microsponges followed by coating with pectin:hydroxypropylmethylcellulose mixture. In vitro release studies exhibited that compression-coated colon-specific formulations started releasing the drug at the sixth hour corresponding to the arrival time at colon. The study presents a new approach 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.     

Colon-Specific Delivery of 5-Fluorouracil from Zinc Pectinate Pellets through In Situ Intracapsular Ethylcellulose–Pectin Plug Formation

Conventional fluid-bed and immersion film coating of hydrophilic zinc pectinate pellets by hydrophobic ethylcellulose is met with fast drug release. This study explored in situ intracapsular pellet coating for colon-specific delivery of 5-fluorouracil (5-FU). The solid coating powder constituted ethylcellulose and pectin in weight ratios of 11:0 to 2:9. Its weight ratio to pellets varied between 2:3 and 3:2. Pectin was used as excipient of core pellets and coating powder in view of its potential use in colon cancer treatment. Delayed 5-FU release and core pectin dissolution were attainable when the weight ratio of solid coating powder to pellets was kept at 3:2, and weight ratio of ethylcellulose and pectin in coating powder was kept at 8:3 with particle size of ethylcellulose reduced to 22 μm. In situ intracapsular wetting of pectin coat by dissolution medium resulted in the formation of ethylcellulose plug interconnecting with pellets through the binding action of pectin. Less than 25% of drug was released at the upper gastrointestinal tract. The majority of drug was released upon prolonged dissolution and in response to colonic enzyme pectinase, which digested core pellets.     

In Vitro Evaluation of Calcium Pectinate: A Potential Colon-Specific Drug Delivery Carrier

Calcium pectinate (CaP)—the insoluble salt of pectin—can potentially be used as a colon-specific drug delivery system. The use of CaP as a carrier was based on the assumption that, like pectin, it can be decomposed by specific pectinolytic enzymes in the colon but that it retains its integrity in the physiological environment of the small bowel. The biodegradation of the carrier was characterized by monitoring the percent cumulative release of the insoluble drug indomethacin, incorporated into pectin or CaP matrices. Compressed tablets of pectin and indomethacin were analyzed for degradation in the presence of Pectinex 3XL, a typical pectinolytic enzyme mixture, and in the presence of the human colonic bacterium Bacteroides ovatus. The degradation of CaP-indomethacin tablets was assessed in the presence of Pectinex 3XL and in rat cecal contents. The release of indomethacin was significantly increased (end-time percentage cumulative release vs control) in the presence of Pectinex 3XL (89 ± 20 vs 16 ± 2 for CaP tablets), Bacteroides ovatus (12 and 22 vs 5.2 for pectin tablets), and rat cecal contents (61 ± 16 vs 4.9 ± 1.1 for CaP tablets). The weight loss of tablet mass was significantly higher (end-time dry weight vs control) in the presence of Pectinex 3XL (0 vs 75 ± 6% of initial weight for CaP tablets). These findings indicate the potential of CaP, compressed into tablets with insoluble drug, to serve as a specific drug delivery system to the colon.     

Characterization of 5-fluorouracil release from hydroxypropylmethylcellulose compression-coated tablets

Hydrogel compression-coated tablets are able to release the core drug after a period of lag time and have potential for colon-specific drug delivery based on gastrointestinal transit time concept. This study investigated the factors influencing in vitro release characteristics of a model drug 5-fluorouracil from hydroxypropylmethycellulose (HPMC) compression-coated tablets. The core tablet, prepared by a wet granulation compression method, was designed to disintegrate and dissolute quickly. To prepare the compression-coated tablets, 50% of the HPMC/lactose coat powder was precompressed first, followed by centering the core tablet and compressing with the other 50% of the coat powder. Release characteristics were evaluated in distilled water by using a Chinese Pharmacopoeia rotatable basket method. Effect of HPMC viscosity, lactose content in outer shell, and overall coating weight of outer shell on release lag time (T(lag)), and zero-order release rate (k) were studied. Release of drug from compression-coated tablets began after a time delay as a result of hydrogel swelling/retarding effect, followed by zero-order release for most of the formulations studied. HPMC of higher viscosity (K4M and K15M) provided better protection of the drug-containing core, showing increased release lag time and slower release rate. Incorporating lactose in outer shell led to decrease of T(lag) and increase of k. T(lag) and k are exponentially and linearly correlated to lactose content, expressed as weight percentage of the outer shell. Larger coating weight (W) of outer shell produced larger coating thickness (D) around core tablet, which resulted in increase in T(lag) and decrease in k. There was good fitting of a linear model for each of the four variables W, D, T(lag), and k. Hardness of the compression-coated tablets and pHs of the release media had little effect on drug release profile. It is concluded that the release lag time and release rate are able to be tailored through adjusting the formulation variables to achieve colon-specific drug delivery of 5-fluorouracil.     

