Studies on the mechanism of action of timolol and on the effects of suppression and redirection of aqueous flow on outflow facility

Ocular surface disease: a known yet overlooked side effect of topical glaucoma therapy

Ocular surface disease (OSD), a disorder affecting the lacrimal and meibomian glands and the corneal and conjunctival epithelium, is a well-known complication of topical glaucoma therapy. OSD can present as a new or pre-existing condition that virtually any anti-glaucoma formulation can exacerbate. As such, both glaucoma and OSD frequently coexist. Typical OSD symptoms include ocular discomfort, redness, burning, and dryness, whereas signs include periorbital and eyelid skin pigmentation, conjunctival scarring, and superficial punctate keratitis. Pressure-lowering eyedrops can cause toxic, allergic, and inflammatory reactions on the ocular surface. The latter can result from either preservatives or direct toxicity from the active molecule. Although usually mild, OSD can cause significant symptoms that lead to poor quality of life, decreased compliance to therapy, glaucoma progression, and worse visual outcomes. Given the chronic nature of glaucoma, lack of curative therapy, and subsequent lifelong treatment, addressing OSD is necessary. This manuscript aims to provide an up-to-date overview of OSD's signs, symptoms, and pathogenic mechanisms from glaucoma therapy toxicity.

RNA-seq analysis of human trabecular endothelial cells after treatment with timolol maleate

PURPOSE

Timolol maleate (timolol), a β-receptor blocker, reduces intraocular pressure by decreasing aqueous humor production. Timolol reportedly also protects ganglion cells, decreases aqueous humor outflow facility, and destroys the extracellular matrix in the trabecular meshwork. In this study, we investigated the effects of timolol on cultured human trabecular endothelial cells purchased from ScienCell using next-generation sequencing.

STUDY DESIGN

Experimental investigation.

METHODS

Total ribonucleic acid (RNA) was extracted after 24 h. More than 100 million RNAs in control and timolol-treated group were sequenced using a next-generation sequencer. The expression of 55,778 RNAs was analyzed.

RESULTS

A total of 2,105 genes were significantly upregulated and 2,125 genes were downregulated, after the addition of timolol. VGF nerve growth factor inducible (VGF) (388-fold) had the maximum increase in expression, followed by amphiregulin (333-fold), a member of the epidermal growth factor family. Moreover, the expression of extracellular matrix-degrading enzymes, matrix metalloproteinases (MMPs) 1, 2, 3, 10, 12, and 14, increased.

CONCLUSION

Timolol exerts various effects on human trabecular endothelial cells. The increase in MMP expression may contribute to the decrease in the aqueous humor outflow facility.

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.

Beta-adrenergic glaucoma drugs reduce lymphatic clearance from the eye: A sequential photoacoustic imaging study

Our study aims to determine whether the beta-adrenergic system is involved in the regulation of lymphatic drainage from the eye. For this purpose, we assessed the effect of 2 topical beta-adrenergic blockers, timolol and betaxolol, commonly used as glaucoma drugs, on lymphatic clearance of albumin from the aqueous humor to neck lymph nodes. Adult mice were treated with either topical timolol, a non-selective β-blocker, 0.5% (n = 8), or topical betaxolol, a selective β₁-adrenergic blocker, 0.5% (n = 6) twice daily for 14 days and compared to respective control groups (n = 5 and n = 7). Changes in lymphatic clearance from the eye were assessed using a quantitative in vivo photoacoustic imaging approach. In all subjects, right eye and neck lymph nodes were longitudinally assessed by sequential photoacoustic imaging just prior to near-infrared dye injection into the anterior chamber of the eye, and 20 min, 2 and 4 h after injection. Repeat measurements of mean pixel intensities (MPIs) of right eyes and nodes were performed at all timepoints. The areas under the curves (AUC) were calculated and the AUC of the treated-group was compared to that of controls using the Mann-Whitney U test. The slopes of MPI of each region of interest over time were compared using the linear mixed model after adjusting for IOP decrease after treatment and other parameters such as sex and body weight. In the timolol-treated group, right neck nodes showed significant decrease in AUC signal intensity compared with controls (P = 0.003), and significant decrease in slope of MPI compared with controls (P = 0.0025). In the betaxolol-treated group, right neck nodes showed significant decrease in AUC signal intensity compared with controls (P = 0.02), and significant decrease in slope of MPI compared with controls (P = 0.0069). Topical treatment with timolol and betaxolol reduced lymphatic clearance of albumin from the aqueous humor to the neck lymph nodes. This finding may be relevant for the management of secondary glaucomas and inflammatory eye disease in which the clearance of accumulated proteins and antigen from the eye is important to disease recovery and sight protection. This study suggests that the beta-adrenergic system plays a role in the regulation of lymphatic clearance from the eye.

Report: The effects of topical pleurotus tuberregium (PT) aqueous extract on intraocular pressure in monkeys

PURPOSE

In earlier experiments in Nigeria, aqueous extract of Pleurotus tuber-regium (PT) had been shown to lower intra ocular pressure (IOP) in a feline model. The aim of the current study was to determine whether PT had the same or a similar IOP-lowering effect in ocularly normal non-human primates.

METHODS

Four monkeys were treated twice daily for 4 days with 2 x 20 μl drops of 50 mg/ml PT (pH = 4.3). The monkeys were sedated with 5-10 mg/kg ketamine HCl IM. PT was administered to the right eye and BSS to the left eye. Baseline IOP was measured just prior to beginning treatment, and on day 5 before treatment and then hourly for 3 hours, beginning 1 hour after treatment. SLEs were performed at baseline and on day 5 pre- and 3 hours post-treatment.

