title: Anatomic and pharmacokinetic properties of intravitreal bevacizumab and ranibizumab after vitrectomy and lensectomy.
abstract: OBJECTIVE
  To determine the anatomic characteristics and pharmacokinetic properties of intravitreally placed bevacizumab and ranibizumab after pars plana lensectomy or pars plana vitrectomy and to compare these with nonoperated control eyes in a rabbit model.
  
  
  METHODS
  Three groups of six Dutch-belted rabbits each underwent pars plana vitrectomy, pars plana lensectomy, or served as nonsurgical controls. Twelve days after surgery, 3 rabbits from each group underwent intravitreal injection in one eye with 1.25 mg/0.05 mL I-124-bevacizumab or 0.5 mg/0.05 mL I-124-ranibizumab. Serial imaging with integrated positron emission and computed tomography (PET/CT) were obtained on Days 0, 2, 5, 7, 14, 21, 28, and 35. Measured radioactivity emission in becquerels/milliliter was used to calculate the half-lives for each agent.
  
  
  RESULTS
  The intravitreally placed radiolabeled agents were contained within the vitreous cavity for the duration of the study. The average clearance half-lives with standard error for bevacizumab and ranibizumab after correction for radioactive decay were, respectively, 4.22 ± 0.07 days and 2.81 ± 0.05 days in unoperated eyes, 2.30 ± 0.09 days (P < 0.0001) and 2.13 ± 0.05 days (P < 0.0001) after vitrectomy, and 2.08 ± 0.07 days (P = 0.0001) and 1.79 ± 0.05 days (P < 0.0001) after lensectomy.
  
  
  CONCLUSIONS
  Intravitreal retention was longer for bevacizumab than ranibizumab within all study groups and was significantly reduced after vitrectomy and lensectomy for both agents. Consideration for more frequent intravitreal anti-vascular endothelial growth factor dosing regimens may be made for patients whose treated eyes have undergone previous vitrectomy or who are aphakic.
authors: Department of Ophthalmology and Vision Science, The University of Arizona Medical Center, Tucson, Arizona 85711, USA. jbchristo@hotmail.com
authors: John B
authors: JB
authors: Christoforidis
authors: Michelle M
authors: MM
authors: Williams
authors: Jillian
authors: J
authors: Wang
authors: Angela
authors: A
authors: Jiang
authors: Cedric
authors: C
authors: Pratt
authors: Mahmoud
authors: M
authors: Abdel-Rasoul
authors: George H
authors: GH
authors: Hinkle
authors: Michael V
authors: MV
authors: Knopp
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000068258:Bevacizumab; D002387:Cataract Extraction; D058449:Intravitreal Injections; D008657:Metabolic Clearance Rate; D023421:Models, Animal; D011817:Rabbits; D000069579:Ranibizumab; D014821:Vitrectomy
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; D000068258:Bevacizumab; D000069579:Ranibizumab