title: Elevated concentration of intraocular cortisol obtained by sequential parabulbar injection in rabbit model.
abstract: 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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Ophthalmology, New York Hospital-Cornell Medical Center, 525 East 68th Street, New York, N.Y. 10021, USA. mcaulfie@mail.med.cornell.edu
authors.forename: H A
authors.initials: HA
authors.lastname: Lincoff
authors.forename: I
authors.initials: I
authors.lastname: Kreissig
authors.forename: N
authors.initials: N
authors.lastname: Lincoff
authors.forename: R
authors.initials: R
authors.lastname: Silverman
authors.forename: J
authors.initials: J
authors.lastname: Nisselbaum
mesh_terms: D000818:Animals; D002404:Catheterization / Q000295:instrumentation; D005123:Eye / Q000187:drug effects* / Q000378:metabolism; D006207:Half-Life; D006854:Hydrocortisone / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology*; D007275:Injections, Intravenous; D009900:Optic Nerve / Q000187:drug effects* / Q000378:metabolism; D011817:Rabbits
chemical_list: C007133:hydrocortisone hemisuccinate; D006854:Hydrocortisone