5-氨基水杨酸结肠定位给药酶控释小丸的制备与体外释放

目的：用水分散体包衣技术制备5-氨基水杨酸(5-ASA)结肠定位释放小丸给药系统。方法：乙基纤维素水分散体(Surlease)和直链淀粉(Amylosf)为控释包衣材料，邻苯二甲酸二乙酯为增塑剂，使用流化床包衣设备，制备酶控释的结肠定位释放小丸，研究小丸在模拟人体胃肠道环境中的释放度，并观察游离包衣膜的消化性。结果：此种小丸在模拟胃肠道上部的介质中不释药，在模拟结肠介质条件下3h释药80％以上，10h内释药完全，具有脉冲释药特征。药物的释放时滞由衣膜厚度和衣膜处方组成控制。增加衣膜厚度以及处方中SurleaseE的用量，可延长释药时滞。膜的消化性试验表明，释放机制是衣膜中Amylose被结肠菌酶特异性降解而使衣膜破裂释药。结论：包衣液中加入被结肠酶特异性降解的Amylose可以使小丸具有结肠定位释放的特性。     

盐酸维拉帕米双脉冲多相释药杯形片的研制

本文制备了盐酸维拉帕米(verapamil hydrochloride， VH)的三层片芯及四层片芯杯形片， 分别达到脉冲控释双相释药及双脉冲多相释药。用混合粉末直接压片法制备多层片芯， 干压包衣技术制备盐酸维拉帕米杯形片， 以释药时滞(T_lag)评价杯形片顶层重量、 羟丙基甲基纤维素HPMC用量及压片压力对药物的释放效果。结果表明， 顶层重量增加及HPMC用量增大时， T_lag延长； 压片压力在6～10 kg·cm^-2时， 压力增大， 时滞延长。杯形片中药物主要通过顶层单面释药， 阻滞层(顶层及多层片芯中的缓释层)的溶蚀速率是决定释药时滞的关键因素。     

盐酸地尔硫延迟起释型缓释片的研制

目的制备盐酸地尔硫(diltiazam hydrochloride,DIL)延迟起释型缓释片,解析释药机制,并考察外衣层组成对药物释放的影响。方法用干压包衣技术制备盐酸地尔硫的延缓片,用释药时滞(T_lag)及释药速率常数(k)将各因素(外衣层中的HPMC用量和粘度,PVP K30用量、EC粘度及压片压力)对药物的释放效果进行评价。结果 HPMC用量或粘度增大,T_lag延长,k减慢;PVP K30用量增大,T_lag减短,k加快;在一定范围内EC粘度及压片压力波动对释药行为无影响。结论延缓片中药物主要是通过溶蚀机制释放,外衣层的溶蚀速率是决定释药时滞的关键因素。     

盐酸地尔硫爆破型脉冲控释片研究

目的以盐酸地尔硫为(diltiazem hydrochloride,DIL)模型药物,研制爆破型脉冲控释片并考察其体内外脉冲释药特性。方法以乙基纤维素和丙烯酸树脂(Eudragit L)为包衣材料,采用薄膜包衣法,制备含盐酸地尔硫60 mg的脉冲控释片。通过体外释放度实验,考察了处方因素对脉冲控释片体外释放的影响;通过吸水实验确定了脉冲控释片的释药机理;以高效液相色谱法测定8名受试者的体内血药浓度,研究脉冲控释片的体内药代动力学和生物利用度。结果片芯处方、包衣组成和包衣厚度影响盐酸地尔硫的脉冲释放。该制剂在体外延迟释放时间T₁₀为4.4 h,释放至最大的时间T_rm为8.0 h,脉冲释放时间T_rm-10为3.6 h;其体内的延迟释放时间T_lag为4.9 h,达峰时间T_max为8.0 h,从开始释放到达峰的时间T_psi为3.1 h。脉冲控释片的相对生物利用度为105%。结论盐酸地尔硫爆破型脉冲控释片在体内外都具有脉冲释放特性。     

双氯芬酸钠脉冲控释微丸的研究

目的制备双氯芬酸钠脉冲控释微丸（DS-PRP）并考察体内外释药特性。方法采用水溶胀性材料为内包衣溶胀层，乙基纤维素水分散体为外包衣控释层制备DS-PRP，考察影响其体外释药的因素，并进行体内药代动力学研究。结果溶胀层材料类型、溶胀层和控释层包衣厚度、释放介质中十二烷基硫酸钠（SDS）的加入对DS-PRP的释药时滞和释药速率有显著影响，在0.1％ SDS溶液中释药时滞t_0.1为3.1 h，体内释药时滞tlag为2.8　h，与DS丸芯的相对生物利用度为（91±1２）%。结论DS-PRP在体内外均具有脉冲释药特性。     

