title: Injection site and pharmacokinetics after intravitreal injection of immunoglobulin G.
abstract: OBJECTIVE
  The aim of this study was to investigate whether the pharmacokinetics differ after immunoglobulin G (IgG) intravitreal injections are done in the different sites of the vitreous cavity of rabbit eyes.
  
  
  METHODS
  To examine the pharmacokinetics in the vitreous and the retina/choroid, fluorescein isothiocyanate-labeled IgG (5  μg/50  μL) was injected from the superior pars plana into the vitreous cavity of rabbit eyes. An original intravitreal injection guide was used to fix the tip of the injection needle, with the tip fixed in either the superior-anterior vitreous (superior group) or in the posterior vitreous (posterior group). At 1  h, 1, 4, and 7 days after injection, the eyes were enucleated and frozen. The vitreous was cut into superior, inferior, and posterior vitreous sections, whereas the retina/choroid was cut into superior, inferior, and posterior retina/choroid sections. The IgG concentrations in the vitreous and the retina/choroid sections were then determined.
  
  
  RESULTS
  In the posterior vitreous, the IgG concentration in the posterior group was significantly higher than that in the superior group at 1  h after injection (P < 0.05). However, 1 day after injection, no significant differences were noted between the 2 groups. At 4 days after injection, the drug was diffusely spread in both groups. In the posterior retina/choroid, the IgG concentration was essentially the same regardless of the injection site or the amount of time after injection. The IgG concentration in the superior retina/choroid was significantly higher in the superior group than in the posterior group at 1  h and 1 day after injection (P < 0.05). There were no differences noted between the 2 groups for the IgG concentrations in the 3 sections at 4 and 7 days after injection.
  
  
  CONCLUSIONS
  Intravitreally injected IgG remains in the area of the injection, with more than 1 day required for it to spread diffusely within the vitreous. In the posterior retina/choroid, results suggested that the concentration of IgG may be equal regardless of the injection site. In the superior retina/choroid area that was near the site of the injection, the concentration of drug tended to be higher.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan. y-miura@nagasaki-u.ac.jp
authors.forename: Yoko
authors.initials: Y
authors.lastname: Miura
authors.forename: Masafumi
authors.initials: M
authors.lastname: Uematsu
authors.forename: Mugen
authors.initials: M
authors.lastname: Teshima
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Suzuma
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kumagami
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Kitaoka
mesh_terms: D000818:Animals; D002829:Choroid / Q000378:metabolism; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D007074:Immunoglobulin G / Q000008:administration & dosage* / Q000378:metabolism*; D007155:Immunologic Factors / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D058449:Intravitreal Injections; D008297:Male; D009994:Osmolar Concentration; D010599:Pharmacokinetics; D011817:Rabbits; D012160:Retina / Q000378:metabolism; D013997:Time Factors; D014822:Vitreous Body / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D007074:Immunoglobulin G; D007155:Immunologic Factors; D016650:Fluorescein-5-isothiocyanate