The Efficacy of Timolol in Gel-Forming Solution After Morning or Evening Dosing in Asian Glaucomatous Patients

The aim of this study was to identify and characterize the receptor system involved in controlling encystment in Acanthamoeba using specific agonists and antagonists and to examine whether endogenous stores of catecholamines are produced by the organism. Acanthamoeba trophozoites suspended in axenic growth medium were exposed to adrenoceptor agonists and antagonists to determine which compounds promoted or prevented encystment. Second, trophozoites were cultured in medium containing a catecholamine synthesis inhibitor to investigate the effect this had on natural encystment. Nonspecific adrenoceptor agonists including epinephrine, isoprotenerol, and the selective β1 adrenoceptor agonist dobutamine were found to cause > 90% encystment of Acanthamoeba trophozoites compared to < 30% with the controls. The selective β1 antagonist metoprolol was able to inhibit epinephrine mediated encystment by > 55%. Cultures of Acanthamoeba with the catecholamine synthesis inhibitor α-methyl-p-tyrosine significantly reduced the level of amoebic encystment compared to controls. In conclusion, Acanthamoeba appear to contain a functional adrenergic receptor system of unknown structure which is involved in initiating the encystment process that can be activated and blocked by β1 agonists and antagonists respectively. Furthermore, the presence of this receptor system in Acanthamoeba indicates that topical β adrenoceptor blockers may be effective adjunct therapy by reducing the transformation of trophozoites into the highly resistant cyst stage.

show abstract

“…Topical βAR antagonists are well tolerated in the eye and are currently used in the management of glaucoma (Ong et al. ).…”

Section: Discussionmentioning

confidence: 99%

The Characterization of an Adrenergic Signalling System Involved in the Encystment of the Ocular Pathogen Acanthamoeba spp.

Heaselgrave

Kilvington

2016

J Eukaryotic Microbiology

View full text Add to dashboard Cite

show abstract

“…As it is well established that a circadian variation exists in the rate of aqueous humour production, with the rate approximately 50% lower at night compared to daytime [100, 101], it is intuitive that the morning administration of β -blockers may provide more benefit. Due to conflicting results of available trials [102, 103], however, it is left to treating clinicians to tailor the dose and administration according to patient characteristics and needs. To that end, it is important to note that the differences in the mean IOP reductions between QD administration of 0.25% and that of 0.5% timolol were not statistically significant.…”

Section: Contemporary Pharmacological Management Of Glaucomamentioning

confidence: 99%

Medical Management of Glaucoma in the 21st Century from a Canadian Perspective

Harasymowycz

Birt

Gooi

et al. 2016

Journal of Ophthalmology

View full text Add to dashboard Cite

Glaucoma is a medical term describing a group of progressive optic neuropathies characterized by degeneration of retinal ganglion cells and retinal nerve fibre layer and resulting in changes in the optic nerve head. Glaucoma is a leading cause of irreversible vision loss worldwide. With the aging population it is expected that the prevalence of glaucoma will continue to increase. Despite recent advances in imaging and visual field testing techniques that allow establishment of earlier diagnosis and treatment initiation, significant numbers of glaucoma patients are undiagnosed and present late in the course of their disease. This can lead to irreversible vision loss, reduced quality of life, and a higher socioeconomic burden. Selection of therapeutic approaches for glaucoma should be based on careful ocular examination, patient medical history, presence of comorbidities, and awareness of concomitant systemic therapies. Therapy should also be individualized to patients' needs and preferences. Recent developments in this therapeutic field require revisiting treatment algorithms and integration of traditional and novel approaches in order to ensure optimal visual outcomes. This article provides an overview of recent developments and practice trends in the medical management of glaucoma in Canada. A discussion of the surgical management is beyond the scope of this paper.

show abstract

“…Paradoxically, melanin competitively inhibits timolol. The net effect is that highly pigmented eyes require a higher concentration than less pigmented eyes, which is reflected in clinical observations in Asians and Africans (Ong et al, 2005;Otaleju and Ajayi, 1999;Katz and Berger, 1979). Zimmerman and Kaufman (1977) reported the first 24-hour dose response to topical timolol 0.25% and 0.5% was similar.…”

Section: Topical Timololmentioning

confidence: 99%

Pressure Lowering Medications

Tajudin¹,

Yaakub²

2011

Glaucoma - Current Clinical and Research Aspects

View full text Add to dashboard Cite

The Efficacy of Timolol in Gel-Forming Solution After Morning or Evening Dosing in Asian Glaucomatous Patients

Abstract: Timolol gel-forming solution is effective in reducing IOP in Asian eyes. Morning dosing was more effective in lowering the IOP compared to evening dosing.

Cited by 9 publications

References 22 publications

The Characterization of an Adrenergic Signalling System Involved in the Encystment of the Ocular Pathogen Acanthamoeba spp.

The Characterization of an Adrenergic Signalling System Involved in the Encystment of the Ocular Pathogen Acanthamoeba spp.

Medical Management of Glaucoma in the 21st Century from a Canadian Perspective

Pressure Lowering Medications

Contact Info

Product

Resources

About