Topical timolol, at conventional, unilateral doses causes bilateral ocular β-blockade in rabbits

Woodward, DF; Dowling, M.C.; Feldmann, Barbara; Chen, J.

doi:10.1016/s0014-4835(87)80015-5

Cited by 10 publications

(5 citation statements)

References 31 publications

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“…Preliminary experiments showed that the hypotensive effect of isoproterenol was not antagonised by contralateral administration of timolol maléate, even though the dose of timolol applied in the present study was greater than that used by other authors (11,16). Thus, the lowest curve in Figure 3 represents the full hypotensive activity of isoproterenol.…”

Section: Antagonism Of Isoproterenol-induced Ocular Hypotensioncontrasting

confidence: 45%

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Intraocular Pressure Reduction and Systemic Absorption of Timolol After Administration of One Side-Coated Inserts in Rabbits

Saettone¹,

Chetoni²,

Cappanera³

et al. 1993

Journal of Ocular Pharmacology and Therapeutics

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The object of this study was to test whether flat, circular ophthalmic inserts releasing drug only from one side, would show improved activity parameters and reduced systemic absorption. To this purpose, uncoated and one-side coated hydroxypropylcellulose inserts containing timolol were prepared and evaluated. An acrylic copolymer (Eudragit® RS) was used as coating material. Timolol release from inserts was studied both in vitro and in vivo. Timolol release in vitro from the coated inserts was much slower than from the uncoated ones, due to the smaller releasing surface area. Compared with timolol eyedrops (0.5%, 50 pi), administration of 250 |!g of timolol in uncoated or coated inserts produced a significantly greater hypotensive effect at 6 and 8 hr post instillation in rabbits with artificially increased intraocular pressure.The coated inserts containing 62.5 p. g of timolol antagonised isoproterenol-induced ocular hypotension significantly more than timolol eyedrops (0.5%, 12.5 pi) and uncoated inserts containing 62.5 pg of timolol. Both uncoated and coated inserts provided a significant sustaining of timolol release in tear fluid and decreased systemic peak concentrations of timolol with respect to the eyedrop control. However, one-side coated inserts failed to show significant improvements with respect to the uncoated samples.

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Section: Antagonism Of Isoproterenol-induced Ocular Hypotensioncontrasting

confidence: 45%

“…Inserts A had average weight 16.0 mg, thickness 0.45 mm, and timolol maléate content of 0.34 mg (0.25 mg as timolol base equivalents), while inserts B had average weight 8 mg, thickness 0.3 mm, and timolol maléate content of 0.17 mg. No insert differed from the average weight by more than 5%.…”

Section: Preparation Of Insertsmentioning

confidence: 99%

Intraocular Pressure Reduction and Systemic Absorption of Timolol After Administration of One Side-Coated Inserts in Rabbits

Saettone¹,

Chetoni²,

Cappanera³

et al. 1993

Journal of Ocular Pharmacology and Therapeutics

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“…5). Moreover, systemic absorption of topical β-antagonists has been well-documented by other investigators (Woodward et al, 1987 ;Lee, Kompella and Lee, 1993 ;Dunham, Spaide and Dunham, 1994 ;Acheampong et al, 1995). Thus, it seems reasonable to assume that both drugs reached the choroid.…”

Section: Discussionmentioning

confidence: 84%

Effects of Timolol and Betaxolol on Choroidal Blood Flow in the Rabbit

Kiel

Patel

1998

Experimental Eye Research

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“…It may be interesting that it does not only lower IOP in the treated eye but also the contralateral eye without treatment. It is assumed that this bilateral effect of timolol occurs as a result of its systemic absorption [46]. Side effects of BBs are usually the result of betablocking action.…”

Section: Beta-adrenergic Blockersmentioning

confidence: 99%

Opportunities to Topically Reduce Intraocular Pressure in Glaucoma

Rahić

Tucak

Sirbubalo

et al. 2021

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Since glaucoma is a serious health problem, numerous therapeutics are being developed to reduce Intraocular Pressure (IOP) as the only modifiable factor of all glaucoma symptoms. IOP-lowering agents are divided into six groups, each of which has a specific mechanism of action and side effects, which are the focus of this article and are explained in detail. All the mentioned agents are formulated as eye drops. However, as conventional topical eye drops have significant disadvantages, of which poor bioavailability and patient noncompliance are the main, novel approaches to designing their drug delivery systems were used and briefly presented in this review.

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Topical timolol, at conventional, unilateral doses causes bilateral ocular β-blockade in rabbits

Cited by 10 publications

References 31 publications

Intraocular Pressure Reduction and Systemic Absorption of Timolol After Administration of One Side-Coated Inserts in Rabbits

Intraocular Pressure Reduction and Systemic Absorption of Timolol After Administration of One Side-Coated Inserts in Rabbits

Effects of Timolol and Betaxolol on Choroidal Blood Flow in the Rabbit

Opportunities to Topically Reduce Intraocular Pressure in Glaucoma

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