title: Ocular tissue distribution of betamethasone after anterior-episcleral, posterior-episcleral, and anterior-intrascleral placement of nonbiodegradable implants.
abstract: OBJECTIVE
  To investigate the intraocular distribution of betamethasone (BM) after implantation of transscleral drug delivery devices at three different sites in the eye: anterior episclera, posterior episclera, and anterior intrasclera.
  
  
  METHODS
  Nonbiodegradable implants designed to release BM for at least 1 month were placed at three different sites in albino rabbit eyes. The concentrations of BM in the aqueous humor, vitreous, and retina-choroid were determined by high-performance liquid chromatography at 4 weeks after placement. The distribution of BM in the retina-choroid was also evaluated.
  
  
  RESULTS
  In the in vitro and in vivo release study, the release of BM from implants in vivo correlated comparatively with those in vitro in all studied devices. The concentrations of BM in ocular tissues were measured after the implantations. The concentrations of BM after anterior-intrascleral placement of the implants were highest in the vitreous and retina-choroid among the three sites. The concentrations of BM in the three different sections of retina-choroid, which were around the placement site, opposite the placement site and posterior pole, were also determined. The concentration of BM in the retina-choroid around the placement site was higher than that in other parts of the retina-choroid after anterior-episcleral and anterior-intrascleral placement of implants. The implants at the anterior-intrascleral site yielded the highest concentrations of BM in the anterior part and posterior pole of the retina-choroid among the three placement sites. Only the implant at the posterior-episcleral site showed a higher concentration of BM at the posterior pole of the retina-choroid than at the other anterior part.
  
  
  CONCLUSIONS
  Transscleral drug delivery devices may be feasible systems to deliver BM to intraocular tissues. The placement site of the device should be selected according to the location of the targeted lesions.
authors.affiliation: Department of Ophthalmology and Visual Science, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Komei
authors.initials: K
authors.lastname: Okabe
authors.forename: Hideya
authors.initials: H
authors.lastname: Kimura
authors.forename: Junko
authors.initials: J
authors.lastname: Okabe
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Ogura
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D001623:Betamethasone / Q000493:pharmacokinetics*; D001682:Biological Availability; D002829:Choroid / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004337:Drug Carriers; D004343:Drug Implants; D005938:Glucocorticoids / Q000493:pharmacokinetics*; D011817:Rabbits; D012160:Retina / Q000378:metabolism*; D012590:Sclera / Q000378:metabolism*; D014018:Tissue Distribution; D014822:Vitreous Body / Q000378:metabolism*
chemical_list: D004337:Drug Carriers; D004343:Drug Implants; D005938:Glucocorticoids; D001623:Betamethasone