Effect of particle size on ocular permeability of prednisolone acetate in rabbits.

The ocular permeability of two sieved fractions of prednisolone acetate with a mean particle size of less than 5 microns and 5-10 microns was studied in rabbits. The results show that there was not significant difference between the corneal uptake of the two fractions of prednisolone acetate. Prednisolone acetate was rapidly taken up by the cornea where it is hydrolyzed rapidly to prednisolone. Only prednisolone was detected in the aqueous humor showing that prednisolone acetate is completely hydrolyzed in the cornea. Both fractions produced similar concentrations of prednisolone in the aqueous humor. For prednisolone acetate, the permeability rate rather than the dissolution rate seems to be the rate-limiting step for corneal transport.