Thermo and PH Responsive Ocular Insitu Gels Formulation: Based on Combination with Natural Polymers

To increase the bioavailability and short ocular residence time of Norfloxacin eye drops, aqueous solutions of drug in chitosan/ Pluronic (poloxamer) were prepared. Mixtures of solutions of Pluronic (5-17.5% w/w) with chitosan (0.1-0.6% w/w) were prepared.  The formulations so prepared were in the liquid state at 4°C while turned into a gel at the temperature of the Cul-de-sac. Naturals polymers i.e., Poloxamer was used as the polymer which exhibited the phase transition behavior and chitosan was used to improve residence time. Norfloxacin release was determined using a membrane less dissolution model in artificial tear solution up to 8 hours and the samples were analyzed spectrophotometrically at 277nm. The rheological behavior of solutions in response to dilution or temperature changes and also the phase change temperature (PCT) were determined. Antimicrobial effect of the solutions was studied in nutrient agar in comparison to all formulations of Norfloxacin using Pseudomonas aueroginosa, Staphylococcus aureus and E.coli by the agar diffusion test using the cup-plate technique. The formulation consisted of 15% Pluronic and 0.5% chitosan, with the highest release efficiency (73.46 ± 0.876%) and an acceptable mean release time, is suggested as a suitable ophthalmic preparation for sustained release of Norfloxacin.