Pharmacokinetics and tolerance of slow-release indomethacin tablets in rheumatoid arthritis

Summary The pharmacokinetics, efficacy and tolerance of a new formulation of slow-release indomethacin tablet were compared with those of a conventional indomethacin capsule in 30 patients with rheumatoid arthritis. The slow-release tablet was absorbed more slowly than the capsule (t_max 3.7 h and < 2 h, respectively) and produced more even serum drug levels in 10 subjects. Side-effects, especially dizziness and diarrhoea, were less frequent after the slow-release tablet than during the capsule period.     

果胶在细菌触发型结肠定位给药制剂中的应用

综述了近年来果胶在细菌触发型结肠定位给药制剂中的应用进展。果胶在胃和小肠部位不降解,但能被结肠细菌酶降解,故以果胶为载体,通过包衣、制成骨架、合成前药及与钙交联等方法制备结肠定位给药制剂,有良好的应用前景。     

Development of Enteric-coated Pectin-based Matrix Tablets for Colonic Delivery of Theophylline

The present work was aimed at developing a new colonic drug delivery system which takes advantage of the combined approaches of a specifically colon-biodegradable pectin matrix with a pH-sensitive Eudragit_® S100 polymeric coating. The developed system was able to suitably retard the onset of drug release and to provide a colon-specific delivery, thus overcoming the problems of pectin solubility in the upper gastrointestinal tract and low site-specificity of simple pH-dependent systems. Due to the poor compactability properties of pectin, it was used in mixture with Emdex_®, a hydrophilic directly-compressible material, in order to make it possible to prepare tablets by direct compression. Theophylline (TP) was used as model drug due to its suitable pharmacokinetic properties for colonic delivery and good absorption in the large intestine. The effects of varying the type of pectin (low and high methoxylated, or amidated), the pectin:Emdex_® ratio and the level of the pH-dependent polymeric coating on drug release behavior were investigated. Release tests were performed using sequential liquids simulating the physiological variation of pH and the effect of the presence or not of pectinolytic enzymes into the simulated colonic medium was evaluated. Thirty percent (w/w) was the the minimum content of Emdex_® for obtaining directly compressible tablets with sufficient hardness to withstand the coating process and 27% (w/w) was the minimum coating amount for obtaining an adequate lag time before the onset of drug release. After lag time, linear nearly zero-order profiles were obtained whose slope (i.e. the drug release rate) depended on both the Emdex_® content and the pectin type. Comparison of the results obtained in the presence or not of pectynolitic enzymes allowed selection of the high methoxylated pectin as the most interesting candidate for specific colonic delivery since it was the least water-soluble and the most susceptible to enzymatic degradation, thus assuring a greater site-specificity of drug release. Finally, the importance of using appropriate dissolution test conditions to adequately characterize the drug release profiles from delivery systems endowed with a microflora-activated drug release triggering mechanism has been demonstrated.     

口服布洛芬原位凝胶的制备及其在Beagle犬体内药代动力学研究

本文设计并制备了口服布洛芬原位凝胶(in situ gel systems for the oral delivery of ibuprofen，IBU-ISG)， 并对其在Beagle犬上药代动力学进行了研究。以去乙酰结冷胶和海藻酸钠为凝胶材料， 分别对此两种凝胶材料进行了单因素考察， 初步确定了辅料的用量。以成胶前的复合黏度值、 体外释放度等参数为评价指标， 采用正交设计法进行处方优化。优化的制剂处方为： 1.0%海藻酸钠、 0.5%去乙酰结冷胶、 0.21%枸橼酸钠和0.056%氯化钙。采用RP-HPLC法测定6只Beagle犬口服IBU-ISG和参比制剂(市售布洛芬混悬液)后不同时间血浆中布洛芬的浓度， 所得药代动力学参数T_max分别为(1.8±0.6)和(0.4±0.1) h， C_max分别为(29.2±7.6)和(37.8±2.2)μg·mL^-1， T_1/2分别为(2.3±0.5)和(2.0±0.9) h， AUC_0-t分别为(131.0±38.6)和(117.3±23.1)μg·mL^-1·h。结果表明， 采用去乙酰结冷胶和海藻酸钠二元骨架制备IBU-ISG可行。     

Enhanced therapeutic effect of LK-423 in treating experimentally induced colitis in rats when administered in colon delivery microcapsules