RESULTS

There was no significant difference between IOP in treated vs control eyes in the protocol. There were no adverse effects or toxicity as seen by SLE.

CONCLUSIONS

The inability of the extract to lower IOP in monkeys, in contrast to ocular hypertensive cats in an earlier study, could be due to species differences or duration of treatment. Since no adverse effects were observed in the monkeys, further studies with varying durations and dosages are recommended.

New considerations for the clinical efficacy of old and new topical glaucoma medications

Glaucoma is the most common form of irreversible blindness in the world. Lowering intraocular pressure (IOP) remains the only clinically established method of treatment to slow the progression of glaucoma. Primary open angle glaucoma is a disease of the optic nerve head and often is associated with changes to the trabecular meshwork that cause a reduction to aqueous humour outflow and an increase in intraocular pressure. Until recently, topical IOP lowering medication has been limited to the mechanisms of action of decreasing aqueous production and/or redirecting outflow to the unconventional uveoscleral outflow pathway. Both of these mechanisms neglect to treat or act on tissue that becomes altered from glaucoma. Latanoprostene-bunod 0.024%, a nitric-oxide donating prostanoid, netarsudil 0.02%, a potent Rho-associated protein kinase (ROCK) inhibitor and norepinephrine transporter inhibitor, and a once daily dosed fixed combination medication with netarsudil 0.02% and latanoprost 0.005% have recently come on the market. This paper will discuss and review the limitations to traditional IOP lowering glaucoma medications as well as the mechanism of actions and clinical efficacy of the new glaucoma medications. It will also discuss how the new class of glaucoma medications might help to overcome some known limitations in treatment and barriers to patient adherence.

Effect of surfactant concentration and sterilization process on intraocular pressure-lowering activity of Δ9-tetrahydrocannabinol-valine-hemisuccinate (NB1111) nanoemulsions

The use of Δ⁹-tetrahydrocannabinol (THC) and Δ⁹-tetrahydrocannabinol-valine-hemisuccinate (THC-VHS; NB1111) has recently been investigated in the management of intraocular pressure (IOP). The current study was undertaken to develop an optimized THC-VHS-loaded nanoemulsion formulation (NE; THC-VHS-NE) that could improve the drug load and duration of activity. THC-VHS-NE formulation was prepared by homogenization followed by ultrasonication. Sesame oil, Tween®80, and Poloxamer®188 were used as the oil, surfactant, and cosurfactant, respectively. Stability of the optimized THC-VHS-NE formulation was observed at 4 °C. The IOP lowering effect of the lead formulations, commercial timolol, and latanoprost ophthalmic solutions, as well as an emulsion in Tocrisolve™ (THC-VHS-TOC), was studied in New Zealand White rabbits following topical administration. The effect of surfactant concentration and sterilization process on IOP-lowering activity was also studied. THC-VHS-NE formulations (0.5, 1.0, and 2.0% w/v) showed dose dependent duration of action. The 1.0%w/v THC-VHS-NE formulation was selected for further evaluation because of its desirable physical and chemical characteristics. THC-VHS-NE formulation prepared with 2% w/v Tween®80 exhibited a higher drop in IOP than the 0.75 and 4.0% w/v of Tween®80 containing formulations. The IOP-lowering duration was, however, similar for the formulations with 0.75 and 2.0% Tween®80, while that with 4.0% Tween®80 was shorter. THC-VHS-NE formulation produced a greater drop in IOP (p < 0.05) and a longer duration of activity compared to THC-VHS-TOC, latanoprost, and timolol. The formulation could be sterilized by filtration without impacting product attributes. Overall, the optimized THC-VHS-NE formulation demonstrated a significantly better IOP reduction profile in the test model compared to the commercial ophthalmic solutions evaluated.

Treatment of glaucoma by prostaglandin agonists and beta-blockers in combination directly reduces pro-fibrotic gene expression in trabecular meshwork

Prostaglandin analogues (PG), beta-blockers (BB) or their combination (PG+BB) are used primarily to reduce the intraocular pressure (IOP) pathologically associated with glaucoma. Since, fibrosis of the trabecular meshwork (TM) is a major aetiological factor in glaucoma, we studied the effect of these drugs on fibrosis-associated gene expression in TM of primary glaucoma patients. In the present study, TM and iris of primary open-angle (n = 32) and angle-closure (n = 37) glaucoma patients were obtained surgically during trabeculectomy and categorized based on the type of IOP-lowering medications use as PG, BB or PG+BB. mRNA expression of pro-fibrotic and anti-fibrotic genes was quantified using qPCR in these tissues. The gene expression levels of pro-fibrotic genes were significantly lower in PG+BB as compared to other groups. These observations and underlying signalling validated in vitro in human TM cells also showed reduced fibrotic gene and protein expression levels following PG+BB treatment. In conclusion, it is observed that PG+BB combination rather than their lone use renders a reduced fibrotic status in TM. This further suggests that IOP-lowering medications, in combination, would also modulate fibrosis-associated molecular changes in the TM, which may be beneficial for maintaining aqueous out-flow mechanisms over the clinical treatment duration.

Fixed-combination topical anti-hypertensive ophthalmic agents

INTRODUCTION

Fixed-combination glaucoma medications have altered the paradigm of ocular hypertension and glaucoma treatment and are in widespread use today. A comprehensive review of fixed-combination medications will help educate and inform providers for optimal patient care.

AREAS COVERED

In this review, the authors describe the composition, mechanism of action, efficacy, side effects, and safety profile of fixed-combination agents for the treatment of ocular hypertension and glaucoma as well as comparisons between the most frequently prescribed medications.

