Gentamicin-loaded discs and microspheres and their modifications: characterization and in vitro release (original) (raw)
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Incorporation of drug-resin complex to improve microsphere performance
Asian Journal of Pharmaceutics, 2012
T he objective of present work was to incorporate drug-resin complex (DRC) to microspheres to achieve improved drug loading, less leakage, and extended zero order release. Ondensetron hydrochloride (ODH), a model drug was complexed with Indion 244, and incorporated to microspheres of hydroxypropyl methyl cellulose (HPMC), and ethyl cellulose (EC). A 3 2 full factorial design was used to prepare microspheres using HPMC and EC as independent variables, X 1 and X 2 respectively. The microspheres obtained were evaluated for yield, topology, micromeritics, drug entrapment, and drug release kinetics. Complexation of ODH with Indion 244 was found to be 28% wt/wt. The incorporation efficiency of DRC to microspheres (DRC1-DRC9) was in the range of 70.41 ± 2.18 to 95.08 ± 0.76% wt/wt. The trend of increase in the drug entrapment (DRC) with high amounts of HPMC and EC was noted for all microspheres. Yield of DRC9 was maximum (84.87% wt/wt), and was lowest for DRC1. Acceptable Hausner's ratio, Carr's compressibility index and angle of repose demonstrated the excellent flowability of microspheres (DRC1 to DRC9). Drug release kinetic studies showed that, ODH dissociation from DRC, and its diffusion through HPMC and EC, both, have contributed for extended zero order release. Especially, from DRC2, maximum extended release was noted up to 19.10 hrs (zero order, R 2 = 0.9239). Hence, it can be concluded that, incorporation of DRC to microspheres can overcome poor drug loading, high drug leakage, and poor drug sustainability problems of microspheres. Especially, the zero order release can be achieved by incorporation of DRC to microspheres.
European Journal of Pharmaceutics and Biopharmaceutics, 2008
Taking ABT627 as a hydrophobic model drug, poly-(lactic-co-glycolic acid) (PLGA) microspheres were prepared by an emulsion solvent evaporation method. Various process parameters, such as continuous phase/dispersed phase (CP/DP) ratio, polymer concentration, initial drug loading, polyvinyl alcohol concentration and pH, on the characteristics of microspheres and in vitro drug release pattern of ABT627 were investigated. Internal morphology of the microspheres was observed with scanning electron microscopy by stereological method. CP/DP is a critical factor in preparing microspheres and drug loading increased significantly with increasing CP/DP ratios accompanied by a remarkably decreased burst release. At CP/DP ratio 20, microspheres with a core-shell structure were formed and the internal porosity of the microspheres decreased with increasing CP/DP ratio. Increase in PLGA concentration led to increased particle sizes and decreased drug release rates. ABT627 release rate increased considerably with increasing PVA concentrations in the continuous phase from 0.1% to 0.5%. The maximum solubility of ABT627 in PLGA was approximately 30%, under which ABT627 was dispersed in PLGA matrix in a molecular state. Increase in initial drug loading had no significant influence on particle size, drug encapsulation efficiency, burst release and internal morphology. However, drug release rate decreased at higher drug loading. Independent of process parameters, ABT627 was slowly released from the PLGA microspheres over 30 days, by a combination of diffusion and polymer degradation. During the first 13 days, ABT627 was mainly released by the mechanism of diffusion demonstrated by the unchanged internal morphology. In contrast, a core-shell structure of the microspheres was observed after being incubated in the release medium for 17 days, independent of drug loading, implying that the ABT627/PLGA microspheres degraded by autocatalytic effect, starting from inside of the matrix. In conclusion, hydrophobic drug release from the PLGA microspheres is mainly dependent on the internal morphology and drug distribution state in the microspheres.
International Journal of Pharma and Bio Sciences MICROENCAPSULATION: A REVIEW
Microencapsulation is the process of surrounding or enveloping one substance within another substance on a very small scale, yielding capsules ranging from less than one micron to several hundred microns in size. The encapsulation efficiency of the microparticles or microsphere or microcapsule depends upon different factors like concentration of the polymer, solubility of polymer in solvent, rate of solvent removal, solubility of organic solvent in water etc. Microencapsulation may be achieved by a myriad of techniques. Substances may be microencapsulated with the intention that the core material be confined within capsule walls for a specific period of time. Alternatively, core materials may be encapsulated so that the core material will be released either gradually through the capsule walls, known as controlled release or diffusion, or when external conditions trigger the capsule walls to rupture, melt, or dissolve. This article is a review of microencapsulation and materials involved in it, morphology of microcapsules, microencapsulation technologies, purposes of microencapsulation, and benefits of microencapsulation, release mechanisms, and application fields, with special emphasis on microencapsulated additives in building construction materials.