LK-423 is a phthalimido-desmuramyl-dipeptide derivative with immunomodulating activity. In the present study the therapeutic efficacy of a colon-specific drug delivery system–LK-423 microcapsules–was examined in the 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced ulcerative colitis model in rats. The colon-specific delivery of the drug using microcapsules relies on the combination of pH (outer gastroresistant coating), time (inner retard coating of Eudragit® RS and RL) and enzyme (pectin core) controlled drug release mechanisms. The optimal in vitro dissolution profile for LK-423 delivery to the colon of rats was obtained after coating newly developed LK-423 loaded pectin cores with 20% w/w of retard coating with a Eudragit® RS/RL ratio of 8.5/1.5 and 30% w/w of enteric coating. Orally administered LK-423 microcapsules were therapeutically more beneficial in treating TNBS-induced ulcerative colitis in rats than orally or rectally administered LK-423 in the form of suspension. Clinical activity scores and colon weight to length ratio were insignificantly lower and the macroscopically estimated degree of healing was significantly greater. On the histological level, the administration of LK-423 microcapsules resulted in most physiological regeneration of intestinal mucosa, indicated by regular architecture of all mucosal tissue components, what is probably related to local drug delivery near the site of inflammation achieved using microcapsules. These results demonstrate that LK-23 colon delivery microcapsules enhance the therapeutic efficacy of the drug and therefore appear to be a useful approach for treating various inflammatory diseases in the large intestine.     

Influence of excipients,drugs, and osmotic agent in the inner core on the time-controlled disintegration of compression-coated ethylcellulose tablets

The effect of excipient, drug, and osmotic agent loaded in the inner core tablet on the time-controlled disintegration of compression-coated tablet prepared by direct compression with micronized ethylcellulose was investigated. The excipients [spray-dried lactose, hydroxypropyl methyl cellulose, sodium starch glycolate, microcrystalline cellulose, different drugs (sodium diclofenac: model drug, salbutamol sulfate, and theophylline anhydrate) and osmotic agent (sodium chloride)] were used to formulate the composition of the inner core tablet. The result indicates that drug release from all the compression-coated tablets was characterized by a distinctive lag of time followed by a faster drug release, dependent on the types of excipient and drug, and osmotic agent used in the inner core tablet. Respectively, the lag of time was 8.5, 12.4, 14.6, or 15.8 h for spray-dried lactose, hydroxypropyl methyl cellulose, sodium starch glycolate, or microcrystalline cellulose-loaded inner core tablet, as compared with 16.4 h for an inner core made of sodium diclofenac alone. The direct-compressible excipients such as spray-dried lactose, sodium starch glycolate, and microcrystalline cellulose seemed not to illustrate a marked disintegration function to rapidly rapture the outer coating layer. The lag of time was only slightly shortened from 16.4 to 14.6 h, >24 to 17.8 h, or >24 to 21.3 h for sodium diclofenac, theophylline anhydrate, or salbutamol sulfate incorporated with sodium starch glycolate into the inner core tablet, respectively, suggesting that sodium starch glycolate did not perform its superdisintegration. Once an osmotic agent of sodium chloride was incorporated into the inner core tablet, the lag of time for the compression-coated tablet was markedly shortened to <1 h, as compared with 16.4 h for drug alone. The more the amount of sodium chloride added, the less the time of lag obtained. Osmotic pressure did have a key role in controlling the drug dissolution. The present result implies that osmotic function is more suitable than superdisintegration function in designing a compression-coated tablet with time-controlled disintegration.     

Microporous bilayer osmotic tablet for colon-specific delivery

Microporous bilayer osmotic tablet bearing dicyclomine hydrochloride and diclofenac potassium was developed using a new oral drug delivery system for colon targeting. The tablets were coated with microporous semipermeable membrane and enteric polymer using conventional pan-coating process. The developed microporous bilayer osmotic pump tablet (OPT) did not require laser drilling to form the drug delivery orifice. The colon-specific biodegradation of pectin could form in situ delivery pores for drug release. The effect of formulation variables like inclusion of osmogen, amount of HPMC and NaCMC in core, amount of pore former in semipermeable membrane was studied. Scanning electron microscopic photographs showed formation of in situ delivery pores after predetermined time of coming in contact with dissolution medium. The number of pores was dependent on the amount of the pore former in the semipermeable membrane. In vitro dissolution results indicated that system showed acid-resistant, timed release and was able to deliver drug at an approximate zero order up to 24 h. The developed tablets could be effectively used for colon-specific drug delivery to treat IBS.     

