Mechanism Of Floatation To Achieve Gastric Retention Biology Essay

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Swapnila D.Vansh iv et al. (2009). Gastric emptying of dosage forms, which are having an ability to prolong and control the emptying time, is a valuable asset, which resides in stomach for longer durations of time than the conventional dosage forms. Many difficulties like the inability to confine the dosage form in desired area of the gastrointestinal tract are faced by designing controlled release systems for the better absorption and enhanced bioavailability. Gastrointestinal drug absorption is a complex procedure and the drug absorption extend is related to the contact time with small intestinal mucosa. Thus, for drugs that are incompletely absorbed, small intestinal transit time is an important parameter. Basic human physiology, with the details of motility patterns, gastric emptying and formulation variables affecting the cosmic emptying are summarized. Prolonged gastric retention improves bioavailability and solubility and decreases drug waste for drugs that are less soluble in a high pH environment. Applications are also present for targeted drug delivery to the stomach and proximal small intestines. Gastro retention helps by providing better availability of new products and substantial benefits for patients with modern therapeutic possibilities.

Shweta Arora, (2005): The purpose of this review study on floating drug delivery systems (FDDS) was to compile the recent literature with special focus on the mechanism of floatation to achieve gastric retention. The recent developments including the formulation variables affecting gastric retention, approaches to design single-unit and multiple-unit floating systems, and their classification and formulation aspects are explained in detail. This review summarizes the in vitro and in vivo studies to evaluate the performance and application of floating systems, and applications of these systems. These FDD systems are useful to several problems encountered during the development of a pharmaceutical dosage form.

Ramesh. R. Putheti, (2009). Studied on floating drug delivery systems and their mechanism for gastric retention. It also discussed various parameters which affect the floating behaviour in oral dosage forms. The invitro and invivo studies are evaluated the applications of the floating systems. From the formulation and technology point of view, the floating drug delivery systems are considerably logical and easy approach. In this review an attempt has been made to introduce the scientists to the current technological developments in floating drug delivery system.

Rajeev Garg, (2009). Studied the preparation and evaluation of floating microspheres of silymarin for prolonged gastric residence time and increased drug bioavailability. In this study cellulose microspheres and Eudragit microspheres were prepared by emulsion-solvent evaporation method. The Cellulose microspheres were formulated by using hydroxypropyl methyl cellulose, ethyl cellulose and Eudragit microspheres were formulated with Eudragit® S 100 (ES) and Eudragit® RL (ERL). The prepared floating microspheres were evaluated for their flow properties based on parameters such as compressibility index and angle of repose, as well as for various other physicochemical properties including incorporation efficiency, particle size, in vitro floatability, and in vitro drug release. The shape and surface morphology of these microspheres were characterised by optical and scanning electron microscopy (SEM). Mean particle size increased and drug release rate decreased with increasing ethyl cellulose and ES contents of cellulose and Eudragit microspheres, respectively. SEM showed pores on the surface and interior of the microspheres. The microspheres showed a prolonged drug release for 12 h while still remained buoyant. The drug release kinetics is evaluated by using the linear regression method, followed Higuchi kinetics and the drug release mechanism was of the non-Fickian type. The prolonged drug release in simulated gastric fluid by the developed floating microspheres of silymarin, improves the bioavailability of the drug as well as patient compliance.

