Floating Microspheres Of Ranitidene Hydrochloride Biology Essay


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V. S. Mastiholimath et al (2008) developed In vitro and in vivo evaluation of ranitidine hydrochloride ethyl cellulose floating microparticles. Preparation of microparticles is done by solvent evaporation technique with modification by using an ethanol co-solvent system. The formulated microspheres were free flowing with good packability and encapsulation efficiencies were up to 96%. Scanning electron microscopy confirmed porous, spherical particles in the size range 300-750 mm. Microspheres showed excellent buoyancy and a biphasic controlled release pattern with 12 h. In vivo bioavailability studies performed on rabbits and Tmax, Cmax, AUC were calculated and confirmed significant improvement in bioavailability. The data obtained thus suggests that a microparticulate floating delivery system can be successfully designed to give controlled drug delivery, improved oral bioavailability and many other desirable characteristics.

Ashish Jain et al (2008) prepared and evaluated a floating granular delivery system for the treatment of mucosal ulcer consisting of (i) calcium silicate (CS) as a porous carrier; (ii) ranitidine hydrochloride (RH), an antiulcer agent; and (iii) hydroxypropyl methylcellulose K4M (HPMC) and ethylcellulose (EC) as matrix-forming polymers. The effect of various formulation and process variables on the particle morphology, particle size, micromeritic properties, percent drug content, in vitro floating behavior, and in vitro drug release from the floating granules was studied. Scanning electron microscopy (SEM) of the granules revealed that that more pores of CS in secondary coated granules (SCG) were covered by the polymer solution than those in primary coated granules (PCG). The formulation demonstrated favorable in vitro floating and sustained drug release characteristics. The in vivo evaluation for the determination of pharmacokinetic parameters was performed in albino rats. Higher plasma concentration was maintained throughout the study period from the floating granules of RH. The enhanced bioavailability and elimination half-life observed in the present study may be due to the floating nature of the dosage form and the reduction of the absolute alcohol induced ulcerogenic index from 3.0 to 0.6. The results suggested that CS is a useful carrier for the development of floating and sustained release preparations.

Hui Yun Zhou et al (2006) prepared a noval cellulose acetate/chitosan multimicrospheres (CACM) by the method of w/o/w emulsion. The concentration of cellulose acetate (CA) and the ratio of CA/chitosan (CS) had influence on the CACM size, and appearance. Ranitidine hydrochloride loading and releasing efficiency in vitro were investigated. The optimal condition for preparation of the microspheres was CA concentration at 2% and the ratio of CA/CS at 3/1. The microspheres size was 200-350 μm. The appearance of microspheres was spherical, porous, and nonaggregated. The highest loading efficiency was 21%. The ranitidine release from the CACM was 40% during 48 hr in buffers.

A. Bye et al (1996) investigated the interaction of ranitidine hydrochloride (150mg twice daily for 15 doses) with single doses (0.15, 0.3 and 0.6 g kg-l) of ethanol in a placebo controlled study in 24 male subjects. Ethanol was given 1 h after a standard breakfast to maximize a drug ethanol effect if there is one. A balanced incomplete block design was used in that each subject received two of the three ethanol doses in the presence or absence of ranitidine. Blood samples (n= 18) were taken for 8h after dosing and blood ethanol concentrations (BAC) were determined by head space analysis using a validated gas liquid chromatographic method.

Yu-meng Wei et al (2008) developed the hollow microspheres as a new dosage form of floating drug delivery systems with prolonged stomach retention time. Hollow microspheres containing Ranitidine hydrochloride (RH) were prepared by a novel solvent diffusion-evaporation method using ethyl cellulose (EC) dissolved in a mixture of ethanol and ether (6:1.0, v/v). The yield and drug loading amount of hollow microspheres were 83.21±0.28% and 20.71±0.32%, respectively. The in vitro release profiles showed that the drug release rate decreased with increasing viscosity of EC and the diameter of hollow microspheres, while increased with the increase of RH/EC weight ratio. Hollow microspheres could prolong drug release time (approximately 24 h) and float over the simulate gastric fluid for more than 24 h. Pharmacokinetic analysis showed that the bioavailability from RH-hollow microspheres alone was about 3.0-times that of common RH gelatin capsules, and it was about 2.8-times that of the solid microspheres. These results demonstrated that RH hollow microspheres were capable of sustained delivery of the drug for longer period with increased bioavailability.

