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Jundishapur Journal of Natural Pharmaceutical Products, 2012
Background: Microencapsulation is a useful method to prolong a drug release from dosage forms and to reduce its adverse effect (1) among various available methods. The microencapsulation of hydrophilic active ingredients requires the use of a polar dispersing phase such as a mineral oil. Acetone/paraffin systems are conventionally used. Objectives: The current study aimed to investigate two different microencapsulation techniques comparatively, water in oil in oil (w/o/o) and oil in oil (o/o), for theophylline (TH) loaded ethylcellulose (EC), cellulose acetate butyrate (CAB), Eudragit RS and RL microspheres with regard to loading efficiency, release and degradation kinetics. Materials and Methods: Microspheres were prepared by the emulsification method by solvent diffusion/evaporation technique and different polymers which were incorporated into microspheres to control the release rate of drug. Theophylline (TH) was chosen as a model drug. The emulsion technique was investigated for to prepare theophylline microparticles. EC and CAB and acrylatemethacrylate copolymer corresponding to the above ratios were selected as microparticles wall materials. The effects of type polymers on the physical characteristics and dissolution of the microparticles were also studied. However, the TH loading efficiency (for w/o/o emulsion about 90.64% and o/o emulsion about 73.90/5 to 95.90%) and the TH release kinetics were influenced by the microencapsulation technique.
The evaluation of Eudragit microcapsules manufactured by solvent evaporation using USP apparatus 1
Dissolution …, 2009
The objectives of this study were to prepare microcapsules containing verapamil and propranolol and to evaluate the kinetics and mechanism of drug release from the microcapsules using USP Apparatus 1. The effects of polymer concentration and polymer type on the cumulative amount of drug released were evaluated. The microcapsules were manufactured using Eudragit RS and RL polymers by solvent evaporation with the ultimate aim of prolonging drug release. Twenty-four formulations were prepared using different drug/polymer ratios. The effects of polymer type and polymer/drug ratios on the size, flow properties, surface morphology, and the release characteristics of the microcapsules were examined. The effects of drug inclusion methods on drug loading, encapsulation efficiency, and release properties of the complex microcapsules were also investigated. The formulations containing drug/polymer ratio 1:4 (w/w) were the most appropriate with respect to encapsulation efficiency (70%), flow properties (HR = 1.2), drug loading (15-20%), and drug release characteristics, in all cases. The release kinetics from the different formulations followed mainly a diffusion-controlled mechanism.
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,
International Journal of Scientific Research in Knowledge, 2014
Present study aims at comparative evaluation of drug release and permeability of diclofenac sodium loaded ethylcellulose (EC), cellulose acetate (CA) and eudragit (EU) microspheres. Microspheres of EC, CA and EU containing diclofenac sodium were prepared by an emulsification-solvent evaporation (oil-in-oil, o/o) method and were investigated for a comparative evaluation of various parameters. The microspheres were found discrete, free flowing, multinucleate, monolithic and spherical. About 5560% of all microspheres prepared were in the size range of-20+30 (715 m) mesh size. The encapsulation efficiency was in the range of 97.1106.4% with various polymers. The wall thickness of microspheres was in the range of 13.69-74.97m which depended on polymer employed and was directly proportional to polymer concentration. Diclofenac release from the microspheres was slow over longer periods of time and depended on the polymer used and coat:core ratio. Release was diffusion controlled and followed first order kinetics. Good linear relationships were observed between percent coat, wall thickness and release rate constant with all the three polymers. The slopes of percent coat vs release rate (k 1) plots were found to be 0.4117, 0.2351 and 0.9762; and those of wall thickness (h) vs drug release rate (k 1) plots were found 0.2549, 0.1863 and 0.7850 respectively for EC, CA and EU microspheres. The lower the slope the better is the controlling effect. Cellulose acetate exhibited better release-controlling effect than that of ethylcellulose and eudragit. The increasing order of diclofenac release rate and permeability observed with various microspheres was, cellulose acetate < ethylcellulose < eudragit RS100. The possible permeability of drug from the prepared porous micrsopheres could be due to osmotic pressure generated by diclofenac.
