Ophthalmic beta-blockers since timolol

Microwave-Assisted Synthesis of 3-Hydroxy-2-oxindoles and Pilot Evaluation of Their Antiglaucomic Activity

Glaucoma is a widespread neurodegenerative disease for which increased intraocular pressure (IOP) is a primary modifiable risk factor. Recently, we have observed that compounds with oxindole scaffolds are involved in the regulation of intraocular pressure and therefore have potential antiglaucomic activity. In this article, we present an efficient method for obtaining novel 2-oxindole derivatives via microwave-assisted (MW) decarboxylative condensation of substituted isatins with malonic and cyanoacetic acids. Various 3-hydroxy-2-oxindoles were synthesized using MW activation for 5–10 min with high yields (up to 98%). The influence of novel compounds applied in instillations on IOP was studied in vivo on normotensive rabbits. The lead compound was found to reduce the IOP by 5.6 Torr (ΔIOP for the widely used antiglaucomatousic drug timolol 3.5 Torr and for melatonin 2.7 Torr).

Nanocarriers for the Delivery of Neuroprotective Agents in the Treatment of Ocular Neurodegenerative Diseases

Retinal neurodegeneration is considered an early event in the pathogenesis of several ocular diseases, such as diabetic retinopathy, age-related macular degeneration, and glaucoma. At present, there is no definitive treatment to prevent the progression or reversal of vision loss caused by photoreceptor degeneration and the death of retinal ganglion cells. Neuroprotective approaches are being developed to increase the life expectancy of neurons by maintaining their shape/function and thus prevent the loss of vision and blindness. A successful neuroprotective approach could prolong patients' vision functioning and quality of life. Conventional pharmaceutical technologies have been investigated for delivering ocular medications; however, the distinctive structural characteristics of the eye and the physiological ocular barriers restrict the efficient delivery of drugs. Recent developments in bio-adhesive in situ gelling systems and nanotechnology-based targeted/sustained drug delivery systems are receiving a lot of attention. This review summarizes the putative mechanism, pharmacokinetics, and mode of administration of neuroprotective drugs used to treat ocular disorders. Additionally, this review focuses on cutting-edge nanocarriers that demonstrated promising results in treating ocular neurodegenerative diseases.

Comparison of Two Fixed Beta-Blocker-Pilocarpine Combinations

Purpose

To compare the efficacy and safety of a newly developed ophthalmic solution containing carteolol 2% and pilocarpine (2% (CBS341A) with a timolol 0.5% and pilocarpine 2% fixed combination.

Patients and Methods.

A randomized, double-masked, multicenter study was conducted in 209 patients with primary open-angle glaucoma or ocular hypertension, whose intraocular pressure (IOP) was higher than 21 mm Hg on bet-blocker twice a day alone. The test medications were administered twice daily for 4 months. IOP was measured at 9 and 11 a.m. at the beginning of the study (with beta-blocker alone) and after one and four months of treatment. Adverse effects were recorded.

Results

Both combinations caused a similar, statistically significant decrease in IOP. At four months, in the CBS341A group a 2.4 mm Hg (9%) reduction in IOP was achieved at 9 a.m. and 4.1 mm Hg (17.3%) at 11 a.m. compared with respectively 3 mm Hg (11%) and 4.5 mm Hg (19.5%) in the timolol-pilocarpine group. No statistical difference was observed between the two groups in safety and efficacy.

Conclusions

The carteolol-pilocarpine combination appears as safe and as effective as the timolol-pilocarpine combination in the medical treatment of primary open-angle glaucoma or ocular hypertension.

TFOS DEWS II Clinical Trial Design Report

The development of novel therapies for Dry Eye Disease (DED) is formidable, and relatively few treatments evaluated have been approved for marketing. In this report, the Subcommittee reviewed challenges in designing and conducting quality trials, with special reference to issues in trials in patients with DED and present the regulatory perspective on DED therapies. The Subcommittee reviewed the literature and while there are some observations about the possible reasons why so many trials have failed, there is no obvious single reason other than the lack of correlation between signs and symptoms in DED. Therefore the report advocates for conducting good quality studies, as described, going forward. A key recommendation for future studies is conduct consistent with Good Clinical Practice (GCP), including use of Good Manufacturing Practice (GMP) quality clinical trial material. The report also recommends that the design, treatments, and sample size be consistent with the investigational treatment, the objectives of the study, and the phase of development. Other recommendations for pivotal studies are a priori selection of the outcome measure, and an appropriate sample size.

The effects of topical antiglaucoma drugs as monotherapy on the ocular surface: a prospective study

Purpose. The aim was to compare the effects of antiglaucoma eye drops on the tear functions and ocular surface. Method. Eighty-five eyes of 43 patients with glaucoma were included into this randomized prospective study. Timolol without preservative (1), timolol with benzododecinium bromide (2), latanoprost (3), bimatoprost (4), travoprost with benzalkonium chloride (5), and brimonidine with purite (6) were given to 6 groups. Schirmer I, tear film breakup time (TBUT), staining scores, and impression cytology samples were evaluated before and during 12-month-follow-up period. Results. At the end of 12 months, there was no detected change in Schirmer I and TBUT tests indicating dry eye. Corneal staining scores were higher in groups 1 and 2, while conjunctival staining scores were higher in group 6. Goblet cell count decreased in groups 1 and 5 in superior and inferior, group 2 in superior, and groups 3 and 6 in inferior conjunctiva. Squamous metaplasia grades showed a significant increase in groups 1 and 2 at 3rd, 6th, and 12th month controls (P < 0.05). Conclusion. We observed nonserious impact on tear functions and ocular surface with antiglaucoma monotherapy. Beta blockers induced more damage on the ocular surface suggesting the role of the dosing and active substances beside preservatives.

