32. Ocular drug delivery: Eyedrops with Nanoparticles with
dexamethasone and cylodextrin that deliver steroids to
the rabbit retina in significant concentration
Einar Stefánsson (Reykjavík)
Purpose: Delivery of steroids to the retina is currently undertaken with invasive injections into
the vitreous cavity.
Methods: This paper describes a noninvasive method to deliver steroids in therapeutic levels
to the retina in rabbits. Dexamethasone was formulated as somewhat water-soluble dexamethasone/
g-cyclodextrin (gCD) microparticles in a low-viscosity aqueous eye drop suspension.
The mean (±standard deviation) diameter of the particles was 20.4±10.3 μm with no particles
larger than 60 μm. The aqueous suspension formulation was tested in rabbits and compared to
an aqueous dexamethasone eye drop solution containing randomly methylated b-cyclodextrin
(RMbCD). The dexamethasone concentration was identical in both formulations, 15 mg/ml.
Results: Two hours after single application of the dexamethasone/gCD eye drops to rabbits the mean (±SD) concentration
in vitreous was 29±16 ng/g, 86 % of which reaching vitreous via topical route and in retina the concentration was
57±22 ng/ml (49 % via topical route).
Conclusion: These steroid levels are comparable with the levels achieved 1 month after intravitreal injection as well as
intravitreal slow release devices. The aqueous dexamethasone/gCD eye drop formulation was chemically stable during
7 months storage and well tolerated with no visible short term side effects.
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