Effects of topical nipradilol and timolol maleate on intraocular pressure, facility of outflow, arterial blood pressure and pulse rate in dogs

Abstract

Nipradilol is an alpha(1), beta-blocker with milder side effects than other beta-blockers used in humans. In this study the effects of nipradilol were compared with those of timolol maleate in dogs. Twelve clinically normal dogs (nine mongrels, two beagles, and one Akita) were used. We applied 0.25% nipradilol or 0.5% timolol maleate drops for a period of 28 days. Intraocular pressure (IOP) was measured before and after administration on the 2nd, 4th, 7th, 14th, 21st and 28th day. Blood pressure, pulse rate and coefficient of aqueous outflow (C-value) were also measured before and after administration on the 7th, 14th, 21st and 28th day. Both nipradilol and timolol maleate significantly lowered IOP from the 2nd day to the end of the study period. Nipradilol lowered IOP to an equivalent degree to timolol maleate. There was no significant change in blood pressure and pulse rate throughout the study period with administration of nipradilol. C-value showed a significant rise from the 14th day with administration of nipradilol, while it did not show any significant change during the study period with administration of timolol maleate. The reduction of IOP by nipradilol was similar to that by an existing beta-adrenergic antagonist, timolol maleate, but nipradilol was associated with fewer systemic side effects in dogs. Nipradilol appears to be a useful drug for treatment of glaucoma in dogs.

Effects of topical levobunolol or fixed combination of dorzolamide-timolol or association of dorzolamide-levobunolol on intraocular pressure, pupil size, and heart rate in healthy cats

“…They decrease IOP by diminishing the inflow rate of aqueous humor, as a result of beta-adrenoceptor blockade in the ciliary body, decreased aqueous secretion, ultrafiltration, or both (Willis, 2004). It was described that nipradilol enhanced uveoscleral outflow in normal dogs (Maehara et al, 2004). For decades, timolol have been used in the management of glaucoma in human and animals (Plumer et al, 2006), and some authors suggested that the most common antiglaucoma medication recommended for cats was timolol maleate (Blocker and van der Woerdt, 2001;Hampson et al, 2002).…”

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

“…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.…”

“…The authors concluded that these results support the use of timolol for treatment of glaucoma in dogs (Wilkie and Latimer 1991a). Maehara et al (2004) also administered timolol for 28 days in clinically normal dogs and demonstrated that the medicine significantly reduced IOP: pre-administration IOP was 15.6 mmmHg and on the 28 th day was 11.5 mmHg. The maximum per cent decrease in IOP was observed on the 7 th day and was 27.1% (Maehara et al 2004).…”

“…Maehara et al (2004) also administered timolol for 28 days in clinically normal dogs and demonstrated that the medicine significantly reduced IOP: pre-administration IOP was 15.6 mmmHg and on the 28 th day was 11.5 mmHg. 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.…”