EXPERT OPINION

Fixed-combination therapeutics provide an effective and efficient means of lowering intraocular pressure with comparable side effects and outcomes to constituent parts with lower patient exposure to preservatives and improvement in compliance.

Ocular Intracameral Pharmacokinetics for a Cocktail of Timolol, Betaxolol, and Atenolol in Rabbits

The mechanisms of drug clearance from the aqueous humor are poorly defined. In this study, a cocktail approach was used to simultaneously determine the pharmacokinetics of three β-blocker agents after intracameral (ic) injection into the rabbit eyes. Aqueous humor samples were collected and analyzed using LC-MS/MS to determine drug concentrations. Pharmacokinetic parameters were obtained using a compartmental fitting approach, and the estimated clearance, volume of distribution, and half-life values were the following: atenolol (6.44 μL/min, 687 μL, and 73.87 min), timolol (19.30 μL/min, 937 μL, and 33.64 min), and betaxolol (32.20 μL/min, 1421 μL, and 30.58 min). Increased compound lipophilicity (atenolol < timolol < betaxolol) resulted in higher clearance and volume of distributions in the aqueous humor. Clearance of timolol and betaxolol is about 10 times higher than the aqueous humor outflow, demonstrating the importance of other elimination routes (e.g., uptake to iris and ciliary body and subsequent elimination via blood flow).

Effects of 0.02% netarsudil ophthalmic solution on intraocular pressure of normotensive dogs

OBJECTIVES

To evaluate the effect of QD or BID 0.02% netarsudil ophthalmic solution (Aerie Pharmaceuticals) on intraocular pressure (IOP) in normotensive dogs and to describe any adverse effects.

ANIMALS STUDIED

Normotensive Labrador retriever dogs were included in this study: 10 received netarsudil in one eye and artificial tears in the contralateral eye QD, and 10 received netarsudil in one eye and artificial tears in the contralateral eye BID.

PROCEDURES

Intraocular pressure curves were acquired over a 3-day acclimation period, 5-day dosing period (QD or BID-10 dogs/group), and 3-day recovery period. Toxicity was assessed daily using slit-lamp biomicroscopy and the semiquantitative preclinical ocular toxicology scoring system.

RESULTS

Once-daily dosing did not lower IOP over the entire 5-day dosing period (95% CI 0.1 to -0.9 mm Hg, P = .20) or on the last day of dosing (95% CI 0.4 to -0.9 mm Hg, P = .65). Twice-daily dosing resulted in a statistically significant, but clinically unimportant, IOP reduction over the entire 5-day dosing period (-0.6 mm Hg; 95% CI 0.05 to -1.1 mm Hg, P = .02) and on the last day of dosing (-0.9 mm Hg; 95% CI 0.2 to -1.5 mm Hg, P = .003). Adverse events were limited to transient mild-to-moderate conjunctival hyperemia during the dosing phase in eyes receiving netarsudil vs control (P < .0001).

CONCLUSIONS

Netarsudil 0.02% ophthalmic solution twice daily resulted in a small, statistically significant, but clinically unimportant, IOP reduction in normotensive dogs. Future studies should investigate efficacy in glaucomatous dogs.

Reduced humidity experienced by mice in vivo coincides with reduced outflow facility measured ex vivo

Mice are routinely used to study aqueous humour dynamics. However, physical factors such as temperature and hydration affect outflow facility in enucleated eyes. This retrospective study examined whether differences in temperature and relative humidity experienced by living mice within their housing environment in vivo coincide with differences in outflow facility measured ex vivo. Facility data and environmental records were collected for one enucleated eye from 116 mice (C57BL/6J males, 9-15 weeks old) at two institutions. Outflow facility was reduced when relative humidity was below the lower limit of 45% recommended by the UK Code of Practice, but there was no detectable effect of temperature on outflow facility. Even when accounting for effects of humidity, there were differences in outflow facility measured between institutions and between individual researchers at the same institution. These data indicate that humidity, as well as additional environmental factors experienced by living mice within their housing environment, may significantly affect outflow facility measured ex vivo.

Effect of Timolol on Aqueous Humor Outflow Facility in Healthy Human Eyes

PURPOSE

Hyposecretion of aqueous humor has been postulated to adversely affect the health of the trabecular meshwork and outflow resistance. However, the effect of medications that reduce aqueous humor production on outflow facility in living human eyes is unclear. This study evaluated the effect of timolol, an aqueous humor flow suppressant, on outflow facility in healthy eyes.

DESIGN

Prospective, before-and-after study.

METHODS

In a multicenter study, 113 healthy participants over 40 years of age were included. Intraocular pressure (IOP) was measured with the participant in the sitting position by using a pneumatonometer. The outflow facility was measured with the participant in the supine position by 2-minute pneumatonography. After participants self-administered drops of timolol 0.5% for 1 week, twice daily in each eye, both measurements were repeated.

RESULTS

Mean IOP decreased from 15.1 ± 3.0 mm Hg at baseline to 12.4 ± 2.4 mm Hg (P < 0.001) after 1 week of timolol use. Mean outflow facility decreased from 0.23 ± 0.08 μL/min/mm Hg at baseline to 0.18 ± 0.08 μL/min/mm Hg (P < 0.001) after timolol. The change in outflow facility was negatively correlated with baseline outflow facility (r = -0.51; P < 0.001).

CONCLUSIONS

Timolol reduces outflow facility in healthy human eyes, and this effect is greater in eyes with higher baseline outflow facility. This phenomenon may be related to reduced aqueous humor flow, but the precise mechanism remains to be determined.

