Design and evaluation of floating multi-layer coated tablets based on gas formation

Floating multi-layer coated tablets were designed based on gas formation. The system consists of a drug-containing core tablet coated with a protective layer (hydroxypropyl methylcellulose), a gas forming layer (sodium bicarbonate) and a gas-entrapped membrane, respectively. The mechanical properties of acrylic polymers (Eudragit^® RL 30D, RS 30D, NE 30D) and ethylcellulose were characterized by the puncture test in order to screen a suitable film for the system. Eudragit^® RL 30D was chosen as a gas-entrapped membrane due to its high flexibility and high water permeability. The obtained tablets enabled to float due to the CO₂-gas formation and the gas entrapment by polymeric membrane. The effect of formulation variables on floating properties and drug release was investigated. The floating tablets using direct-compressed cores had shorter time to float and faster drug release than those using wet-granulated cores. The increased amount of a gas forming agent did not affect time to float but increased the drug release from the floating tablets while increasing coating level of gas-entrapped membrane increased time to float and slightly retarded drug release. Good floating properties and sustained drug release were achieved. These floating tablets seem to be a promising gastroretentive drug delivery system.     

雷公藤胃漂浮缓释微丸的制备

目的:制备雷公藤胃漂浮缓释微丸,考察其漂浮和释药性能。方法:以微丸的体外释放度、漂浮性能为考察指标,采用挤出滚圆法制备胃漂浮空白微丸,采用流化床包衣设备依次进行载药层和缓释层包衣,制备雷公藤胃漂浮缓释微丸。结果:以90%十八醇为助漂剂,10%微晶纤维素为稀释剂制得空白胃漂浮微丸;以1%羟丙基甲基纤维素和0.5%十二烷基硫酸钠为载药层包衣材料,以含3%聚维酮的乙基纤维素水分散体为缓释层包衣材料。制得的雷公藤胃漂浮缓释微丸在人工胃液中立即起漂,8h漂浮率均>80%,体外释药机制符合一级释药方程。结论:所制雷公藤胃漂浮缓释微丸具有良好的漂浮性能和缓释特性。     

二氢杨梅素胃内漂浮片处方研究

目的为了延长二氢杨梅素在胃内停留的时间,延缓药物的释放,将其制备成胃内漂浮片。方法采用粉末直接压片法制片,运用单因素的平行实验和L9（3^4）正交设计,以起漂时间、漂浮持续时间及释放度为指标选择最佳处方。结果最佳处方：片剂重量为300mg,其他各成分的含量分别为：HPMCK4M75mg,PVPK3040mg,NaHC0340mg,主药80mg,乳糖65mg,该制剂在37℃的人工胃液中立即起漂,12h释放〉90％,持漂时N〉10h。结论制备的胃漂浮片具有优良的漂浮能力和释药行为,可增加二氢杨梅素在胃部的滞留时间,提高药物的稳定性,增强保肝作用。     

一种产气型胃漂浮微丸的制备及其漂浮性和体外释放度的考察

目的以法莫替丁为模型药物,制备一种胃漂浮微丸,以延长胃内存留时间,提高药物的生物利用度。方法采用挤出滚圆法制备载药丸芯,以粉体学性质为指标进行处方筛选;采用流化床包衣的方法在载药丸芯外部包上产气层(含有碳酸氢钠的羟丙基甲基纤维素)和阻滞层(EudragitRL30D,RS30D,NE30D),并分别考察各处方微丸的漂浮性和体外释放性质。结果制得的微丸可以在5 min内起漂,持续漂浮达8 h以上,药物5 h缓释率达到93.5%。微丸的起漂时间随着产气物质[碳酸氢钠(NaHCO3)]质量的增加而缩短,随着外层阻滞层包衣增量的增加(EudragitNE30D)或Eudragit RS30D质量的增加(Eudragit RL30D/RS30D)而延长。结论试验制得的胃漂浮型微丸既能快速起漂、持续漂浮达8 h以上,又能缓慢释放药物。     

硝苯地平胃漂浮型延迟缓释微丸的制备

目的:制备硝苯地平胃漂浮型延迟缓释微丸并考察其体外漂浮行为.方法:挤出滚圆法制备漂浮型空白丸芯,空白丸芯上药法制备载药丸芯,分别以Surelease水分散体和Eudragit L30D-55为包衣材料,进行流化床包衣.采用正交试验设计对处方进行优化.结果:模拟人体胃肠道条件下溶出,自制漂浮型微丸在人工胃液中6 h累计释放小于10%,换人工肠液后12 h释放完全,体外漂浮10 h以上. 结论:自制微丸达到了漂浮和延迟缓释的效果.     

