title: The transcorneal penetration of commercial ophthalmic formulations containing timolol maleate in rabbit eyes.
abstract: OBJECTIVE
  We investigated the transcorneal penetration of commercial ophthalmic formulations containing timolol maleate in rabbit eyes.
  
  
  METHODS
  One drop (30 μL) of each ophthalmic solution (Xalacom(®), DuoTrav(®), Cosopt(®), and Timoptol(®)) was administered to the conjunctival sac of the rabbits' eyes and the timolol maleate aqueous humor concentration was measured by high-performance liquid chromatography 15, 60, 120, and 240 min after the completion of administration. The effect of timolol ophthalmic solution pH (5.7-6.8) on ocular penetration was also examined.
  
  
  RESULTS
  The concentration [Cmax (μg/mL)] of timolol maleate, found in each of the 4 ophthalmic solutions, penetrated to the aqueous humor was as follows: DuoTrav>Cosopt>Timoptol>Xalacom. The concentration of timolol maleate penetrated to the aqueous humor was highest with solutions in the vicinity of pH 6.8.
  
  
  CONCLUSIONS
  The concentration of timolol maleate penetrated to the aqueous humor was highest in DuoTrav followed by Cosopt, Timoptol, and Xalacom, and the pH and Benzalkonium chloride (BAK) concentration of the ophthalmic solution were believed to be factors that influenced this phenomena.
authors.affiliation: Department of Ophthalmology, Kanazawa Medical University , Ishikawa, Japan .
authors.forename: Masamichi
authors.initials: M
authors.lastname: Fukuda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sasaki
mesh_terms: D000818:Animals; D001548:Benzalkonium Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics; D002853:Chromatography, Liquid / Q000379:methods; D003008:Cloprostenol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D003315:Cornea / Q000187:drug effects / Q000378:metabolism*; D004338:Drug Combinations; D005123:Eye / Q000187:drug effects / Q000378:metabolism*; D005901:Glaucoma / Q000188:drug therapy; D008297:Male; D009883:Ophthalmic Solutions / Q000008:administration & dosage; D011310:Preservatives, Pharmaceutical / Q000008:administration & dosage; D011461:Prostaglandins F, Synthetic / Q000008:administration & dosage / Q000493:pharmacokinetics; D011817:Rabbits; D013449:Sulfonamides / Q000008:administration & dosage / Q000493:pharmacokinetics; D013876:Thiophenes / Q000008:administration & dosage / Q000493:pharmacokinetics; D013999:Timolol / Q000008:administration & dosage* / Q000493:pharmacokinetics*
chemical_list: D001548:Benzalkonium Compounds; D004338:Drug Combinations; C571754:Duotrav; D009883:Ophthalmic Solutions; D011310:Preservatives, Pharmaceutical; D011461:Prostaglandins F, Synthetic; D013449:Sulfonamides; D013876:Thiophenes; C571753:Xalacom; C479140:dorzolamide-timolol combination; D003008:Cloprostenol; D013999:Timolol