盐酸地尔硫Zhuo结肠释药片的研制

以丙烯酸树脂Ⅱ和乙基纤维素为包衣材料，采用锅包衣法制得盐酸地尔硫Zhuo口服结肠释药片。通过正交设计和体外释放度实验，考察处方和工艺对结肠定位释药的影响。结果表明影响片子释药时滞的主要因素是包衣液处方中丙烯酸树脂Ⅱ与乙基纤维素的比例，比例越小，时滞效应越强。通过调整处方和工艺，可制得在酸性条件下不释药，在模拟胃肠液pH条件下经5—6h时滞后形成爆破释药的结肠释药片。     

5-氨基水杨酸时控结肠定位控释微丸及其制剂的研制

目的制备5-氨基水杨酸微丸及其时控结肠定位控释释药系统的研究。方法首先采用挤出滚圆机制备了含药微丸,然后使用流化床包衣设备将微丸包衣,以羟丙甲纤维素和微粉硅胶的混合物包衣作为溶胀控释层,以乙基纤维素水分散体Surelease包衣作为时滞包衣层,并将包衣微丸装入肠溶胶囊。用释放度测定法研究微丸的释放行为。结果药物通过时滞层破裂开始释放,该层厚度增加可显著延长释药时滞。调节羟丙甲纤维素的型号、包衣增重及羟丙甲纤维素与微粉硅胶两者比例,可以控制药物释放速度。在模拟胃肠道pH情况下延迟5 h释药,之后的10 h内释药完全。结论可通过调整溶胀控释层包衣混合物的比例、型号、包衣厚度及时滞层的包衣厚度,制备5-氨基水杨酸时控结肠定位控释释药系统。     

盐酸地尔硫(艹卓)结肠释药片的研制

以丙烯酸树脂 和乙基纤维素为包衣材料 ,采用锅包衣法制得盐酸地尔硫口服结肠释药片。通过正交设计和体外释放度实验 ,考察处方和工艺对结肠定位释药的影响。结果表明影响片子释药时滞的主要因素是包衣液处方中丙烯酸树脂 与乙基纤维素的比例 ,比例越小 ,时滞效应越强。通过调整处方和工艺 ,可制得在酸性条件下不释药 ,在模拟胃肠液 p H条件下经 5～ 6 h时滞后形成爆破释药的结肠释药片。     

氟比洛芬乙基纤维素水分散体包衣小丸的制备及体外释药特性

目的：制备氟比洛芬包衣小丸，评价其体外释药特性。方法：离心造粒法制备空白丸芯及载药小丸；以乙基纤维素水分散体为包衣材料，羟阿基甲基纤维素为致孔剂，流化床制备氟比洛芬包衣小丸；释放度实验考察小丸的体外释药特性。结果：包衣小丸缓释胶囊的释放曲线与进口缓释胶囊ForbensR相似，羟丙基甲基纤维素的用量和介质pH值对释药影响显著，而热处理时间和胶囊壳对释药无显著性影响。结论：氟比洛芬包衣小丸具有较理想的体外缓释效果。     

复方丹参pH依赖型延迟释药微丸在家犬体内的药效动力学

目的制备复方丹参pH依赖型延迟释药微丸填充胶囊并进行家犬体内药效动力学研究。方法分别用HPMC，Eudragit L-30D-55，Eudragit L100/S100 (1∶6)包衣制备pH依赖型延迟释药微丸，测定体外释放曲线，并用血清药理学方法进行家犬体内的药效动力学研究。结果制备了复方丹参pH依赖型延迟释药微丸，体外溶出曲线呈pH依赖特征。单剂量给药后自制速释片R的药效动力学参数T_max为0.58 h，E_max为34.63%，延迟释药胶囊T1和T2的T_max分别延长至2.42和3.17 h，E_max分别降低至13.57%和14.52%，相对生物利用度分别为99.3%和133.6%。多剂量给药后自制速释片R波动度DF 7.32，延迟释药胶囊T1和T2的波动度DF 3.40和3.03。结论复方丹参pH依赖型延迟释药胶囊体外释放具有pH依赖特征，体内具有明显的延迟释药作用，多剂量达到稳态时，药效动力学波动系数低于普通片。     