Development and evaluation of new sustained-release floating microspheres

A type of multi-unit floating alginate (Alg) microspheres was prepared by the ionotropic gelation method with calcium carbonate (CaCO(3)) being used as gas-forming agent. Attempts were made to enhance the drug encapsulation efficiency and delay the drug release by adding chitosan (Cs) into the gelation medium and by coating with Eudragit, respectively. The gastrointestinal transit of optimized floating sustained-release microspheres was compared with that of the non-floating system manufactured from identical material using the technique of gamma-scintigraphy in healthy human volunteers. It was found that the drug encapsulation efficiency of Cs-Alg microspheres was much higher than that of the Ca-Alg microspheres, and coating the microspheres with Eudragit RS could extend the drug release significantly. Both uncoating and coating microspheres were able to continuously float over the simulated gastric fluid (SGF) for 24h in vitro. Prolonged gastric-retention time (GRT) of over 5h was achieved in the volunteer for the optimized coating floating microspheres (FM). In contrast, non-floating system (NFM) could be emptied within 2.5h. In the present study, a multi-unit system with excellent floating ability, optimum drug entrapment efficiency and suitable drug release pattern has been developed.     

Floating matrix dosage form for dextromethorphan hydrobromide based on gas forming technique: In vitro and in vivo evaluation in healthy volunteers

The objective of this study was to develop the dextromethorphan hydrobromide sustained-release (DMB-SR) tablets using floating technique to prolong the gastric residence time and compared their pharmacokinetic behavior with conventional sustained release tablets. DMB-SR floating tablets were prepared employing hydroxypropyl methylcellulose (HPMC) as hydrophilic gel material, sodium bicarbonate as gas-generating agent and hexadecanol as floating assistant agent. An orthogonal experiment design method was used to select the optimized formulation. The floating tablets were evaluated for uniformity of weight, hardness, friability, drug content, floating characteristics, in vitro release and in vivo bioavailability. The optimized tablets were prepared with HPMC K4M 25 mg, sodium bicarbonate 20 mg and hexadecanol 18 mg. The prepared tablets could float within 3 min and maintain for more than 24 h. The data of physical parameters were all lie within the limits. Drug release at 12 h was more than 85%. The comparative pharmacokinetic study was performed by administration of the DMB-SR floating tablets and conventional DMB-SR tablets. The area under curve of plasma concentration–time (AUC) of floating tablets was slightly higher than that of reference tablets, T_max was prolonged apparently. The results showed the floating tablets are a feasible approach for the sustained-release preparation of drugs, which have limited absorption sites in the stomach.     

甲硝唑胃部滞留制剂的制备

目的为更好地清除幽门螺旋杆菌,制备同时具有缓释、漂浮、黏附特性的甲硝唑胃部滞留制剂。方法采用挤出滚圆法制备丸心,流化床包衣法制备甲硝唑缓释漂浮黏附微丸。EudragitNE30D为缓释层,NaHCO3为产气层,EudragitRL 30D为阻滞层,Carbopol 934P为黏附层,考察不同包衣增量情况下,各微丸的释药行为,在0.1 mol.L-1HCl中的漂浮性能,及离体大鼠胃黏膜上的黏附能力。结果丸心外包质量分数为3%的EudragitNE 30D,质量分数为9%的NaHCO3,质量分数为10%的EudragitRL 30D,质量分数为5%的Carbopol 934P的微丸,能实现缓释12 h、4 min起漂、持续漂浮12 h,漂浮率大于95%、黏附率为100%。结论所制备的甲硝唑胃部滞留制剂,同时具备缓释的释药行为、优良的漂浮能力、良好的黏附特征。进而能增加甲硝唑的胃部滞留时间,延长药物与幽门螺旋杆菌的接触时间,提高甲硝唑抗幽门螺旋杆菌的疗效。     

Development and evaluation of new multiple-unit levodopa sustained-release floating dosage forms

