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)
Objective—To determine effects of topical antimicrobial
and antimicrobial-corticosteroid preparations on
the ocular flora of horses.
Procedure—One eye was treated 3 times daily for 2
weeks with one of the following ointments: 1) neomycinbacitracin-
polymyxin B, 2) 0.6% prednisolone-0.3% gentamicin,
3) neomycin-polymyxin B-0.05% dexamethasone,
or 4) treated (artificial tears) control. Contralateral eyes of
treated control eyes served as untreated control eyes.
Corneal and conjunctival specimens for bacterial and fungal
cultures were collected prior to initiation of treatment,
after 1 and 2 weeks of treatment, and 2 weeks after concluding
treatment. Changes in culture growth quantity
scores of bacterial and fungal species were analyzed.
Results—The most common species before treatment
were the following: gram-positive bacteria included
Streptomyces spp (66%) , Staphylococcus spp (46%) ,
Bacillus spp (32%) , and Streptococcus spp (32%); gramnegative
bacteria included Moraxella spp (28%) ,
Escherichia coli (24%) , Acinetobacter spp (18%), and
Enterobacter spp (14%); and fungi included Aspergillus
nidulans (56%) , Cladosporium spp (32%), and
Aspergillus fumigatus (22%). In all groups, the percentage
of positive bacterial culture results, growth quantity
score of gram-positive bacteria, and number of bacterial
species isolated decreased at week 1 and increased at
week 2, whereas growth quantity score of gram-negative
bacteria decreased throughout treatment. Differences
were not significant among groups. Fungal growth quantity
score decreased during treatment in all groups.
Repopulation of bacterial and fungal species occurred.
Conclusions and Clinical Relevance—All interventions
decreased the number of microorganisms.
Repopulation of normal flora occurred during and after
treatment. (Am J Vet Res 2005;66:800–811)
Objective—To evaluate the effect of topical administration
of 2% dorzolamide hydrochloride or 2% dorzolamide
hydrochloride-0.5% timolol maleate on intraocular
pressure (IOP) in clinically normal horses.
Animals—18 healthy adult horses without ocular
Procedure—The IOP was measured at 5 time points
(7 AM, 9 AM, 11 AM, 3 PM, 7 PM) over 11 days. On days
1 and 2, baseline values were established. On days 3
through 5, horses received 2% dorzolamide HCl
(group D, n = 9) or 2% dorzolamide HCl-0.5% timolol
maleate (group DT, 9) in 1 randomly assigned eye
every 24 hours immediately following each daily 7 AM
IOP measurement. On days 6 through 9, each drug
was given every 12 hours (7 AM and 7 PM) in the treated
eye. Measurements on days 10 and 11 assessed
return to baseline. Mixed linear regression models
compared mean IOP difference for each drug at each
Results—Mean IOP decreased significantly in all
eyes during the 2 dose/d period, compared with the
baseline, 1 dose/d, and follow-up periods.
Conclusions and Clinical Relevance—Administration
of either drug every 24 hours for short-term
treatment does not reduce IOP significantly.
Administering either drug every 12 hours induced a
significant reduction of IOP; however, controlling for
all variables, the reduction was less than 2 mm Hg.
(Am J Vet Res 2001;61:709–713)
Objective—To determine the anesthetic, cardiorespiratory,
and metabolic effects of 4 IV anesthetic regimens
in Thoroughbred horses recuperating from a
brief period of maximal exercise.
Animals—6 adult Thoroughbreds.
Procedure—Horses were preconditioned by exercising
them on a treadmill. Each horse ran 4 simulated
races, with a minimum of 14 days between races.
Races were run at a treadmill speed that caused horses
to exercise at 120% of their maximal oxygen consumption.
Horses ran until fatigued or for a maximum
of 2 minutes. Two minutes after exercise, horses
received a combination of xylazine hydrochloride (2.2
mg/kg of body weight) and acepromazine maleate
(0.04 mg/kg) IV. Five minutes after exercise, horses
received 1 of the following 4 IV anesthetic regimens:
ketamine hydrochloride (2.2 mg/kg); ketamine (2.2
mg/kg) and diazepam (0.1 mg/kg); tiletamine
hydrochloride-zolazepam hydrochloride (1 mg/kg); and
guaifenesin (50 mg/kg) and thiopental sodium (5
mg/kg). Treatments were randomized. Cardiopulmonary
indices were measured, and samples of
blood were collected before and at specific times for
90 minutes after each race.
Results—Each regimen induced lateral recumbency.
The quality of induction and anesthesia after ketamine
administration was significantly worse than after
other regimens, and the duration of anesthesia was
significantly shorter. Time to lateral recumbency was
significantly longer after ketamine or guaifenesinthiopental
administration than after ketaminediazepam
or tiletamine-zolazepam administration.
Arterial blood pressures after guaifenesin-thiopental
administration were significantly lower than after the
Conclusions and Clinical Relevance—Anesthesia
can be safely induced in sedated horses immediately
after maximal exercise. Ketamine-diazepam and tiletamine-
zolazepam induced good quality anesthesia
with acceptable perturbations in cardiopulmonary and
metabolic indices. Ketamine alone and guaifenesinthiopental
regimens are not recommended. (Am J Vet
Objective—To evaluate intra-articular autologous protein solution (APS) for the treatment of osteoarthritis in horses.
Animals—40 client-owned horses with naturally occuring osteoarthritis.
Procedures—APS was generated from a dual-device system that concentrated plasma and WBC proteins and enriched platelet growth factors. Horses were randomly assigned to receive an intra-articular injection of 5 mL of saline (0.9% NaCl) solution (n = 20) or APS (20), exercised on a treadmill, and evaluated on the basis of lameness grades, kinetic gait analysis, joint circumference, and range of motion for 14 days. Horses that received saline solution were administered APS at termination of the study, and clients scored horses for lameness and discomfort before, 12 weeks after, and 52 weeks after the APS injection.
Results—The APS group had significant improvements in lameness grade, asymmetry indices of vertical peak force, and range of joint motion by 14 days, compared with baseline or control group values. No adverse effects associated with APS treatment were evident. Clients assessed lameness and comfort as improved at 12 and 52 weeks. The APS had greater likelihood (OR, 4.3 to 30.0) of a therapeutic response in horses with a lameness score < 4, < 10% vertical force asymmetry, or absence of marked osteophyte formation, subchondral sclerosis, or joint space narrowing. Concentration of interleukin-1 receptor antagonist in APS was 5.8 times that in blood.
Conclusions and Clinical Relevance—Intra-articular administration of APS can be considered an effective treatment option for equine osteoarthritis, with the potential for disease-modifying effects.