Radioactive dexamethasone-1,2,4-3H was used in 0.1% solutions in two vehicles to demonstrate the marked uptake of steroid by ocular tissue in rabbits. Radioactivity was detectable in ocular tissue by ten minutes after instillation of the ophthalmic solutions. Retention of steroid was demonstrable as long as 24 hours after removal of steroid from the eye. A dispersion vehicle containing hydroxyethylcellulose (Cellosize QP) was found to more than double the steroid level in eye segments over the concentrations produced by an aqueous vehicle containing no viscosity increasing agent. The occurrence of systemic absorption was shown by the presence of radioactivity in the urine, plasma, kidneys, and livers of experimental animals, about equally from both media studied.
Charles Rosenblum, Robert E. Dengler, Raymond F. Geoffroy. Ocular Absorption of Dexamethasone Phosphate Disodium by the Rabbit. Arch Ophthalmol. 1967;77(2):234–237. doi:10.1001/archopht.1967.00980020236017