title: Transscleral permeability of fluorescent-labeled antibiotics.
abstract: OBJECTIVE
  To determine the in vitro transscleral permeability of antibiotics for posterior segment infection.
  
  
  METHODS
  Scleral sections from moist chamber-stored human globes were mounted in a 2-compartment perfusion chamber. Fluorescent-labeled vancomycin, polymyxin B, or penicillin G was added to the episcleral surface, while the choroidal side was slowly perfused with balanced salt solution (Alcon Laboratories, Inc., Ft. Worth, TX). The perfusate was collected and fluorescence was measured using a fluorometer. From the measurements, permeability (Ktrans) was calculated. Photomicrographs were taken with a fluorescent microscope to evaluate tissue absorption.
  
  
  RESULTS
  The Ktrans values (cm/s, mean +/- standard error) were 6.66 +/- 1.46 x 10(-7) for vancomycin, 3.90 +/- 0.59 x 10(-7) for polymyxin B, and 1.89 +/- 0.21 x 10(-6) for penicillin G. The percent of antibiotic that diffused across the sclera from the donor chamber in 24 hours was 20.6 +/- 4.2 for vancomycin, 12.6 +/- 2.0% for polymyxin B, and 50.8 +/- 4.8% for penicillin G.
  
  
  CONCLUSIONS
  This study shows that human sclera is more permeable to lower molecular weight, water-soluble penicillin G than to vancomycin or polymyxin B. The data suggests that a local, noninvasive, transscleral drug-delivery method may be reasonable for treating intraocular infections.
authors.affiliation: Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Kao
authors.forename: Dayle H
authors.initials: DH
authors.lastname: Geroski
authors.forename: Henry F
authors.initials: HF
authors.lastname: Edelhauser
mesh_terms: D000042:Absorption; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D015194:Diffusion Chambers, Culture; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D005470:Fluorometry; D006801:Humans; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D008970:Molecular Weight; D009883:Ophthalmic Solutions / Q000493:pharmacokinetics; D010400:Penicillin G / Q000493:pharmacokinetics*; D010539:Permeability; D011112:Polymyxin B / Q000493:pharmacokinetics*; D012590:Sclera / Q000378:metabolism*; D014018:Tissue Distribution; D014640:Vancomycin / Q000493:pharmacokinetics*
chemical_list: D000900:Anti-Bacterial Agents; D005456:Fluorescent Dyes; D009883:Ophthalmic Solutions; D014640:Vancomycin; D011112:Polymyxin B; D010400:Penicillin G