Penetration of β-Blockers through Ocular Membranes in A1bino Rabbits

The purpose of this study was to investigate the barrier properties of ocular membranes for controlling the extent and pathway of ocular absorption of instilled β-blockers.

The penetration of β-blockers was measured across the isolated corneal, conjunctival and scleral membranes of the albino rabbit using a two-chamber glass diffusion cell. β-Blockers tested were atenolol, carteolol, tilisolol, timolol and befunolol.

Corneal penetration of befunolol was much higher than that of atenolol. Scraping the epithelium increased corneal penetration of β-blockers. Conjunctival membranes showed higher permeability than corneal and scleral membranes. The penetration parameters were estimated according to Fick's equation. The corneal permeability coefficient showed an apparent linear relationship with penetrant lipophilicity. The lipophilic character of the corneal barrier was determined by the partition coefficient of drug to corneal surface, not by the diffusion coefficient. Conjunctival and scleral permeability coefficients were not determined by the lipophilicity of β-blockers.

These results indicate that the conjunctiva, sclera and cornea of the rabbit eye are sufficiently different in permeation character to control the extent and pathway for ocular absorption.

Comparative study of topical application of timolol and verapamil in patients with glaucoma within 6 months

INTRODUCTION

As glaucoma is one of the most significant causes of blindness, and administration of calcium channel blockers is effective in reducing intraocular pressure (IOP) in rabbits and patients with normotensive glaucoma, we administered topical verapamil 0.25% in the human eye to compare its effect with timolol 0.5% in reducing IOP.

PURPOSE

To compare the effect of timolol 0.5% and topical verapamil 0.25% in patients with open-angle glaucoma.

METHODS

It was a double-blinded study in which 118 eyes (59 individuals) were chosen and divided into 2 groups (30 individuals related to timolol and 29 individuals related to verapamil). Patients who used drugs (systemic or topical) that could alter IOP and those with IOP <22 mmHg were excluded from the study (19 eyes). We chose patients who did not use any drugs 24 h prior to the study. Then applanation tonometry was done exactly before the administration of drugs and 90 min later and the results were compared.

RESULTS

In timolol group, mean intraocular pressure in 52 eyes (27 right eyes and 25 left eyes) decreased from 32.545 to 30.230 and mean pressure in verapamil group decreased from 33.195 to 30.835.

CONCLUSION

It seems that topical verapamil has a similar effect to timolol in patients with open-angle glaucoma, so it can be considered as a lowering intraocular pressure agent in glaucoma patients.

Glaucoma and systemic diseases

Glaucoma management may be extremely challenging, especially in elderly patients who have a variety of systemic diseases and take multiple medications. We obtained a comprehensive medical history in patients with primary open-angle glaucoma to determine which systemic diseases are most prevalent and which systemic medications are most commonly used. We have also reviewed the literature that addresses how these concomitant diseases and medical treatments influence the management of glaucoma. Knowledge of systemic diseases and potential drug interactions, especially between various systemic and glaucoma medications, is important for the safe management of glaucoma patients.

Decrease of optic disc cupping and pallor of ocular hypertensives with timolol therapy

PURPOSE

The purpose of this study was to determine whether timolol drops compared to placebo drops had a significant effect on optic disc cupping and pallor in ocular hypertensives.

METHODS

Thirty-seven ocular hypertensives were randomly assigned to placebo or 0.5% timolol drops to both eyes in a double masked clinical trial. Measurements of ocular pressure and photographs of the optic disc for cupping by photogrammetry and pallor by computerized image analysis were made at about 3 month intervals, for 18 to 24 months of follow-up.

RESULTS

None of the subjects developed visual field loss when tested with the Goldmann perimeter by kinetic and static means at six month intervals. Subjects treated with timolol developed a significant decrease in ocular pressure and a significant decrease in optic disc cupping with a smaller decrease in pallor compared to subject treated with placebo. Multivariate analyses indicated that the decrease of optic disc cupping and pallor was not associated with the ocular pressure on treatment or the decrease in ocular pressure during the trial.

CONCLUSION

Timolol treatment was associated with a decrease in optic disc cupping and pallor. The effect of timolol appears to be related to mechanisms other than the decrease in ocular pressure.

Increase of retinal vessel width in ocular hypertensives with timolol therapy

PURPOSE

The purpose of this study was to determine whether timolol drops compared to placebo drops had a significant effect on retinal vessel width in ocular hypertensives.

METHODS

Thirty-seven ocular hypertensives were randomly assigned to receive placebo or 0.5% timolol drops to both eyes for 18 to 24 months in a double masked clinical trial. Measurements of ocular pressure and retinal vessel width by computerized image analysis from fundus photographs were made at about 3 month intervals for 18 to 24 months of follow-up.

RESULTS

None of the subjects developed visual field loss when tested with the Goldmann perimeter by kinetic and static means at six month intervals. Subjects treated with the placebo showed no change in ocular pressure and a significant decrease in retinal vessel width over time especially in the right eye. Subjects treated with timolol had an increase in retinal vessel width compared to the placebo group significant especially for the superior temporal vein. Multivariate analyses indicated that the increase of retinal vessel width was not associated mainly with the ocular pressure on treatment or decrease in ocular pressure on treatment.

CONCLUSION

Timolol treatment was associated with an increase of retinal vessel width. The effect of timolol appears to be related primarily to mechanisms other than the decrease in ocular pressure.