Ehab R. Bendas et al (2008) developed leaky enteric-coated pellets formulations that are able to provide sustained input for drugs that have an absorption window, such as ranitidine hydrochloride, without jeopardizing their bioavailability. Leaky enteric coats were formulated using a commonly used enteric polymer, Eudragit L 30 D-55, combined with soluble compounds including lactose, PEG 8000 and surfactants (Span 60 (hydrophobic) or Tween 80 (hydrophilic)). The rate of drug release from the formulations in simulated gastric fluid can be tailored by varying the additive's amount or type. All leaky enteric-coated formulations studied completely released the drugs within 30 min after changing dissolution medium to phosphate buffer, pH 6. Predictions of plasma concentration-time profiles of the model drug ranitidine hydrochloride from leaky enteric-coated pellets in fasted conditions and from immediate-release formulations were performed using computer simulations. Simulation results are consistent with a hypothesis that leaky enteric-coated pellets formulations provide sustained input for drugs shown to have an absorption window without decreasing bioavailability. The sustained input results from the combined effects of the formulation and GI transit effects on pellets.

R Garg et al (2008) investigated the recent literature and current technology used in the development of gastroretentive dosage forms. Controlled release (CR) dosage forms have been extensively used to improve therapy with several important drugs. However, the development processes are faced with several physiological difficulties such as the inability to restrain and localize the system within the desired region of the gastrointestinal tract and the highly variable nature of the gastric emptying process. This variability may lead to unpredictable bioavailability and times to achieve peak plasma levels. On the other hand, incorporation of the drug in a controlled release gastroretentive dosage forms (CR-GRDF) which can remain in the gastric region for several hours would significantly prolong the gastric residence time of drugs and improve bioavailability, reduce drug waste, and enhance the solubility of drugs that are less soluble in high pH environment. Gastroretention would also facilitate local drug delivery to the stomach and proximal small intestine. Thus, gastroretention could help to provide greater availability of new products and consequently improved therapeutic activity and substantial benefits to patients. Controlled gastric retention of solid dosage form may be achieved by the mechanisms of floatation, mucoadhesion, sedimentation, expansion or by a modified shaped system.

Ferreira, M.O et al (2004) investigated the stability of ranitidine hydrochloride in the following solutions ranitidine hydrochloride 25 mg/ml in aqueous solution, stored at room temperature (15- 25°C) for 153 days; ranitidine hydrochloride 25 mg/ml in simple syrup, stored at room temperature for 153 days; ranitidine hydrochloride 25 mg/ml in aqueous solution, stored at +4°C for 139 days; ranitidine hydrochloride 50 mg/ml in aqueous solution, stored at room temperature for 139 days; and ranitidine hydrochloride 25 mg/ml in four buffered aqueous solutions (pH 5.0, 5.5, 6.0 and 6.6), stored at room temperature for 144 days. At different intervals during the storage period, color, clarity and solution pH were examined and ranitidine hydrochloride concentration was tested using a stability-indicating high-performance liquid chromatographic assay.

J M Patil etal (2006) investigated rate controlled drug delivery system overcoming physiological problems, such as short gastric residence time (GRT) and unpredictable gastric emptying times. Prolonged GRT may widen the stomach potential as the drug absorbing organ. Several approaches are currently utilized in GRT, including Floating Drug Delivery System (FDDS), swelling and expanding systems, polymorphic bioadhesive systems, modified shape systems, high density systems and other delayed gastric emptying devices.

J. Varshosaz et al (2007) prepared floating microspheres (FM) of Cinnarizine (CN) by diffusion solvent evaporation technique to increase drug solubility and hence its bioavailability. The effect of process variables such as: Eudragit type, stirring rate and time of stirring after addition of oily phase to the aqueous phase were evaluated on the yield, particle size, loading, release and floating behaviors of microspheres using a factorial design. Release of CN from microspheres was studied in pHs: 1.2 and 7.2 using paddle technique. The samples of dissolution test were analyzed spectrophotometrically at 256.1nm and 256.5nm respectively. particle size of microspheres was studied using microscopic method and their floating behavior was studied in HCl (0.1 N, pH 1.2) medium with Tween 20 (0.5% w/v). Eight formulations were produced by changing 3 variables each at 2 levels: Eudragit S100 (Ps) or a combination of two Eudragits S100:RLPO (1:3) (PSR), stirring rate of 200 (R2) or 300 rpm (R3) and stirring time after addition of oily phase to the aqueous phase 0 (T0) or 1 hr (T1). The average size of microspheres was 300 mm. The highest yield efficiency (94%) was seen in PSRR3T0 formulation and the greatest loading percentage was 8.5% in PSRR2T1 formulation. The microspheres containing just Eudragit S100, didn't show suitable releasing profile during 8 hours in pH 1.2 but those containing combination of Eudragit S100:RL released approximately whole amount of CN during 10 hours (8 hours in pH 1.2 and 2 hours in pH 7.2). The highest floating percentage up to 6 hours was 77.5% in PSR2T1 formulation.

