title: Preservative alteration of corneal permeability in humans and rabbits.
abstract: Isotonic, neutral buffered solutions of benzalkonium chloride or chlorhexidine digluconate were applied topically to one eye of rabbits or human subjects. Contralateral control eyes received phosphate buffered saline as placebo. One-half hour later, the tear film of both eyes was loaded with nonpreserved sodium fluorescein. Anterior chamber fluorescence levels were measured at 1 hr intervals to determine corneal permeability changes attributable to preservative action. In rabbits, corneal permeability increased with rising preservative concentration. Benzalkonium chloride 0.01% increased anterior chamber fluorescence level 1.8 (+/- 0.2 SEM) times over control eyes, while chlorhexidine digluconate 0.01% caused 1.5 (+/- 0.2 SEM) to one ratio of fluorescence in treated/untreated eyes. In human subjects, neither preservative produced significant permeability change at 0.01% concentration. However, benzalkonium chloride 0.02% caused 1.23 (+/- 0.08 SEM) permeability increase. The results support the hypothesis that rabbits are more sensitive to single-dose applications of preservatives than humans.
mesh_terms: D000818:Animals; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D002710:Chlorhexidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003315:Cornea / Q000378:metabolism*; D004342:Drug Hypersensitivity / Q000453:epidemiology; D005123:Eye / Q000187:drug effects; D019793:Fluorescein; D005452:Fluoresceins; D006801:Humans; D010539:Permeability; D011309:Preservation, Biological; D011817:Rabbits / Q000378:metabolism*
chemical_list: D001548:Benzalkonium Compounds; D005452:Fluoresceins; C010882:chlorhexidine gluconate; D002710:Chlorhexidine; D019793:Fluorescein