Acute versus chronic effects of brimonidine on aqueous humor dynamics in ocular hypertensive patients

Severe Central Nervous System and Respiratory Depression in a Neonate Following Accidental Oral Ingestion of Brimonidine Tartrate

Brimonidine is a third-generation alpha-2 adrenergic agonist and is classified as an ocular hypotensive agent. It is used for chronic glaucoma treatment by lowering intraocular pressure, crucial for preventing blindness. Brimonidine works by reducing aqueous humor production and increasing uveoscleral outflow. The improper use of brimonidine in children can result in severe adverse effects. If brimonidine eye drops are ingested orally, it can cause significant depression of the cardiorespiratory and central nervous systems. This is a case report of a 27-day-old neonate, who presented with central nervous system and respiratory depression after accidental ingestion of one drop of brimonidine tartrate ophthalmic solution. On arrival, he was having shallow breathing, a low Glasgow Coma Scale score, pinpoint pupils, and absent deep tendon reflexes. Gastric lavage was performed and supportive treatment was started. The patient showed gradual improvement and completely recovered within 48 hours.

Brimonidine as a possible treatment for myopia

BACKGROUND

Myopia is becoming a huge burden on the world's public health systems. The purpose of this study was to explore the effect of brimonidine in the treatment of form-deprivation myopia (FDM) and the relationship between intraocular pressure (IOP) and myopia development.

METHODS

Monocular form deprivation myopia (FDM) was induced in three-week-old pigmented male guinea pigs. They were treated with 3 different methods of brimonidine administration (eye drops, and subconjunctival or intravitreal injections). Four different concentrations of brimonidine were tested for each method (2µg/µL, 4µg/µL, 20µg/µL, and 40µg/µL). All treatments continued for a period of 21 days. Tonometry, retinoscopy, and A-scan ultrasonography were used to monitor intraocular pressure, refractive error and axial length (AL), respectively.

RESULTS

Treatment with subconjunctival brimonidine at 40µg/µL, and intravitreal brimonidine at 2µg/µL and 4µg/µL, inhibited the development of FDM. The myopic refraction, excessive axial length, and elevation of IOP were significantly decreased. Brimonidine in eye drops was ineffective.

CONCLUSION

Brimonidine at appropriate doses significantly reduced the development of FD myopia in guinea pigs. The IOP may change with FD myopia.

Effect of a fixed combination of ripasudil and brimonidine on aqueous humor dynamics in mice

Ripasudil-brimonidine fixed-dose combination (K-232) simultaneously targets three different intraocular pressure (IOP) lowering mechanisms, increasing trabecular meshwork outflow and uveoscleral outflow, and reducing aqueous humor production Vascularly, ripasudil induces transient vasodilation, brimonidine transient vasoconstriction. Investigating effects on IOP, aqueous dynamics, and EVP in mice eyes by microneedle and constant-pressure perfusion methods, and on cytoskeletal and fibrotic proteins changes in HTM cells by a gel contraction assay and immunocytochemistry. Ripasudil, K-232, and brimonidine droplets significantly reduced IOP at 30 min, with K-232 sustaining the effect at 60 min. For EVP, only K-232 exhibited reduced EVP until 60 min after instillation. In vitro, ripasudil inhibited gel contractility and TGFβ2-induced fibrotic changes, whereas brimonidine did not. K-232 significantly lowered IOPs in mice by combining the effects of ripasudil and brimonidine. Brimonidine alone also showed IOP reductions with enhanced outflow facility, and the drug did not interfere with the effects of ripasudil on the trabecular meshwork outflow; K-232 and ripasudil alone both significantly lowered the EVP and enhanced outflow facility, demonstrating that K-232 efficiently reduces IOPs.

Reusable nano-catalyzed green protocols for the synthesis of quinoxalines: an overview

Heterocyclic compounds are very widely distributed in nature and are essential for life activities. They play a vital role in the metabolism of all living cells, for example, vitamins and co-enzyme precursors thiamine, riboflavin etc. Quinoxalines are a class of N-heterocycles that are present in a variety of natural and synthetic compounds. The distinct pharmacological activities of quinoxalines have attracted medicinal chemists considerably over the past few decades. Quinoxaline-based compounds possess extensive potential applications as medicinal drugs, presently; more than fifteen drugs are available for the treatment of different diseases. Diverse synthetic protocols have been developed via a one-pot approach using efficient catalysts, reagents, and nano-composites/nanocatalysts etc. But the use of homogeneous and transition metal-based catalysts suffers some demerits such as low atom economy, recovery of catalysts, harsh reaction conditions, extended reaction period, expensive catalysts, the formation of by-products, and unsatisfactory yield of products as well as toxic solvents. These drawbacks have shifted the attention of chemists/researchers to develop green and efficient protocols for synthesizing quinoxaline derivatives. In this context, many efficient methods have been developed for the synthesis of quinoxalines using nanocatalysts or nanostructures. In this review, we have summarized the recent progress (till 2023) in the nano-catalyzed synthesis of quinoxalines using condensation of o-phenylenediamine with diketone/other reagents with plausible mechanistic details. With this review, we hope that some more efficient ways of synthesizing quinoxalines can be developed by synthetic chemists.

Comparisons of efficacy and safety between preserved and preservative-free brimonidine tartrate in glaucoma and ocular hypertension: a parallel-grouped, randomized trial

This multicenter (four institutions), randomized, investigator-masked, parallel-group clinical trial evaluated and compared the efficacy and safety of preservative-free and preserved brimonidine tartrate 0.15% in open-angle glaucoma and ocular hypertension. Sixty eyes of 60 patients with intraocular pressure (IOP) ≥ 15 mmHg diagnosed with open-angle glaucoma or ocular hypertension were randomized to preserved (n = 31) and preservative-free (n = 29) brimonidine groups. The enrolled eyes received brimonidine monotherapy three times daily. Main outcome measures were corneal/conjunctival staining score, ocular surface disease index, patient satisfaction score, drug tolerance, and drug adherence rate 12 weeks post first administration. Secondary outcome measurements included visual acuity, IOP, drug tolerance, tear-film break-up time, hemodynamic changes including blood pressure and heart rates, and ocular adverse events. After 12 weeks, both preserved and preservative-free groups showed similar IOP reduction, corneal and conjunctival staining scores, drug tolerance, and adherence rates. The preservative-free group showed significantly better tear-film break-up time and higher patient satisfaction regarding drug use and management. Systolic and diastolic blood pressure reductions during the 12 weeks were significantly lower in the preserved group than in the preservative-free group. Preservative-free brimonidine tartrate showed comparable efficacy and safety, better corneal tear film stability, and patient satisfaction than preserved brimonidine.

The Multifarious Effects of Various Glaucoma Pharmacotherapy on Corneal Endothelium: A Narrative Review

Corneal endothelium is a single cell layer that is mainly responsible for maintaining corneal clarity. Endothelial damage secondary to toxicity, stress, or genetic predisposition are common and in conjunction with the low regenerative ability of the cells, making their preservation critical for maintaining visual acuity. Patients with glaucoma, who are estimated to be close to 80 million worldwide, have a plethora of reasons for developing endothelial damage, being exposed to a spectrum that extends from various medical and surgical interventions to the disease itself. The wide spectrum of glaucoma pharmacotherapy that has been recently extended by addition of newer classes of medications has been the focus of extensive research on its effects on corneal endothelium. Both basic and clinical research have attempted to shine a light on the complex mechanisms associated with the effects of glaucoma medication on corneal endothelium and to answer the important question as to whether these findings are clinically significant. The aim of this review is to summarize and present current literature of the various findings, both from in vivo and in vitro studies that have focused on the complex relationship between different classes of glaucoma medication and their effect on corneal endothelium.

