title: Ophthalmic timolol in a hydrogel vehicle leads to minor inter-individual variation in timolol concentration in aqueous humor.
abstract: Ophthalmic timolol has been used for decades in the treatment of glaucoma and ocular hypertension, traditionally in aqueous 0.5% eye drops. Recently a timolol 0.1% hydrogel has been developed to improve systemic safety. The aim of the present study was to compare aqueous humor timolol concentrations after administration of 0.1% hydrogel and aqueous 0.5% timolol in patients scheduled for a cataract operation. The concentration in the aqueous humor was 210+/-175 ng/ml (mean+/-S.D.) 2h after administration of timolol 0.1% hydrogel and 538+/-304 ng/ml after aqueous 0.5% timolol. In the aqueous 0.5% timolol group more patients had unnecessarily high concentrations of timolol in the aqueous humor. beta(1)-receptors and beta(2)-receptors were practically 100% occupied after administration of both products. The hydrogel proved to be an excellent formulation in giving smaller inter-individual variation in penetration of timolol into the aqueous humor. Only a weak correlation was seen between corneal thickness and the aqueous humor concentration of timolol in the aqeuous 0.5% timolol group. In conclusion, in contrast to the conventional aqueous 0.5% timolol, 0.1% timolol hydrogel caused only slight inter-individual variation in timolol concentration in the aqueous humor.
authors.affiliation: Institute of Biomedicine, Pharmacology, University of Helsinki, Helsinki, Finland; Santen Oy, Tampere, Finland.
authors.forename: Marjo
authors.initials: M
authors.lastname: Volotinen
authors.forename: Jukka
authors.initials: J
authors.lastname: Mäenpää
authors.forename: Hannu
authors.initials: H
authors.lastname: Kautiainen
authors.forename: Ari
authors.initials: A
authors.lastname: Tolonen
authors.forename: Jouko
authors.initials: J
authors.lastname: Uusitalo
authors.forename: Auli
authors.initials: A
authors.lastname: Ropo
authors.forename: Heikki
authors.initials: H
authors.lastname: Vapaatalo
authors.forename: Esko
authors.initials: E
authors.lastname: Aine
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001082:Aqueous Humor / Q000378:metabolism*; D003315:Cornea / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D008297:Male; D008875:Middle Aged; D014677:Pharmaceutical Vehicles / Q000737:chemistry*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D013666:Tears / Q000187:drug effects / Q000378:metabolism; D013999:Timolol / Q000008:administration & dosage* / Q000378:metabolism / Q000493:pharmacokinetics*
chemical_list: D000319:Adrenergic beta-Antagonists; D014677:Pharmaceutical Vehicles; D011943:Receptors, Adrenergic, beta; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D013999:Timolol