Topical Dexamethasone Lowers Rabbit Ocular Tension, as Does Topical Mifepristone (RU 486), a Peripheral Blocker of Dexamethasone and Progesterone

Abstract

The variability of the response of the rabbit eye to topical 1 % dexamethasone has been shown in two groups of 20 young albino rabbits each (total 40) tested in succession. The pressure anomalously fell significantly (but by only 1 mm Hg) in both groups in the first 4 weeks of administration, but not in subsequent weeks. Mifepristone (RU 486), a peripheral antagonist of dexamethasone and progesterone, reduced the pressure significantly, again by only 1 mm Hg, in the first group of 20 rabbits, not the second. Accordingly, no conclusion was possible on the originating question: does pre-treatment with mifepristone prevent the dexamethasone-induced rise in rabbit intra-ocular pressure?

Immunosuppression by a subconjunctival implant releasing dexamethasone in a rabbit model of penetrating keratoplasty

“…Note that, for steroids in general, subconjunctival injection has been widely used for decades and been proven safe, with adverse events (except for IOP rise) reported only exceptionally. With this model, we did not measure IOP for two reasons: (1) the main purpose of the study was to explore immunosuppression and (2) the corticosensitivity of the rabbit model regarding IOP elevation is unknown, and there is even a contradictory publication with IOP falling under dexamethasone16 and a series of intravitreal injections without IOP rising 17. Also, in humans, IOP elevation after topical, subconjunctival, subtenonian or intravitreal administration of steroids is a class effect, which there is no reason to think will not occur after subconjunctival injection of a dexamethasone implant.…”