Trends in development and quality assessment of pharmaceutical formulations - F2α analogues in the glaucoma treatment

The ocular delivery route presents a number of challenges in terms of drug administration and bioavailability. The low bioavailability following topical ophthalmic administration shows that there is a clear need for in-depth research aimed at finding both more efficacious molecules and formulations precisely targeted at the site of action. Continuous technological development will eventually result in improved bioavailability, lower dosages, reduced toxicity, fewer adverse effects, and thus better patient compliance and treatment efficacy. Technological development, as well as increasingly stringent quality requirements, help stimulate analytical progress. This is also clearly evident in the case of medicinal products used in the treatment of glaucoma, which are the subject of this review. Impurity profiling of PGF2α analogues, either in the pure substance or in the finished formulation, is a crucial step in assessing their quality. The development of specific, accurate and precise stability-indicating analytical methods for determining the content and related substances seems to be an important issue in relation to this tasks. A total of 27 official and in-house analytical methods are presented that are used for the analysis of latanoprost, travoprost and bimatoprost. The conditions for chromatographic separation with UV or MS/MS detection and the available results obtained during method validation are described. In addition, several aspects are discussed, with particular emphasis on the instability of the analogues in aqueous solution and the phenomenon of isomerism, which affects a potentially large number of degradation products.

Brimonidine and timolol concentrations in the human vitreous and aqueous humors after topical instillation of a 0.1% brimonidine tartrate and 0.5% timolol fixed-combination ophthalmic solution: An interventional study

PURPOSE

To evaluate the concentrations of brimonidine and timolol in the vitreous and aqueous humors after instillation of a 0.1% brimonidine tartrate and 0.5% timolol fixed-combination ophthalmic solution.

METHODS

This single-arm open-label interventional study included patients with macular holes or idiopathic epiretinal membranes who were scheduled for vitrectomy. Written informed consent was obtained from all participants. A 0.1% brimonidine tartrate and 0.5% timolol fixed-combination ophthalmic solution was administered topically twice daily for 1 week preoperatively. The vitreous and aqueous humors were sampled before vitrectomy, and brimonidine and timolol concentrations were quantified using liquid chromatography-tandem spectrometry. This study was registered with the Japan Registry of Clinical Trials (jRCT, ID jRCTs051200008; date of access and registration: April 28, 2020). The study protocol was approved by the University of Fukui Certified Review Board (CRB) and complied with the tenets of the Declaration of Helsinki.

RESULTS

Eight eyes of eight patients (7 phakic eyes and 1 pseudophakic eye) were included in this study. The mean brimonidine concentrations in the vitreous and aqueous humors were 5.04 ± 4.08 nM and 324 ± 172 nM, respectively. Five of the eight patients had brimonidine concentrations >2 nM in the vitreous humor, which is necessary to activate α2 receptors. The mean timolol concentrations in the vitreous and aqueous humors were 65.6 ± 56.0 nM and 3,160 ± 1,570 nM, respectively. Brimonidine concentrations showed significant positive correlations with timolol concentrations in the vitreous humor (P < 0.0001, R2 = 0.97) and aqueous humor (P < 0.0001, R2 = 0.96).

CONCLUSIONS

The majority of patients who received a 0.1% brimonidine tartrate and 0.5% timolol topical fixed-combination ophthalmic solution showed a brimonidine concentration >2 nM in the vitreous humor. Brimonidine and timolol may be distributed in the ocular tissues through an identical pathway after topical instillation.

Changes in Ocular Biometric Parameters Over a 24-Hour Period in Ocular Hypertensive Patients

Purpose: To identify 24-h changes in ocular biometric parameters in subjects with ocular hypertension (OHT), and to determine if an intraocular pressure (IOP)-lowering drug alters these parameters. Methods: Thirty volunteers with OHT (58.6 ± 9.2 years of age) were enrolled in this randomized, double-masked, placebo-controlled, crossover study. Participants self-administered 0.2% brimonidine or placebo 3 times daily for 6 weeks. Measurements of seated and supine IOP, central cornea thickness (CCT), anterior chamber depth (ACD), axial length (AXL), and lens thickness were made at 8 am, 3 pm, 8 pm, and 3 am. Statistical tests were Student's 2-tailed paired t-tests or 2-way analysis of variance (ANOVA) followed by one-way ANOVA and post hoc testing. Results: Time of day had a significant effect on IOP, CCT, ACD, and AXL. In placebo-treated eyes, CCT was greater at 3 am than at any other time (P < 0.01), ACD and AXL were greater at 3 am and 8 pm than at 3 pm (P < 0.01). Daytime IOPs were higher than nighttime (seated, P = 0.007; supine, P = 0.018), and supine IOP at night was higher than seated IOP during the day (P < 0.001). Brimonidine did not lower IOP at night nor did it alter the 24-h patterns of CCT, ACD, and AXL. Conclusions: Ocular biometric parameters exhibit characteristic 24-h fluctuations in patients with OHT. At night compared with day, the supine IOP increases, the cornea thickens, the anterior chamber deepens, and the AXL increases. Brimonidine does not alter these parameters at times when it lowers IOP (day) nor when it does not (night). Clinical Trial Registration number: NCT0132419.

Anti-glaucoma medications lowered decorin and altered profibrotic proteins in human tenon's fibroblasts

Long term exposure to anti-glaucoma medications (AGMs) leads to an increase in extracellular matrix (ECM) accumulation in primary glaucoma patients. This study aims to evaluate the effect of topical AGMs in primary human tenon's fibroblasts (HTFs) and analyze the expression of profibrotic and anti-fibrotic proteins. Primary HTFs were cultured from patients undergoing cataract (control) and trabeculectomy. The different types of AGMs in single/multiple combinations (BB, PG, AA, CAI, CH, combinations of 3- PG + AA + CAI, 4A- BB + PG + AA + CAI, 4B- BB + PG + CAI + CH and 5- BB + PG + AA + CAI + CH) on chronic exposure were tested for cell viability using MTT assay and morphological alterations. Profibrotic proteins mainly SPARC, LOXL2, COL1A1 and anti-fibrotic DCN were analyzed in treated HTFs using q-PCR and ELISA. Sirius red staining and collagen gel contraction (CGC) assay were performed to assess collagen synthesis and the contractility of HTFs, respectively. Except for AA and CH, the other AGMs at a higher concentration were found to decrease the cell viability of HTFs. The morphology of HTFs were altered on exposure to BB, CH and AA; Profibrotic proteins i.e., SPARC, LOXL2 and COL1A1 were significantly increased (p < 0.05) on exposure to a combination of AGMs with TGF-β1, whereas the anti-fibrotic DCN expression was significantly lowered (p < 0.05) in single/multiple AGM exposure. Sirius red staining showed increased collagen synthesis with combinations of AGMs with TGF-β1. Meanwhile, HTFs showed increased collagen gel contraction with TGF-β1, CAI and CH. This study reveals that altered profibrotic proteins, with significantly lowered DCN on chronic exposure of AGMs in HTFs.

Screening for Glaucoma in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

Two 2013 systematic reviews to inform the US Preventive Services Task Force (USPSTF) found insufficient evidence to assess benefits and harms of screening for primary open-angle glaucoma (OAG) in adults.

OBJECTIVE

To update the 2013 reviews on screening for glaucoma, to inform the USPSTF.

DATA SOURCES

Ovid MEDLINE, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews (to February 2021); surveillance through January 21, 2022.

STUDY SELECTION

Randomized clinical trials (RCTs) of screening, referral, and treatment; and studies of screening test diagnostic accuracy.

DATA EXTRACTION AND SYNTHESIS

One investigator abstracted data and a second checked accuracy. Two investigators independently assessed study quality.