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 and pharmacokinetics in dogs of guar gum and Eudragit FS30D-coated colon-targeted pellets of indomethacin

A pH- and enzyme-dependent colon-targeted multi-unit delivery system of indomethacin was developed by coating guar gum and Eudragit FS30D sequentially onto drug-loaded pellets in a fluidized bed coater. In vitro studies showed that smaller coating weight gain of guar gum resulted in reduced release lag time t10 (10% release time), but favored degradation by enzymes (galactomannanase). A cumulative weight gain (CWG) of 44% provided sufficient enzymatic sensitivity and protection of the core. Under gradient pH conditions (pH = 1.2, 6.8, 7.4 and 6.5 for 2, 2, 1 and 15 h, respectively), indomethacin was released from Eudragit FS30D-coated pellets quickly after changing pH to 7.4. For guar gum/Eudragit FS30D double-coated pellets, only about 5% of the drug was released after another 1 h, showing retarding effect by guar gum coating. After changing pH to 6.5 and addition of galactomannanase, enzyme-dependent drug release was observed. Pharmacokinetic study in beagle dogs showed that fastest absorption with the smallest Tmax and Tlag was observed for uncoated pellets. The Tmax and Tlag of Eudragit FS30D-coated pellets were postponed to about 2.5 and 1 h, respectively. After a further guar gum coating, Tlag was further postponed to about 2.8 h, about 2 h of additional lag time on the basis of Eudragit FS30D coating. It is indicated that the guar gum/Eudragit FS30D-coated system has potential to be used to deliver drugs to the colon.     

Optimization and pharmacotechnical evaluation of compression‐coated colon‐specific drug delivery system of triphala using factorial design

The purpose of the present investigation was to achieve successful delivery specifically to the colon using guar gum as a compression coat over a core tablet of triphala. In this study, guar gum along with hydroxy propyl methyl cellulose (HPMC) was used as a compression‐coating polymer. The drug delivery system was based on the gastrointestinal transit time concept, assuming colon arrival time to be 6 h. Rapidly disintegrating core tablets containing 100‐mg triphala extract were compression coated with guar gum and HPMC. A 3² full factorial design was applied for optimization of the formulation. Both variables, the proportion of guar gum in polymer blend (X₁) and coat weight of the tablet (X₂), had an influence on the percent drug release after 4 h of dissolution of tablet in the presence of rat cecal content (Y240) and difference in percent drug release between 4 h and 10 h of dissolution of tablet in the presence of rat cecal content (YD).The results revealed that for protecting the rapidly disintegrating core of triphala in the physiological conditions of stomach and upper intestine, the core tablet should be coated with 50% of guar gum in coat formulation and higher coat weight. The proportion of guar gum exhibited predominant action as compared to coat weight. In vivo performance was assessed via an x‐ray roentgenography study by placing barium sulfate as an x‐ray opaque material instead of triphala. The guar gum–HPMC coating was found to be a promising drug delivery system for drugs such as triphala and sennosides to be delivered to the colon. Drug Dev. Res. 65:34–42, 2005. © 2005 Wiley‐Liss, Inc.     

Pectin/Ethylcellulose as film coatings for colon-specific drug delivery: preparation and in vitro evaluation using 5-fluorouracil pellets