Cardiovascular and respiratory considerations with pharmacotherapy of glaucoma and ocular hypertension

Glaucoma and ocular hypertension are highly prevalent conditions in individuals over the age of 40 and are commonly seen together in patients with cardiovascular disease. Many of the antiglaucoma medications, when systemically absorbed, affect the sympathetic and parasympathetic nervous systems of patients and can cause cardiovascular toxicity. Such adverse effects are frequently associated with the long-term use of potentially toxic agents in elderly people, who are most prone to chronic eye disease. Moreover, patients may not associate their symptoms with the topical eye medications, and consequently may not report adverse drug effects. Drug-drug interactions can also occur when patients are taking medications for both cardiovascular disease and glaucoma. In this review, the systemic toxicity of these agents is reviewed, along with possible drug-drug interactions. Mention is made of other antiglaucoma medications used alone and in combination with topical beta-blockers. Identification of genetic loci-a bold new step toward glaucoma treatment-is mentioned briefly at the end of the article.

Topical Drug Therapy in Glaucoma

Glaucoma is defined as a progressive optic neuropathy involving characteristic structural changes in the optic nerve head and corresponding visual field defects. Elevated intraocular pressure (IOP) is a major risk and causative factor for glaucomatous optic neuropathy. Although mechanisms other than elevated IOP may contribute to the underlying pathophysiology of glaucoma, reducing IOP remains the primary goal of therapy. Recent clinical studies have shown that decreasing the IOP can delay, or in some cases prevent progression of this chronic ocular disease. Over the past decade, several new medical therapies have become available for the treatment of glaucoma. In this article a review of topical glaucoma therapy is presented.

Transport of Timolol and Tilisolol in Rabbit Corneal Epithelium

The purpose of this study is to characterize the transport of tilisolol and timolol through the corneal epithelium, which is believed to be a tight barrier of ocular drug absorption. Cultured normal rabbit corneal epithelial cells (RCEC) were used to investigate drug transport. Primary RCEC were seeded on a filter membrane of Transwell-COL insert coated with fibronectin and grown in Dulbecco's modified Eagle's medium/nutrient mixture F-12 with various supplements. Beta-blocker permeability through the RCEC layer was measured to assess the transcellular permeability coefficient (P(transcell)) in the absence or presence of inhibitors. The transcellular permeability of tilisolol was dependent on drug concentration although timolol showed no concentration dependency. Tilisolol flux from the apical to the basal side was larger than in the opposite direction although timolol showed no direction dependency. The transcellular permeability of tilisolol from the apical to the basal side was inhibited by sodium azide, tetraethylammonium, quinidine, taurocholic acid, guanidine and carnitine. Tilisolol had an active mechanism in uptake to the corneal epithelium, probably by the organic cation transporter family, although timolol predominantly permeated via passive diffusion. This RCEC system was useful to characterize the ocular permeation mechanism of drugs.

Glucocorticoid eye drops inhibit growth in the newborn rabbit

AIM

To investigate if postoperative treatment with dexamethasone eye drops has the capacity to affect longitudinal growth in newborn rabbits.

METHODS

Thirty-four male and female rabbits had clear lens extraction performed in one eye at 3 wk of age and were then treated either intensively (group 1) or less intensively (group 2) with de-escalating doses of dexamethasone eye drops for 8 wk (average doses 0.27 and 0.10 mg/kg body weight/day, respectively). The control group (group 3) received vehicle eye drops only. Body weight and crown-rump length were recorded every week. After 8 wk of treatment, all rabbits were killed and the left femur was measured.

RESULTS

Rabbits treated with dexamethasone eye drops gained weight slower (711+/-42 and 989+/-153 g weight increase for groups 1 and 2, respectively) than control animals (group 3; 1224+/-87 g weight increase; p<0.001 vs group 1, p<0.01 vs group 2). Longitudinal growth, determined as increase in crown-rump and femur lengths, was impaired by dexamethasone eye drops in a dose-dependent way. Crown-rump length increased by 8.25+/-0.86, 10.90+/-1.19 and 15.35+/-1.31 cm in groups 1, 2 and 3, respectively (p<0.001 for all comparisons). At endpoint, i.e. after 8 wk of treatment, the average femur length was 6.36+/-0.21, 7.39+/-0.27 and 8.37+/-0.28 cm in groups 1, 2 and 3, respectively (p<0.001 for all comparisons).

CONCLUSION

Dexamethasone, administered topically as eye drops, has systemic effects and impairs longitudinal growth in young rabbits. Therefore, we propose that growth should be closely monitored in all children intensively treated with glucocorticoid eye drops.

Gold standard medical therapy for glaucoma: defining the criteria identifying measures for an evidence-based analysis

BACKGROUND

Over the past decade, several new medical therapies have become available for the treatment of primary open-angle glaucoma (POAG). A systematic evidence-based approach for identifying an optimal therapeutic agent is lacking.

OBJECTIVES

The aims of this review were to critically evaluate published treatment recommendations for POAG and, based on a systematic review of the literature, to develop criteria that would define a "gold standard" medical therapy that reflects new treatment advances and established therapeutic goals.

METHODS

A MEDLINE search spanning the years 1966 to 2002 and using the search terms gold standard, drug of choice, agent of choice, benchmark, ophthalmology, eye, and glaucoma was conducted and the results reviewed by a panel of 15 experts in the field of glaucoma. Published treatment recommendations for POAG were discussed. Criteria, anchored to medical evidence, for distinguishing a standard of medical therapy for POAG were defined.

RESULTS

The terms connoting a gold standard therapy were found in only 258 of approximately 368,000 ophthalmology-related citations and 53 of almost 23,000 glaucoma citations, validating the need to define therapeutic standards. The lack of recommendations for the use of new classes of ocular hypotensive agents was acknowledged. Criteria identified to evaluate intraocular pressure (IOP)-lowering agents as gold standards included the following: efficacy in reducing IOP consistently over a 24-hour period to a level that will preserve the visual field and protect the optic nerve without inducing tachyphylaxis and tolerance, paucity of local and systemic adverse effects, promotion of patient compliance, and applicability in diverse patient populations.