RESULTS

Eighty-three studies (N = 75 887) were included (30 trials and 53 diagnostic accuracy studies). One RCT (n = 616) found screening of frail elderly persons associated with no difference in vision outcomes vs no screening but with significantly greater falls risk (relative risk [RR], 1.31 [95% CI, 1.13-1.50]). No study evaluated referral to an eye health professional. For glaucoma diagnosis, spectral domain optical coherence tomography (providing high-resolution cross-sectional imaging; 15 studies, n = 4242) was associated with sensitivity of 0.79 (95% CI, 0.75-0.83) and specificity of 0.92 (95% CI, 0.87-0.96) and the Humphrey Visual Field Analyzer (for perimetry, or measurement of visual fields; 6 studies, n = 11 244) with sensitivity of 0.87 (95% CI, 0.69-0.95) and specificity 0.82 (95% CI, 0.66-0.92); tonometry (for measurement of intraocular pressure; 13 studies, n = 32 892) had low sensitivity (0.48 [95% CI, 0.31-0.66]). Medical therapy for ocular hypertension and untreated glaucoma was significantly associated with decreased intraocular pressure and decreased likelihood of glaucoma progression (7 trials, n = 3771; RR, 0.68 [95% CI, 0.49-0.96]; absolute risk difference -4.2%) vs placebo, but 1 trial (n = 461) found no differences in visual acuity, quality of life, or function. Selective laser trabeculoplasty and medical therapy had similar outcomes (4 trials, n = 957).

CONCLUSIONS AND RELEVANCE

This review found limited direct evidence on glaucoma screening, showing no association with benefits. Screening tests can identify persons with glaucoma and treatment was associated with a lower risk of glaucoma progression, but evidence of improvement in visual outcomes, quality of life, and function remains lacking.

In vitro and in vivo evaluation of brimonidine loaded silica nanoparticles-laden silicone contact lenses to manage glaucoma

Glaucoma is treated by frequent instillation of 0.2% w/v brimonidine tartrate eye drop solution, which showed poor ocular bioavailability of 1-3%. Medicated contact lenses can be used to improve the ocular drug bioavailability. However, drug loading in the contact lens matrix showed high burst release and changes the optophysical properties of the contact lens material. In this paper, a novel brimonidine loaded silica nanoparticles-laden silicone contact lenses (Bri-Si) were designed to achieve controlled drug delivery without altering the optophysical properties of the contact lens. Silica nanoparticles were prepared by polymerizing octadecyltrimethoxysilane (OTMS) molecules at the oil/water interface of microemulsion. Traditional soaking method (Bri-SM), direct brimonidine-loading method (Bri-DL) and microemulsion-laden contact lens (Bri-ME) were developed for comparison. The Bri-Si lens showed improved swelling, transmittance, oxygen permeability and lysozyme adherence compared to Bri-SM, Bri-DL and Bri-ME lenses. The Bri-DL lens showed high brimonidine leaching during extraction and sterilization steps, with low cumulative drug release. While, Bri-Si lens show controlled brimonidine release for 144 h. In a rabbit tear fluid model, the Bri-Si lens showed high brimonidine concentration for 96 h compared to Bri-ME lens and eye drop therapy. Based on histopathological studies of cornea, the Bri-Si lens was found to be safe for human applications. The data demonstrated the novel application of silica nanoparticles to control brimonidine release from the contact lens without altering the optophysical properties of the contact lens.

Synthesis, molecular docking, and 2D-QSAR modeling of quinoxaline derivatives as potent anticancer agents against triple-negative breast cancer

BACKGROUND

Breast carcinomas aka triple-negative breast cancers (TNBC) are one of the most complex and aggressive forms of cancers in females. Recently, studies have shown that these carcinomas are resistant to hormone-targeted therapies, which makes it a priority to search for effective and potential anticancer drugs. The present study was aimed to synthesize and develop the 2D-quantitative structural activity relationship model (QSAR) of quinoxaline derivatives as a potential anticancer agent.

METHODS

Quinoxaline derivatives were designed and synthesized (8a-8i and 9a-9d) and the 2D-QSAR model against TNBC was developed using VLife MDS v4.4. The anticancer activity was investigated against the TNBC MDA-MB-231 cell line using an MTT cytotoxicity assay. Molecular docking studies along with the estimation of ADMET parameters were done, using Discovery Studio. The most potent compound was docked against the β-tubulin protein target (PDB: 4O2B), using the Autodock Vina v0.8 program.

RESULTS

Eleven derivatives of quinoxaline were designed and synthesized (8a-8i and 9a-9d) and a 2D-QSAR model was developed against the TNBC MDA-MB231 cell line. The regression coefficient values for the training set were (r2) 0.78 and (q2) 0.71. Further, external test set regression (pred_r2) was 0.68. Five molecular descriptors viz., energy dispersive (Epsilon3), protein-coding gene (T_T_C_6), molecular force field (MMFF_6), most hydrophobic hydrophilic distance (XA), and Zcomp Dipole were identified. After ADMET, the best analog 8a showed the best activity against the TNBC cell line. The best-predicted hit '8a' was found to bind within the active site of the β-tubulin protein target. Conclusion The newly synthesized quinoxaline compounds could serve as potent leads for the development of novel anti-cancer agents against TNBC.

The prophylactic effect of betaxolol 0.5% versus brimonidine 0.2% on IOP elevation after Nd:YAG laser posterior capsulotomy

CLINICAL RELEVANCE

Posterior capsule opacification is a common late complication of cataract surgery. Posterior capsule opening with Nd:YAG laser, which is the standard treatment, may cause transient elevation of intraocular pressure (IOP).

BACKGROUND

To evaluate the efficacy of betaxolol 0.‌5% compared to brimonidine 0.2%, in prevention of intraocular pressure increase after Nd:YAG Laser posterior capsulotomy.

METHODS

In a double masked randomised clinical trial, 38 eyes from 38 pseudophakic patients over 21 years of age who had significant posterior capsule opacification after phacoemulsification were randomly assigned to receive either betaxolol 0.‌5% (18 eyes) or brimonidine 0.‌2% (20 eyes) one hour before Nd:YAG Laser posterior capsulotomy.‌ Exclusion criteria were: glaucoma or history of glaucoma surgery, active uveitis, active ocular infection, pregnancy, unstable cardiovascular condition and severe asthma and lung diseases. Intraocular pressure was measured by Goldmann applanation tonometry, 1 hour before applying the laser and 4 hours after the laser application.

RESULTS

There was no statistically significant difference between the two groups regarding the baseline mean IOP and the 4-hour post-laser mean IOP. There was a statistically significant decrease in the 4-hour post-laser mean IOP as compared to the baseline mean IOP in each group. The mean IOP change in the betaxolol group, was -2.39 ± 1.79 mm Hg and in the brimonidine group was -4.25 ± 2.20 mm Hg. The difference was statistically significant (P = 0.007). None of the patients experienced clinically significant IOP increase (≥5 mm Hg) in either group.

CONCLUSION

Use of a single topical dose of betaxolol 0.5% and brimonidine 0.2%, 1 hour before laser treatment, can prevent significant acute IOP increase after Nd:YAG laser posterior capsulotomy, and betaxolol may provide a new alternative for prophylactic use.