Ali, J., Hasan, (2006). The study developed a delivery system where the ofloxacin retension could be achieved for increased local action in gastric region against the infection of Helicobacter pylori. The optimization of the formulation was based on the in vitro buoyancy and also in vitro release in citrate phosphate buffer (pH 3). The preparation of hydrodynamically balanced capsules is by physical mixing of various grades of hydroxyl propyl methyl cellulose (HPMC) and polyethylene oxide (PEO) only as well as in various combinations. Cellulose acetate pthalate, ethyl cellulose, liquid paraffin and were used as release modifiers to maintain release of drug over a period of 12 hour. The best in vitro percentage release is given by the capsules formed with PEOWSR 60K and drugs coated in 2.5% ethyl cellulose and were taken as the optimized formulations. The technique followed for formulating these floating microspheres was solvent diffusion technique, by using different grades of Eudragit and PEO during the preparation of multiple unit system. The use of 2 different solvents (ethanol and dichloromethane) which differed in the rate of diffusion led to the formation of a hollow core in the microspheres, which was partially responsible for their flotation ability. The in vitro release of the floating capsules and microspheres were found to be 95.83% and 96.02% in 12 hour, respectively. The Higuchi models for release from formulations were followed by both these dosages. By keeping the in vitro release data of a single unit dosage form into zero-order, first-order, and Higuchi model, it is concluded that the release followed Higuchi model as the correlation coefficient (R2 value) was greater than those in the other two release models. In both cases of single and multiple unit dosage form, the R2 values for the Higuchi model was found to be good, showing that drug release follows non-Fickian diffusion mechanism.

SolmazAsnaashari, (2010).‌ In this study, metronidazole was used for preparing floating dosage forms which are designed to retain in the stomach for a long periods of time and have developed as a drug delivery system for the better eradication of Helicobacter Pylori in peptic ulcer diseases. Various formulations were designed using multi-factorial design for formulation optimization. HPMC, carbopol and psyllium in different concentrations were used as floating agents and sodium bicarbonate was added as a gas-forming agent. Hardness, drug loading, friability, floating ability and release profiles as well as release kinetics were assessed. Formulations containing HPMC as filler shown prolonged lag times for buoyancy. Adding psyllium to these formulations reduces the relative lag times. Most of the selected formulations were able to float continuously and showed buoyancy for at least 8h. Meanwhile, sustained drug release was also obtained. The kinetic studies among the 10 assessed models, release pattern of metronidazole from the tablets fitted best to Weibull, Power law and Higuchi models in respect overall to mean the percentage error values of 4.73, 3.8 and 5.77, respectively, for calcium carbonate-based tablets and 6.39, 2.95 and 3.9, respectively, for calcium silicate-based tablets. These systems can float in the gastric condition and controls the drug release from the tablets.

ASHA PATEL, (2006). The floating microspheres of metformin hydrochloride has been prepared in this study by non-aqueous emulsification solvent evaporation technique in which ethyl cellulose is the rate controlling polymer.The advantage of this preparation includes short time processing, high encapsulation efficiencies and lack of exposure of ingredients to high temperature. The formulation obtains the prolonged and uniform release in the stomach. The formulation is evaluated for optimization of floatation, prediction of release and drug release pattern to match target release profile. The in vitro performance was evaluated by tests like drug polymer compatibility (FTIR scan), particle size analysis, yield (%), surface topography, drug entrapment efficiency and in vitro floatation and release studies. The results showed that the various mixing ratios of components in the organic phase affected the size, size distribution (250-1000 μm), yield (58 - 87%), drug content (61 - 134% of theoretical load), and drug release of microspheres (47 - 87% after 8 h), floating time (> 8 hr). The best results were obtained with the ratio of drug: polymer: solvent (250:750:12 and 250:146.45:9 [mg: mg: ml]), when both batches were mixed in equal proportions. In most formulations good in vitro floating behaviour was observed and a wide variety of drug release pattern could be achieved by variation of the polymer and solvent ratio. The developed microspheres of metformin hydrochloride may be used in clinic for the prolonged drug release in stomach for at least 8 hrs and thereby improving the bioavailability and patient compliance.