The aim of the present study is to develop colon-targeted drug delivery systems for 5-fluorouracil using pectin combined with ethylcellulose as a film coat with fluidized bed coater. Pellets (0.8-1.0 mm in diameter) containing 40% 5-fluorouracil and 60% microcrystalline cellulose were prepared by extrusion and spheronization. Film-coated pellets of 5-fluorouracil containing various proportions (1:0, 0:1, 1:1, 1:2, w/w) of pectin and ethylcellulose (Surelease) were prepared and subjected to in vitro drug release. The amount of 5-fluorouracil released from pellets at different time intervals was estimated by high-performance liquid chromatography. Drug release was assessed using flow testing in the presence and absence of rat caecal contents. The film thickness is expressed as the theoretical percentage of the weight gained (TWG-%) used relative to the weight of the coated pellets. Coated pellets with pectin alone and TWG-20% released 100% of the 5-fluorouracil in the simulated gastric and small intestinal conditions and failed to control the drug release in the first 5 h of the dissolution study in the simulated gastric and small intestinal conditions; while coated pellets with ethylcellulose alone and TWG-20% released 11.7 +/- 0.9% of the 5-fluorourail at the end of 24 h. When the ratio of pectin to Surelease was 1:1 (w/w) and film coat TWG-20%, the release was rapid and was accompanied by splitting of the coat. When the ratio of pectin to Surelease was 1:2 (w/w) and film coat TWG-13% and TWG-20%, the formulations released 9.8 +/- 0.7% and 4.1 +/- 0.4%, respectively, of 5-fluorouracil in the first 5 h of the dissolution study in the simulated gastric and small intestinal conditions. When the dissolution study was continued in simulated colonic fluids (4% w/v rat caecal content medium) for another 19 h, the film coat with the formulations of TWG-13% and TWG-20% released 96 +/- 1.3% and 85.0 +/- 0.3%, respectively, of 5-fluorourail in simulated colonic fluids at the end of 24 h of the dissolution study, whereas in the control study the formulations released 51.4 +/- 1.0% and 34 +/- 0.5%, respectively, of 5-fluorouracil in absence of rat caecal contents at the end of 24 h. The results of the study show that the formulation of TWG-20% (pectin to Surelease 1:2, w/w) is most likely to provide targeting of 5-fluorouracil for local action in the colon, as it released only 4.1 +/- 0.4% of the drug in the simulated gastric and small intestinal conditions, and it released 85.0 +/- 0.3% of 5-fluorourail in simulated colonic fluids at the end of 24 h. The 5-fluorouracil-coated pellets showed no change in physical appearance, drug content, or dissolution pattern after storage at 40 degrees C/75% relative humidity for 6 months. Differential scanning calorimetric study indicated no possibility of interaction between 5-fluorouracil and pectin or other excipients used in the coated pellets.     

Mechanisms Controlling Theophylline Release from Ethanol-Resistant Coated Pellets

Purpose

To elucidate the mass transport mechanisms controlling drug release from recently proposed, ethanol-resistant, polymeric film coatings.

Methods

Theophylline matrix pellets were coated with ethylcellulose: guar gum blends. Drug release from single pellets and ensembles of pellets was measured in various release media. Changes in the systems’ morphology, composition and mechanical properties were monitored using SEM, gravimetrical analysis and a texture analyzer. Based on the obtained experimental results a mechanistically realistic mathematical model was identified and used to quantitatively predict drug release from coated pellets in ethanol-free and ethanol-containing bulk fluids.

Results

Drug diffusion though the intact polymeric film coatings is likely to be the dominant mass transport mechanism in the investigated systems, irrespective of the ethanol content in the surrounding environment. An appropriate solution of Fick’s law could be used to quantitatively predict theophylline release from pellets coated with different ethylcellulose:guar gum blends at different coating levels. Importantly, independent experiments confirmed the theoretical predictions.

Conclusions

In silico simulations can help facilitating the optimization of the novel ethanol-resistant polymeric film coatings, avoiding time-consuming and cost-intensive series of trial-and-error experiments. The presence/absence of ethanol does not affect the underlying drug release mechanisms.     

Ethanol-resistant ethylcellulose/guar gum coatings – Importance of formulation parameters

Recently, ethylcellulose/guar gum blends have been reported to provide ethanol-resistant drug release kinetics from coated dosage forms. This is because the ethanol insoluble guar gum effectively avoids undesired ethylcellulose dissolution in ethanol-rich bulk fluids. However, so far the importance of crucial formulation parameters, including the minimum amount of guar gum to be incorporated and the minimum required guar gum viscosity, remains unclear. The aim of this study was to identify the most important film coating properties, determining whether or not the resulting drug release kinetics is ethanol-resistant. Theophylline matrix cores were coated in a fluid bed with blends of the aqueous ethylcellulose dispersion “Aquacoat® ECD 30” and guar gum. The polymer blend ratio, guar gum viscosity, and degree of dilution of the final coating dispersion were varied. Importantly, it was found that more than 5% guar gum (referred to the total polymer content) must be incorporated in the film coating and that the apparent viscosity of a 1% aqueous guar gum solution must be greater than 150 cP to provide ethanol-resistance. In contrast, the investigated degree of coating dispersion dilution was not found to be decisive for the ethanol sensitivity. Furthermore, all investigated formulations were long term stable, even upon open storage under stress conditions for 6 months.     

The use of formulation technology to assess regional gastrointestinal drug absorption in humans.