Additive Intraocular Pressure-Lowering Effects of a Novel Selective EP2 Receptor Agonist, Omidenepag Isopropyl, Combined with Existing Antiglaucoma Agents in Conscious Ocular Normotensive Monkeys

Purpose: To investigate the intraocular pressure (IOP)-lowering effects of omidenepag isopropyl (OMDI), a potent and highly selective prostanoid EP2 receptor agonist, as a potential first-line ocular hypotensive agent when combined with existing antiglaucoma agents in conscious ocular normotensive monkeys. Methods: Male cynomolgus monkeys were examined under conscious conditions. OMDI ophthalmic solution alone was topically applied to an eye or combined with other ophthalmic solutions at 5-min intervals. The contralateral eye was left untreated. IOP was measured before and at 2, 4, 6, and 8 h after instillation. Results: Topical application of OMDI to the eye resulted in statistically significant IOP reduction, which lasted for at least 6 h. The IOP-lowering effects of OMDI concomitantly administered with any of the tested antiglaucoma agents (timolol, brinzolamide, netarsudil, ripasudil, and brimonidine) were greater than those of OMDI alone. Furthermore, these enhanced IOP responses to their concomitant use were statistically significant compared with those of the tested antiglaucoma agents alone. Any combination of OMDI with the tested agents did not lead to serious abnormalities either systemically or locally in the eye. Conclusions: We demonstrated that OMDI has additive IOP-lowering effects when administered in combination with various antiglaucoma agents, namely, β-adrenergic antagonist, carbonic anhydrase inhibitor, Rho-associated coiled-coil containing protein kinase inhibitors, and α2-adrenergic agonist. These results suggest that OMDI provides additional clinical benefits because of its unique mechanisms of action when combination therapy is required.

Glaucoma: Management and Future Perspectives for Nanotechnology-Based Treatment Modalities

Glaucoma, being asymptomatic for relatively late stage, is recognized as a worldwide cause of irreversible vision loss. The eye is an impervious organ that exhibits natural anatomical and physiological barriers which renders the design of an efficient ocular delivery system a formidable task and challenge scientists to find alternative formulation approaches. In the field of glaucoma treatment, smart delivery systems for targeting have aroused interest in the topical ocular delivery field owing to its potentiality to oppress many treatment challenges associated with many of glaucoma types. The current momentum of nano-pharmaceuticals, in the development of advanced drug delivery systems, hold promises for much improved therapies for glaucoma to reduce its impact on vision loss. In this review, a brief about glaucoma; its etiology, predisposing factors and different treatment modalities has been reviewed. The diverse ocular drug delivery systems currently available or under investigations have been presented. Additionally, future foreseeing of new drug delivery systems that may represent potential means for more efficient glaucoma management are overviewed. Finally, a gab-analysis for the required investigation to pave the road for commercialization of ocular novel-delivery systems based on the nano-technology are discussed.

Potential neuroprotective biomolecules in ophthalmology

PURPOSES

Retinal neurodegenerative diseases are responsible for a huge number of ocular problems worldwide. It seems that the progression of these diseases can be managed by the application of neuroprotective molecules particularly in the early stages. This article focuses on the most common neuroprotective bioagents under investigation in ophthalmology.

METHODS

We searched the web of science, PubMed and Scopus databases with these keywords: "glaucoma," "diabetic retinopathy," "age-related macular degeneration," "optic neuropathy and retinal degeneration" and/or "neuroprotection."

RESULTS

The most commonly utilized neuroprotective drugs for ophthalmology diseases were introduced in this study. It seems that these agents can be divided into three categories according to their mechanism of action: (A) neurotrophins, (B) decreasing effect on intraocular pressure and (C) inhibition of retinal neuron apoptosis.

CONCLUSION

A broad range of drugs has been illustrated in the literature for treatment of neuro-ophthalmic diseases. A good classification of the most applied drugs in this field can help specialists to prescribe the best matched drug considering the stage and progression of disease. However, controlled clinical trials are needed for better evaluation of the effects of these products.

Prolonged central nervous system and respiratory depression in preterm neonates after exposure to brimonidine tartrate and timolol maleate ophthalmic drops

Objective: We report three cases of preterm neonates who presented with central nervous system (CNS) and respiratory depression after inadvertent exposure to brimonidine tartrate 0.2% and timolol maleate 0.5% fixed-combination ophthalmic drops. Case descriptions: CNS and respiratory depression were observed in the three neonates within two hours of administration of brimonidine tartrate 0.2% and timolol maleate 0.5% eye drops. Respiratory support was initiated upon admission to the neonatal intensive care unit (NICU). The effects of the drug combination lasted for 24 to 48 hours. Conclusion: This case series suggests that the drug combination of brimonidine tartrate and timolol maleate causes a prolonged depression of the central nervous and respiratory systems in preterm neonates.

Nanotechnology for Medical and Surgical Glaucoma Therapy-A Review

Glaucoma is the second leading cause of blindness worldwide. Even though significant advances have been made in its management, currently available antiglaucoma therapies suffer from considerable drawbacks. Typically, the success and efficacy of glaucoma medications are undermined by their limited bioavailability to target tissues and the inadequate adherence demonstrated by patients with glaucoma. The latter is due to a gradual decrease in tolerability of lifelong topical therapies and the significant burden to patients of prescribed stepwise antiglaucoma regimens with frequent dosing which impact quality of life. On the other hand, glaucoma surgery is restricted by the inability of antifibrotic agents to efficiently control the wound healing process without causing severe collateral damage and long-term complications. Evolution of the treatment paradigm for patients with glaucoma will ideally include prevention of retinal ganglion cell degeneration by the successful delivery of neurotrophic factors, anti-inflammatory drugs, and gene therapies. Nanotechnology-based treatments may surpass the limitations of currently available glaucoma therapies through optimized targeted drug delivery, increased bioavailability, and controlled release. This review addresses the recent advances in glaucoma treatment strategies employing nanotechnology, including medical and surgical management, neuroregeneration, and neuroprotection.

Treatment choices for newly diagnosed primary open angle and ocular hypertension patients

Despite advances in our knowledge of the aetiology and pathophysiology of glaucoma, the sole proven, effective intervention for treating primary open-angle glaucoma (POAG) and ocular hypertension (OHT) remains lowering of intraocular pressure (IOP) to prevent further progression and visual loss. The purpose of this review is to evaluate the treatment choices available to newly diagnosed POAG and OHT patients. We review the existing literature on treatments currently available to newly diagnosed POAG and OHT patients and discuss their role in the treatment paradigm of POAG and OHT. We consider different factors that may be important when offering a choice of treatment to newly diagnosed POAG and OHT patients as well as describing new glaucoma treatments in development and future directions for treatment.

How many aqueous humor outflow pathways are there?

The aqueous humor (AH) outflow pathways definition is still matter of intense debate. To date, the differentiation between conventional (trabecular meshwork) and unconventional (uveoscleral) pathways is widely accepted, distinguishing the different impact of the intraocular pressure on the AH outflow rate. Although the conventional route is recognized to host the main sites for intraocular pressure regulation, the unconventional pathway, with its great potential for AH resorption, seems to act as a sort of relief valve, especially when the trabecular resistance rises. Recent evidence demonstrates the presence of lymphatic channels in the eye and proposes that they may participate in the overall AH drainage and intraocular pressure regulation, in a presumably adaptive fashion. For this reason, the uveolymphatic route is increasingly thought to play an important role in the ocular hydrodynamic system physiology. As a result of the unconventional pathway characteristics, hydrodynamic disorders do not develop until the adaptive routes cannot successfully counterbalance the increased AH outflow resistance. When their adaptive mechanisms fail, glaucoma occurs. Our review deals with the standard and newly discovered AH outflow routes, with particular attention to the importance they may have in opening new therapeutic strategies in the treatment of ocular hypertension and glaucoma.

[Influence of α2-adrenomimetics on incidence of choroidal effusion following laser trabeculoplasty in primary open angle glaucoma]

PURPOSE

To evaluate the influence of different topical hypotensive drugs on incidence of choroidal effusion (CE) following laser trabeculoplasty as the second stage of combined laser-surgical treatment plan in patients with primary open-angle glaucoma (POAG).

