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Elevated concentration of intraocular cortisol obtained by sequential parabulbar injection in rabbit model
H A Lincoff1, I Kreissig, N Lincoff
1Department of Ophthalmology, New York Hospital-Cornell Medical Center, 525 East 68th Street, New York, N.Y. 10021, USA. mcaulfie@mail.med.cornell.edu
Background:
Parabulbar injections of corticosteroids yield a high intraocular concentration, but the half-life is short. We determined the concentration of cortisol that might be obtained by sequential parabulbar infusions of hydrocortisone.
Materials And Methods:
Single parabulbar injections of hydrocortisone sodium succinate were made in a rabbit model and the time of maximum concentration and half-life determined in the retina-choroid, vitreous, serum, and the tissues of the paired eye by radio-immune assay. Based upon the half-life, sequential injections were made at 3 hour intervals to obtain a steady concentration.
Results:
The maximum concentration of cortisol in the ocular tissues occurred two hours after a single injection and was 98 times greater in the choroid-retina and 72 times greater in the optic nerve than in the paired eye and the serum. The half-life of cortisol was 15 minutes. Elevated levels could be sustained by sequential injections at 3 hour intervals.
Conclusion:
Sequential injections of hydrocortisone through a retained parabulbar catheter could make it possible to titrate and maintain a therapeutic level of cortisol in the eyes of patients with posterior uveitis or optic neuritis.