title: A medical device/drug delivery system for treatment of glaucoma.
abstract: BACKGROUND
  The aim of this study was to investigate the uptake and release kinetics of two common glaucoma drugs delivered onto hydrogel contact lenses using analytical chemistry and to evaluate this device's ability to control intraocular pressure in a limited number of volunteers.
  
  
  METHODS
  Contact lenses were incubated in a source solution containing timolol maleate or brimonidine tartrate to determine uptake kinetics. The lenses were then immersed in fresh saline to determine release kinetics. Analysis was performed by high-pressure liquid chromatography (HPLC). HPLC column retention times were determined for drugs released from the lens individually and under co-elution conditions. To evaluate clinical feasibility and toxicity, three volunteers (patients being treated for glaucoma) were provided with contact lenses that had been passively impregnated with either drug. After a three-week wash-out period, the volunteers were instructed to wear the lenses for 30 minutes per day for two weeks.
  
  
  RESULTS
  HPLC analysis showed that maximum uptake and release of both drugs had occurred by approximately 60 minutes, with the slopes tending to flatten after this point. The retention time on the HPLC column was 8.08 minutes for timolol maleate and 2.16 minutes for brimonidine tartrate after incubation for one hour, with no changes after seven hours. Patient data showed that use of the lenses maintained IOP at levels equivalent to those obtained with previous treatment. No ocular toxicity was observed.
  
  
  CONCLUSIONS
  Drugs commonly used for glaucoma treatment can be passively transferred to a hydrogel contact lens and then eluted from the polymer. Data obtained from a limited number of patients suggest that this contact lens/drug delivery system may be a feasible means of controlling IOP.
authors.affiliation: University of Calgary, Calgary, Alberta, Canada. schultzc@ucalgary.ca
authors.forename: Clyde L
authors.initials: CL
authors.lastname: Schultz
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Poling
authors.forename: Janet O
authors.initials: JO
authors.lastname: Mint
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000493:pharmacokinetics; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000493:pharmacokinetics; D000328:Adult; D000068438:Brimonidine Tartrate; D002851:Chromatography, High Pressure Liquid; D003261:Contact Lenses; D016503:Drug Delivery Systems / Q000379:methods*; D005260:Female; D005901:Glaucoma / Q000188:drug therapy*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D011810:Quinoxalines / Q000008:administration & dosage / Q000493:pharmacokinetics; D013999:Timolol / Q000008:administration & dosage / Q000493:pharmacokinetics
chemical_list: D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D011810:Quinoxalines; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D000068438:Brimonidine Tartrate; D013999:Timolol