Objective—To determine the effect of 0.005%
latanoprost solution on intraocular pressure (IOP) of
eyes of clinically normal horses and establish the frequency
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). Latanoprost was
administered to 1 randomly assigned eye of each
horse every 24 hours during the treatment period, following
the 7 AM IOP recording. Pupil size and the
presence or absence of conjunctival hyperemia,
epiphora, blepharospasm, blepharedema, and aqueous
flare were recorded prior to IOP measurement.
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.
Conjunctival hyperemia, epiphora, blepharospasm,
and blepharedema were present in 100, 57, 42, and
12% of treated eyes, respectively, 2 to 24 hours following
drug administration. Aqueous flare was not
observed at any time point.
Conclusions and Clinical Relevance—Although IOP
was reduced with every 24-hour dosing of
latanoprost, the frequency of prostaglandin-induced
adverse events was high. Because recurrent uveitis
appears to be a risk factor for glaucoma in horses,
topical administration of latanoprost may potentiate
prostaglandin-mediated inflammatory disease in
affected horses. (Am J Vet Res 2001;62:1945–1951)