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Rajeev Garg and GD Gupta et.al., (2010) 23 The floating microspheres of silymarin were prepared and evaluated for prolonged gastric residence time and increased drug bioavailability. Cellulose microsphere were formulated with hydroxylpropyl methylcellulose , ethylcellulose and Eudragit microspheres were formulated with Eudragit® S 100 and Eudragit® RL. The microspheres were prepared by emulsion-solvent evaporation method. The microspheres were evaluated for flow properties (angle of repose and compressibility index) and for various other physicochemical properties including particle size, incorporation efficiency, in vitro floatability and in vitro drug release. The shape and surface morphology of the microspheres were characterised by optical and scanning electron microscopy. The microspheres exhibited extended drug release for 12 h while still remained in buoyant condition. The floating microspheres of silymarin were developed and exhibited to prolonged drug release in simulated gastric fluid for at least 12 h, and, to improve the bioavailability of the drug potentially.
Yuveraj Singh Tanwar et.al.,(2007) 24 The floating microspheres of verapamil hydrochloride were prepared and evaluated for improving the drug bioavailability by prolongation of gastric residence time. Cellulose acetate, acrycoat S100 and eudragit S100 microspheres loaded with verapamil hydrochloride were prepared by solvent diffusion evaporation method. The microspheres had smooth surfaces, with free-flowing characteristic and cellulose acetate microspheres showed higher entrapement efficiency of the drug. Scanning electron microscopy confirmed that hollow structures were in the size range between 251.80 to 350.75 μm. The prepared microspheres were exhibited to prolonged drug release and remained buoyant for more than 12 h.
K.Punitha et.al., (2010) 25 The floating microspheres of Ranitidine Hydrochloride were prepared with HPMC 15 cps and Eudragit E-100. The microspheres were evaluated for FTIR, drug loading, entrapment, particle size, SEM, buoyancy, dissolution study, and the drug release kinetics .Ranitidine Hydrochloride posses that with both acrylic and hydrophilic polymers the GI retention can be enhanced and the frequency of administration can be decreased.
Anand kumar srivastava et.al.,(2005) 26 The floating microspheres of cimetidine. were prepared by solvent evaporation method using hydroxyl propyl methyl cellulose and ethyl cellulose. The shape and surface morphology of prepared microspheres were characterized by optical and scanning electron microscopy. In vitro drug release studies were performed and drug release kinetics was evaluated. Effects of the stirring rate, polymer concentration, solvent composition , and the size of microspheres drug release were also observed. The prepared microspheres were exhibited to prolonged drug release (~8 h) and remained buoyant for more than 10 h.
Shashikant D. Barhate et.al.,(2009) 27 were aimed to study the multiparticulate gastro retentive drug delivery system of ketorolac trometamol.. The floating microspheres of ketorolac trometamol was prepared by emulsion solvent diffusion method by using ethyl cellulose, HPMC K4M, Eudragit R 100, Eudragit S 100 polymers in different concentration and were evaluated for percent yield, particle size, entrapment efficiency, in vitro buoyancy and in vitro release studies. The particle size of the formulated microspheres was ranged from 23.551±13.059 μm to 37.107 ± 16.512 μm. The formulated microspheres showed average percentage buoyancy more than 52 %.
Moreshwar P. Patil et.al.,(2009) 28 The floating microspheres of acyclovir were prepared by using different viscositiy grades of ethyl cellulose to achieve an extended retention in upper GIT. The floating microspheres were prepared by emulsion solvent diffusion technique by using triethyl citrate as a plasticizer. The prepared microspheres were evaluated for particle size analysis, drug entrapment, floating ability, in-vitro drug release and characterized by scanning electron microscopy and x-ray diffractometry. The particle size of all formulations was found in the range of 135.103 - 229.418 μm. The drug entrapment efficiency was in the range of 63 % - 84 % w/w. The in-vitro release study indicated that when the polymer concentration was increased and the drug loading was decreased, the release of drug from microspheres was decreased
Rajeev Garg et.al(2009) 29 prepared and evaluated floating microspheres with Ketoprofen as for prolongation of gastric residence time. The microspheres were prepared by the solvent evaporation method using polymers hydroxy propylmethyl cellulose and ethyl cellulose. The prepared floating microspheres were evaluated for flow properties, compressibility index and various physicochemical parameters including particle size, percentage yield, entrapment efficiency, in vitro floating behavior, in vitro drug release studies.The mean particle size increased with increasing ethyl cellulose concentration. The prepared microspheres exhibited prolonged drug release of 12 h and remained buoyant.
