Effects of topical administration of 0.5% apraclonidine on intraocular pressure, pupil size, and heart rate in clinically normal cats

Paul E. Miller From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, 2015 Linden Dr W, Madison, WI 53706-1102.

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Suzanne L. Rhaesa From the Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, 2015 Linden Dr W, Madison, WI 53706-1102.

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Abstract

Objective

To evaluate the effect of a topical α2-agonist, 0.5% apraclonidine, on intraocular pressure (IOP), pupil size, and heart rate in clinically normal cats.

Design

Randomized masked saline-controlled case study.

Animals

Nine clinically normal conditioned adult cats of either sex.

Procedure

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 μl 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.

Clinical Relevance

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. (Am J Vet Res 1996;57:83-86)

Abstract

Objective

To evaluate the effect of a topical α2-agonist, 0.5% apraclonidine, on intraocular pressure (IOP), pupil size, and heart rate in clinically normal cats.

Design

Randomized masked saline-controlled case study.

Animals

Nine clinically normal conditioned adult cats of either sex.

Procedure

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 μl 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.

Clinical Relevance

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. (Am J Vet Res 1996;57:83-86)

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