K. R. Vinod, (2010). This study achieved a prolonged and a predictable drug delivery profile in the GIT to control the gastric residence time (GRT) using gastroretentive dosage forms. In this study the floating microspheres of lansoprazole were prepared and sustain the drug release for a longer time to overcome the short half life of the drug. Floating microspheres of four different ratios of polymer and drug were prepared by modified nonaqueous solvent evaporation method and in vitro evaluations were performed. Under CO2 gas the drug polymer dispersions were pressurized, which upon release of the pressure cavities formed the polymeric surface helps the microspheres to remain buoyant for prolonged time. Drug: polymer of 1:4 ratio showed the %buoyancy of 98.4%. The results showed that, as the polymer concentration increases the buoyancy of microspheres also extended proportionally. SEM studies of prepared microspheres showed good topology and the size was 280 μ. The cumulative percentage drug release in simulated gastric fluid after 10 h was 82.0%-94.80%. Model fitting analysis results revealed the release pattern was following Higuchi model for all formulations by obtaining the maximum R2 value.

Shashikant D. Barhate1, (2005). The study was conducted to develop multiparticulate gastroretentive drug delivery system of ketorolac trometamol for improving absorption and bioavailability by retaining in the stomach for longer periods of time. The floating microspheres of ketorolac trometamol were prepared by emulsion solvent diffusion method in varying concentrations of ethyl cellulose, HPMC K4M, Eudragit S 100, Eudragit R 100 polymers. The prepared microspheres were evaluated for particle size, entrapment efficiency, percent yield, in vitro buoyancy and release studies. The formulations show good buoyancy and controlled release of drug.

M. NAJMUDDIN, (2010). In this study the floating microspheres of ketoprofen using Eudragit L 100 and Eudragit S 100 as polymer were prepared. Floating drug delivery system have a density less than gastric fluids and so remains floating in the stomach for a prolonged period of time without affecting gastric emptying rate. Ketoprofen is NSAID with short elimination half life 1‐3 hours. The short half life and multiple administration dose makes ketoprofen a very good drug for formulation of floating drug delivery system. The floating microspheres of ketoprofen were prepared by emulsion solvent diffusion method. The floating microspheres was evaluated for micromeritic properties, particle size, percentage yield, incorporation efficiency, in vitro buoyancy, scanning electron microscopy, drug polymer compatibility (IR study ) and drug release of microspheres. The micromeritic properties results showed that it was good and scanning electron microscopy confirmed their smooth surface with hollow structure. Formulation prepared with Eudragit S 100, drug : polymer ratio (1:2), exhibited excellent micromeritic properties, in vitro buoyancy, percentage yield, incorporation efficiency and percentage drug release of 92.26 % for a period of 12 hrs. Results show that the increase in drug:polymer ratio affects the particle size, in vitro buoyancy , percentage yield and drug release of microspheres. The results suggested that, floating microspheres of ketoprofen are sustained drug delivery which can reduce the dosing frequency.

ANAND KUMAR SRIVASTAVA, (2005). The study involves preparation and evaluation of cimetidine floating microspheres for prolongation of gastric residence time. The method involves the solvent evaporation technique using s hydroxyl propylmethyl cellulose and ethyl cellulose polymers. The shape and surface morphology of prepared cimetidine microspheres were characterized by the optical and scanning electron microscopy. The in vitro release studies were performed, the release kinetics was evaluated by using linear regression method. The effects of the stirring rate during preparation, polymer concentration solvent composition and dissolution medium on size of the microspheres and drug release were also observed. The prepared microspheres showed prolonged state of drug release (> 8 h) and they remained buoyant for > 10 h. With higher the polymer concentration, mean particle size increased and lower drug release rate. No significant effect of stirring rate during formation on drug release was observed. In vitro studies results showed the diffusion- controlled drug release from the microspheres.