M. Najmuddin et.al.,(2010) 30 prepared floating microspheres of ketoprofen using different polymers Eudragit S 100 and Eudragit L 100. Ketoprofen elimination half
life 1â€3 hours. Floating microspheres of ketoprofen were prepared by emulsion solvent diffusion method. The floating microspheres was evaluated such as micromeritic properties, particle size, percentage yield, in vitro buoyancy, incorporation efficiency, drug polymer compatibility (IR study ), scanning electron microscopy and drug release kinetics.Eudragit S 100 drug:polymer ratio (1:2) which exhibited brilliant micromeritic properties, percentage yield, in vitro buoyancy, incorporation efficiency and percentage drug release 92.26 % for a period of 12 hrs.
Ambati Brahma Reddy, K Sudheer Karna et.al.,(2010) 31 developed floating microspheres of Cyclobenzaprine HCl by emulsion solvent diffusion technique using Ethyl cellulose polymer to achieve an extended retention in upper part of GIT and there by improved bioavailability. The microspheres were evaluated for particle size analysis, drug entrapment efficiency, buoyancy studies, polymer compatibility study, In-vitro release studies and surface morpholog by Scanning electron microscopy (SEM) and X- ray diffractometry. The Microspheres with Ethyl Cellulose have an average size range of 199.86 ± 07.67 to 387.58 ± 05.99 µm. The entrapment efficiency was found to be in the range of 72.75 to 84.1%. The In-vitro release studies of the drug from the best formulation exhibited a sustained release of 72.60 % as studied over 24hrs. Release was best explained by zero-order kinetics model and it shows that the drug release follows diffusion mechanism.
B.Arul.et.al., (2003) 32 Prepared loaded chitosan microspheres by
glutaraldehyde cross linking method. The microspheres were spherical in shape and having a good entrapment efficiency of 60%. Stablity studies done at a different temperatures showed that all the formulations were more stable at 4οC, and roomtemperature.
Ashish jain et.al., (2009) 33 investigated the in-vitro release properties of Lisinopril from different vehicles: (i) an oil-in-water cream; (ii) a gel: and (iii) an ointment. In-vitro release of Lisinopril from the three bases to an aqueous receptor phase through the pig skin was monitered spectrometrically at a wavelength of 258 nm. In-vitro release study showed that the steady state fluxes of the drug from vehicles rank according to the following order: ointment > cream > gel.
A.R.Shabaraya and R.Narayanacharya. et.al., (2003). 34 Reported that a study has been carried out on the design and evaluation of chitosan microspheres of Metoprolol Tartarate for sustaied release. Metoprolol was encapsulated with chitosan by phase separation emulsification technique. The microspheres obtained were spherical, free flowing and showed an in vitro drug release over a peroid of 10 hrs.
J.Akbuga and N.Bergisadi .et.al., (1998) 35 investigated the effect of formulation variables on cis-platin loaded chitosan microsphere properties. Chitosan microspheres were prepared using w/o emulsion system. Microsphere properties were investigated ,these include; chitosan, cis-platin and glutaraldehyde concentrations, the types of chitosan and oil, the cross-linking process and stirring rate. Incorporation efficiency was high and ranged from 28-99%. The type and concentration of chitosan affected cis-platin release from microspheres.
E.B.Denkbas. et.al., (1998), 36 developed 5-Fluorouracil loaded chitosan microspheres for chemoembolization. Chitosan microspheres were prepared by a suspension cross-linking technique. Petroleum ether:mineral oil mixture was used as the suspension medium which includes an emulsifier tween80. Glutaraldehyde was used as the cross-linking agent. The size distribution of the chitosan microspheres varied in the range of 100 ± 200µm. The variation like changing the emulsifier concentration, stirring rate, polymer:solvent ratio and drug:chitosan ratio were studied. The size of the microspheres found to be increased in emulsifier concentration and stirring rate.