Biological & Pharmaceutical Bulletin, 2007
The microencapsulation techniques are widely used in the pharmaceutical field. 1) Among them, emulsion solvent evaporation method has taken considerable attention in recent years, and numerous methods to manipulate a drug release behavior have been reported. 2) Several preparation variables influencing on the properties of microspheres have been identified, including solvent type, solvent removal rate, preparation temperature, composition and viscosity of polymer, and drug loading amount. In a previous study, we illustrated the effect of temperature-increase rate in the solvent evaporation process (referred to as the temperature-increase method hereafter) on the drug release property of the microspheres. 3) In this method, the preparative vessel was heated up at the constant rate in order to evaporate the dispersed solvent. By means of the temperature-increase method, microspheres showing constant drug release were prepared over a short period of time. Although a variety of studies has been conducted, the effects of poor solvent in the dispersed phase on the physical properties and drug release characteristics are not well-documented. The aim of the current work was to evaluate the effects of poor solvent in the dispersed phase on drug release from the microspheres when the temperature-increase method was employed for the emulsion solvent evaporation process. In this study, model microspheres were prepared from theophylline (TH) and hydrophobic dextran derivative (PDME). TH was used as a representative drug since sustained-release formulations are desirable because of the short elimination half-life in humans. PDME was selected as a water-insoluble polymer; it is used for contact lenses in the industrial field. Mixtures of acetone and water were used as the dispersed phase and liquid paraffin as the continuous phase. The microspheres were characterized by their size and drug loading efficiency. The morphology of the microspheres was then observed by scanning electron microscopy. In addition, drug release was examined and its kinetics were analyzed. MATERIALS AND METHODS Materials TH as an anhydrous form was purchased from Sigma Chemical Co. (St. Luis, MO, U.S.A.) and was used after sieving through a 200-mesh sieve (less than 75 mm). PDME was kindly donated by Meito Sangyo Co., Ltd. (Nagoya, Japan) and was used without further purification. PDME is prepared from dextran (Mw 40000) by substitution of 0.58 mol acetyl, 0.81 mol propionyl, 1.42 mol butyryl and 0.16 mol methacryloyl per anhydroglucose unit of dextran. Acetone was purchased from Wako Pure Chemical Industry, Ltd. (Osaka, Japan). Liquid paraffin conforming to JP standard was obtained from Iwaki Seiyaku Co., Ltd. (Tokyo, Japan). Sucrose-ester (DKF-10) was generously supplied by Dai-ichi Kogyo Seiyaku Co., Ltd. (Kyoto, Japan) and was used as an emulsifier. Polyoxyethylene (20) sorbitan monolaurate (Tween 20) was purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). Ultra purified water generated by Direct-Q (Nihon Millipore Ltd., Tokyo, Japan) was used for preparation of the dispersed phase. All other chemicals were of special reagent grade and were used as received. Preparation of Microspheres PDME (6.75 g) was dissolved into 15 ml of a mixture of acetone and water. TH (2.25 g) was then suspended in the PDME solution by stirring with a magnetic stirrer. The resultant suspension was poured into 150 ml of liquid paraffin containing 0.75 g of DKF-10 in a vessel settled into a water bath under agitation (400 rpm, 1 propeller) at 20°C. Following emulsification for 30 min at this temperature in the water bath, the system was heated up to 60°C at the temperature-increase rate of 30°C/h. In order to remove the organic solution completely,
A Novel Drug Delivery System: Review on Microspheres
Journal of Drug Delivery and Therapeutics, 2021
Microspheres are multiparticulate drug delivery systems that are designed to deliver drugs to a particular location at a fixed rate. Microspheres are free-flowing powders made up of biodegradable proteins or synthetic polymers with particle sizes ranging from 1 to 1000µm. Benefits of the use of microspheres in fields such as drug delivery, bone tissue manufacturing, and the absorption and desorption of contaminants by regeneration. The study shows the method of planning and measurement of microsphere parameters. Microspheres are complex, such as bioadhesive microspheres, polymeric microspheres, magnetic microspheres, floating microspheres, radioactive microspheres. Microspheres may be used in various fields such as cosmetics, oral drug delivery, target drug delivery, ophthalmic drug delivery, gene delivery, and others listed in the study. In order to achieve optimal therapeutic effectiveness, it is important to deliver the agent to the target tissue at an optimum level within the ri...