MATERIAL AND METHODS

The study included 60 patients with previously operated stage I and II POAG who has 'b-c' intraocular pressure (IOP) on maximum hypotensive therapy. Fistulizing subscleral removal of the outer wall of Schlemm's canal (a.k.a. subscleral sinusotomy) was the first stage of treatment plan. The second stage took place 14 days later in the form of laser trabeculoplasty. In order to reduce the risk of IOP spikes, all patients were prescribed specific hypotensive therapy 5 days prior to the procedure. The 1^st group included 30 patients (30 eyes) who were asked to use Brimonidine-Purite (0.15%). The 2^nd group included 30 patients (30 eyes) who used either nonselective β-blockers, or carbonic anhydrase inhibitors. IOP was measured on days 1, 5, 9, and 12 after stage 1, as well as after laser trabeculoplasty. Ophthalmic examination included ultrasound imaging and optical coherence tomography.

RESULTS

After the combined laser-surgical treatment, the IOP reliably decreased in both groups. Choroidal effusion was observed in 7 cases in the 1^st group and in 15 cases in the 2^nd group. Change in IOP was less prominent in patients who had received instillations of α₂-adrenomimetic (p<0.05).

CONCLUSION

Patients who received Brimonidine-Purite 0.15% before laser trabeculoplasty had lower IOP drop than those on pre-surgical therapy with nonselective β-blockers or carbonic anhydrase inhibitors. Topical application of 0.15% Brimonidine-Purite 5 days prior to laser trabeculoplasty as the second stage of combined laser-surgical treatment resulted in statistically significant reduction of the incidence of postoperative choroidal effusion, likely due to α₂-adrenomimetics inhibiting the secretory function of the ciliary Body to the lesser extent than drugs of other groups that were tested.

Rho Kinase Inhibitors as a Novel Treatment for Glaucoma and Ocular Hypertension

In an elegant example of bench-to-bedside research, a hypothesis that cells in the outflow pathway actively regulate conventional outflow resistance was proposed in the 1990s and systematically pursued, exposing novel cellular and molecular mechanisms of intraocular pressure (IOP) regulation. The critical discovery that pharmacologic manipulation of the cytoskeleton of outflow pathway cells decreased outflow resistance placed a spotlight on the Rho kinase pathway that was known to regulate the cytoskeleton. Ultimately, a search for Rho kinase inhibitors led to the discovery of several molecules of therapeutic interest, leaving us today with 2 new ocular hypotensive agents approved for clinical use: ripasudil in Japan and netarsudil in the United States. These represent members of the first new class of clinically useful ocular hypotensive agents since the US Food and Drug Administration approval of latanoprost in 1996. The development of Rho kinase inhibitors as a class of medications to lower IOP in patients with glaucoma and ocular hypertension represents a triumph in translational research. Rho kinase inhibitors are effective alone or when combined with other known ocular hypotensive medications. They also offer the possibility of neuroprotective activity, a favorable impact on ocular blood flow, and even an antifibrotic effect that may prove useful in conventional glaucoma surgery. Local adverse effects, however, including conjunctival hyperemia, subconjunctival hemorrhages, and cornea verticillata, are common. Development of Rho kinase inhibitors targeted to the cells of the outflow pathway and the retina may allow these agents to have even greater clinical impact. The objectives of this review are to describe the basic science underlying the development of Rho kinase inhibitors as a therapy to lower IOP and to summarize the results of the clinical studies reported to date. The neuroprotective and vasoactive properties of Rho kinase inhibitors, as well as the antifibrotic properties, of these agents are reviewed in the context of their possible role in the medical and surgical treatment of glaucoma.

Preoperative Brimonidine Tartrate 0.2% Does not Prevent an Intraocular Pressure Rise During Prostatectomy in Steep Trendelenburg Position

PURPOSE

This study evaluated the effect of preoperative brimonidine tartrate 0.2% on intraocular pressure (IOP) during robotic-assisted laparoscopic radical prostatectomy in steep Trendelenburg position (sTBURG).

MATERIALS AND METHODS

In this prospective randomized controlled masked interventional trial, eligible patients scheduled for robotic-assisted laparoscopic radical prostatectomy in sTBURG at the Toronto General Hospital had one eye randomized to placebo (artificial tears) or drug (brimonidine tartrate 0.2%) preoperatively. Visual acuity (VA), tonometry, disc photography, visual field (VF), and retinal nerve fiber layer (RNFL) assessments were performed preoperatively and postoperatively. A standardized anesthetic protocol was followed intraoperatively. IOP was measured using Tono-Pen AVIA (Reichert Inc., New York, NY) as follows: preanesthesia supine, anesthetized supine, hourly in sTBURG and awake supine. The primary outcome was IOP in sTBURG in the drug group compared with the placebo group. Secondary outcomes were changes in VA, VF, RNFL thickness, mean arterial pressure, and ocular perfusion pressure. This study was approved by University Health Network Research Ethics Board.

RESULTS

In total, 26 eligible patients, mean age 61.9±5.1 years, were randomized to brimonidine (11 patients) and placebo (15 patients). Baseline IOP was not significantly different between the drug and placebo groups (P=0.42). Significant and sustained IOP elevation of >1.5X baseline in the sTBURG was noted in both groups. The mean IOP 1 hour after sTBURG was 29.4±6.9 and 27.2±3.4 mm Hg in the drug and placebo groups, respectively (P=0.35). No significant changes were noted in VA, VF, or RNFL.

CONCLUSIONS

Significant and sustained IOP increases occur during sTBURG. Preoperative brimonidine does not prevent IOP spikes in sTBURG.

Effects of a Novel Selective EP2 Receptor Agonist, Omidenepag Isopropyl, on Aqueous Humor Dynamics in Laser-Induced Ocular Hypertensive Monkeys

PURPOSE

To investigate the mechanism of the intraocular pressure (IOP)-lowering effect of a novel selective prostaglandin E2 receptor 2 (EP2) receptor agonist, omidenepag isopropyl (OMDI).

METHODS

The effect of OMDI on IOP and aqueous humor dynamics was evaluated in cynomolgus monkeys with unilateral laser-induced ocular hypertension. In a crossover manner, the hypertensive eye of each monkey was dosed once daily with 20 μL of either 0.002% OMDI or vehicle. On day 7 of dosing, IOP was measured by pneumatonometry, aqueous humor flow and outflow facility were evaluated by fluorophotometry, and uveoscleral outflow was calculated mathematically. Treatments were compared by paired t-tests.

RESULTS

OMDI at 0.002% significantly lowered IOP by 27%, 35%, and 44% at 0.5, 1.5, and 4 h after the last dosing, respectively. There was no difference in aqueous humor flow between vehicle and OMDI treatments. When comparing OMDI to the vehicle treatment, outflow facility and uveoscleral outflow were significantly (P < 0.05) increased by 71% and 176%, respectively.

CONCLUSIONS

OMDI, a novel IOP-lowering compound, reduced IOP by increasing outflow facility and uveoscleral outflow in nonhuman primates.

Effect of Brimonidine on Intraocular Pressure in Normal Tension Glaucoma: A Short Term Clinical Trial

Purpose

To evaluate the efficacy and safety of 0.2% brimonidine eye drops given twice daily in normal tension glaucoma.

Patients and Methods

Sixteen consecutive patients fulfilling eligibility criteria (glaucomatous optic neuropathy associated with visual field defect in at least one eye, intraocular pressure (IOP) = 18 mmHg (average of the two highest readings of the round-the-clock curve, including one reading at midnight in supine position), no prior glaucoma therapy, angle wide open, visual acuity 20/40 or better) were enrolled in this prospective, randomized, placebo-controlled clinical trial with crossover design, lasting 30 days for each treatment phase plus 15-day washout in between. Main outcome was IOP (average of the two highest readings of the round-the-clock curve).