CONCLUSIONS

These criteria should be employed as measures for evidence-based analyses to evaluate available and future IOP-lowering medical therapies for POAG. The conceptual framework presented may be applicable to other therapeutic areas.

The effects of antiglaucoma and systemic medications on ocular blood flow

Based on the body of evidence implicating ocular blood flow disturbances in the pathogenesis of glaucoma, there is great interest in the investigation of the effects of antiglaucoma drugs and systemic medications on the various ocular vascular beds. The primary aim of this article was to review the current data available on the effects of antiglaucoma drugs and systemic medications on ocular blood flow. We performed a literature search in November 2002, which consisted of a textword search in MEDLINE for the years 1968-2002. The results of this review suggest that there is a severe lack of well-designed long-term studies investigating the effects of antiglaucoma and systemic medications on ocular blood flow in glaucomatous patients. However, among the 136 articles dealing with the effect of antiglaucoma drugs on ocular blood flow, only 36 (26.5%) investigated the effects of medications on glaucoma patients. Among these 36 articles, only 3 (8.3%) were long-term studies, and only 16 (44.4%) were double-masked, randomized, prospective trials. Among the 33 articles describing the effects of systemic medications on ocular blood flow, only 11 (33.3%) investigated glaucoma patients, of which only one (9.1%) was a double-masked, randomized, prospective trial. Based on this preliminary data, we would intimate that few antiglaucoma medications have the potential to directly improve ocular blood flow. Unoprostone appears to have a reproducible antiendothelin-1 effect, betaxolol may exert a calcium-channel blocker action, apraclonidine consistently leads to anterior segment vasoconstriction, and carbonic anhydrase inhibitors seem to accelerate the retinal circulation. Longitudinal, prospective, randomized trials are needed to investigate the effects of vasoactive substances with no hypotensive effect on the progression of glaucoma.

New glaucoma medications in the geriatric population: efficacy and safety

Glaucoma can be considered a disease of the aging eye. Most medications used to treat glaucoma are in topical eyedrop form and may cause numerous untoward systemic effects in older persons. In recent years, several new ocular hypotensive medications have become available. These medications are being used more commonly because there is a growing trend by ophthalmologists to aggressively lower intraocular pressure. Therefore, geriatricians require a comprehensive knowledge of medications used to treat glaucoma, in addition to an understanding of their mechanism of action profiles of untoward effects and possible interactions with other diseases or medications. Therefore, we performed a review of the medications recently introduced into clinical practice. We selected drugs approved by the U.S. Food and Drug Administration between 1996 and September 2001. The safety profiles of these agents and their untoward side effects were reviewed by class: topical carbonic anhydrase inhibitors (brinzolamide: ocular tolerance, taste perversion), beta-adrenoceptor antagonists (timolol: bradycardia and bronchospasm), alpha-adrenergic agonists (brimonidine: oral dryness, headache, and fatigue), and prostaglandin analogs (latanoprost, bimatoprost, travoprost, and unoprostone isopropyl: ocular hyperemia, iris color changes). The function of this review is to make geriatricians more aware of the efficacy and untoward effects of medications recently introduced into clinical practice. We recommend that geriatricians perform a medication review on all medications their patients use, including eye drops.

Ocular absorption behavior of palmitoyl tilisolol, an amphiphilic prodrug of tilisolol, for ocular drug delivery

The objective of this study was to examine the ocular absorption behavior of an amphiphilic prodrug after instillation onto the cornea of rabbits. A micellar solution of O-palmitoyl tilisolol (PalTL), an amphiphilic prodrug, was prepared. After instillation of tilisolol (TL) and PalTL, the drug concentrations in the tear fluid, cornea, aqueous humor, iris-ciliary body, vitreous body, and blood were measured. In addition, in situ ocular absorption behavior was also evaluated. After instillation of TL, the concentration of TL in the tear fluid quickly decreased. After instillation of PalTL, prolonged retention and high concentrations of PalTL in tear fluid and the cornea were observed. In addition, more prolonged retention of the TL concentration after instillation of PalTL than after instillation of TL was observed in the cornea, aqueous humor, and iris-ciliary body. In situ experiments demonstrated that PalTL was mainly absorbed by the corneal route and the improvement effects of PalTL under in vivo conditions was due to an enhanced transit time of PalTL in ocular tissues. PalTL, an amphiphilic prodrug, exhibited increased retention in the precorneal area compared with the parent drug, TL, resulted in improved ocular absorption of the parent drug.

Cardiovascular considerations in using topical, oral, and intravenous drugs for the treatment of glaucoma and ocular hypertension: focus on beta-adrenergic blockade

Glaucoma and ocular hypertension are highly prevalent conditions in individuals over the age of 40 and are commonly seen together in patients with cardiovascular disease. Many of the antiglaucoma medications, when systemically absorbed, affect the sympathetic and parasympathetic nervous systems of patients and can cause cardiovascular toxicity. Such adverse effects are frequently associated with the long-term use of potentially toxic agents in elderly people, who are most prone to chronic eye disease. Moreover, patients may not associate their symptoms with the topical eye medications, and consequently may not report adverse drug effects. Drug-drug interactions can also occur when patients are taking medications for both cardiovascular disease and glaucoma. This review focuses on beta-adrenergic blockers as topical antiglaucoma medications and other topical antiglaucoma drugs. The systemic toxicity of these agents is reviewed, along with the possible drug interactions. Brief mention is also made of other antiglaucoma medications used alone and in combination with topical beta-blockers.