VENKATESWARAMURTHY, (2010). studied the preparation and evaluation of Clarithromycin Mucoadhesive Microspheres by emulsion Solvent Evaporation method. The prepared microspheres were evaluated with particle size, production yield, mucoadhesive property, encapsulation efficiency, shape and surface properties, in vitro drug release and suitability for anti Helicobactor pylori effect respectively. The solvent system was acetone/liquid paraffin, Eudragit RL 100 was used to form a matrix of microspheres and mucoadhesive polymer is Carbopol 974P. Eudragit RL 100 was dissolved in acetone and weighed quantity of Clarithromycin, Carbopol 974P were dispersed it. This homogeneous dispersion was cooled to 5°C and poured slowly with stirring (700 rpm) into 80 ml of liquid paraffin containing 1% w/v span 80, which was previously also cooled to 5°C. The obtained emulsion was stirred at 40°C for 40 min. The suspension of microspheres in liquid paraffin was filtered and microspheres were washed by n‐hexane and dried. The microspheres were well‐rounded spheres with the size ranging 155 to 306 μm and having good bioadhesive property ranging from 83±0.153% to 95±1.644%. The effect of Eudragit RL100 concentration on Clarithromycin release from were observed a significant decrease in the rate and extent of drug release was observed with the increase in polymer concentration in microspheres and could be attributed to increase in the density of the polymer matrix and also increase in the diffusional path length which the drug molecules have to traverse. Similarly, the effect carbopol 974p concentration on release properties of Clarithromycin was also studied. An increase in carbopol 974p concentration caused retardation in drug release from the microspheres because of an increase in the viscosity of polymer solution and formation larger size microspheres. The bioadhesive properties enable the microspheres to adhere to the gastric mucosal surface and stay in stomach for prolonged periods and could ensure the stability of Clarithromycin in gastric environment, which eventually resulted in better eradication of H. pylori than the conventional dosage forms.

Jayvadan K. Patel, (2007). Studied the formulation and evaluation of in vitro and in vivo actions of amoxicillin mucoadhesive microspheres for the treatment of gastric and duodenal and ulcers, which were involved with the Helicobacter pylori. These microspheres were formed by simple emulsification phase separation technique, where chitosan was used as mucoadhesive polymer and glutaraldehyde as a cross-linking agent. Preliminary Results indicate that the volume of cross-linking agent, time for cross-linking, polymer: drug ratio and the speed of rotation affects the characteristics of microspheres. Prepared microspheres were discrete, spherical, free flowing and also show high percentage of drug entrapment efficiency. The in vitro mucoadhesive test showed that mucoadhesive microspheres of amoxicillin adhered more strongly to the gastric mucous layer and retain in gastrointestinal tract for increased duration of time. The best batch exhibited the high drug entrapment efficiency of 70 % and swelling index of 1.39 and percentage mucoadhesion after 1 hour was 79 %. The drug release was maintained for more than 12 hour. The polymer:drug ratio had greater significant effect on the dependent variables. The scanning electron micrcopy was used to study morphological characteristics of mucoadhesive microspheres . In vitro release test showed that amoxicillin released slightly faster in pH 1.0 hydrochloric acid than in the pH 7.8 phosphate buffer. In vivo H. pylori clearance tests were also conducted by inducing amoxicillin mucoadhesive microspheres and powder to the infectious H. pylori Wistar rats under fed conditions, in oral administration. The results showed that microspheres had a better clearance effect than amoxicillin powder. The study concluded that prolonged gastrointestinal residence time and improved stability of amoxicillin resulting from the mucoadhesive microspheres of amoxicillin may make contribution for complete eradication of H. pylori.

A. Jayakrishnan, (2001). A floating dosage form (FDF) of piroxicam in hollow polycarbonate microspheres. It is capable of floating on simulated gastric and intestinal fluids prepared by a method of solvent evaporation technique. Entrapment efficiencies of over 95% were achieved for encapsulation. In vitro release of piroxicam from polycarbonate microspheres into the simulated gastric fluid at 370C shows no significant burst effect. The released amount increases with time for about 8 hour after which only little was found to be released up to 24 hour. The intestinal fluid showed faster release at high drug payloads, the cumulative release reached above 90% in about 8 hour. The In vivo evaluation of different dosage forms of piroxicam such as free drug, drug-encapsulated microspheres and microspheres along with the loading dose of free drug among rabbits shows multiple peaking in the plasma concentration-time curve suggests the enterohepatic recirculation of drug. The elimination half life was increased by 3 times for the microsphere preparation alone and nearly 6 times for the dosage form comprising of microspheres, and a loading dose in comparison to the free drug. The data obtained in this study showed that FDF of piroxicam in polycarbonate microspheres was capable of sustained delivery of drugs for longer duration with the increased bioavailability.