Medical Management of Glaucoma in Exfoliation Syndrome

The treatment of glaucoma in exfoliation syndrome is similar to primary open-angle glaucoma. Frequently, exfoliation glaucoma (XFG) patients require early polytherapy with topical medications. Little emphasis has been placed on tailoring treatment specifically to XFG. New outflow enhancing agents with novel mechanisms of action, such as Rho Kinase inhibition, NO signaling (both recently FDA-approved drugs) and adenosine α1-receptor stimulation, act directly on the trabecular meshwork. These agents may prove to be effective in lowering intraocular pressure and perhaps altering the pathogenesis of XFG aid in the long-term management of this disease.

Therapeutic Contact Lenses with Polymeric Vehicles for Ocular Drug Delivery: A Review

The eye has many barriers with specific anatomies that make it difficult to deliver drugs to targeted ocular tissues, and topical administration using eye drops or ointments usually needs multiple instillations to maintain the drugs’ therapeutic concentration because of their low bioavailability. A drug-eluting contact lens is one of the more promising platforms for controllable ocular drug delivery, and, among various manufacturing methods for drug-eluting contact lenses, incorporation of novel polymeric vehicles with versatile features makes it possible to deliver the drugs in a sustained and extended manner. Using the diverse physicochemical properties of polymers for nanoparticles or implants that are selected according to the characteristics of drugs, enhancement of encapsulation efficiency and prolonged drug release are possible. Even though therapeutic contact lenses with polymeric vehicles allow us to achieve sustained ocular drug delivery, drug leaching during storage and distribution and the possibility of problems related to surface roughness due to the incorporated vehicles still need to be discussed before application in a real clinic. This review highlights the overall trends in methodology to develop therapeutic contact lenses with polymeric vehicles and discusses the limitations including comparison to cosmetically tinted soft contact lenses.

The Ocular Hypotensive Efficacy of Topical Fasudil, a Rho-Associated Protein Kinase Inhibitor, in Patients With End-Stage Glaucoma

To investigate the effects of topical administration of a selective Rho-associated kinase (ROCK) inhibitor, fasudil 0.5% and 1.2% in glaucomatous patients. In this interventional case series study, 4 eyes of 4 patients with unilateral end-stage primary open-angle glaucoma and no light perception vision were assigned to receive topical fasudil 0.5% (in 3 eyes) or 1.2% (in 1 eye) ophthalmic solution twice daily for 8 weeks. At weeks 1, 2, 3, 4, and 8, intraocular pressure (IOP) and adverse events were evaluated. Baseline mean IOP was 53.5 ± 3.4 mm Hg and mean IOP reductions of the last visit were -8.25 ± 1.2 mm Hg at 2 hours and -8.75 ± 2.2 mm Hg at 4 hours. Mean IOP reductions were clinically and statistically significant with 0.5% and 1.2% fasudil and peak effects occurred 2-4 hours after application (P = 0.0002). The largest IOP reductions were produced by 1.2% fasudil (up to -12 mm Hg). Conjunctival hyperemia was found in 1 patient with 1.2% fasudil. Topical administration of fasudil in end-stage primary open-angle glaucoma patients, caused reduction in IOP and was well tolerated. ROCK inhibitors could be considered as a candidate for glaucoma therapy in future.

[Histological structure of the trabecular meshwork in the eyeball: challenging the traditional concept and preliminary findings in rabbits, rats and mice]

OBJECTIVE

To verify that the trabecular meshwork (TM) in the wall of the eyeball consists of smooth muscle fibers instead of collagen fibers or endothelial cells.

METHODS

Eighteen fresh eyeballs from 3 rabbits, 3 SD rats and 3 mice were sectioned along the sagittal plane and sliced after paraffin embedding for HE staining, VG staining, Masson staining, α-SMA immunohistochemistry or CD31 immunohistochemistry. These slices were observed under microscope and the structure of the TM was compared with those of scleral collagen fibers, ciliary muscles and endothelial cells.

RESULTS

HE staining of the eyeball slices from the 3 animal species resulted in purplish red staining of the TM, which was highly consistent with ciliary muscle fibers. The cell?like structures on the surface of the TM were not clearly outlined, with flat nuclei showing a dark purple staining; these structures did not show obvious boundaries from the TM. Ciliary muscle fibers, which were smooth muscle cells in nature, were aligned in bundles in various directions. The longitudinally sectioned cells were flat and contained purplish cytoplasm and highly flattened nuclei. Scleral collagen fibers were stained dark red with a few fibroblasts sandwiched among them. The long axis of the fibroblasts was in parallel with that of the collagen fibers. The outline of the fibroblast was not clear and the nucleus was flat in dark blue. The vascular endothelial cells presented with different morphologies and contained light purplish cytoplasm and dark nuclei, protruding into the vascular cavity. VG staining of the TM revealed a pale red filamentous structure, and the collagen fibers were stained bright red. Masson staining of the TM showed a reticular structure consisting mainly of dark red fibers intermingled with thin green fibers. Scleral collagen fibers presented with a cord?like green wavy structure. The endothelial cells were green and flat, while the ciliary smooth muscle fibers were purple. In immunohistochemistry for α?SMA, the TM and the ciliary smooth muscle fibers showed a strong positivity in the cytoplasm, while the scleral collagen fibers and vascular endothelial cells showed negative staining; immunohistochemistry for CD31 showed no obvious positive staining in the TM, collagen fibers or ciliary smooth muscle cells from all the animals in spite of slight differences among them.

CONCLUSION

The TM consists mainly of smooth muscle fibers with a thin layer of peripheral endomysium without endothelial cells.

