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The real issue in the development of oral controlled release dosage forms is not just to prolong the delivery of drugs but also to prolong the presence of dosage forms in the stomach in order to improve the bioavailability of drugs with a 'narrow absorption window'. In the present study, an anti-ulcer drug, ranitidine hydrochloride, is delivered through a gastroretentive ethyl cellulose-based microparticulate system capable of floating on simulated gastric fluid for > 12 h. 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 microm. Microspheres showed excellent buoyancy and a biphasic controlled release pattern with 12h. In vivo bioavailability studies performed on rabbits and T(max), C(max), 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.

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Sodium alginate (SA) floating beads containing cefpodoxime proxetil, a third-generation cephalosporin antibiotic, were prepared by precipitation method using calcium carbonate as gas generating agent. Hydroxypropyl methylcellulose (HPMC) was used in all the four formulations in different proportions (F1, F2, F3, and F4) as swelling agent to control the release of the drug. Gas generating agent forms pores on the surface of the beads because of the rapid escape of CO 2 during the curing process in precipitating media. Scanning electron microscopy confirmed their porous and grossly spherical structure, and the size of the beads were in the range of 700-1000 lm. The size of the beads increases with the increase in the concentration of gas-forming agent and decreases with the increase in the concentration SA. The drug entrapment efficiency was found to be in the range of 85.3-91.1%. F2shows least entrapment, whereas F3 shows maximum entrapment. The percentage porosity was 82.1-89.1%, and the mean pore diameter was 0.41-0.52 lm. The porosity depends on the concentration of gas-forming agent. The mechanical strength of the beads was 591-1073 g. All the formulations showed good floating time. The in vitro release was performed in glycine dissolution media according to USP for about 12 h. The cumulative % drug release was found to be 67.5-87.3%. The in vitro dissolution study reveals that the concentration of the gas generating agent and SA affects the release rate.

Ophthalmic nanosuspensions (ONS) have shown a potential for ophthalmic delivery over the conventional ocular formulations. The objective of the study was to assess the effect of surfactants and polymers on particle size and drug release. Sparfloxacin ONS were prepared by optimizing the concentration of HPMC E5 and water soluble chitosan by using solvent diffusion method followed by probe sonication. The Poloxamer 407 and Kolliphor P188 were used as a surfactant. The produced nanosuspensions were characterized for particle size, shape, zeta potential and drug release. The average particle size of the nanosuspension was 300 to 500 nm. The in vitro drug release study showed that the optimized nanosuspension of water soluble chitosan sustained drug release up to 9 h compared to 6 h for the hydroxypropylmethylcellulose (HPMC) nanosuspension. Further, the sparfloxacin ONS formulation showed excellent ocular tolerance and biocompatibility as determined by hen's egg test chorioallantoic membrane (HET CAM) and resazurin assay on Vero cell lines. Moreover, optimized formulation was found to be stable, isotonic, non-toxic with higher in vitro and in vivo antimicrobial potential.

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Gemcitabine-loaded solid lipid nanoparticles (SLNs) were produced by double emulsification technique using stearic acid as lipid, soy lecithin as surfactant and sodium taurocholate as cosurfactant. Prepared nanoparticles are characterized for particle size and surface morphology using scanning electron microscopy (SEM). Particle yield, entrapment efficiency and zeta potential were also determined. In-vitro release studies were performed in phosphate-buffered saline (PBS) pH 7.4 using metabolic shaker. The formulation F6 with maximum entrapment efficiency 72.42% and satisfactory in-vitro release was selected. In-vivo tissue distribution to liver, spleen, lung, heart and kidneys of optimized formulation followed by stability study under specific conditions were also determined. This investigation has shown preferential drug targeting to liver followed by spleen, lungs, kidneys and heart. Stability studies showed no significant change in the particle size followed with very slight decrease in entrapment efficiency at 25 AE 2 C/60 AE 5% RH over a period of three months.

The aim of the present study was to formulate and evaluate controlled release polymeric ocular delivery of acyclovir. Reservoir-type ocular inserts were fabricated by sandwiching hydroxypropyl methylcellulose (HPMC) matrix film containing acyclovir between two rate controlling membranes of cellulose acetate phthalate (CAP). The solubility and dissolution rate of poorly soluble acyclovir was enhanced by preparing binary systems with beta-cyclodextrin and then incorporated into HPMC matrix. Nine formulations (AB-1 to AB-9) with varying ratio of HPMC (drug matrix) and CAP (rate controlling membrane) were developed and sterilized by gamma radiation. The formulations were subjected to various physico-chemical evaluations. The in vitro release profile of all the formulations showed a steady, controlled drug release up to 20 h with non-Fickian diffusion behavior. A high correlation coefficient found between in vitro/in vivo release rate studies. Formation of acyclovir complex was confirmed by differential scanning calorimetry. In addition, dissolution rate studies revealed improved solubility of acyclovir when complexed with beta-cyclodextrin. Stability studies showed that the ocular inserts could be stored safely at study storage conditions. In conclusion, the present study demonstrated controlled release formulation of acyclovir inserts for ocular delivery using biodegradable polymers.