Ajit P. Rokhade, (2007). Studied the preparation of hollow microspheres of cellulose acetate butyrate (CAB) and poly(ethylene oxide) (PEO) by emulsion solvent evaporation method. Repaglinide was successfully encapsulated into the floating microspheres. Various formulations were prepared by different ratio of CAB and PEO, drug loading and the concentration of poly (vinyl alcohol) (PVA) solution. Encapsulation of drug up to 95% was achieved. The prepared microspheres tend to float over the simulated gastric fluid for more than 10 h. Micromeritic properties of microspheres revealed the excellent flow and good packing properties. The percentage buoyancy of microspheres was found to be up to 87%. SEM showed that the microspheres have many pores on their surfaces and particle size ranges from 159 to 601 mm. In vitro release studies were performed in simulated gastric fluid and indicated the dependence of release rate on extent of drug loading and amount of PEO in the microspheres, slow release was extended up to 12 h. The release data of preparation were fitted to an empirical equation to compute the diffusional exponent, which indicates that the release mechanism follow the non-Fickian trend.

Paruvathanahalli Siddalingam RAJINIKANTH et. al, (2008). This study developed a stomach-specific drug delivery system, to control release of

clarithromycin for eradication of Helicobacter pylori (H. pylori). Floating-bioadhesive microspheres of clarithromycin (FBMC) were prepared by emulsification solvent evaporation method. They used Carbopol 934P as mucoadhesive polymer and ethylcellulose as matrix polymer. The microspheres were subjected to evaluation for their particle size, incorporation efficiency,in vitro buoyancy, in vitro mucoadhesion and in vitro drug release studies. The formed microspheres showed good buoyancy and a strong mucoadhesive property. The formulation parameters like polymer concentration and drug concentration influenced in vitro drug release significantly in the simulated gastric fluid (pH. 2.0). The prepared microsphere shows a significant anti-H. Pylori effect in in vivo gerbil model. It was also noted that, the eradication of H. Pylor, required decreased amount of clarithromycin in FBMC than from the corresponding clarithromycin suspension. The results further suggested that FBMC improved the gastric stability of clarithromycin due to the entrapment and helps in eradicating H. pylori from gastrointestinal tract more effectively than clarithromycin suspension because of prolonged duration of gastrointestinal residence time of formulation.

Jianhua Zheng, (2006). Studied the development of gastric floating-bioadhesive drug delivery system to increase efficacy of the clarithromycin against Helicobacter pylori. This clarithromycin Floating bioadhesive microparticles were prepared by a combined method of the emulsification/ evaporation and internal/ion gelation for treatment of H. pylori infection. Ethylcellulose microspheres (EMs) were prepared by, dispersion of clarithromycin, chitosan and ethylcellulose in dichloromethane and subsequent solvent evaporation. These microspheres were coated with alginate by internal gelation process to obtain the alginate-ethylcellulose microparticles (AEMs); then, AEMs were dispersed in a chitosan solution, and the chitosan- alginate-ethylcellulose microparticles (CAEMs) were obtained by ion gelation to enhance the bioadhesive properties. The morphologies of prepared microsphere were investigated under optical and scanning electron microscopes. In vitro buoyancy and drug-release evaluation confirmed the good floating and sustained- release properties of CAEMs. In vivo mucoadhesive study showed that 61% of the CAEMs could be retained in stomach for 4 h. The results suggested that CAEMs might be a promising drug delivery system for treatment of the H. pylori infection.