This work relates to the development and the in vitro evaluation of sustained-release minitablets (MT), prepared by melt granulation and subsequent compression, which are designed to float over an extended period of time. Levodopa was used as a model drug. The importance of the composition and manufacturing parameters of the MT on their floating and dissolution properties was then examined. The investigation showed that MT composition and MT diameter had the greatest influence on drug release, which was sustained for more than 8h. By using the same formulation, the best floating properties were obtained with 3mm MT prepared at low compression forces ranging between 50 and 100N. Their resultant-weight (RW) values were always higher than those obtained with a marketed HBS dosage form within 13h. When they were filled into gelatin capsules, no sticking was observed. By evaluating the dissolution profiles of levodopa at different pH values, it was found that dissolution profiles depend more on the prolonged-release ability of Methocel K15M than on the pH-dependent solubility of levodopa. Finally, the robustness of the floating MT was assessed by testing the drug release variability in function of the stirring conditions during dissolution tests.     

A New Approach in Gastroretentive Drug Delivery System Using Cholestyramine

We prepared cellulose acetate butyrate (CAB)-coated cholestyramine microcapsules as a intragastric floating drug delivery system endowed with floating ability due to the carbon dioxide generation when exposed to the gastric fluid. The microcapsules also have a mucoadhesive property. Ion-exchange resin particles can be loaded with bicarbonate followed by acetohydroxamic acid (AHA) and coated with CAB by emulsion solvent evaporation method. The drug concentration was monitored to maintain the floating property and minimum effective concentration. The effect of CAB: drug-resin ratio (2:1, 4:1, 6:1 w/w) on the particle size, floating time, and drug release was determined. Cholestyramine microcapsules were characterized for shape, surface characteristics, and size distribution; cholestyramine/acetohydroxamic acid interactions inside microcapsules were investigated by X-ray diffractometry. The buoyancy time of CAB-coated formulations was better than that of uncoated resin particles. Also, a longer floating time was observed with a higher polymer:drug resin complex ratio (6:1). With increasing coating thickness the particle size was increased but drug release rate was decreased. The drug release rate was higher in simulated gastric fluid (SGF) than in simulated intestinal fluid (SIF). The in vivo mucoadhesion studies were performed with rhodamine-isothiocyanate (RITC) by fluorescent probe method. The amount of CAB-coated cholestyramine microcapsules that remained in the stomach was slightly lower than that of uncoated resin particles. Cholestyramine microcapsules were distributed throughout the stomach and exhibited prolonged gastric residence via mucoadhesion. These results suggest that CAB-coated microcapsules could be a floating as well as a mucoadhesive drug delivery system. Thus, it has promise in the treatment of Helicobacter pylori.     

A new approach in gastroretentive drug delivery system using cholestyramine

We prepared cellulose acetate butyrate (CAB)-coated cholestyramine microcapsules as a intragastric floating drug delivery system endowed with floating ability due to the carbon dioxide generation when exposed to the gastric fluid. The microcapsules also have a mucoadhesive property. Ion-exchange resin particles can be loaded with bicarbonate followed by acetohydroxamic acid (AHA) and coated with CAB by emulsion solvent evaporation method. The drug concentration was monitored to maintain the floating property and minimum effective concentration. The effect of CAB: drug-resin ratio (2:1, 4:1, 6:1 w/w) on the particle size, floating time, and drug release was determined. Cholestyramine microcapsules were characterized for shape, surface characteristics, and size distribution; cholestyramine/acetohydroxamic acid interactions inside microcapsules were investigated by X-ray diffractometry. The buoyancy time of CAB-coated formulations was better than that of uncoated resin particles. Also, a longer floating time was observed with a higher polymer:drug resin complex ratio (6:1). With increasing coating thickness the particle size was increased but drug release rate was decreased. The drug release rate was higher in simulated gastric fluid (SGF) than in simulated intestinal fluid (SIF). The in vivo mucoadhesion studies were performed with rhodamine-isothiocyanate (RITC) by fluorescent probe method. The amount of CAB-coated cholestyramine microcapsules that remained in the stomach was slightly lower than that of uncoated resin particles. Cholestyramine microcapsules were distributed throughout the stomach and exhibited prolonged gastric residence via mucoadhesion. These results suggest that CAB-coated microcapsules could be a floating as well as a mucoadhesive drug delivery system. Thus, it has promise in the treatment of Helicobacter pylori .     

