The effect of a single dose of topical 0.005% latanoprost and 2% dorzolamide/0.5% timolol combination on the blood-aqueous barrier in dogs: a pilot study.

Author(s): Johnstone McLean NS, Ward DA, Hendrix DV

Affiliation(s): Department of Small Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, TN 37996, USA.

Publication date & source: 2008-05, Vet Ophthalmol., 11(3):158-61.

Publication type:

OBJECTIVE: To determine the effects of 0.005% latanoprost and 2% dorzolamide/0.5% timolol on the blood-aqueous barrier (BAB) in normal dogs. ANIMALS STUDIED: Eight mixed-breed and pure-breed dogs. PROCEDURES: Baseline anterior chamber fluorophotometry was performed on eight normal dogs. Sodium fluorescein was injected and the dogs were scanned 60-90 min post-injection. Seventy-two hours following the baseline scan, one eye received one drop of latanoprost. Fluorophotometry was repeated 4 h after drug administration. Following a washout period, the identical procedure was performed 4 h after the administration of dorzolamide/timolol. The degree of BAB breakdown was determined by comparing the concentrations of fluorescein within the anterior chamber before and after drug administration. BAB breakdown was expressed as a percentage increase in the post-treatment fluorescein concentration over the baseline concentration: %INC [Fl] = {([Fl](post)-[Fl](baseline))/[Fl](baseline)} x 100. The percentage increase in fluorescein concentration in the treated eye was compared to that in the nontreated eye using a paired t-test with significance set at P < or = 0.05. RESULTS: Following administration of latanoprost, the fluorescein in the treated eyes increased 49% (+/- 58%) from baseline compared to 10% (+/- 31%) in the untreated eyes (P = 0.016). Following administration of dorzolamide/timolol, the fluorescein concentration increased 38% (+/- 54%) compared to baseline vs. 24% (+/- 38%) in the untreated eyes (P = 0.22). CONCLUSIONS: The results of this study show that topical latanoprost may cause BAB disruption in normal dogs while topical dorzolamide/timolol may have no effect on the BAB in normal dogs.