title: Comparison of the release profile and pharmacokinetics of intact and fragmented dexamethasone intravitreal implants in rabbit eyes.
abstract: OBJECTIVE
  Dexamethasone intravitreal implant (DEX implant, Ozurdex(®); Allergan, Inc.) is used to treat noninfectious posterior uveitis and macular edema associated with retinal vein occlusion and diabetic retinopathy. Two recently published reports of DEX implant fragmentation shortly after injection have raised concerns about the potential for faster implant dissolution and elevated ocular dexamethasone concentrations. This study compared the in vivo release profile and pharmacokinetic behavior of intact and fragmented DEX implants.
  
  
  METHODS
  DEX implant was surgically implanted as a single unit or fragmented into 3 pieces in the posterior segment of opposing eyes of 36 New Zealand white rabbits. The release of dexamethasone over time from 1-piece and 3-piece fragmented implants dissolved in solution in vitro was compared with that from the 1-piece and 3-piece fragmented implants placed in the rabbit eyes. In addition, dexamethasone concentrations in the vitreous and aqueous humors of each eye were measured at 3 h and days 1, 7, 14, 21, and 28. High-performance liquid chromatography and liquid chromatography-tandem mass spectrometry were used for assays.
  
  
  RESULTS
  Dexamethasone release from the 1-piece and 3-piece DEX implants in vivo was not different and was consistent with the in vitro release pattern. Moreover, the concentration profile of dexamethasone in the vitreous and aqueous humors was similar for the 1-piece and 3-piece DEX implants at each time point measured.
  
  
  CONCLUSIONS
  DEX implant fragmentation neither accelerated its dissolution nor increased the dexamethasone concentration delivered at a given time. Accordingly, DEX implant fragmentation is unlikely to have clinically significant effects in patients.
authors.affiliation: 1 Allergan, Inc. , Irvine, California.
authors.forename: Rahul
authors.initials: R
authors.lastname: Bhagat
authors.forename: Jean
authors.initials: J
authors.lastname: Zhang
authors.forename: Sidiq
authors.initials: S
authors.lastname: Farooq
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Li
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003907:Dexamethasone / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D004343:Drug Implants; D005123:Eye / Q000378:metabolism*; D005938:Glucocorticoids / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D058449:Intravitreal Injections; D009520:New Zealand; D011817:Rabbits; D053719:Tandem Mass Spectrometry; D014822:Vitreous Body / Q000378:metabolism
chemical_list: D004343:Drug Implants; D005938:Glucocorticoids; D003907:Dexamethasone