Formulation of Carbopol 940 ophthalmic vehicles, and in vitro evaluation of the influence of simulated lacrimal fluid on their physico-chemical properties.

Carbopol 940 ophthalmic vehicles were prepared in order to investigate the interaction between the simulated lacrimal fluid and the polymer, and to examine the influence of sodium fluorescein - a tracer for the fluorophotometric studies - on the physico-chemical properties of the polymer vehicles. Four kinds of vehicles containing mannitol (5%), sodium fluorescein (0.05%) and disodium edetate (0.01%) were formulated. Physicochemical properties of the preparations including pH, osmolality, surface tension and viscosity were measured after neutralization and sterilization, and also after 1 and 2 weeks, 1, 2 and 3 months of storage at 4 degrees C. The viscosity significantly decreased by adding sodium fluorescein and disodium edetate to Carbopol 940 vehicles. It was observed no significant effect of sterilization and storage on the viscosity, pH and osmolality. Significant change in the flow property of the vehicles was observed when the simulated lacrimal fluid was added. Three concentrations of Carbopol 940 vehicles (0.20%, 0.15% and 0.10%) both containing and not containing disodium edetate were proposed for in vivo evaluation.