Effects of topical administration of 0.5% apraclonidine on intraocular pressure, pupil size, and heart rate in clinically normal cats.
OBJECTIVE
To evaluate the effect of a topical alpha 2-agonist, 0.5% apraclonidine, on intraocular pressure (IOP), pupil size, and heart rate in clinically normal cats.


METHODS
Randomized masked saline-controlled case study.


METHODS
Nine clinically normal conditioned adult cats of either sex.


METHODS
Normal diurnal variation in IOP, pupil size, and resting heart rate was determined from 7 AM to 7 PM (day 1). On day 2, the same measurements were made after the topical application of 30 microliters of 0.5% apraclonidine to 1 randomly chosen eye of each cat. The contralateral eye received saline solution.


RESULTS
Apraclonidine lowered IOP a mean of 4.8 mm of Hg (24.0%) when compared with IOP in the fellow saline-treated eye 6 hours after treatment. Unilateral administration of the drug also may have reduced IOP in both eyes. Pupil size was reduced a mean 46% in only the apraclonidine-treated eye, and miosis persisted for up to 24 hours. Heart rate was significantly lower (11.8%) at 3 hours, and 8 of 9 cats vomited after topical administration of the drug. Mild blanching of the conjunctiva occurred in all apraclonidine-treated eyes.


CONCLUSIONS
Apraclonidine reduced IOP, pupil size, and resting heart rate in clinically normal cats, but also induced undesirable systemic side-effects. In contrast to dogs where the drug induced mydriasis, apraclonidine caused miosis in cats.


CONCLUSIONS
The current commercially available formulation of topical 0.5% apraclonidine is too toxic for clinical use in cats. Reformulation, or identification of a less toxic congener, may result in a clinically useful antiglaucoma preparation for cats.
Miller
P E
PE
Department of Surgical Sciences, University of Wisconsin, Madison 53706-1102, USA.
Rhaesa
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SL
D000287:Administration, Topical; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D003000:Clonidine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D011680:Pupil / Q000187:drug effects*; D012016:Reference Values; D012025:Reflex, Pupillary / Q000187:drug effects; D013997:Time Factors
D000316:Adrenergic alpha-Agonists; C016986:apraclonidine; D003000:Clonidine