2015
Irin Dewan *1, , Swarnali Islam Khandaker 2 and Md. Sohel Rana 1 Department of Pharmacy , Jahangirnagar University, Savar, Dhaka, Bangladesh Pharmaceutical Technology Research Laboratory , Department of Pharmacy, University of Asia Pacific, Dhanmondi, Dhaka-1209, Bangladesh ABSTRACT: Glibenclamide is an oral anti-hyperglycemic agent designed intended for the management of non-insulin-dependent diabetes mellitus (NIDDM). In certain conditions conventional drug release pattern is not suitable similar to Diabetes mellitus, cardiovascular diseases and many more diseases, this present study has taken a challenge to formulate controlled release microspheres by using different polymers. An effort has been given to prepare controlled release microspheres along with Ethyl cellulose, Eudragit RS/RL100 and Methocel K15, 100M by using non-aqueous emulsion solvent evaporation method. UV-Spectrophotometric was applied to assay the drug content and in vitro dissolution studies according to USP pad...
Aspirin dissolution profiles from different particle size ranges of Eudragit RS100 microcapsules were studied in relation to the studied microcapsule structures. The results showed that there is no burst effect and the total amount of drug released from different particle size ranges prepared with the same or different TDC are more than 80% during 12 hr. The release data indicated the closest of the dissolution profile in every case. The values of standard deviation at every time unit were also used as an indication for the release data distribution around the mean of drug release. The model independent methods were used to prove the dissolution profile similarity of Aspirin from different particle size ranges microcapsules prepared by using the same theoretical drug content. Accordingly the mean dissolution profile of Aspirin from different particle size ranges of Eudragit RS100 prepared by using the same TDC was used to represent the drug release profile and also to study the effect of increasing TDC. The mean release data showed the closest of the dissolution profiles from different products prepared by using different TDC. Again the independent models were used to prove the similarity of the dissolution profile of Aspirin from different Eudragit RS100 microcapsules prepared on using different TDC. Accordingly it was concluded that the overall Aspirin dissolution profile can be used to represent the drug release profile from different particle size ranges of Eudragit RS100 microcapsules prepared by using the same or different TDC.
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.
2009
Flurbiprofen loaded PCL/PVP blend microspheres were prepared by o/w solvent evaporation method using various concentrations of gelatin as emulsifying agent. Microsphere recovery decreased with a decrease in the concentration of the emulsifier in the dispersion. Encapsulation efficiency and drug loading of microspheres increased with decrease in concentration of emulsifying agent. Hydration rate, encapsulation efficiency and drug loading of microspheres increased with increase in concentration of PVP. Rheological properties showed free flowing nature of microspheres. SEM (Scanning electron microscope) revealed microspheres were discrete, spherical and became porous with decrease in concentration of emulsifying agent but smooth with higher concentration of emulsifying agent. FTIR (Fourier transform infrared spectroscopy) spectra of pure and encapsulated flurbiprofen in all formulation showed no significant difference in characteristic peaks, suggesting stability of flurbiprofen during encapsulation process. X-RD (X-ray powder diffractometry) of pure flurbiprofen shows sharp peaks, which decreases on encapsulation, indicating dispersion at molecular level and hence decrease in the crystallinity of drug in microspheres. Microspheres showed an enteric nature at pH 1.2 and a sustained release pattern at pH 6.8. Rapid drug release was observed in microspheres with higher concentration of PVP (polyvinylpyrrolidone), PVP acts as channeling agent. Formulation with low concentration of emulsifying agent also showed a fast release due to porous structure. Drug release kinetics followed zero order at pH 1.2 while at pH 6.8 Higuchi model was best fitted and was found non fickian.
Tropical Journal of Pharmaceutical Research, 2008
The purpose of the present investigation was to formulate and evaluate microencapsulated glipizide produced by the emulsion -solvent evaporation method, Method: Microspheres were prepared using polymethacrylate polymers (Eudragit ® RS 100 and RL 100) by solvent evaporation method and characterized for their micromeritic properties and drug loading, as well as by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. In vitro release studies were performed in phosphate buffer (pH 7.4). Result: The resulting microspheres obtained by solvent evaporation method were white and free flowing in nature. The mean particle size of microspheres ranged from 420 -660 µm and the encapsulation efficiencies ranged from 40.27 -86.67 %. The encapsulation efficiency was also found to be dependant on nature of polymer used in the formulation. The infrared spectra confirmed the stable character of glipizide in the drug-loaded microspheres. Scanning electron microscopy revealed that the microspheres were spherical in nature. From the in vitro drug dissolution studies it was found that the sustaining effect of microspheres depended on the polymer concentration, amount of dispersant used and the type of polymer used in the formulation. The mechanism of drug release from the microspheres was found to be non-Fickian type. Conclusion: Eudragit ® microspheres containing glipizide could be prepared successfully by using an emulsion solvent evaporation technique using polymethacrylate polymers, which will not only sustain the release of drug but also manage the complicacy of the diabetes in a better manner.