A bioavailability comparison in rabbits of two steroids formulated as high-viscosity gels and reference aqueous preparations.

In order to assess the bioavailability of steroids from a high-viscosity gel, rabbit cornea and aqueous humor levels were measured over 12 hr following topical instillation of a gel and reference preparation. Concentrations associated with a 1% tritiated prednisolone acetate gel were found to be approximately four times larger than those of the reference preparation. A graphical comparison of the 1% tritiated prednisolone sodium phosphate data showed the area under corneal and aqueous time curves to be five and 10 times greater, respectively, with the gel than data associated with the reference preparation. The gel vehicle is well retained in the rabbit eye and is responsible for the large increases in bioavailability.