Evaluation of water uptake and mechanical properties of blended polymer films for preparing gas-generated multiple-unit floating drug delivery systems

Among various strategies of gastroretentive drug delivery systems (DDSs) developed to prolong the gastric residence time and to increase the overall bioavailability, effervescent multiple‐unit floating DDSs (muFDDSs) were studied here. These systems consist of drug (losartan)‐ and effervescent (sodium bicarbonate)‐containing pellets coated with a blended polymeric membrane, which was a mixture of gastrointestinal tract (GIT)‐soluble and GIT‐insoluble polymers. The addition of GIT‐soluble polymers, such as hydroxypropyl methylcellulose, polyethylene glycol (PEG) 6000, PEG 600, and Kollicoat® IR, greatly increased the water uptake ability of the GIT‐insoluble polymers (Eudragit® NE, RS, and RL; Surelease®; and Kollicoat® SR) and caused them to immediately initiate the effervescent reaction and float, but the hydrated films should also be impermeable to the generated CO₂ to maintain floatation and sufficiently flexible to withstand the pressure of carbon dioxide to avoid rupturing. The study demonstrated that the water uptake ability and mechanical properties could be applied as screening tools during the development of effervescent muFDDSs. The optimized system of SRT(5)P600(5) (i.e., a mixture of 5% Kollicoat® SR and 5% PEG 600) with a 20% coating level began to completely float within 15 min and maintained its buoyancy over a period of 12 h with a sustained‐release effect.     

巴洛沙星胃漂浮缓释片的制备及体外释放

以体外漂浮性能和释放度为指标优化巴洛沙星胃漂浮缓释片的处方。结果表明,每片用量HPMCK100M为120mg、碳酸氢钠为200mg和羧甲淀粉钠为100mg的片剂能在1min内起漂,持续漂浮时间达8．2h,8h累积释放率达90％。按优化处方制备的片荆在高温（60℃）、强光（4500h）下贮存10d,均保持稳定,高温（相对湿度75％）条件下有吸湿现象。     

The evaluation of a column-type dissolution apparatus.

An improved column-type dissolution apparatus is described. The column of the apparatus is built from standard screw-cap connected "Sovirel" glass tubes which should enable inter-apparatus variability to be reduced. The main problem with this type of device is the build up to back pressure as fragments from the disintegrating solid dosage form progressively block the filtration system, itself necessary to stop the solution process and present the solution for analysis. A simple type of light-activated switch is therefore used which works across the indicator float of a flow meter to drive a motor connected to a needle valve. As the float falls the motor is switched on to open the valve and increase the flow rate until the float rises again and causes the motor to switch off. Observation on the dissolution characteristic of dyed lactose tablets and the injection of dye solutions into the flowing stream of liquid around tablets showed that there was back-flow of solution at Reynolds Numbers below 10 but visible instability to flow at Re greater than 100. Over a range of flow rates between Re 10-70 the mass of drug released at a given time was a direct function of flow rate for a film coated product but an inverse function for a sugar coated tablet. The results are discussed in relation to the main problems which can be experienced with a column-type dissolution apparatus.     

Preparation of Eudragit E100 microspheres by modified solvent evaporation method

The objective of this investigation was to develop the hollow microspheres as a new dosage form of floating drug delivery system with prolonged stomach retention time. Hollow microspheres containing ranitidine hydrochloride were prepared by solvent evaporation method using Eudragit RLPO dissolved in a mixture of dichloromethane and ethanol. The maximum yield and drug loading amount of hollow microspheres were 88.45% and 80 +/- 4.0%, respectively. The in vitro release profiles showed that the drug release rate decreased with increasing viscosity of Eudragit RLPO, while diameter of hollow microspheres increased with the increase of drug polymer weight ratio. Hollow microspheres could prolong drug release time (approximately 24 h) and float over stimulate gastric fluid for more than 12 h. These results demonstrated that ranitidine HCl hollow microspheres were capable of sustained delivery of the drug for longer period with increased bioavailability.     

