Effects of topical administration of latanoprost, timolol, or a combination of latanoprost and timolol on intraocular pressure, pupil size, and heart rate in clinically normal dogs

Abstract

Topical administration of latanoprost alone was as effective at lowering IOP as was administration of the latanoprost-timolol combination when both were given every 12 hours to clinically normal dogs. Timolol, either alone or in combination with latanoprost, appeared to have little or no effect on IOP in clinically normal dogs but was associated with a reduction in HR.

Autonomic drugs in the treatment of canine and feline glaucoma – Part II: Medications that lower intraocular pressure by reducing aqueous humour production

“…Nevertheless, the cited results on the effect of timolol on IOP in normotensive dogs disagree with results obtained by other researchers (Gum et al 1991, Gelatt et al 1995, Smith et al 2010. Smith et al (2010) did not demonstrate any larger IOP reduction in clinically normal dogs following the administration of timolol (0.5%). Likewise, another team of scientists did not observe timolol (0.25% and 0.5%) causing an IOP-lowering effect in healthy Beagles (Gum et al 1991).…”

“…The maximum per cent decrease in IOP was observed on the 7 th day and was 27.1% (Maehara et al 2004). Nevertheless, the cited results on the effect of timolol on IOP in normotensive dogs disagree with results obtained by other researchers (Gum et al 1991, Gelatt et al 1995, Smith et al 2010. Smith et al (2010) did not demonstrate any larger IOP reduction in clinically normal dogs following the administration of timolol (0.5%).…”

“…It should be assumed that the above undesirable side effects can also appear in small animals. It has been found that topical application of 0.5% timolol in dogs is associated with a significant reduction in heart rate (Maehara et al 2004, Plummer et al 2006, Smith et al 2010) and blood pressure (Maehara et al 2004). …”

“…The available literature contains several reports discussing the influence of timolol on IOP in normotensive and glaucomatous dogs and cats (Gum et al 1991, Wilkie and Latimer, 1991a,b, Gelatt et al 1995, Maehara et al 2004, Plummer et al 2006, Dietrich et al 2007, Smith et al 2010 and one report on the efficacy of betaxolol in prophylactic antiglaucoma therapy in primary angle closure glaucoma (PACG) in dogs (Miller et al 2000). To the best of the author's knowledge, there are no published data on the influence of other topical β-blockers on IOP in small animals.…”

“…Reported local side effects include stinging, conjunctival hyperemia, superficial punctate keratitis, photophobia and worsening dry eye symptoms (Coakes et al 1981). During the administration of timolol in dogs and cats, distinct reduction in the pupil size occurs although the same drug given to people has a negligible effect on the pupillary diameter (Wilkie and Latimer 1991a,b, Gelatt et al 1995, Plummer et al 2006, Smith et al 2010. Apart from the impact on the pupil size, we lack data concerning local adverse effects attributed to the use of β-blockers in small animals.…”