Controlled release and ocular absorption of tilisolol utilizing ophthalmic insert-incorporated lipophilic prodrugs

To control ocular drug delivery, the O-butyryl ester prodrug of tilisolol (BUTL) and the O-palmitoyl ester prodrug of tilisolol (PalTL) were incorporated into an ophthalmic insert. The released TL from BUTL inserts and PalTL inserts in pH 7.4 phosphate-buffered saline until 5 h were approximately 25% and 3% of that from TL inserts, respectively. In addition, BUTL was also released from BUTL inserts. However, PalTL was not released from the PalTL insert. The release of drugs from TL inserts and BUTL inserts was little affected by the addition of bovine serum albumin (BSA) in pH 7.4 phosphate-buffered saline. In contrast, the release of drugs from PalTL inserts were enhanced by the addition of BSA. After application of TL, BUTL, and PalTL inserts to the rabbit eye, the aqueous humor concentration of TL was prolonged compared with TL instillation, and the plasma concentration of TL was much lower than that of TL instillation. The ratios of the area under the TL concentration-time curve (AUC) in the aqueous humor to AUC in the plasma (AUC(aqueous)/AUC(plasma)) after application of BUTL until 8 h were 3.1-fold and 3.8-fold higher than those of the TL insert and PalTL insert, respectively.

Topically applied betaxolol attenuates ischaemia-induced effects to the rat retina and stimulates BDNF mRNA

It has previously been reported that the beta(1)-adrenoceptor antagonist, betaxolol, can protect retinal neurones from ischaemia when applied topically. It has further been shown that betaxolol can reduce influx of both sodium or calcium into neurones through interaction at neurotoxin site 2 of the sodium channel and the L-type calcium channel, respectively. The present study sought to further investigate the neuroprotective mode of action of betaxolol in the rat retina. Rats were treated topically with L-betaxolol for 10, 5 and 1 min before ischaemia, induced by raising the intraocular pressure above systolic blood pressure for 45 min. This was followed by reperfusion of 3 or 5 days where L-betaxolol was applied topically twice daily. Ischaemia plus reperfusion caused both a loss of immunoreactivity for choline acetyl transferase (ChAT) and a marked reduction of the b-wave of the electroretinogram (ERG). Treatment, as described, with topical L-betaxolol, completely blunted the effects upon ChAT immunoreactivity and caused a significant reversal of the ERG changes. Furthermore, other rats treated topically with commercially available racemic betaxolol (Betoptic Solution, 0.5%) for 6 hr had raised levels of mRNA for brain derived neurotrophic factor (BDNF) but not for basic fibroblast growth factor (bFGF) in their retinas. The combined data provide further evidence that betaxolol can blunt the effects of ischaemia to the rat retina when applied topically just before the insult. Furthermore, the finding that retinal levels of BDNF mRNA are raised following topical betaxolol treatment shows that not only can this drug reach the retina but that it can also induce changes in expression of factors which are known, themselves, to provide neuroprotection to retinal neurones.

Antiglaucoma medications: a review of safety and tolerability issues related to their use

BACKGROUND

Much experience has been gained with the use of older classes of antiglaucoma agents--topical beta-adrenergic-receptor antagonists, nonselective adrenergic-receptor agonists, oral carbonic anhydrase inhibitors, and cholinergic agents. In the past decade, new drugs and classes of drugs used to treat glaucoma have become available, including topical carbonic anhydrase inhibitors, prostaglandin analogues, and alpha2-adrenergic-receptor agonists. Extensive community-based use of antiglaucoma medications has led to an increased understanding of the acute and long-term safety and tolerability issues associated with their use.

OBJECTIVE

This paper reviews the side effects associated with the various classes of topical antiglaucoma drugs, with a particular focus on long-term safety issues.

Efficacy and adverse effects of medications used in the treatment of glaucoma

With the advent of several new topically active medications for glaucoma therapy, intraocular pressure (IOP) can be reduced to target levels in more patients before resorting to surgery. Some of these newer agents have a number of advantages over some of the older medications, several of which are seldom used now. The topically active carbonic anhydrase inhibitors are better tolerated than oral formulations, which are infrequently used despite their greater efficacy compared with the topical formulations. The alpha2-adrenergic agonists effectively reduce IOP with few systemic adverse effects. The prostaglandin analogues are even more effective and well tolerated when applied once daily without known systemic adverse effects. The variety of glaucoma medications forces the physician to be selective with various combinations before proceeding with surgery. This article critically reviews the literature pertaining to the newer glaucoma medications, thereby providing guidelines to make rational choices from among the available options.

Efficacy of carteolol hydrochloride 1% vs timolol maleate 0.5% in patients with increased intraocular pressure. Nocturnal Investigation of Glaucoma Hemodynamics Trial Study Group

PURPOSE

To evaluate the ocular hypotensive effect and safety of carteolol hydrochloride 1% vs timolol maleate 0.5%.

METHODS

One hundred seventy-six patients with ocular hypertension or primary open-angle glaucoma were randomly assigned to receive either carteolol 1% twice a day or timolol maleate 0.5% solution twice a day in a randomized, double-masked, multicenter, parallel-group, active-control comparison trial during a 3-month period.

RESULTS

After 12 weeks, carteolol 1% reduced the mean +/- SE intraocular pressure from 25.0 +/- 0.3 to 19.5 +/- 0.3 mm Hg; timolol maleate 0.5% reduced the mean intraocular pressure from 25.2 +/- 0.3 to 19.6 +/- 0.3 mm Hg. The mean difference in trough intraocular pressure between carteolol and timolol maleate of -0.14 mm Hg was not significantly (P = .745) different (95% confidence limits, -0.97 to 0.70 mm Hg). Trough pulse and blood pressure also showed no consistent statistically significant differences between groups. The 2-hour postdose pulse, however, demonstrated a greater decrease in the timolol maleate than in the carteolol group (P < .001). Systemic and ocular signs and symptoms were similar between the groups except that the number of treatment-emergent reports of bradycardia was greater in the timolol maleate group (P = .039), and the carteolol group reported fewer ocular symptoms than the timolol maleate group did (P < .01).