Development of Timolol-Loaded Galactosylated Chitosan Nanoparticles and Evaluation of Their Potential for Ocular Drug Delivery

This study was conducted to develop timolol maleate (TM)-loaded galactosylated chitosan (GC) nanoparticles (NPs) (TM-GC-NPs) followed by optimization via a four-level and three-factor Box-Behnken statistical experimental design. The optimized nanoparticles showed a particle size of 213.3 ± 6.83 nm with entrapment efficiency of 38.58 ± 1.31% and drug loading of 17.72 ± 0.28%. The NPs were characterized with respect to zeta potential, pH, surface morphology, and differential scanning calorimetry (DSC). The determination of the oil-water partition coefficient demonstrated that the TM-GC-NPs had a high liposolubility at pH 6 as compared to timolol-loaded chitosan nanoparticles (TM-CS-NPs) and commercial TM eye drops. The in vitro release study indicated that TM-GC-NPs had a sustained release effect compared with the commercial TM eye drops. Ocular tolerance was studied by the hen's egg chorioallantoic membrane (HET-CAM) assay and the formulation was non-irritant and could be used for ophthalmic drug delivery. The in vitro transcorneal permeation study and confocal microscopy showed enhanced penetration, and retention in the cornea was achieved with TM-GC-NPs compared with the TM-CS-NPs and TM eye drops. Preocular retention study indicated that the retention of TM-GC-NPs was significantly longer than that of TM eye drops. The in vivo pharmacodynamic study suggested TM-GC-NPs had a better intraocular pressure (IOP) lowering efficacy and a prolonged working time compared to commercial TM eye drops (P ≤ 0.05). The optimized TM-GC-NPs could be prepared successfully promising their use as an ocular delivery system.

Long-term assessment of prostaglandin analogs and timolol fixed combinations vs prostaglandin analogs monotherapy

AIM

To draw a Meta-analysis over the comparison of the intraocular pressure (IOP)-lowering efficacy and safety between the commonly used fixed-combinations of prostaglandin analogs and 0.5% timolol with prostaglandin analogs (PGAs) monotherapy.

METHODS

After searching the published reports from MEDLINE, EMBASE, the Cochrane Library, all randomized controlled clinical trials (RCTs) comparing the fixed combination of PGAs/timolol therapy (FCs) and PGAs monotherapy with treatment duration at least 6mo were included. The efficacy outcomes were mean diurnal IOP, percentage of participants whose IOP were lower than 18 mm Hg, incidence of visual field change, while the safety outcomes included corneal side effects, hyperemia and eye irritation. The analysis was carried out in RevMan version 5.3 software.

RESULTS

After six-month medical intervention, the mean diurnal IOP of FCs was lower than PGAs (MD -1.14, 95% CI -1.82 to -0.46, P=0.001); the percentage of target IOP achieving between FCs and PGAs showed no significant difference (RR 1.18, 95% CI 0.97 to 1.43, P=0.10). No statistically significant differences of the incidence of hyperemia (RR 0.67, 95% CI 0.45 to 1.01, P=0.06) and eye irritation (RR 1.20, 95% CI 0.95 to 1.51, P=0.12) between the FCs and PGAs monotherapy were detected. Only one research involved in corneal events, result of this trial revealed no difference between two intervention groups regarding corneal effects (central endothelial cell density, MD -0.20, 95% CI -0.72 to 0.32, P=0.45; central corneal thickness, MD -0.01, 95% CI -0.02 to 0.00, P=0.23). The evaluation of visual field change was not performed due to the limited duration of the trials included in this Meta-analysis.

CONCLUSION

The long-term efficacy of the FCs overweighed the PGAs monotherapy in lowering IOP, but in the incidence of hyperemia and eye irritation syndromes, the differences are not statically significant. More RCTs with detailed and authentic data over the assessments of visual functions and morphology of optic nerve heads are hoped to be conducted.

Efficacy of single glaucoma medication in combined latanoprost and timolol XE therapy in patients with open-angle glaucoma and ocular hypertension: a discontinuation study

PURPOSE

To study the effect of single drug discontinuation in combined timolol XE 0.5% and latanoprost 0.005% treatment.

METHODS

Fifty patients with open-angle glaucoma or ocular hypertension who had received both latanoprost and timolol XE for at least 6 months were enrolled in this study. Timolol XE and latanoprost were administered once daily, timolol XE in the morning and latanoprost in the evening. Twenty-five patients discontinued timolol XE and the remaining 25 patients discontinued latanoprost. Either latanoprost or timolol XE was discontinued and 8 weeks later it was resumed. A change in intraocular pressure (IOP) was studied.

RESULTS

All patients had complete follow-up visits. A significant increase in mean IOP was found following drug discontinuation in the 2 groups. Mean change in IOP 8 weeks after discontinuation of the drug was +1.6±1.2 mmHg (10.3%±8.0%) in the timolol XE group and +4.3±1.6 mmHg (+27.2%±11.8%) in the latanoprost group. The change in the latanoprost group was significantly greater compared with that in the timolol XE group (P<0.0001). There was no significant difference in mean IOP between before drug discontinuation and at 8 weeks after drug resumption in any group.

CONCLUSIONS

There was a significant increase in IOP from discontinuation of timolol XE and latanoprost. The hypotensive effect of latanoprost in the combined drug therapy is significantly greater compared with timolol XE.

Efficacy of single glaucoma drug in combined timolol XE, latanoprost and brinzolamide therapy: a discontinuation study

PURPOSE

To study the efficacy of a single drug in patients with primary open angle glaucoma and ocular hypertension who were receiving timolol XE 0.5%, latanoprost 0.005% and brinzolamide 1% with its discontinuation.

METHODS

Sixty patients with open-angle glaucoma or ocular hypertension who were administered timolol XE, latanoprost, and brinzolamide were studied. One drug consisting of timolol XE, brinzolamide, and latanoprost was discontinued and 8 weeks later, it was resumed. A change in intraocular pressure (IOP) was studied.