Results

Mean IOP was significantly reduced by brimonidine (from 17.1 ± 0.7 mm Hg to 13.9 ± 2.2 mmHg, p<0.001 (paired Student t-test)). At the end of the 30-day brimonidine phase, 4 of 16 subjects showed a ≥30% IOP decrease over baseline.

Conclusions

In the short term, 0.2% brimonidine eye drops can induce a significant IOP decrease in eyes with normal tension glaucoma.

Effect of Cromakalim Prodrug 1 (CKLP1) on Aqueous Humor Dynamics and Feasibility of Combination Therapy With Existing Ocular Hypotensive Agents

Purpose

Cromakalim prodrug 1 (CKLP1) is a water-soluble ATP-sensitive potassium channel opener that has shown ocular hypotensive properties in ex vivo and in vivo experimental models. To determine its mechanism of action, we assessed the effect of CKLP1 on aqueous humor dynamics and in combination therapy with existing ocular hypotensive agents.

Methods

Outflow facility was assessed in C57BL/6 mice by ex vivo eye perfusions and by in vivo constant flow infusion following CKLP1 treatment. Human anterior segments with no trabecular meshwork were evaluated for effect on pressure following CKLP1 treatment. CKLP1 alone and in combination with latanoprost, timolol, and Rho kinase inhibitor Y27632 were evaluated for effect on intraocular pressure in C57BL/6 mice and Dutch-belted pigmented rabbits.

Results

CKLP1 lowered episcleral venous pressure (control: 8.9 ± 0.1 mm Hg versus treated: 6.2 ± 0.1 mm Hg, P < 0.0001) but had no detectable effect on outflow facility, aqueous humor flow rate, or uveoscleral outflow. Treatment with CKLP1 in human anterior segments without the trabecular meshwork resulted in a 50% ± 9% decrease in pressure, suggesting an effect on the distal portion of the conventional outflow pathway. CKLP1 worked additively with latanoprost, timolol, and Y27632 to lower IOP, presumably owing to combined effects on different aspects of aqueous humor dynamics.

Conclusions

CKLP1 lowered intraocular pressure by reducing episcleral venous pressure and lowering distal outflow resistance in the conventional outflow pathway. Owing to this unique mechanism of action, CKLP1 works in an additive manner to lower intraocular pressure with latanoprost, timolol, and Rho kinase inhibitor Y27632.

Open-angle glaucoma: therapeutically targeting the extracellular matrix of the conventional outflow pathway

INTRODUCTION

Ocular hypertension in open-angle glaucoma is caused by a reduced rate of removal of aqueous humour (AH) from the eye, with the majority of AH draining from the anterior chamber through the conventional outflow pathway, comprising the trabecular meshwork (TM) and Schlemm's Canal. Resistance to outflow is generated, in part, by the extracellular matrix (ECM) of the outflow tissues. Current pressure-lowering topical medications largely suppress AH production, or enhance its clearance through the unconventional pathway. However, therapies targeting the ECM of the conventional pathway in order to decrease intraocular pressure have become a recent focus of attention. Areas covered: We discuss the role of ECM of the TM in outflow homeostasis and its relevance as a target for glaucoma therapy, including progress in development of topical eye formulations, together with gene therapy approaches based on inducible, virally-mediated expression of matrix metalloproteinases to enhance aqueous outflow. Expert opinion: There remains a need for improved glaucoma medications that more specifically act upon sites causative to glaucoma pathogenesis. Emerging strategies targeting the ECM of the conventional outflow pathway, or associated components of the cytoskeleton of TM cells, involving new pharmacological formulations or genetically-based therapies, are promising avenues of future glaucoma treatment.

Discovery of Molecular Therapeutics for Glaucoma: Challenges, Successes, and Promising Directions

Glaucoma, a heterogeneous ocular disorder affecting ∼60 million people worldwide, is characterized by painless neurodegeneration of retinal ganglion cells (RGCs), resulting in irreversible vision loss. Available therapies, which decrease the common causal risk factor of elevated intraocular pressure, delay, but cannot prevent, RGC death and blindness. Notably, it is changes in the anterior segment of the eye, particularly in the drainage of aqueous humor fluid, which are believed to bring about changes in pressure. Thus, it is primarily this region whose properties are manipulated in current and emerging therapies for glaucoma. Here, we focus on the challenges associated with developing treatments, review the available experimental methods to evaluate the therapeutic potential of new drugs, describe the development and evaluation of emerging Rho-kinase inhibitors and adenosine receptor ligands that offer the potential to improve aqueous humor outflow and protect RGCs simultaneously, and present new targets and approaches on the horizon.

Clinical effectiveness of brinzolamide 1%-brimonidine 0.2% fixed combination for primary open-angle glaucoma and ocular hypertension

The main first-line treatment strategy for glaucoma is to reduce intraocular pressure (IOP) by topical ocular hypotensive medications, but many patients require multiple medications for adequate IOP control. Fixed-combination therapies provide several benefits, including simplified treatment regimens, theoretical improved treatment adherence, elimination of the potential for washout of the first drug by the second, and the reduction in ocular exposure to preservatives. β-Adrenoceptor antagonists (particularly 0.5% timolol) are the most commonly used agents in combination with other classes of drugs as fixed-combination eyedrops, but they are contraindicated in many patients, owing to local allergy or systemic side effects. A fixed-combination preparation without a β-blocker is therefore warranted. This paper reviews the clinical effectiveness of brinzolamide 1% and brimonidine 0.2% fixed combination (BBFC) for use in patients with primary open-angle glaucoma and ocular hypertension. We searched PubMed and the ClinicalTrials.gov registry, and identified three randomized controlled trials comparing BBFC vs its constituents (brimonidine vs brinzolamide), and one comparing BBFC with unfixed brimonidine and brinzolamide. All of the studies demonstrated mean diurnal IOP to be statistically significantly lower in the BBFC group compared with constituent groups and noninferior to that with the concomitant group using two separate bottles. The safety profile of BBFC was consistent with that of its individual components, the most common ocular adverse events being ocular hyperemia, visual disturbances, and ocular allergic reactions. Common systemic adverse effects included altered taste sensation, oral dryness, fatigue, somnolence, and decreased alertness. BBFC seems to be a promising new fixed combination for use in glaucoma patients. However, long-term effects of BBFC on IOP, treatment adherence, and safety need to be determined.

Contralateral intraocular pressure lowering effect of prostaglandin analogues

Background:

Though the use of prostaglandin analogues (PGA) for reduction of intraocular pressure (IOP) has shown a marked increase, studies evaluating the contralateral effects of PGA are limited.

Aims:

To evaluate if PGA treatment in one eye has an effect on the IOP of the untreated fellow eye.

Design:

Retrospective study.

Materials and Methods:

Thirty patients of open-angle glaucoma with no previous antiglaucoma treatment underwent 24-hour diurnal IOP phasing. They subsequently were started on a uniocular trial with PGA, and had office diurnal IOP measurements 6 weeks later. Twenty-four hour diurnal consisted of 8 IOP readings over 24 hours and office diurnal consisted of 4 IOP readings between 8 AM and 6 PM at 3 hourly intervals.

Statistical Analysis:

IOPs of the fellow eye during the office diurnal were compared with IOPs at similar time points during the 24-hour diurnal using paired t-tests.