CONCLUSIONS

Both carteolol 1% and timolol maleate 0.5% are highly effective in lowering intraocular pressure when measured at the end of the dosing interval. Carteolol 1% demonstrates an ocular hypotensive effect and safety profile similar to those of timolol maleate 0.5% solution.

In-situ ocular absorption of ophthalmic beta-blockers through ocular membranes in albino rabbits

Ocular membranes have been characterized by in-situ absorption of the ophthalmic beta-blockers carteolol (hydrophilic) and timolol and befunolol (lipophilic) using a cylindrical cell. After introduction of drug solution into the cell on the cornea, sclera (bulbar conjunctival and scleral layer) or palpebral conjunctiva, the disappearance of the drug from the cell was determined as in-situ absorption. The ophthalmic drugs disappeared from the conjunctival and scleral membranes although disappearance from the cornea was hardly observed. The conjunctival membrane showed the highest permeability. Lipophilic drugs were more permeable than hydrophilic. In-situ apparent permeability coefficients of the ophthalmic drugs through the conjunctiva and sclera correlated with the lipophilicity of drugs. A high drug concentration in the aqueous humor was observed after corneal application. There is a relationship between concentration in the aqueous humor was observed after corneal application. There is a relationship between concentrations of drugs in the aqueous humor and previously reported in-vitro apparent permeability coefficients of the drugs in the cornea. This in-situ method using a cylindrical cell is a useful method of investigating the ocular absorption of ophthalmic drugs.

In situ ocular absorption of tilisolol through ocular membranes in albino rabbits

The purpose of this study is to characterize the in situ absorption properties of ocular membranes using a cylindrical cell. Drug disappearance in the cell was determined as in situ absorption after an application of drug solution into the cell on the comea, sclera (bulbar conjunctiva and sclera layer), or palpebral conjunctiva. Tilisolol was used as a model of an ophthalmic beta-blocker. Tilisolol disappeared from the conjunctival and scleral surfaces although hardly any disappearance of tilisolol from the corneal surface was observed. Depletion of drug from the precorneal space was much faster in situ than extrapolated from permeability measurements (in vitro) of the separate tissues. This may arise from an influence of blood flow. The in situ apparent permeability coefficient of tilisolol through the conjunctiva was almost constant at various concentrations of drug (5-100 mM), suggesting a passive diffusion of tilisolol that was affected by medium pH. A high concentration of tilisolol in the aqueous humor was observed in the corneal application although the scleral and conjunctival applications showed a slight concentration of tilisolol. The corneal route was a dominant route of access to the aqueous humor. Access to the vitreous body for tilisolol was 4 times more effective through the sclera than through the cornea. On the other hand, the corneal application showed an extremely low concentration of tilisolol in plasma compared to the scleral and conjunctival applications. Thus, the in situ method using a cylindrical cell is a useful method for investigation of the ocular absorption of ophthalmic drugs.

Timolol hemihydrate vs timolol maleate to treat ocular hypertension and open-angle glaucoma

PURPOSE

We compared the therapeutic efficacy and safety of timolol hemihydrate to timolol maleate in patients with ocular hypertension and chronic open-angle glaucoma.

METHODS

We conducted this three-month study as a multicentered, masked, parallel group comparison. Both the 0.25% and 0.5% concentrations were evaluated against similar concentrations of timolol maleate. Dosing was twice daily. An open-label, nine-month study followed the masked portion of the protocol, in which all patients received either 0.25% or 0.5% timolol hemihydrate. A total of 371 patients were included in both the 0.25% and 0.5% studies.

RESULTS

We found statistically similar intraocular pressures with both the 0.25% (18.3 and 18.6 mm Hg for the hemihydrate and maleate groups, respectively) and 0.5% (19.9 and 19.5 mm Hg for the hemihydrate and maleate groups, respectively) concentrations of timolol hemihydrate and timolol maleate after three months of masked treatment. Likewise, peak intraocular effect at two hours after taking the medication was statistically similar between medicines at both concentrations. Likewise, both ocular and systemic safety were similar between the maleate and hemihydrate preparations at both concentrations. In the nine-month open-label protocol, therapeutic efficacy (19.9 and 19.1 mm Hg for the 0.25% and 0.5% concentrations, respectively) and safety of timolol hemihydrate were similar to effect and safety of the three-month protocol.

CONCLUSIONS

This study suggests that timolol hemihydrate had an ocular hypotensive efficacy and safety profile statistically equivalent to that of timolol maleate for up to three months of therapy. Timolol hemihydrate showed efficacy and safety similar to that observed within the first three months, for up to one year of therapy.

Comparison of the ocular beta-blockers

OBJECTIVE

To compare the similarities and differences among the ocular beta-blockers. Important considerations when comparing these agents are the differences in systemic adverse effects, local tolerability, and cost.

DATA SOURCE

Information was retrieved from a MEDLINE search of the English-language literature and bibliographic reviews of review articles. Index terms included beta-blockers, glaucoma, timolol, levobunolol, betaxolol, metipranolol, and carteolol.

STUDY SELECTION

Emphasis was placed on eyedrop studies, as well as properly designed and executed clinical trials that assessed dosage, dosing interval, therapeutic response, adverse effects, and cost.

