Impact of Vehicle Physicochemical Properties on Modeling-Based Predictions of Cyclosporine Ophthalmic Emulsion Bioavailability and Tear Film Breakup Time.

Several physicochemical parameters are thought to affect in vivo performance of cyclosporine ophthalmic emulsion, including globule size distribution, viscosity profile as a function of applied shear, pH, zeta potential, osmolality, and surface tension. Using a modeling approach, this study predicts cyclosporine ophthalmic emulsion drug bioavailability to the cornea and conjunctiva and tear film breakup time for human subjects as a function of the vehicle physicochemical properties viscosity, surface tension, and osmolality for products that are qualitatively (Q1) and quantitatively (Q2) the same. The change in tear film breakup time from baseline, a potential indirect measure of therapeutic benefit, was predicted to characterize the direct effect of the vehicle on efficacy. Bioavailability predictions showed that while individual predictions were sensitive to variations in corneal and conjunctival permeabilities, geometric mean ratios of the test-to-reference comparisons for formulations that are Q1 and Q2 the same showed little sensitivity. Parameter sensitivity analysis showed that bioavailability and change in tear film breakup time from baseline values were both very sensitive to viscosity, slightly sensitive to surface tension, and insensitive to osmolality. With further improvements, the modeling framework developed for this study may be useful for informing future recommendations of cyclosporine ophthalmic emulsion bioequivalence for potential generic drug products.