Effects of topical administration of 0.005% latanoprost solution on eyes of clinically normal horses

Objective-To determine the effect of 0.005% latanoprost solution on intraoc ular pressure (IOP) of eyes of clinically normal horses and establish the f requency of adverse effects of drug administration. Animals-20 adult clinically normal horses. Procedure-IOP was recorded (7, 9, and 11 AM; 3, 5, and 7 PM) on days 1 and 2 (baseline), days 3 to 7 (treatment), and days 8 to 9 (follow-up), Latanop rost was administered to 1 randomly assigned eye of each horse every 24 hou rs during the treatment period, following the 7 AM IOP recording. Pupil siz e and the presence or absence of conjunctival hyperemia, epiphora, blepharo spasm, blepharedema, and aqueous flare were recorded prior to IOP measureme nt. Results-IOP was reduced from baseline by a mean value of 1.03 mm Hg (5%) in males and 3.01 mm Hg (17%) in females during the treatment period. Miosis developed in all treated eyes and was moderate to marked in 77% of horses, with the peak effect observed 4 to 8 hours after drug administration. Conju nctival hyperemia, epiphora, blepharospasm, and blepharedema were present i n 100, 57, 42, and 12% of treated eyes, respectively, 2 to 24 hours followi ng drug administration. Aqueous flare was not observed at any time point. Conclusions and Clinical Relevance-Although IOP was reduced with every 24-h our dosing of latanoprost, the frequency of prostaglandin-induced adverse e vents was high. Because recurrent uveitis appears to be a risk factor for g laucoma in horses, topical administration of latanoprost may potentiate pro staglandin-mediated inflammatory disease in affected horses.