J. H. Lee et al (1999) prepared floating acrylic resin microspheres with an internal hollow structure by a solvent diffusion and evaporation method. The yield of microspheres depended on the diffusion rate of ethanol and/or isopropanol in the organic phase. They were successfully produced when a mixture of ethanol and isopropanol was used instead of ethanol alone. The mixing ratio of components in the organic phase affected the size and the yield of microspheres and the best results were obtained at the volume ratio of ethanol: isopropanol: dichloromethane (8: 2: 5). Direct introduction of the organic phase into the aqueous phase through a glass tube also significantly improved the yield by avoiding the contact of organic phase with the surface of water. The optimum rotation speed and temperature were 250rpm and 258C, respectively. Several different drugs with various physico-chemical properties were used as model drugs for encapsulation and release tests. When a drug had low solubility in dichloromethane and high solubility in both water and a mixture of ethanol/isopropanol, the loading efficiency was the lowest. The release profiles were significantly different depending on the solubility of a drug in the release medium and the physico-chemical properties of an encapsulated drug.

J. H. Lee et al (2001) prepared Eudragit microspheres, to float in the gastrointestinal tract, to prolong a gastrointestinal transit time. To enhance their buoyancy, non-volatile oil was added to the dispersed phase. When an oil component was not miscible with water, over 90%was entrapped within the microspheres and prolonged the floating time of the microspheres. Depending on the solvent ratio, the morphologies of the microspheres were different and the best result was obtained when the ratio of dichloromethane:ethanol:isopropanol was 5:6:4. As the isopropanol portion increased, the time to form microspheres was delayed and the amount of fiber-like substance produced was decreased, due to the slow diffusion rate of the solvent. Compared with microspheres prepared without non-volatile oil, the release rate of the drug from microspheres was faster in all cases tested, except the microspheres containing mineral oil. The solubility of the drug in the non-volatile oil affected the release profiles of the drugs. The non-volatile oil tends to decrease the glass transition temperature of prepared microspheres and change the release profile.

Sunil K. Jain et al (2008) investigated two important approaches utilized to prepare and improve the performance of floating microspheres. A controlled drug delivery system with prolonged residence time in the stomach can be of great practical importance for drugs with an absorption window in the upper small intestine. The main limitations are attributed to the inter- and intra-subject variability of gastro-intestinal (GI) transit time and the non-uniformity of drug absorption throughout the alimentary canal. Floating drug delivery systems (FDDSs) are expected to remain buoyant in a lasting way upon the gastric contents and consequently to enhance the bioavailability of drugs. The various buoyant preparations include hollow microspheres, granules, powders, tablets, capsules, pills and laminated films. Floating microspheres are specially gaining attention due to their wide applicability in the targeting of drugs to stomach. These floating microspheres have the advantage that they remain buoyant and distributed uniformly over the gastric fluid to avoid the vagaries of gastric emptying and release the drug for prolonged period of time. A major drawback of low-density floating drug delivery systems is that their performance is strongly dependent upon the gastric emptying process of stomach. Multiparticulate low-density particles can successfully prolong the gastric retention time of drugs.

Anand Kumar Srivastava et al (2005) prepared microspheres by the solvent evaporation method using polymers hydroxypropylmethyl cellulose and ethyl cellulose and drug Cimetidine. The shape and surface morphology of prepared microspheres were characterized by optical and scanning electron microscopy, respectively. In vitro drug release studies were performed and drug release kinetics was evaluated using the linear regression method. Effects of the stirring rate during preparation, polymer concentration, solvent composition and dissolution medium on the size of microspheres and drug release were also observed. The prepared microspheres exhibited prolonged drug release (8 h) and remained buoyant for > 10 h. The mean particle size increased and the drug release rate decreased at higher polymer concentration. No significant effect of the stirring rate during preparation on drug release was observed. In vitro studies demonstrated diffusion-controlled drug release from the microspheres.