Results:

Mean (± standard deviation) IOP in the treated eye reduced (P < 0.001) from 17.17 ± 3.2 mm Hg at baseline to 13.7 ± 2.4 mm Hg at 6 weeks, while that in the untreated eye reduced from 16.4 ± 3.1 mm Hg to 14.8 ± 2.7 mm Hg (P = 0.01). The decrease in IOP in the untreated fellow eye was statistically significant at 8 AM (2.7 mm Hg, P = 0.003) and 11 AM (2.3 mm Hg, P = 0.01) but not so at 2 PM (1.2 mm Hg, P = 0.10) and 5 PM (0.9 mm Hg, P = 0.19). The amount of IOP reduction in the untreated eye was significantly associated with the magnitude of IOP reduction in the treated eye (β = 0.69, P = 0.008).

Conclusion:

Uniocular PGA treatment tends to reduce the IOP of the untreated fellow eye.

Comparison of dorzolamide/timolol versus brimonidine/timolol fixed combination therapy in the management of steroid-induced ocular hypertension

PURPOSE

To compare the efficacy of fixed combinations of dorzolamide-timolol (FCDT) and brimonidine-timolol (FCBT) in patients with intraocular pressure (IOP) elevations after intravitreal triamcinolone acetonide (IVTA) injections.

MATERIALS AND METHODS

This was a prospective, randomized, open-label study. Patients who received IVTA injections due to diffuse diabetic macular edema and who had an IOP of 24 mm Hg or higher after IVTA treatment were included. They were randomized to receive either FCBT or FCDT twice daily. Follow-up visits were scheduled on week 4 and 12 weeks after starting the study medication. At all follow-up visits, IOP was measured with Goldmann applanation tonometry. The primary outcome measure was mean IOP, the secondary outcome was reduction in mean IOP at 4 and 12 weeks compared with postinjection values.

RESULTS

Sixty patients were randomized in 1:1 ratio. The FCBT and FCDT groups were similar in terms of age, sex, and preinjection IOP (P>0.05 for all). Mean postinjection IOP was 31.95±7.39 and 29.83±5.17 mm Hg in FCBT and FCDT groups, respectively (P=0.239). After 4 weeks, mean IOP was 17.05±3.61 mm Hg in FCBT and 18.93±3.30 mm Hg in FCDT groups (P=0.063). After 12 weeks, mean IOP in the FCBT and FCDT study groups was 16.35±2.70 and 18.43±2.82 mm Hg, respectively (P=0.012). Both fixed combinations significantly reduced IOP in comparison with the postinjection values (P<0.05). Mean reduction in IOP after 4 weeks were 14.90±7.28 mm Hg in FCBT and 10.90±4.83 mm Hg in FCDT groups (P=0.024); after 12 weeks, these values were 15.60±7.77 and 11.40±5.89 mm Hg in FCBT and FCDT groups, respectively (P=0.035).

CONCLUSIONS

Both FCBT and FCDT are effective in controlling IOP elevations after IVTA injections. The results of this study suggest that FCBT is superior to FCDT in reducing IOP and provides better IOP control after IVTA injections.

Pharmacotherapy of glaucoma

Glaucoma is a group of diseases involving the optic nerve and associated structures, which is characterized by progressive visual field loss and typical changes of the optic nerve head (ONH). The only known treatment of the disease is reduction of intraocular pressure (IOP), which has been shown to reduce glaucoma progression in a variety of large-scale clinical trials. Nowadays, a relatively wide array of topical antiglaucoma drugs is available, including prostaglandin analogues, carbonic anhydrase inhibitors, beta-receptor antagonists, adrenergic agonists, and parasympathomimetics. In clinical routine, this allows for individualized treatment taking risk factors, efficacy, and safety into account. A major challenge is related to adherence to therapy. Sustained release devices may help minimize this problem but are not yet available for clinical routine use. Another hope arises from non-IOP-related treatment concepts. In recent years, much knowledge has been gained regarding the molecular mechanisms that underlie the disease process in glaucoma. This also strengthens the hope that glaucoma therapy beyond IOP lowering will become available. Implementing this concept with clinical trials remains, however, a challenge.

An “all-water” strategy for regiocontrolled synthesis of 2-aryl quinoxalines

CascadeN-aroylmethylation–reduction–condensation process as novel strategy of “all water chemistry” for first generalized regioselective synthesis of 2-aryl quinoxalines.

The impact of timolol maleate on the ocular tolerability of fixed-combination glaucoma therapies

Glaucomatous optic atrophy is the second most common cause of blindness worldwide, and lowering intraocular pressure (IOP) is the only proven method to slow or stop the progression of the disease. Approximately 40% of patients with elevated IOP will require more than one medication to obtain a modest 20% reduction in IOP, and as a result, some patients may require two medications, provided in either two separate bottles or in one bottle with the use of fixed-combination therapies. Each therapy has its own unique safety and efficacy profile. Topical beta-blockers have a particularly favorable ocular-tolerability profile, and several studies of fixed-combination medications containing the beta-blocker timolol maleate have shown a lower prevalence of some ocular adverse events for the fixed-combination therapy compared to the non-beta-blocker individual component. In this review, we examined clinical data pertaining to the ocular surface tolerability of fixed-combination medications containing timolol maleate in comparison to the individual components. In particular, preference was given to prospective, randomized, multicenter trials of 3 months in duration or longer that compared a fixed-combination therapy to monotherapy with the individual components. A review of the literature revealed that some fixed-combination therapies can provide a reduced risk of common side effects compared to their individual components, with conjunctival hyperemia and ocular allergy being less frequent in some timolol-containing fixed-combination therapies. This effect appears to be most significant for latanoprost 0.005%, bimatoprost 0.03%, and brimonidine 0.2%.

Daytime and nighttime effects of brimonidine on IOP and aqueous humor dynamics in participants with ocular hypertension

PURPOSE

The effects of brimonidine on daytime and nighttime intraocular pressure (IOP) and aqueous humor dynamics were evaluated in volunteers with ocular hypertension (OHT).

PATIENTS AND METHODS

Thirty participants with OHT (58.6±1.7 years old, mean±SEM) were enrolled into this randomized, double-masked, cross-over study. For 6 weeks, participants self-administered 0.2% brimonidine or placebo 3 times daily. During daytime and nighttime visits, measurements included aqueous flow (Fa) by fluorophotometry, outflow facility (C) by tonography, episcleral venous pressure (Pev) by venomanometry, and seated and supine IOP by pneumatonometry. Uveoscleral outflow (U) was calculated mathematically.

RESULTS

When treated with placebo, nighttime supine Pev (11.2±0.25 mm Hg) was higher (P<0.05) compared with daytime seated Pev (10.2±0.25 mm Hg), and Fa and U were significantly reduced at night. Brimonidine significantly lowered seated IOP at 9:00 AM and 11:00 AM, 9:00 PM and 11:00 PM and supine IOP at 9:00 AM and 11:00 AM. Brimonidine increased U at 9 AM and 11 AM (P<0.01) and had no effect on daytime and nighttime Fa, C, or Pev.

CONCLUSIONS

In subjects with OHT, brimonidine treatment for 6 weeks significantly reduces seated IOP during the day by increasing uveoscleral outflow. The lack of IOP effect at night can be explained by failure to overcome a normal nighttime reduction of uveoscleral outflow.

Brinzolamide plus brimonidine for the treatment of glaucoma: an update

INTRODUCTION

Glaucoma is a common sight-threatening condition that is primarily treated by lowering intraocular pressure (IOP). Today the mainstay of treatment is topical ocular hypotensive medications; many patients require more than one agent to achieve target IOP. For such patients, fixed combination formulations have several advantages including simplicity of treatment regimen, adherence to the treatment regimen, efficacy, improved ocular surface comfort and reduced cost. All currently available fixed combinations contain a β-blocker, which is contraindicated in some patients. Hence there is a clinical need for fixed-combination preparations without a β-blocker. This paper reviews the current literature on a new fixed-combination drug containing brinzolamide 1% and brimonidine 0.2% (BBFC).

