DESIGN, DEVELOPMENT AND EVALUATION OF CATIONIC GUAR AND HYDROXYPROPYL GUAR BASED IN SITU GELS FOR OPHTHALMIC DRUG DELIVERY

The poor bioavailability and therapeutic response exhibited by the conventional eye drops due to rapid corneal loss is overcome by the use of ion-activated gel forming systems that are instilled as drops;these undergo gelation in cul-de-sac mode. The present study describes the design, development and evaluation of in situ ophthalmic drug delivery of antibacterial agent, linezolid, based on ion-activated guar gum derivatives. Novel polymers such as Cationic guar with hydroxypropyl guar are being used as gelling as well as viscosity enhancing agents. Differential scanning calorimetric studies have revealed that linezolid is compatible with all the excipients in the formulation. The study also aims at rheological characterization, effect of sterilization (moist heat) and effect of aging on the viscosity of in situ gels by calculating consistency index (K), flow behaviour index (n value) using power law model. The in vitro drug diffusion study for the developed formulations has also been carried out. The formulation CGHPG2,exhibiting good physical stability subsequent to sterilization and storage and further retaining the consistency index (K) and flow behavior index (n value), was chosen as the optimized formulation. The gel formed in situ revealed the sustained release of the drug for up to 12 hrs. Stability data recorded over a period of 6 months at elevated temperature conditions revealed the formulation to be stable. In vivo ocular toxicity studies revealed non irritant and non toxic nature of the formulation. Therefore, the developed guar gum derivative based ophthalmic in situ gel by virtue of its prolonged corneal residence time and sustained drug release could be considered a viable alternative to the conventional eye drop formulation in achieving enhanced bioavailability.