title: Ocular distribution and toxicity of intravitreal injection of triamcinolone acetonide in normal equine eyes.
abstract: OBJECTIVE
  To determine ocular distribution and toxicity of a single injection of intravitreal triamcinolone acetonide (TA) in normal horses.
  
  
  METHODS
  Six adult horses, donated to North Carolina State University.
  
  
  METHODS
  Six horses were injected intravitreally with either 10, 20, or 40 mg (n = 2 each) of TA. The opposite eye of each horse was injected with balanced salt solution (BSS). Ocular toxicity was assessed by biomicroscopy, tonometry, indirect ophthalmoscopy, and electroretinogram. Aqueous humor (AH), vitreous humor (VH), and plasma samples were collected. Horses were euthanized 7 or 21 days after injection and eyes enucleated for histopathology. TA concentrations in AH, VH, and plasma were measured by HPLC.
  
  
  RESULTS
  Three control eyes and one TA eye developed inflammation after injection or collection of AH. Positive bacterial cultures (Corynebacterium spp., Staphylococcus spp., and Streptococcus spp.) were obtained from three of these eyes. Other than transient corneal edema in TA injected eyes, which resolved by 7 days after injection, no other changes were observed. TA crystals were visible within the vitreous body. No evidence of TA toxic effect was noted on histopathology. TA was detected in all AH and VH samples from treated eyes following injection. Drug was not detected in the plasma.
  
  
  CONCLUSIONS
  There was no evidence of overt toxicity from intravitreal TA in normal horses and a single intravitreal injection resulted in TA ocular levels for 21 days. However, the risk for bacterial infections with intravitreal injection or anterior chamber aspirations in horses is high. Use of topical and systemic antibiotics after injection is recommended.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
authors.forename: N Y
authors.initials: NY
authors.lastname: Yi
authors.forename: J L
authors.initials: JL
authors.lastname: Davis
authors.forename: J H
authors.initials: JH
authors.lastname: Salmon
authors.forename: B C
authors.initials: BC
authors.lastname: Gilger
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000493:pharmacokinetics / Q000633:toxicity*; D001082:Aqueous Humor / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000662:veterinary; D004305:Dose-Response Relationship, Drug; D004596:Electroretinography / Q000662:veterinary; D006736:Horses / Q000097:blood / Q000378:metabolism; D007267:Injections / Q000009:adverse effects / Q000662:veterinary; D012160:Retina / Q000187:drug effects; D014018:Tissue Distribution; D014222:Triamcinolone Acetonide / Q000493:pharmacokinetics / Q000633:toxicity*; D014822:Vitreous Body / Q000737:chemistry*
chemical_list: D000893:Anti-Inflammatory Agents; D014222:Triamcinolone Acetonide