AREAS COVERED

A PubMed, Embase and ClinicalTrials.gov registry search was performed to identify all relevant studies. Four published clinical papers pertaining to three randomized controlled trials were identified for review. All studies demonstrated a significant reduction (p < 0.01) in mean IOP in patients administered with BBFC compared with its individual components, brinzolamide 1% or brimonidine 0.2%. Adverse effects from BBFC were no different from each of the individual components, the most common being blurred vision, eye irritation and dysgeusia (abnormal taste sensation). Although BBFC use was associated with more adverse effects compared with the individual components used as monotherapy (p < 0.001), the cumulative adverse effect profile from BBFC did not appear greater than one would expect from the simultaneous use of the two components.

EXPERT OPINION

BBFC is a potential alternative to other fixed-combination medications and is especially useful when topical β-blockers are contraindicated. Longer-term experience will determine if additional adverse effects occur or if efficacy is maintained over longer periods.

Targeted delivery of antiglaucoma drugs to the supraciliary space using microneedles

PURPOSE

In this work, we tested the hypothesis that highly targeted delivery of antiglaucoma drugs to the supraciliary space by using a hollow microneedle allows dramatic dose sparing of the drug compared to topical eye drops. The supraciliary space is the most anterior portion of the suprachoroidal space, located below the sclera and above the choroid and ciliary body.

METHODS

A single, hollow 33-gauge microneedle, 700 to 800 μm in length, was inserted into the sclera and used to infuse antiglaucoma drugs into the supraciliary space of New Zealand white rabbits (N = 3-6 per group). Sulprostone, a prostaglandin analog, and brimonidine, an α₂-adrenergic agonist, were delivered via supraciliary and topical administration at various doses. The drugs were delivered unilaterally, and intraocular pressure (IOP) of both eyes was measured by rebound tonometry for 9 hours after injection to assess the pharmacodynamic responses. To assess safety of the supraciliary injection, IOP change immediately after intravitreal and supraciliary injection were compared.

RESULTS

Supraciliary delivery of both sulprostone and brimonidine reduced IOP by as much as 3 mm Hg bilaterally in a dose-related response; comparison with topical administration at the conventional human dose showed approximately 100-fold dose sparing by supraciliary injection for both drugs. A safety study showed that the kinetics of IOP elevation immediately after supraciliary and intravitreal injection of placebo formulations were similar.

CONCLUSIONS

This study introduced the use of targeted drug delivery to the supraciliary space by using a microneedle and demonstrated dramatic dose sparing of antiglaucoma therapeutic agents compared to topical eye drops. Targeted delivery in this way can increase safety by reducing side effects and could allow a single injection to contain enough drug for long-term sustained delivery.

Small-interfering RNAs (siRNAs) as a promising tool for ocular therapy

RNA interference (RNAi) can be used to inhibit the expression of specific genes in vitro and in vivo, thereby providing an extremely useful tool for investigating gene function. Progress in the understanding of RNAi-based mechanisms has opened up new perspectives in therapeutics for the treatment of several diseases including ocular disorders. The eye is currently considered a good target for RNAi therapy mainly because it is a confined compartment and, therefore, enables local delivery of small-interfering RNAs (siRNAs) by topical instillation or direct injection. However, delivery strategies that protect the siRNAs from degradation and are suitable for long-term treatment would be help to improve the efficacy of RNAi-based therapies for ocular pathologies. siRNAs targeting critical molecules involved in the pathogenesis of glaucoma, retinitis pigmentosa and neovascular eye diseases (age-related macular degeneration, diabetic retinopathy and corneal neovascularization) have been tested in experimental animal models, and clinical trials have been conducted with some of them. This review provides an update on the progress of RNAi in ocular therapeutics, discussing the advantages and drawbacks of RNAi-based therapeutics compared to previous treatments.

Glaucoma management: relative value and place in therapy of available drug treatments

Lowering intraocular pressure (IOP) is the only proven therapeutic intervention for glaucomatous optic neuropathy. Despite advances in laser and microsurgical techniques, medical IOP reduction remains the first-line treatment option for the majority of patients with open-angle glaucoma. Prostaglandin analogs are the most efficacious topical agents and carry a remarkable safety profile. Topical beta-blockers, alpha-agonists, and carbonic anhydrase inhibitors are often employed as adjunctive agents for further IOP control. Newer preserved and nonpreserved formulations are available and appear to be less toxic to the ocular surface. Oral carbonic anhydrase inhibitors, miotic agents, and hyperosmotics are infrequently used due to a host of potentially serious adverse events. Medical therapies on the horizon include rho-kinase inhibitors, neuroprotective interventions, and gene therapies.

In vivo assessment of aqueous humor dynamics upon chronic ocular hypertension and hypotensive drug treatment using gadolinium-enhanced MRI

PURPOSE

Although glaucoma treatments alter aqueous humor (AH) dynamics to lower intraocular pressure, the regulatory mechanisms of AH circulation and their contributions to the pathogenesis of ocular hypertension and glaucoma remain unclear. We hypothesized that gadolinium-enhanced magnetic resonance imaging (Gd-MRI) can visualize and assess AH dynamics upon sustained intraocular pressure elevation and pharmacologic interventions.

METHODS

Gadolinium contrast agent was systemically administered to adult rats to mimic soluble AH components entering the anterior chamber (AC) via blood-aqueous barrier. Dynamic Gd-MRI was applied to examine the signal enhancement in AC and vitreous body upon microbead-induced ocular hypertension and unilateral topical applications of latanoprost, timolol maleate, and brimonidine tartrate to healthy eyes.

RESULTS

Gadolinium signal time courses in microbead-induced hypertensive eyes possessed faster initial gadolinium uptake and higher peak signals in AC than control eyes, reflective of reduced gadolinium clearance upon microbead occlusion. Opposite trends were observed in latanoprost- and timolol-treated eyes, indicative of their respective drug actions on increased uveoscleral outflow and reduced AH production. The slowest initial gadolinium uptake but strongest peak signals were found in AC of both brimonidine-treated and untreated fellow eyes. These findings drew attention to the systemic effects of topical hypotensive drug treatment. Gadolinium leaked into the vitreous of microbead-induced hypertensive eyes and brimonidine-treated and untreated fellow eyes, suggestive of a compromise of aqueous-vitreous or blood-ocular barrier integrity.

CONCLUSIONS

Gadolinium-enhanced MRI allows spatiotemporal and quantitative evaluation of altered AH dynamics and ocular tissue permeability for better understanding the physiological mechanisms of ocular hypertension and the efficacy of antiglaucoma drug treatments.

Secondary neuroprotective effects of hypotensive drugs and potential mechanisms of action

Primary open-angle glaucoma, a long-term degenerative ocular neuropathy, remains a significant cause of vision impairment worldwide. While many risk factors have been correlated with increased risk for primary open-angle glaucoma, intraocular pressure (IOP) remains the only modifiable risk factor and primary therapeutic target. Pharmacologic therapies are administered topically; these include α(2)-agonists, β-antagonists, prostaglandin analogs and carbonic anhydrase inhibitors. Some of these topical medications exhibit secondary neuroprotective effects independent of their effect on IOP. This review covers the possible mechanisms of neuroprotection stimulated by drugs currently marketed for the lowering of IOP, based on known literature. While the neuroprotective properties of many glaucoma pharmaceuticals are promising from an experimental standpoint, key challenges for the development of new clinical practices include unknown systemic side effects, limited methods of drug delivery to the retina and optic nerve, and development of extended-release formulations.