Jitendra banweer.et.al., (2008) 37 investigated the formulation, optimization and evaluation of matrix type transdermal system of lisinopril dihydrate using permeation enhancers. The patches were prepared by employing hydroxy propyl methyl cellulose and poly vinyl acetate in the ratio of 1:1 as polymer matrix using glycerol as plasticizer in 6% concentration. Solvent system (water:methanol) in the ratio of 70:30 was taken for the study. The transdermal devices were fabricated using solvent casting technique. Oleic acid and isopropyl alcohol were used as the permeation enhancers. In vitro diffusion rate studies were performed using Keshary-Chein diffusion cell on goat skin. The patch containing oleic acid and isopropyl alcohol in the ratio of 50:50, at 15% shows best promising in vitro drug flux and posses excellent physico-chemical properties at normal and accelerated temperature conditions.
Aceves-Hernandez.et.al., (2007) 38 investigated the degradation of lisinopril: A physico-chemical study. Thermo gravimetric analyses indicating weight losses were observed when this powder was heated up to the fusion temperatures. Differential scanning colorimetry was applied, endothermic transitions were found at 88.8,110.4 and 179.4οC. The analysis of the X-ray diffraction pattern obtained at room temperature showed that the unit cell of the lisinopril crystal correspond to monoclinic system with β angle (β=99.39ο); where as the diffraction pattern obtained at 125οC indicated that the unit cell of the lisinopril crystal corresponds to the monoclinic system with different β angle (β=105.16ο)
N.Mani . et.al., (2005). 39 Reported that a study has been carried out on the in vitro evaluation of floating and drug releasing behaviors of hollow microspheres prepared by the emulsion solvent diffusion method. The loading efficiency affect because of type of the dispersant, the amount of wetting agent, and initial stirring time. While the volume of external phase and emulsification speed affected the particle size of the microspheres to a greater extent.
Y.Sato .et.al.,(2003). 40 Investigated the in vitro evaluation of floating and drug releasing behaviours of hollow microspheres prepared by the emulsion solvent diffusion method. Microballoons were prepared by utilizing enteric acrylic polymers co-dissolved with drug in a mixture of ethanol and dichloromethane. The profiles of five different drugs exhibiting distinct water solublities (aspirin, salicylic acid, ethoxybenzamide, indomethacin and riboflavin) were investigated. The drug release profiles of aspirin, salicylic acid and ethoxybenzamide microballoons proved a linear relationships by Higuchi plotting.
Tamilvanan et.al., (2000) 41 prepared Ibuprofen-loaded polystyrene microparticles by the emulsion solvent evaporation process from an aqueous system. The drug content in all the formulations was less than the theoretical drug loading. The lower drug content was due to partitioning to the external aqueous phase during formulation. The effect of size of the microparticles in drug release was more important for the low drug-loaded microparticles than that for the high drug-loaded microparticles.
M.K. Deepaa,, M. Karthikeyan et.al., (2009) 42 investigated Cefpodoxime Proxetil Floating Microspheres Formulation and In Vitro Evaluation. They were developed floating microspheres of cefpodoxime proxetil in order to achieve an extended retention in the upper GIT, which may result in enhanced absorption and thereby improved bioavailability. The microspheres were prepared by non-aqueous solvent evaporation method using polymers such as hydroxyl propyl methyl cellulose, ethyl cellulose in different ratios and cefpodoxime proxetil in each formulation. The percentage yield, particle size, Buoyancy percentage, drug entrapment efficiency, and in vitro drug release were studied. The result showed that microspheres yielded 50.5-72.2%. The particle size was distributed between75-600 μm, drug entrapment efficiency was 14.1- 28.2%, and Buoyancy percentage was 70.1-88.3%. The best drug release profiles were seen with formulation 2 at the ratio of drug to polymer of 1:2.