A relative bioavailability study of 500 mg calcium p-aminosalicylate film coating tablet in healthy individuals

The purpose of this study is to evaluate the only available calcium p-aminosalicylate (Ca PAS) commercial product, which is one of the most commonly prescribed non-surveillance products from the Bureau of National Health Insurance (BNHI) database in Taiwan. An open-randomized, balanced, two-way crossover study was designed to evaluate the relative bioavailability (F) of a 500 mg Ca PAS F.C. tablet with a 500 mg Ca PAS suspension in 13 healthy individuals. Blood samples were collected according to a planned time schedule. The plasma concentrations of PAS were measured by a validated liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) method. Pharmacokinetic parameters of area under the plasma concentration-time curve from the time zero to the time of last quantifiable concentration (AUC_0–t), area under the plasma concentration-time curve from time zero to infinity (AUC_0–∞), maximum plasma concentration (C_max), time to reach measured maximum plasma concentration (T_max), elimination half-life (T_1/2), and mean residence time (MRT) were determined by non-compartment methods. F was calculated by [AUC_0–∞] of the test drug divided by [AUC_0–∞] of the reference drug. The mean geometric ratios of pharmacokinetic parameters, including AUC_0–t, AUC_0–∞, and C_max obtained were 0.873, 0.874, and 0.569, respectively. The 90% confidence intervals of ln (AUC_0–t), ln (AUC_0–∞), and ln (C_max) after being back natural log-transformed were (74.0–103.0%), (74.1–103.0%), and (38.4–84.3%), respectively. The relative bioavailability of the Ca PAS tablet was 87.4%.     

Colon-specific drug delivery for mebeverine hydrochloride

Mebeverine Hydrochloride (MB-HCl), an effective spasmolytic drug, was formulated as CODES?. A colon-specific drug delivery technology CODES? was designed to avoid the inherent problems associated with pH- or time-dependent systems. To achieve more protection and control of drug release, MB-HCl was prepared as microspheres and compressed as core tablets of CODES? (modified CODES?). The core tablets contained the drug either in free form [Formula 1 (F₁)], or as microspheres with 2 different polymer:drug:lactulose ratios (1:1:0.5 [Formula 2 (F₂)] and 2:1:0.5 [Formula 3 (F₃)]. The release profiles of the coated CODES? systems were compared with uncoated compressed tablets. The uncoated tablet showed a drug release of 94% after 1 h in simulated gastric condition (pH = 1.2). The release characteristics of the coated systems revealed that the enteric coating (Eudragit®L₁₀₀) prevented any drug release in simulated gastric or duodenal conditions in the first 3 h (pH 1.2–6.1), after which drug was slightly liberated in simulated intestinal fluid (pH 7.4) {Phase 1 (P1)}. After 4 h the pH was adjusted to 7 and β-glucose-oxidase was added, which is an enzyme produced by enterobacteria present in the colon. The acid-soluble coat (Eudragit®E₁₀₀) dissolved and the drug release suddenly increased to reach 95, 72 and 60.4% for F₁–F₃, respectively. IR spectrum study showed a covalent bond between the drug and the polymer in the formulae F₂ and F₃ resulting in the sustained drug release from the microspheres with a significant difference (p>0.05) to F₁. The findings were confirmed by in vivo investigation using X-ray images for Guinea pigs ingested tablets containing barium sulphate (F₄), where the tablet began to disintegrate after 10 h of tablet intake. The results of the study indicated that MB-HCl CODES? colon-specific drug delivery can act as a successful trigger for drug targeting in the colon. Furthermore, a sustained release of the drug can be achieved from modified CODES containing the drug in the form of microspheres.     

Application of pectin in oral drug delivery

Introduction: Biopolymers have been used extensively in the pharmaceutical field. Pectin, a biopolymer, has several unique properties that enable it to be used as an excipient or carrier for oral drug delivery systems. Accordingly, several investigators have identified the benefits of pectin-based delivery systems for oral drug administration.

Areas covered: This review first describes the chemical structure, source and production, degree of esterification and gel formation properties of pectin. The application of pectin in various oral drug delivery platforms is also discussed, that is, controlled release systems, gastro-retentive systems, colon-specific delivery systems and mucoadhesive delivery systems.

Expert opinion: Pectin from different sources provides different gelling abilities, due to variations in molecular size and chemical composition. Like other natural polymers, a major problem with pectin is inconsistency in reproducibility between samples, which may result in poor reproducibility in delivery characteristics. Scintigraphic studies and in vivo studies, in both animals and human volunteers, demonstrate the successful development of a pectin-based colon-specific drug delivery system. Pectin-based controlled release systems, gastro-retentive systems and mucoadhesive systems present promising approaches for increasing the bioavailability of drugs, but are in their infancy. A lack of direct correlation between in vitro release and in vivo absorption studies is a major concern with these systems.     

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。