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.
OBJECTIVE
To determine the effects of 0.005% latanoprost and 2% dorzolamide/0.5% timolol on the blood-aqueous barrier (BAB) in normal dogs.


METHODS
Eight mixed-breed and pure-breed dogs.


METHODS
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.
Johnstone McLean
Nancy S
NS
Department of Small Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, TN 37996, USA.
Ward
Daniel A
DA
Hendrix
Diane V H
DV
D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018916:Blood-Aqueous Barrier / Q000187:drug effects* / Q000378:metabolism; D018592:Cross-Over Studies; D004283:Dog Diseases / Q000188:drug therapy; D004285:Dogs / Q000378:metabolism*; D004359:Drug Therapy, Combination; D005260:Female; D019793:Fluorescein; D000077338:Latanoprost; D008297:Male; D010865:Pilot Projects; D011461:Prostaglandins F, Synthetic / Q000008:administration & dosage / Q000493:pharmacokinetics*; D011897:Random Allocation; D013449:Sulfonamides / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013876:Thiophenes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013999:Timolol / Q000008:administration & dosage / Q000493:pharmacokinetics*
D000959:Antihypertensive Agents; D011461:Prostaglandins F, Synthetic; D013449:Sulfonamides; D013876:Thiophenes; D000077338:Latanoprost; D013999:Timolol; C062765:dorzolamide; D019793:Fluorescein