In situ gelation

  Gastro retentive drug delivery system has been widely used to prolong retention of dosage forms in stomach. Amongst the various approaches, the Raft formulation offers sustained drug release as well as prolonged gastric retention, along with the added advantage of liquid oral dosage form. The present study was an attempt to formulate and evaluate Raft forming floating drug delivery system for Verapamil Hydrochloride which undergoes pH dependent sol-gel transition at gastric pH; thereby prolonging the retention of the system in stomach. Gellan gum (Gelrite®) was employed as gelling agent whose gelation is triggered by source of Ca2+ ions in the form of Calcium Carbonate. The evaluation was carried out for In Vitro parameters and the results substantiated that the optimized formulation revealed excellent floating characteristics and gastric retention.

  Formulation and characterization of an ophthalmic delivery system of an antibacterial agent, ofloxacin, based on the concept of pH triggered in situ gelation. Polyacrylic acid (Carbopol 974P) was used as the gelling agent in combination with Noveon® AA-1 USP Polycarbophil as a viscosity enhancer. Formulation optimization was carried out using a 32 full factorial design. The effect of independent variables was evaluated using dependent variables such as gel strength, bioadhesive force, viscosity and in vitro drug release of the formulation. The multiple regression analysis of the results led to equations that adequately describe the influence of the independent variables on the selected responses. Polynomial regression equations and surface plots were used to relate the dependent and independent variables. Furthermore, the desirability function was employed in order to determine the best batch which was then evaluated for in vivo antimicrobial efficacy study, effect of sterilization, ocular irritation study and accelerated stability study. It was found that the optimum values of the responses for pH triggered in situ ophthalmic gel formulation could be obtained at medium levels of Carbopol 974P and Noveon® AA-1 USP Polycarbophil (0.5/0.5%w/w respectively). The formulation retained antimicrobial efficacy, showed insignificant effect over sterilization and found non irritant to the corneal surface confirmed by microscopy of the corneal mucosal membrane compared with reference marketed formulation. The optimized formulation was found to be stable, therapeutically efficacious and providing sustained release of the drug over an 8 h period even after accelerated stability study over three months. The developed system is thus a viable alternative to conventional ophthalmic formulations.   Key words: In situ gelation; Factorial design; Desirability function; Carbopol 974P;Noveon® AA-1 USP Polycarbophil; Ofloxacin