RESULTS

Mean IOP at baseline and at 8 weeks after discontinuation of each drug was 15.8 ± 1.3 and 17.3 ± 1.4 mmHg in the timolol XE group, 15.8 ± 1.0 and 20.0 ± 1.4 mmHg in the latanoprost group, and 16.0 ± 1.4 and 18.1 ± 1.4 mmHg, respectively. A significant increase in mean IOP was found after drug discontinuation (timolol XE: P = 0.0012; latanoprost: P<0.0001; brinzolamide: P<0.0001). The mean change in IOP by discontinuation of the drug was +1.6 ± 0.9 mmHg (+9.6% ± 5.6%) in the timolol XE group, +4.3 ± 1.7 mmHg (27.4% ± 12.4%) in the latanoprost group, and +2.2 ± 0.9 mmHg (+13.7% ± 6.1%) in the brinzolamide group. The change in the latanoprost group was significantly greater compared with those in the timolol XE and brinzolamide groups (timolol XE: mmHg and percent: P<0.0001; brinzolamide: mmHg and percent: P<0.0001). The IOP change in the brinzolamide group was significantly greater than that in the timolol XE group (mmHg: P = 0.0417; percent: P = 0.0328). No significant difference was observed in mean IOP between before drug discontinuation and at 8 weeks after drug resumption in any group.

CONCLUSIONS

There was a significant increase in IOP from discontinuation of timolol XE, latanoprost, and brinzolamide in the multiple drug treatment. The hypotensive effect of latanoprost in the combined drug therapy is significantly greater than the effects of timolol XE and brinzolamide.

Fixed combination of topical brimonidine 0.2% and timolol 0.5% for glaucoma and uncontrolled intraocular pressure

Lowering IOP is the most readily modifiable risk factor to delay the development and progression of glaucoma (POAG). The fixed combination of brimonidine tartrate 0.2% and timolol maleate 0.5% (FCBT) combines a highly selective α2-adrenergic agonist (brimonidine) with a non-selective β-blocker (timolol). FCBT reduces aqueous production and enhances uveoscleral outflow. Concomitant brimonidine and timolol have additive effects on reducing intraocular pressure (IOP). Multi-center randomized control trials have documented superiority of FCBT twice daily on IOP control compared with monotherapy with the individual components, and equal efficacy compared with concomitant therapy. IOP reduction with FCBT versus fixed combination dorzolamide 2% and timolol 0.5% (FCDT) was similar in a small study. Other studies (n > 293) evaluating concomitant brimonidine and timolol have shown that it is not inferior to FCDT. However, concomitant brimonidine and timolol administered twice daily was significantly less efficacious in IOP reduction than fixed combination latanoprost 0.005% and timolol 0.5% (FCLT). There are no published studies comparing FCBT with FCLT. The side effect profile for FCBT reflects that of its individual components. FCBT was generally well tolerated, with less ocular side effects than brimondine alone, but more than timolol alone. Documented systemic effects were few, although this could be confounded by selection bias. FCBT is a safe and effective IOP lowering agent for POAG and ocular hypertension.

Improved ocular absorption kinetics of timolol maleate loaded into a bioadhesive niosomal delivery system

BACKGROUND

Application of timolol maleate (TM) in a conventional dosage form (solution) into the eye results in almost 80% of the instilled dose being lost either through spillage or due to drainage into the nasolacrimal duct. Later results in systemic side-effects especially in patients suffering from heart diseases or bronchial asthma thus limiting the usefulness of TM for the control of glaucoma. Earlier we had reported on the development of a mucoadhesive coated niosomal system for TM (TM REV(bio)) containing 0.25% TM. Presently we establish and report the pharmacokinetic and pharmacodynamic superiority of the developed ocular formulation of TM.

METHODS

Aqueous humor concentration of TM in male albino rabbits, after instillation of one drop of TM solution (TMS) or TMREV(bio) was measured using the microdialysis method.

RESULTS

Peak concentration of drug in aqueous humor from TMREV(bio) (12.46 microg/ml achieved at 60 min) was almost 1.7 times that of the control drug solution (TMS, 0.25%; 7.2 microg/ml). An important observation was that the high drug concentrations achieved upon TMREV(bio) administration were maintained for up to 2 h. AUC for TMREV(bio) formulation was 2.34 times that of the TMS.

CONCLUSIONS

This study confirms a sustained and controlled effect of the developed formulation.

Gene therapy targeting glaucoma: where are we?

In a chronic disease such as glaucoma, a therapy that provides a long lasting local effect with minimal systemic side effects, while circumventing the issue of patient compliance, is very attractive. The field of gene therapy is growing rapidly and ocular applications are expanding. Our understanding of the molecular pathogenesis of glaucoma is leading to greater specificity in ocular tissue targeting. Improvements in gene delivery techniques, refinement of vector construction methods, and development of better animal models combine to bring this potential therapy closer to reality.

Ascorbic acid concentration is reduced in the secondary aqueous humour of glaucomatous patients

BACKGROUND

We aimed to evaluate the ascorbic acid concentration in secondary aqueous humour (AH) from glaucomatous patients and to compare it with primary AH from primary open-angle glaucoma patients and non-glaucomatous patients.

METHODS

Primary AH samples were prospectively obtained from clinically uncontrolled primary open-angle glaucoma patients and senile cataract patients (controls) prior to trabeculectomy and cataract surgery. Secondary AH samples were obtained from eyes with previous intraocular surgery, prior to trabeculectomy or cataract surgery. AH (0.1 mL) was aspirated by inserting a 26-gauge needle into the anterior chamber just before surgery and then immediately stored at -80 degrees C. The ascorbic acid concentration was determined in a masked fashion by high-pressure liquid chromatography.