DATA EXTRACTION

Data from several studies were evaluated according to the study design, therapeutic response, and adverse effects.

DATA SYNTHESIS

Timolol maleate, levobunolol, metipranolol, and carteolol have similar effectiveness in lowering intraocular pressure; however, levobunolol and timolol gel forming solution may have an advantage of once-daily dosing. Studies have not been published comparing the clinical efficacy of timolol hemihydrate with that of other ocular beta-blockers. Metipranolol is cost effective in treating primary open-angle glaucoma; however, it has been associated with more ocular burning, stinging, and granulomatous anterior uveitis than other agents. The intrinsic sympathomimetic activity of carteolol has not yet displayed a definite advantage over the other agents in terms of optic disk perfusion and systemic adverse effects. The control of intraocular pressure with betaxolol has not always been as good as with timolol; however, betaxolol has some advantages over timolol and the other topical beta-blockers in terms of systemic adverse effects.

CONCLUSIONS

Considering cost, efficacy, and safety, timolol maleate is the recommended formulary agent because the other agents cannot consistently show an outstanding advantage.

Ophthalmic arachidonylethanolamide decreases intraocular pressure in normotensive rabbits

Arachidonylethanolamide (AEA) was the first anandamide to be identified as an endogenous ligand for the cannabinoid receptor of porcine brain. Since cannabinoids have shown some value in the reduction of ocular hypertension, the title compound was evaluated in normotensive rabbits as a possible topically applied agent for reducing intraocular pressure. AEA was dissolved in an aqueous solution of 2-hydroxy-propyl-beta-cyclodextrin. Single eyedrops (25 microliters) containing 3.13, 6.25, 31.25, 62.5 or 125.0 micrograms of AEA were instilled unilaterally into eyes of normotensive albino and pigmented rabbits. The intraocular pressures (IOPs) of these rabbits were then measured at fixed time intervals. The effect of AEA on IOP in treated and untreated (contralateral) eyes was similar in both types of rabbits. Administration of 31.25 micrograms of AEA caused an immediate IOP reduction in the treated eyes. AEA doses of 62.5 micrograms caused an initial increase and subsequent decrease of IOP in the treated eyes. In the untreated eyes, a marginal ocular hypotensive response of limited duration occurred immediately after administration of AEA at doses 31.25 or 62.5 micrograms. A significant increase (without subsequent decrease below baseline) in IOP occurred in treated eyes after a dose of 125.0 micrograms. The lowest dose (3.13 micrograms) did not have an effect on IOP. This study constitutes the first published demonstration that topical, unilateral administration of AEA significantly decreases IOP in normotensive albino and pigmented rabbits. Although the mechanism of action by which this compound produces its hypotensive effect in the eye is not known, the results suggest that AEA may prove useful in the investigation of glaucoma therapy.

Different effects of absorption promoters on corneal and conjunctival penetration of ophthalmic beta-blockers

PURPOSE

The purpose of this study was to investigate the improvement in corneal penetration of ophthalmic beta-blockers of various lipophilicities afforded by absorption promoters and to compare the corneal against conjunctival penetration in response to absorption promoters.

METHODS

The penetration of the beta-blockers, atenolol, carteolol, tilisolol, timolol, and befunolol, in the presence of absorption promoters, across the isolated corneal and conjunctival membranes of albino rabbits was measured using a two-chamber glass diffusion cell. EDTA, taurocholic acid, capric acid, and saponin were used as the absorption promoters.

RESULTS

The absorption promoters significantly increased the corneal permeability of most beta-blockers, especially the hydrophilic agents. The absorption promoters also enhanced the conjunctival permeability of beta-blockers, although their effect in promoting conjunctival penetration was less than that on corneal penetration. There was a differing penetration of instilled beta-blockers in the cornea and conjunctiva in response to absorption promoters. Capric acid and saponin showed significant promoting action on corneal penetration, but not on conjunctival penetration. Taurocholic acid had a significant effect on conjunctival penetration but not on corneal penetration. Saponin caused slight irritation.

CONCLUSIONS

Absorption promoters can improve the ocular delivery of beta-blockers and a selective use of absorption promoter can improve the extent and pathway of drug ocular absorption.

A comparison of timolol maleate and levobunolol. Length of use per 5-ml bottle

PURPOSE

The authors analyzed the actual length of use of commercially available 5-ml bottles of 0.5% timolol maleate (Timoptic) and 0.5% levobunolol (Betagan) among patients who routinely use topical beta-blockers (1 drop twice daily in both eyes) for glaucoma treatment.

METHODS

Patients were randomized to receive two 5-ml bottles of either timolol or levobunolol in a double-blind fashion. The patients used the drops independently and the bottles in sequence. The dates were recorded when each of the two 5-ml bottles were used. Sixty patients were enrolled, 15 were excluded from the study, and the data from the remaining 45 were analyzed.

RESULTS

There was a 21% greater length of use per 5-ml bottle among patients who were randomized to 0.5% timolol maleate (36.6 +/- 10.4 days) compared with 0.5% levobunolol (28.9 +/- 8.1 days) (P = 0.009). The length of use of the first bottle versus the second bottle was compared and was found not to be significantly different in either group. There was no statistical difference in intraocular pressure control among patients before and after the study.

CONCLUSION

There is a markedly greater length of use of the 5-ml bottle of timolol compared with the 5-ml bottle of levobunolol. The difference is believed to be due to the configuration of the levobunolol's bottle tip and the vehicle used to deliver the drug. The data may be extrapolated to a substantial patient savings and should be considered in prescription recommendations.