Microencapsulation techniques, factors influencing encapsulation efficiency: a review
The Internet Journal of …, 2009
Microencapsulation is one of the quality preservation techniques of sensitive substances and a method for production of materials with new valuable properties. Microencapsulation is a process of enclosing micron-sized particles in a polymeric shell. There are different techniques available for the encapsulation of drug entities. The encapsulation efficiency of the microparticle or microsphere or microcapsule depends upon different factors like concentration of the polymer, solubility of polymer in solvent, rate of solvent removal, solubility of organic solvent in water, etc. The present article provides a literature review of different microencapsulation techniques and different factors influencing the encapsulation efficiency of the microencapsulation technique.
MICROSPHERES FOR THE DRUG DELIVERY APPLICATIONS
Conventional dosage forms provide a sharp increase in plasma drug levels that falls below the therapeutic range after short interval of time until the re-administration of drug. There is a need of such dosage forms which provide not only sustained drug delivery but also reduce the plasma drug levels fluctuations. Microspheres used in drug delivery systems due to their ability to sustain the drug release, their biodegradability and compatibility and targeted drug delivery. In this review different types of microspheres their methods for the preparation with different hydrophilic and hydrophobic polymers, drug loading capacities will be discussed. Different characterizations like SEM, FTIR, XRD, DSC, rheological properties and invitro drug release are successfully described.
Discussion and outlook 145 Curriculum Vitae 149 Publications 149 [2] A. Smith, I.M. Hunneyball, Evaluation of poly(lactic acid) as a biodegrad¬ able drug delivery system for parenteral administration, Int. J. Pharm. 30 (1986)215-220. Background and purpose 3 [3] J.M. Anderson, M.S. Shive, Biodegradation and biocompatibility of PLA and PLGA microspheres, Adv. Drug. contribution to over¬ coming the problem of residual solvents in biodegradable microspheres prepared by coacervation, Eur. irradiation for terminal sterilization of 17ß-estradiol loaded poly-(D.L-lactide-co-glycolide) microspheres, J. Control. Release 61 (1999) 203-217. [7] A. Hausberger, R. Kenley, P.P. De Luca, Gamma irradiation effects on molecular weight and in vitro degradation of poly(D,L-lactide-coglycolide) microparticles, Pharm. Res. 12 (1995) 851-856. 4 Background and purpose Abstract 5 Abstract
DESIGN AND CHARACTERIZATION OF POLYMERIC MICROSPHERES FOR ORAL ADMINISTRATION
An appropriately designed sustained or controlled release drug delivery system can be a major advance towards solving the problem associated with the existing drug delivery system. Microspheres as a novel drug delivery system for oral administration are having the feasibility of carrying the drug. These are the monolithic spheres or therapeutic agent distributed throughout the matrix as a molecular dispersion of particles. Rational behind the drug encapsulation into microspheres is preparation of suitable formulation with longer duration of action for control release thereby sustaining the role of release of core material by rupture of polymeric wall. This will also reduce the dosing frequency and helps to improve the patient compliance. The aim of present work was to produce and characterize Repaglinide (Rg) polymeric microspheres by solvent evaporation method, in an attempt to obtain a delivery system adequate for the treatment of diabetes. Batches were prepared with different ratios of drug and polymer. Polymeric microspheres of Repaglinide were successfully prepared using Eudragit RSPO as polymer by emulsion solvent evaporation method. The prepared microspheres were evaluated for percentage yield, particle size, and drug entrapment efficiency, scanning electron microscopy, micromeritic studies and in vitro drug release study. From all the evaluation parameters the batch which is considered to be optimized batch, the final formulation i.e. tablet were prepared from the microspheres prepared in that optimized batch.