RESULTS

A total of 18 patients with senile cataract, 16 glaucomatous patients with primary AH (no previous intraocular surgery) and 11 glaucomatous patients with secondary AH (previous intraocular surgery) were included. There was no difference in mean age between groups (P = 0.15). The mean +/- standard deviation concentration of ascorbic acid in the secondary AH from glaucomatous patients (504 +/- 213 micromol/L [95% confidence interval {CI}, 383-624]) was significantly lower than the concentration of ascorbic acid found in the primary aqueous of primary open-angle glaucoma (919 +/- 427 micromol/L [95% CI, 709-1128]) and control patients (1049 +/- 433 micromol/L [95% CI, 848-1249]; P < 0.01, Kruskal-Wallis test).

CONCLUSIONS

The ascorbic acid concentration in secondary AH of glaucomatous patients was approximately twofold lower in comparison with primary AH of glaucomatous and cataract patients. The implications of a reduced concentration of ascorbic acid in the secondary AH deserve further investigation.

Brinzolamide/timolol: in open-angle glaucoma and ocular hypertension

Brinzolamide 1%/timolol 0.5% fixed combination (brinzolamide/timolol) is a twice-daily eyedrops suspension comprising the carbonic anhydrase-II inhibitor brinzolamide and the beta-adrenergic receptor antagonist timolol. Brinzolamide/timolol produced clinically relevant reductions in mean intraocular pressure (IOP) from baseline and was more effective than brinzolamide or timolol monotherapy in lowering IOP in a 6-month, randomized, phase III trial in patients with open-angle glaucoma or ocular hypertension (n = 523). The proportion of patients achieving a mean IOP of <18 mmHg was significantly greater in recipients of brinzolamide/timolol than in recipients of brinzolamide or timolol monotherapy. The IOP-lowering efficacy of brinzolamide/timolol was maintained for up to 12 months, and was no less effective than dorzolamide 2%/timolol 0.5% solution (dorzolamide/timolol) in a randomized, phase III, noninferiority trial (n = 437). Brinzolamide/timolol was generally well tolerated and was associated with significantly lower ocular discomfort scores than dorzolamide/timolol. Moreover, a significantly greater number of patients expressed a preference for brinzolamide/timolol over dorzolamide/timolol. The main ocular adverse event was blurred vision, and was not considered to be a safety issue.

Bimatoprost/timolol: a review of its use in glaucoma and ocular hypertension

Topically administered bimatoprost 0.03%/timolol 0.5% ophthalmic solution (bimatoprost/timolol: Ganfort) comprises the synthetic prostamide bimatoprost (structurally related to prostaglandin F2 alpha) and the beta-adrenergic receptor antagonist timolol. Bimatoprost/timolol (one drop administered in the affected eye[s] once daily in the morning or evening) is an effective and well tolerated fixed combination for lowering intra-ocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension (OHT), including individuals uncontrolled on monotherapy with a beta-adrenergic receptor antagonist or prostaglandin analogue/prostamide.

Observational study results in glaucoma patients undergoing a regimen replacement to fixed combination travoprost 0.004%/timolol 0.5% in Germany

With the launch of the fixed combination of travoprost 0.004%/timolol 0.5% (trav/tim) in Germany in May 2006, a noninterventional observational study designed as an open-label, multicenter, 6-week trial was initiated in order to evaluate the efficacy and tolerability of this new drug combination in glaucoma patients. Participants were grouped into categories according to previous drug regimens: those on timolol monotherapy; those on prostaglandin analog (PGA) monotherapy; those on concomitant therapy with a PGA and timolol; and those on fixed combinations. Trav/tim was well accepted by the patients, with 87.9% judging the tolerability of the therapy as good, very good, or excellent. Analysis of intraocular pressure (IOP) measurements showed statistically significant IOP decreases in all four categories examined in our study after regimen substitution with fixed-combination trav/tim. Fixed-combination prostaglandin analog/beta-blocker formulations are an attractive therapeutic option due to their strong IOP-lowering efficacy with once-daily dosing. In this study, glaucoma patients who underwent a regimen modification to fixed-combination trav/tim showed further reductions in IOP, irrespective of which selected monoor multiple therapies had been used previously.

Efficacy and safety of bimatoprost/timolol fixed combination in the treatment of glaucoma or ocular hypertension

When a single medication does not adequately control intraocular pressure, additional intraocular hypotensive agents are often added to the therapeutic regime. However, regimen complexity has been associated with reduced patient compliance. Treatment with a fixed combination may, therefore, increase compliance as a result of simplifying the dosage regimen. Bimatoprost/timolol fixed combination (BTFC) combines two clinically effective agents that decrease elevated intraocular pressure by independent mechanisms. In two clinical studies, BTFC was more effective than its individual components. Furthermore, in a non-inferiority study BTFC has been shown to be as effective as the association of its individual components. BTFC was clinically effective and generally well tolerated, with no unexpected adverse reactions reported for the BTFC compared with those reported for bimatoprost or timolol monotherapies.