Intestinal permeability of ophthalmic beta-blockers for predicting ocular permeability

The purpose of this study was to investigate the intestinal permeability of ophthalmic beta-blockers and evaluate the utility of intestinal membrane for predicting the ocular permeability. The penetrations of beta-blockers were measured across the isolated jejunum and colon of the albino rabbit using a two-chamber glass diffusion cell. beta-Blockers tested include atenolol, carteolol, tilisolol, timolol, and befunolol. Colonic membrane showed lower permeability of hydrophilic drugs than jejunal membrane. Scraping the entire cell monolayer of jejunum increased the drug permeability. There was a significant correlation between colonic permeability coefficients and lipophilicities of beta-blockers. The permeability coefficients through jejunum and scraped jejunum were not susceptible to drug lipophilicities. Jejunum, scraped jejunum, and colon showed permeability coefficients almost equal to those of sclera, conjunctiva, and cornea, respectively. There was a significant correlation between permeability coefficients through colon and cornea. These results indicate that the steady-state permeability of ophthalmic beta-blockers through ocular membranes may be predicted by measuring the permeability through certain intestinal membranes. However, the analyses of intestinal permeability using Fick's equation showed the functional difference of intestinal permeability from ocular permeability of ophthalmic beta-blockers.

Topical ophthalmic beta-adrenergic blockade for the treatment of glaucoma and ocular hypertension

Since the late 1970s, topical beta-adrenergic blockers have been the drugs of choice in treating ocular hypertension and associated glaucoma. The currently available drugs are timolol, betaxolol, levobunolol, metipranolol, and carteolol. All reduce intraocular pressure by decreasing the production of aqueous humor. Although these drugs are applied locally in the eye, they may enter the general circulation and reach concentrations high enough to cause systemic effects, including alterations in heart rate and rhythm, bronchoconstriction, dyslipidemia, and central nervous system abnormalities. Interactions with other drugs may also occur. Ocular beta- blockers differ in beta 1-selectivity (betaxolol is beta 1-selective, whereas the other drugs are nonselective) and in intrinsic sympathomimetic activity (ISA) or partial agonist properties (only carteolol possesses ISA). These differences give betaxolol and carteolol potential advantages in minimizing certain side effects. The advantage of betaxolol vis-à-vis systemic side effects is more clearly established than that of carteolol. Further systematic study is needed to determine what advantages, if any, are conferred by the presence of ISA.

Intranasal delivery of cardiovascular agents: an innovative approach to cardiovascular pharmacotherapy

The intranasal administration of drugs has long been used for the topical treatment of various nasal disorders. Many features of the intranasal mucosa also make it useful for delivery of systemically active agents. It has been shown that intranasal drug administration can provide plasma drug levels similar to those observed with comparable doses of parenteral drugs. The feasibility of intranasal administration of propranolol, nifedipine, and nitroglycerin has been investigated in several small clinical studies. Intranasal propranolol has been shown to improve exercise tolerance in patients with angina pectoris. Intranasal nifedipine has been used to treat patients with perioperative hypertension and hypertensive crisis. Intranasal administration of nitroglycerin was shown to blunt the hypertensive response to endotracheal intubation. These studies and others suggest that intranasal delivery of cardiovascular drug treatment could be used in those clinical situations where a rapid or intermittent drug effect is desired and can potentially serve as an alternative to parenteral drug administration.

A double-masked comparison of betaxolol and dipivefrin for the treatment of increased intraocular pressure

Noncardioselective beta-adrenoceptor antagonists are used for treatment of increased intraocular pressure. Because these agents may be absorbed systemically, their use is of concern in patients with restricted pulmonary function. We compared the efficacy of betaxolol, a cardioselective beta-adrenoceptor antagonist, and dipivefrin, an alpha/beta-adrenergic agonist. Seventy-six patients with open-angle glaucoma or ocular hypertension were randomly assigned to receive either betaxolol 0.5% or dipivefrin 0.1%. Patients were examined at two weeks, one month, two months, and three months. Intraocular pressure reductions were similar, with a mean decrease of 4.1 mm Hg in the betaxolol group and 3.5 mm Hg in the dipivefrin group. Both treatments caused similar minor increases in heart rate, typical with alpha-adrenergic agonists but atypical with beta-blockers. Stinging or burning in the betaxolol group was significantly (P = .008) greater than in the dipivefrin group. Our findings suggest that betaxolol and dipivefrin therapy are effective, equivalent ocular hypotensive agents.

Adverse effects of topical antiglaucomatous medications on the conjunctiva

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The efficacy of brimonidine in decreasing elevations in intraocular pressure after laser trabeculoplasty

PURPOSE

The authors explored the empirical dosing requirement for administration of an alpha 2-adrenoceptor agonist, brimonidine, and determined its efficacy in decreasing elevations in intraocular pressure (IOP) after 360 degrees argon laser trabeculoplasty (ALT).

METHODS

This vehicle-controlled, double-masked, multicenter trial evaluated three dosing regimens of brimonidine. Two hundred thirty-two patients for whom 360 degrees ALT was indicated were randomized into one of four treatment groups: 0.5% brimonidine both before and after ALT; brimonidine before but vehicle after ALT; vehicle before but brimonidine after ALT; or vehicle at both times.

RESULTS

During the first 3 hours after 360 degrees ALT, the overall incidence of IOP elevations of 5 mmHg or greater was 38% (23 of 60 eyes) in the group receiving vehicle only, and it ranged from 3% to 9% (2 of 62 to 5 of 53 eyes) in the groups receiving any brimonidine treatment. There was little difference in efficacy between the three dosing regimens of brimonidine. Brimonidine was well tolerated by the patients.

CONCLUSION

Based on this large, controlled, multicenter study, 0.5% brimonidine was an effective agent for reducing elevations in IOP after 360 degrees ALT. Only one dose, administered either before or after 360 degrees ALT, was required.