Varaporn Buraphacheep Junyaprasert et al (2008) prepared hollow microspheres loaded with Acyclovir to improve bioavailability and patient compliance by prolonging the residence time in the gastrointestinal tract. The hollow microspheres of acyclovir were prepared by solvent evaporation diffusion method using Eudragit S 100 as a controlled polymer. They found that the process conditions that provided the high % yield of the hollow microspheres were the use of 5:8:2 of dichloromethane: ethanol: isopropanol as a solvent system and stirring at 300 rpm for 60 min. The size of the microspheres prepared from different ratios of acyclovir and Eudragit S 100 was 159-218 μm. When the drug-to-polymer ratio was increased, the size and percent drug content increased. The highest percent drug entrapment was obtained at the ratio of 600 mg acyclovir: 1 g Eudragit S 100. The hollow microspheres tended to float over 0.1 M hydrochloric acid containing 0.02% Tween 20 solution for 24 hr. The rate of acyclovir released from the microspheres was generally low in simulated gastric fluid without enzyme due to the low permeability of the polymer. However, in phosphate buffer pH 6.8, the drug release increased as the drug load increased due to the swelling property of the polymer. In simulated intestinal fluids without enzymes, the polymer completely dissolved resulting in instant release of the drug in this medium.

R. B. Umamaheswari et al (2002) prepared floating microspheres containing the antiurease drug acetohydroxamic acid (AHA) by a novel quasi-emulsion solvent diffusion method. The microballons were characterized for size distribution, morphology, drug content, drug release, and in vitro floating property. The microballons were coated with 2% w/v solution of polycarbophil by the air suspension coating method. The bioadhesive property of the microspheres was investigated by the detachment force measurement method. In vitro growth inhibition studies were performed in isolated H. pylori culture. The results suggest that AHA-loaded floating microspheres are superior as potent urease inhibitors whereas urease plays an important role in the colonization of H. pylori.

Kumaresh S. Soppimath et al (2001) prepared and characterized of the floating microspheres for the peroral route of administration of the drug. Gastric emptying is a complex process, which is highly variable and makes in vivo performance of the drug-delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug delivery systems for more than 12 h. The floating or hydrodynamically controlled drug-delivery systems are useful in such applications. The approaches toward this goal is to develop the floating microspheres so as to increase the gastric retention time. Such systems have more advantages over the single-unit dosage forms. The development of floating microspheres involves different solvent evaporation techniques to create the hollow inner core.

Yogesh S Gattani et al (2008) formulated and evaluated the floating microparticulate oral drug delivery system of Diltiazem Hydrochloride, which can provide a sustain release. Floating microspheres were prepared by non-aqueous emulsification solvent evaporation technique, using ethyl cellulose and eudragit RS-100 as the rate controlling polymer. The in vitro evaluation, drug-polymer compatibility, % yield, particle size analysis, drug entrapment efficiency, in vitro floatability, surface topography and in vitro release were performed.

Pallab Roy et al (2009) prepared a specific technology, based on combining floating and pulsatile principles to develop drug delivery system, intended for chronotherapy in nocturnal acid breakthrough. This approach will be achieved by using a programmed delivery of ranitidine hydrochloride from a floating tablet with time-lagged coating. In this study, investigation of the functionality of the outer polymer coating to predict lag time and drug release was statistically analyzed using the response surface methodology (RSM). RSM was employed for designing of the experiment, generation of mathematical models and optimization study. The chosen independent variables, i.e. percentage weight ratios of ethyl cellulose to hydroxypropyl methyl cellulose in the coating formulation and coating level (% weight gain) were optimized with a 32 full factorial design. Lag time prior to drug release and cumulative percentage drug release in 7 h were selected as responses.