Topical dorzolamide 2%/timolol 0.5% ophthalmic solution: a review of its use in the treatment of glaucoma and ocular hypertension

Topically administered dorzolamide 2%/timolol 0.5% (dorzolamide/timolol ophthalmic solution; Cosopt) is a fixed combination of two ocular hypotensive drugs (the carbonic anhydrase inhibitor dorzolamide and the beta-adrenoceptor antagonist timolol) that have an additive effect on lowering intraocular pressure (IOP) when administered together. This product is indicated for the treatment of elevated IOP in patients with open-angle glaucoma or ocular hypertension (OH) who are insufficiently responsive to topical beta-adrenoceptor antagonist monotherapy. As such, it can be considered for use in individuals who, as a consequence of failing to achieve target IOP with beta-adrenoceptor antagonist monotherapy, require the addition or substitution of another class of topical antiglaucoma medication. Clinical trials have demonstrated that dorzolamide/timolol (1 drop per eye twice daily) is an effective and generally well tolerated fixed combination for lowering IOP in patients with open angle glaucoma or OH, including individuals uncontrolled on beta-adrenoceptor antagonist monotherapy. Compared with concomitant therapy with the individual components, the primary advantage of fixed combination dorzolamide/timolol is convenience.

Antioxidant activity of timolol on endothelial cells and its relevance for glaucoma course

PURPOSE

A growing evidence in the scientific literature suggests that oxidative damage plays a pathogenic role in primary open-angle glaucoma. Therefore, it is of interest to test whether drugs effective against glaucoma display antioxidant activity. We test the hypothesis that the classic beta-blocker therapy for glaucoma with timolol involves the activation of antioxidant protective mechanisms towards endothelial cells.

METHODS

Oxidative stress was induced in cultured human endothelial cells by iron/ascorbate with or without timolol pretreatment. Analysed parameters included cell viability (neutral red uptake and tetrazolium salt tests), lipid peroxidation (thiobarbituric reactive substances), and occurrence of molecular oxidative damage to DNA (8-hydroxy-2'-deoxyguanosine).

RESULTS

Oxidative stress decreased 1.8-fold cell viability, increased 3.0-fold lipid peroxidation and 64-fold oxidative damage to DNA. In the presence of timolol, oxidative stress did not modify cell viability, whereas lipid peroxidation was increased 1.3-fold, and DNA oxidative damage 3.6-fold only.

CONCLUSIONS

The obtained results indicate that timolol exerts a direct antioxidant activity protecting human endothelial cells from oxidative stress. These cells employ mechanisms similar to those observed in the vascular endothelium. It is hypothesized that this antioxidant activity is involved in the therapeutic effect of this drug against glaucoma.

Topical brimonidine 0.2%/timolol 0.5% ophthalmic solution: in glaucoma and ocular hypertension

A fixed combination of brimonidine (a highly selective alpha(2)-adrenergic agonist) and timolol (a non-selective beta-blocker) [brimonidine 0.2%/timolol 0.5% ophthalmic solution; brimonidine/timolol] is available for the topical treatment of glaucoma and ocular hypertension (OH). Brimonidine and timolol decrease elevated intraocular pressure (IOP) by complementary mechanisms of action and have an additive effect when coadministered to healthy volunteers and patients with glaucoma or OH. When assessed over a 3- or 12-month period in large, well designed clinical studies, brimonidine/timolol instilled twice daily (one drop in each eye) was superior to monotherapy with the individual components instilled two (brimonidine) or three (timolol) times daily, and noninferior to concomitant therapy with the individual components instilled twice daily, in lowering raised IOP in patients with glaucoma or OH. In small, randomised, comparative studies of 1 or 3 months' duration, the IOP-lowering effect of brimonidine/timolol twice daily was similar or superior to that of fixed combination dorzolamide 2%/timolol 0.5% ophthalmic solution (dorzolamide/timolol) twice daily (preliminary data). Brimonidine/timolol is generally well tolerated with a predictable local and systemic adverse event profile based on that of the individual components used alone and concomitantly. No unexpected or serious adverse events associated with the fixed combination were reported in key clinical trials. Brimonidine/timolol may be advantageous over dorzolamide/timolol with respect to ocular tolerability and comfort (preliminary data).

Changes in aqueous humor dynamics with age and glaucoma

Changes in aqueous humor dynamics with age and in glaucoma have been studied for several decades. More recently, techniques have been developed which confirm earlier studies showing that outflow facility decreases with age and in glaucoma and add the newer finding that uveoscleral outflow also decreases. Morphologic studies in aging and glaucoma eyes have shown an increase in accumulation of extracellular material in both the trabecular meshwork and ciliary muscle and a loss of trabecular meshwork cells, which contribute to this reduction in outflow and result in an increase in intraocular pressure. A reduction in hyaluronic acid and increases in fibronectin and thrombospondin contribute to the change in the extracellular environment. Imbalances in responses to age-related stresses such as oxidative damage to long-lived molecules, protein cross-linking and loss of elasticity could trigger excess production of factors such as transforming growth factor beta, interleukin-1 and CD44S that could stimulate pathways leading to increases in fibronectin, transformation of trabecular meshwork cells to a myoepithelial state and decrease the breakdown in extracellular matrix material, allowing excess to accumulate. Ultimately trabecular outflow and uveoscleral outflow are reduced and intraocular pressure becomes elevated, adding more stress and perpetuating the pathological condition. Future research to identify additional factors and clarify their roles in these processes could lead to alternative therapies for age and glaucoma related changes in the eye.

Glaucoma medication and aqueous humor dynamics

PURPOSE OF REVIEW

This review evaluates current concepts regarding the effects of glaucoma medication on aqueous humor dynamics and the impact of this on intraocular pressure control and drug selection in clinical practice.

RECENT FINDINGS

Calculations based on the Friedenwald and Goldmann equations have predicted that glaucoma medications that increase pressure-sensitive aqueous outflow will dampen intraocular pressure spikes and therefore may be advantageous over drugs that do not increase outflow facility.

SUMMARY

Further experimental research is required to verify the influence of increased outflow facility on intraocular pressure fluctuation and the effect of this on glaucoma progression.