The aim of this study was to assess the feasibility of using oral modified-release formulations for the purposes of site-specific targeting and regional drug absorption assessment in man. An immediate release pellet formulation containing ranitidine as the model drug of choice for the study was fabricated by extrusion-spheronisation, and then film coated with either the enteric polymer polyvinyl acetate phthalate or the bacteria-degradable polymer amylose, in combination with ethylcellulose, to effect drug release within the small intestine and colon, respectively. Optimised formulations were evaluated in vivo in ten healthy volunteers, who each received, on four separate occasions, the immediate release, small intestinal release and colonic release formulations (each equivalent to 150mg ranitidine), and an intravenous injection of ranitidine (equivalent to 50mg ranitidine). Blood samples were collected and assessed for ranitidine concentration, and radiolabelled placebo pellets were co-administered with the coated ranitidine pellets to monitor their gastrointestinal transit using a gamma camera. Ranitidine was rapidly released and absorbed from the immediate release formulation, whereas the enteric formulation (10% coat weight gain) delayed drug release until some or all of the pellets had emptied into the small intestine. The amylose-ethylcellulose coated formulation (coat ratio 1:3, coat weight gain 25%) retarded ranitidine release until the pellets had reached the colon. The mean absolute bioavailability of ranitidine from the immediate release, small intestinal release and colonic release formulations were 50.6, 46.1 and 5.5%, respectively. These data are in general agreement to those obtained from a previous regional intubation study. The present study therefore demonstrates the practical potential of utilising a non-invasive, formulation-based approach to assess drug absorption from different regions of the human gastrointestinal tract.     

The encapsulation of ribozymes in biodegradable polymeric matrices

The aim of the present study is to develop colon targeted drug delivery systems for metronidazole using guar gum as a carrier. Matrix, multilayer and compression coated tablets of metronidazole containing various proportions of guar gum were prepared. All the formulations were evaluated for the hardness, drug content uniformity, and were subjected to in vitro drug release studies. The amount of metronidazole released from tablets at different time intervals was estimated by high performance liquid chromatography method. Matrix tablets and multilayer tablets of metronidazole released 43-52% and 25-44% of the metronidazole, respectively, in the physiological environment of stomach and small intestine depending on the proportion of guar gum used in the formulation. Both the formulations failed to control the drug release within 5 h of the dissolution study in the physiological environment of stomach and small intestine. The compression coated formulations released less than 1% of metronidazole in the physiological environment of stomach and small intestine. When the dissolution study was continued in simulated colonic fluids, the compression coated tablet with 275 mg of guar gum coat released another 61% of metronidazole after degradation by colonic bacteria at the end of 24 h of the dissolution study. The compression coated tablets with 350 and 435 mg of guar gum coat released about 45 and 20% of metronidazole, respectively, in simulated colonic fluids indicating the susceptibility of the guar gum formulations to the rat caecal contents. The results of the study show that compression coated metronidazole tablets with either 275 or 350 mg of guar gum coat is most likely to provide targeting of metronidazole for local action in the colon owing to its minimal release of the drug in the first 5 h. The metronidazole compression coated tablets showed no change either in physical appearance, drug content or in dissolution pattern after storage at 40 degrees C/75% RH for 6 months.     

Design and in vitro evaluation of oral colon targeted drug delivery systems for tinidazole

The aim of the present investigation is to develop colon targeted drag delivery sytems for tinidazole using guar gum as a carrier in the treatment of amoebiasis. Fast-disintegrating tinidazole core tablets were compression-coated with 55, 65 and 75% of guar gum. All the formulations were evaluated for the hardness, drug content uniformity, and subjected to in vitro drug release studies. The amount of tinidazole released from tablets at different time intervals was estimated by HPLC method. The compression-coated formulations released < 0.5% of tinidazole in the physiological environment of stomach and small intestine. When the dissolution study was continued in simulated colonic fluids, the compression coated tablet with 55% of guar gum coat released 99% of tinidazole after degradation by colonic bacteria at the end of 24 h of the dissolution study. The compression coated tablets with 65 and 75% of guar gum coat released about 67 and 20% of tinidazole, respectively in simulated colonic fluids indicating the susceptibility of the guar gum formulations to the rat caecal contents. The results of the study show that compression coated tinidazole tablets with either 55 or 65% of guar gum coat is most likely to provide targeting of tinidazole for local action in the colon owing to its minimal release of the drug in the first 5 h of physiological environment of stomach and small intestine. The tinidazole compression coated tablets showed no change either in physical appearance, drug content or in dissolution pattern after storage at 40 degrees C/75% RH for 6 months.