J. A. Raval et al (2007) investigated the effects of formulation and processing parameters on a floating matrix controlled drug delivery system consisting of a poly (styrene-divinyl benzene) copolymer low density powder, a matrix-forming polymer(s), drug, and diluents (optional). The tablets were prepared by the direct compression technique, using hydrophilic matrix polymers HPMC K4M, HPMC K15M, HPMC K100M, sodium alginate, psyllum, sesbania gum, guar gum, and gum acacia, with or without low density copolymer. Tablets were physically characterized and evaluated for in vitro release characteristics for 8 h in 0.1 mol/l HCl at 37°C. The effect of the addition of low density copolymer and the drug release pattern were also studied. The release rate was modified by varying the type of matrix-forming polymer, the tablet geometry (radius), and the addition of water-soluble or water-insoluble diluents. At the same time, different concentrations of low-density copolymer were taken to examine any differences in the floating lag-time of the formulation. The in vitro release mechanism was evaluated by kinetic modeling. The similarity factor, floating lag-time, and t50 and t90 were used as parameters for selection of the best batch.

M. Jamrogiewicz et al (2009) investigated the effects of degradation of ranitidine hydrochloride exposed to UVB radiation (l = 310 nm) and oxygen in a weathering chamber were studied by Fourier Transform Infrared spectroscopy (FTIR) and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). ATR-FTIR profile indicated that the degradation was spatially heterogeneous. Significant amounts of photoproducts were detected only in a directly irradiated layer. Major damage/change was reflected in the appearance of broad, extended group of signals near the wavenumber 3600-3200 cm-1 or/and 3500-3400 cm-1.

Ashish K. Jain et al (2006) prepared and evaluated the floating granular delivery system consisting of (i) calcium silicate (CS) as porous carrier; (ii) ranitidine hydrochloride (RH), an anti-ulcer agent; and (iii) hydroxypropyl methylcellulose K4M (HPMC) and ethylcellulose (EC) as matrix forming polymers. The effect of various formulation and process variables on the particle morphology, particle size, micromeritic properties, percent drug content, in vitro floating behavior, and in vitro drug release from the floating granules was studied. The scanning electron microscopy (SEM) of granules revealed that that more pores of CS in secondary coated granules (SCG) were covered by the polymer film than those in primary coated granules (PCG). The formulation demonstrated favorable in vitro floating and drug release characteristics. The in vivo evaluation for the determination of pharmacokinetic parameters was performed in albino rats. Higher plasma concentration was maintained throughout the study period from the floating granules of RH. The enhanced bioavailability and elimination half-life observed in the present study may be due to the floating nature of the dosage form. The results suggested that CS is a useful carrier for the development of floating and sustained release preparations.

Shweta Arora et al (2004) investigated floating drug delivery systems (FDDS) to compile the recent literature with special focus on the principal mechanism of floatation to achieve gastric retention. The recent developments of FDDS including the physiological and formulation variables affecting gastric retention, approaches to design single-unit and multiple-unit floating systems, and their classification and formulation aspects are covered in detail. This review also summarizes the in vitro techniques, in vivo studies to evaluate the performance and application of floating systems, and applications of these systems. These systems are useful to several problems encountered during the development of a pharmaceutical dosage form.

R. B. Umamaheswari et al (2003) prepared cellulose acetatebutyrate (CAB)-coated cholestyramin 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 rhodamineisothiocyanate (RITC) by fluorescent probe method.

Yasunori Sato et al (2003) prepared hollow microspheres (microballoons) floatable on JPXIII No.1 solution were developed as a dosage form capable of floating in the stomach. Hollow microspheres were prepared by the emulsion solvent diffusion method using enteric acrylic polymers with drug in a mixture of dichloromethane and ethanol. It was found that preparation temperature determined the formation of cavity inside the microsphere and the surface smoothness, determining the floatability and the drug release rate of the microballoon. The correlation between the buoyancy of microballoons and their physical properties, e.g. apparent density and roundness of microballoons were elucidated. The drug loading efficiency of microballoons with various types of drug was investigated and correlated to the distribution coefficient of drug between dichloromethane and water. The optimum loading amount of riboflavin in the microballoon was found to impart ideal floatable properties to the microballoons. On the other hand, little entrapment was observed for aspirin due to the low distribution coefficient; however, entrapment improved to some extent upon reduction of the pH of the process.