Visualized intravesical floating hydrogel encapsulating vaporized perfluoropentane for controlled drug release

Intravesical drug delivery is the main strategy for the treatment of bladder disorders. To reduce the relief arising from frequent intravesical instillation, mucoadhesive hydrogel was used for the controlled release of the drug. However, the viscosity of mucoadhesive gel might cause severe urinary obstruction and bladder irritation. To solve all these problems, a floating hydrogel delivery system was developed using perfluoropentane (PFP) as the floating agent. After intravesical instillation of the floating hydrogel, the increased temperature in bladder vaporized PFP, resulting in the generation of microbubbles in the hydrogel. Then, it can float in urine to avoid the urinary obstruction and bladder irritation. In this study, systematic experiments were conducted to investigate the influences of PFP vaporization on the morphology and floating ability of hydrogels. The floating process is much milder and safer than other floating methods published before. In addition, PFP had been used as contrast agent, which affiliated the monitoring of gels during the operation. Therefore, this new drug delivery system addresses the problems of conventional intravesical instillation and is promising for clinic use.     

芍药苷胃漂浮片的制备

目的 制备芍药苷胃漂浮片,优选芍药苷胃漂浮片的制备工艺。方法 采用湿法制粒压片制备芍药苷胃漂浮片,以漂浮性能和体外累积释放率为考查指标,采用单因素筛选及正交设计法,优化芍药苷胃漂浮片处方。结果 以HPMC K4M(20%)为骨架材料、NaHCO₃(15%)为起泡剂、PVPP(7%)为释放促进剂、乳糖200为填充剂制得的胃漂浮片能立即起漂,持续漂浮12 h以上,累积释放率达90%以上。结论 优选的芍药苷胃漂浮片达到了持续漂浮及缓慢释放的要求,可操作性强。     

辛伐他汀胃漂浮型缓释片的制备及体外释放研究

目的筛选辛伐他汀胃漂浮型缓释片最优处方,并考察其漂浮性能及体外释药情况。方法采用正交法筛选出辛伐他汀胃漂浮型缓释片最优处方,采用湿法制粒压片制备胃漂浮型缓释片,对制备的胃漂浮型缓释片进行漂浮性与体外释放度测定。结果辛伐他汀胃漂浮型缓释片起漂时间小于1min,持续漂浮时间大于14h,在2,8和14h药物累积释放度分别达到8.66%,56.44%和95.17%,体外释药符合Higuchi方程。结论制备的辛伐他汀胃漂浮型缓释片漂浮性能良好,达到缓释药物的目的。     

Design and in vitro evaluation of floating drug delivery system for an antipsychotic agent: a technical report

Floating drug delivery systems are used to target drug release in the stomach or to the upper parts of the intestine. The oral delivery of the anti-psychotic agent carbamazepine was facilitated by preparing a non-disintegrating floating dosage form which can increase its absorption in the stomach by increasing the drug's gastric residence time. The polymers used were HPMC (low and high viscosity), guar gum, and carbopol, along with sodium bicarbonate as the gas-generating agent. The prepared tablets were evaluated for their physicochemical properties and drug release. In vitro release studies indicated that the carbamazepine release from the floating dosage forms was uniform and followed a zero-order release. It was observed that the devices containing higher proportions of HPMC (high viscosity) showed slower release than those containing lower proportions while also maintaining the integrity of the device (> or = 24 h). The incorporation of guar gum helps to maintain the device's integrity, and due to its viscolysing property also affects the drug's release profile. Sodium bicarbonate which was used as the gas-generating agent causes the tablet to float for the required time (> or = 24 h).     

A floating multiparticulate system for ofloxacin based on a multilayer structure: In vitro and in vivo evaluation

The purpose of this research was to develop a novel gastroretentive multiparticulate system with floating ability. This system was designed to provide drug-loaded pellets coated with three successive coatings-the retarding film (ethyl cellulose), the effervescent layer (sodium bicarbonate) and the gas-entrapped polymeric membrane (Eudragit RL 30D). The floating pellets were evaluated for SEM, floating characteristic parameters, in vitro release and bioavailability in New Zealand rabbits. The zero-order release theory model is designed to interpret the release processes. Due to the swelling property, high flexibility and high water permeability, Eudragit RL 30D was used as a gas-entrapped polymeric membrane. The obtained pellets exhibit excellent floating ability and release characteristics. Analysis of the release mechanism showed a zero-order release for the first 8h because of the osmotic pressure of the saturated solution inside of the membrane, which was in accordance with that predicted. Abdominal X-ray images showed that the gastroretention period of the floating barium sulfate-labeled pellets was no less than 6h. The relative bioavailability of the floating pellets compared with reference tablets was 113.06 ± 23.83%. All these results showed that the floating pellets are a feasible approach for the gastroretentive drug delivery system.