title: Evaluation of ocular and general safety following repeated dosing of dexamethasone phosphate delivered by transscleral iontophoresis in rabbits.
abstract: OBJECTIVE
  To evaluate the toxicokinetics and tolerability (local ocular and general toxicity) of the anti-inflammatory agent, dexamethasone phosphate (a prodrug of dexamethasone) delivered to the eye in rabbits by transscleral iontophoresis.
  
  
  METHODS
  Female rabbits (n=6/group) received dexamethasone phosphate (40 mg/mL ophthalmic solution, EGP-437) transsclerally to the right eye (OD) using the Eyegate(®) II ocular iontophoresis delivery system once biweekly for 24 consecutive weeks at current doses of 10, 14, and 20 mA-min and current levels up to, and including -4 mA for 3.5-5 min. The study included 2 control groups (n=6/group): (1) a noniontophoresis control [an ocular applicator-loaded citrate buffer (placebo) without current] and (2) an iontophoresis control (a citrate buffer plus cathode iontophoresis at 20 mA-min, -4 mA for 5 min). Recoverability was evaluated 4 weeks following the last dose in 2 animals per group. The left eye (OS) was untreated and served as an internal control for each animal. Ocular and general safety of dexamethasone phosphate and dexamethasone were assessed. Other evaluations included toxicokinetics, ophthalmic examinations, intraocular pressure (IOP) measurements, electroretinographs, clinical observations, body weight, hematology and serum chemistry, gross necropsy, organ weight, and microscopic histopathology.
  
  
  RESULTS
  The biweekly transscleral iontophoresis with either the citrate buffer or dexamethasone phosphate at cathodic doses up to, and including 20 mA-min and currents up to, and including -4 mA for 24 weeks was well-tolerated. Transient signs of conjunctival hyperemia and chemosis, mild corneal opacity, and fluorescein staining of the cornea were noted and attributed to expected ocular reactions to the temporary placement of the ocular applicator and application of iontophoresis. There were no dexamethasone phosphate-, dexamethasone-, or iontophoresis-related effects on IOP, electroretinography, or histopathology. Reductions in body weight gain, anemia, decreased leukocyte and lymphocyte counts, compromised liver function, enlarged liver, and reduced spleen weight were consistent with systemic corticosteroid-mediated pharmacology, repeated use of anesthesia, stress, and sedentariness, and unlikely to be related to iontophoresis application.
  
  
  CONCLUSIONS
  The results of this investigation suggest that repeated transscleral iontophoresis with dexamethasone phosphate may be safe for use as a treatment for inflammatory ocular disorders that require prolonged and/or repeated corticosteroid therapy.
authors.affiliation: Eyegate Pharmaceuticals, Inc. , Waltham, Massachusetts.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Patane
authors.forename: William
authors.initials: W
authors.lastname: Schubert
authors.forename: Thomas
authors.initials: T
authors.lastname: Sanford
authors.forename: Raymond
authors.initials: R
authors.lastname: Gee
authors.forename: Melissa
authors.initials: M
authors.lastname: Burgos
authors.forename: William P
authors.initials: WP
authors.lastname: Isom
authors.forename: Begona
authors.initials: B
authors.lastname: Ruiz-Perez
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003907:Dexamethasone / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D016503:Drug Delivery Systems; D005123:Eye / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D007478:Iontophoresis; D009883:Ophthalmic Solutions; D009929:Organ Size / Q000187:drug effects; D009928:Organ Specificity; D011817:Rabbits
chemical_list: D005938:Glucocorticoids; D009883:Ophthalmic Solutions; C004180:dexamethasone 21-phosphate; D003907:Dexamethasone