Sunil K. Jain et al (2006) prepared floating microspheres consisting of (1) calcium silicate as porous carrier; (2) orlistat, an oral anti-obesity agent; and (3) Eudragit S as polymer, by solvent evaporation method and to evaluate their gastro-retentive and controlled-release properties. The effect of various formulation and process variables on the particle morphology, micromeritic properties, in vitro floating behavior, percentage drug entrapment, and in vitro drug release was studied. The gamma scintigraphy of the optimized formulation was performed in albino rabbits to monitor the transit of floating microspheres in the gastrointestinal tract. The orlistat-loaded optimized formulation was orally administered to albino rabbits, and blood samples collected were used to determine pharmacokinetic parameters of orlistat from floating microspheres. The microspheres were found to be regular in shape and highly porous. Microsphere formulation CS4, containing 200mg calcium silicate, showed the best floating ability (88% ± 4% buoyancy) in simulated gastric fluid as compared with other formulations. Release pattern of orlistat in simulated gastric fluid from all floating microspheres followed Higuchi matrix model and Peppas-Korsmeyer model.

N.J. Joseph et al (2002) prepared floating type dosage form (FDF) of piroxicam in hollow polycarbonate (PC) microspheres capable of floating on simulated gastric and intestinal fluids was prepared by a solvent evaporation technique. Incorporation efficiencies of over 95% were achieved for the encapsulation. In vitro release of piroxicam from PC microspheres into simulated gastric fluid at 378C showed no significant burst effect. The amount released increased with time for about 8 h after which very little was found to be released up to 24 h. In intestinal fluid, the release was faster and continuous and at high drug payloads, the cumulative release reached above 90% in about 8 h.

Hetal Paresh Thakkar et al (2008) investigated the characteristics of microspheres of chitosan prepared using two different cross linking agent namely, formaldehyde and glutraldehyde and by simple heat treatment. Chitosan microspheres were prepared by emulsification cross linking method. Microspheres were characterized for entrapment efficiency, particle size, in vitro drug release and surface morphology were studied by scanning electron microscopy.

V G Somani et al (2009) developed hollow calcium pectinate beads for floating pulsatile release of aceclofenac intended for chronopharmacotherapy. Floating pulsatile concept was applied to increase the gastric residence of the dosage form having lag phase followed by a burst release. The method used for the development of the beads was a simple process of acid-base reaction during ionotropic cross linking. The floating beads obtained were porous, hollow with a bulk density < 1 and had Ft50 of 14-24 h. The floating beads showed a two-phase release pattern with initial lag phase during floating in an acidic medium followed by rapid pulse in phosphate buffer.

Abhishek Kumar Jain et al (2009) prepared and evaluated floating microspheres using famotidine (FM) as a model drug for prolongation of the gastric retention time. The microspheres were prepared by the solvent evaporation method using different polymers, i.e. acrycoat S100 and cellulose acetate. The size or average diameter (d) and surface morphology of the prepared microspheres were recognized and characterized by the optical and scanning electron microscopic methods respectively.

R. D. Kale et al (2007) prepared floating drug delivery system piroxicam in the form of microspheres using enteric polymer and emulsification solvent evaporation technique. The microspheres remained buoyant continuously over the surface of acidic media containing surfactant for the period of 8-12 hrs in vitro. DSC and XRD studies showed that drug incorporated in the outer shell of polymer was completely amorphous. SEM indicated that the microsphere is perfect sphere with an internal hollow cavity enclosed by a rigid shell of poymer.

S. Thamizarasi et al (2008) prepared pentoxifylline loaded microspheres by solvent evaporation technique with different drug to carrier ratio. The microspheres were characterized for practical size, SEM, FT-IR study, percentage yield, drug entrapment, stability studies and in vitro drug release. The shape of microspheres were found to be spherical by SEM.

Jain AK et al (2009) prepared and evaluated buoyant microspheres using famotidine as a model drug. The microspheres were prepared by solvent evaporation method using different polymers i.e., acrycoat S 100 and cellulose acetate. The size or average diameter characterized by optical microscopy method and surface morphology was recognized by SEM.

Thamizarasi S. et al (2009) prepared and evaluated poly(É›-caprolactone) microspheres of repaglinide by using solvent evaporation technique with different drug to carrier ratio. The microspheres were characterized for practical size, SEM, FT-IR study, percentage yield, drug entrapment, stability studies and in vitro drug release. The shape of microspheres were found to be spherical by SEM.

J. A. Raval et al (2007) prepared Ranitidine hydrochloride floating matrix tablets based on low density powder: effects of formulation and processing parameters on drug release. The absorbance of Ranitidine hydrochloride solutions was measured at 315 nm using a Shimadzu UV-1601 UV/Vis double beam spectrophotometer.

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