Preparation and Evaluation of in Situ Gels Containing Diclofenac Sodium

Background and purpose: In ocular delivery the physiological constraints imposed by the protective mechanisms of the eye lead to low absorption of drugs, resulting in a short duration of the therapeutic effect. Thus using in-situ gelling systems could increase the residence time of the drug in the eye. These systems are instilled as drops into the eye and undergo a sol-to-gel transition in the cul-de-sac. The aim of this study was to formulate and evaluate an ophthalmic delivery system for diclofenac sodium (a nonsteroidal anti-inflammatory drug), based on the concept of ion-activated in situ gelation. Materials and methods: Ion-activated in situ gelling systems (sodium and calcium) consisting of sodium alginate and hydroxyl propyl methyl cellulose were prepared in different concentrations under aseptic condition. Diclofenac sodium was added after hydration. Formulations were evaluated for gelling capacity, physical stability, pH, drug content, viscosity and in-vitro drug release. Results: The clarity, pH and drug content of the developed formulation were found to be satisfactory. The developed formulation was stable and provided sustained drug release over an 8-h period. The viscosity was found to be in the range of 29 to 63 centipoise in shear rate of 20 rpm. The formulations showed pseudoplastic flow behavior. The ideal formulation showed no significant changes during a 90-day period and was found stable. Conclusion: The developed formulation can be used as an in-situ gelling vehicle to enhance ocular bioavailability and the reduction in the frequency of instillation, thereby resulting in better patient compliance.