Efficacy of combining timolol with other antiglaucoma medications

Adrenergic agonists and antagonists as antiglaucoma agents: a literature and patent review (2013-2019)

Introduction: Glaucoma is a neurodegenerative disease of the eye characterized by selective retinal ganglion cell loss that provokes progressive defects in the visual field. Elevated intraocular pressure (IOP) is an important contributor for the progression of glaucoma. The current therapeutic arsenal for reducing IOP includes prostaglandin analogs, β-blockers, carbonic anhydrase inhibitors, α-adrenergic agonist, miotics, rho-kinase inhibitors and combinations thereof, generally administered as eye drops. Areas covered: This manuscript reviews the state of art on adrenergic modulators for treating glaucoma. Both monotherapy and fixed-drugs combinations including α₂-adrenergic agonists and β-blockers are discussed as well as drug delivery systems where these classes of drugs are used. The review then covers the patent literature involving adrenoceptors modulators over the period 2013-2019. Expert opinion: While the scientific community is moving forward novel targets and related modulators for treating glaucoma and ocular hypertension, adrenergic modulators held a prominent position in the therapy of glaucoma and related disorders. Indeed, though not embodying anymore the first-choice monotherapy, they are widely marketed worldwide ordinarily in combination with other drugs, are subjects of many studies for identifying new drug compositions and have been assessed as active ingredients in several innovative ocular drug delivery systems.

A Double-Masked, Randomized, Parallel Comparison of a Fixed Combination of Bimatoprost 0.03%/Timolol 0.5% with Non-Fixed Combination use in Patients with Glaucoma or Ocular Hypertension

PURPOSE

To compare the safety and efficacy of the fixed combination product with non-fixed combination use of the same active ingredients in separate bottles (bimatoprost once-daily [qd], and timolol twice-daily [bid]). A bimatoprost 0.03% qd treatment arm was used for validation of the study.

METHOD

This was a double-masked, randomized, parallel study in 445 patients with open-angle glaucoma or ocular hypertension. They were randomized in a ratio of 2:2:1 to receive bilateral treatment with the fixed combination, non-fixed combination treatment, or bimatoprost alone.

RESULTS

Comparing the fixed combination and non-fixed combination, the non-inferiority margin of 1.5 mm Hg was met at all three timepoints for mean intraocular pressure (IOP), and a margin of 1.0 mm Hg for mean diurnal IOP. The incidence of conjunctival hyperemia was statistically significantly lower (p=0.014) in the fixed combination group (8.5%, 15/176) compared with the bimatoprost group (18.9%, 17/90) and the non-fixed combination group (12.5%, 22/176).

CONCLUSIONS

The fixed combination of bimatoprost 0.03%/timolol 0.5% administered once daily was comparable in ocular hypotensive efficacy to the non-fixed combination. The lower propensity of the fixed combination to elicit conjunctival hyperemia suggests a superior comparative benefit/risk assessment of the fixed combination in the treatment of elevated IOP.

Managing refractory glaucoma with a fixed combination of bimatoprost (0.03%) and timolol (0.5%)

Glaucoma is a chronic progressive optic neuropathy characterized by progressive loss of retinal ganglion cells, which manifests clinically with loss of optic disc neuroretinal rim tissue, defects in the retinal nerve fiber layer, and deficits on functional visual field testing. The goal of glaucoma treatment is to reduce the intraocular pressure to a level that prevents or minimizes the progressive loss of vision. The current standard of management for the newly diagnosed primary open angle glaucoma (PAOG) patient is to start topical medication. Available topical medications include: beta-adrenergic antagonists, alpha-adrenergic agonists, carbonic anhydraze inhibitors, prostaglandin analogues and miotics. In some patients, IOP is not adequately controlled by monotherapy. In those refractory patients, where more efficacy is required, shifting to another medication or adding a second medication is indicated. The complimentary action between two drugs serves as the basis for combination medications. One avenue of delivering a second medication is through a fixed combination medication that has the advantage of providing two medicines within one drop. Bimatoprost/timolol represents a new fixed combination which is clinically and statistically more effective than either of its active constituents for patients with refractory glaucoma. As regard the safety of the combination, there were no signs or symptoms of intolerance and the incidence of conjunctival hyperemia was clinically and statistically significantly less than each of the two components separately. Bimatoprost/timolol fixed combination offers cost and time savings, which may enhance compliance; also reducing the amount of preservative applied to the eye, will improve tolerability and may also favorably improve eventual surgical outcomes in patients who might require filtering procedures.

Changing therapeutic paradigms in glaucoma management

Glaucoma is a family of diseases commonly characterised by progressive optic neuropathy with associated visual field deficits for which elevated intraocular pressure (IOP) is one of the primary risk factors. For more than a century the main goal of glaucoma management has been to eliminate the risk associated with elevated IOP. In recent years, accumulating evidence of pressure-independent causes of glaucomatous optic neuropathy has led to the recognition that lowering IOP alone may often be insufficient for the long-term preservation of visual function. An innovative therapeutic approach is now emerging to prevent progression of glaucomatous optic neuropathy and preserve vision, irrespective of disease aetiology: direct protection of the optic nerve. In addition to reducing the risk associated with elevated IOP, this neuroprotective approach will augment the overall goal of preserving the optic nerve through direct promotion of retinal ganglion cell (RGC) survival and/or prevention of RGC death. Although no currently available compounds have been clinically demonstrated to provide neuroprotective benefit in glaucoma, recent preclinical studies have shown that alpha-adrenergic agonists, such as brimonidine, provide neuroprotective benefits, as well as excellent IOP lowering efficacy. In addition, new agents with promising neuroprotective utility that are emerging from other studies are now being investigated for efficacy in glaucoma. The review discusses recently introduced compounds and new drugs in development with regard to their potential value in conventional and/or neuroprotective strategies for vision sparing in glaucoma.

Risk factors for open-angle glaucoma: a case-control study

The objective of this study was to identify possible risk factors associated with open-angle glaucoma (OAG). A case-control study included patients seen at an ophthalmologic clinic. Cases were all consecutive new patients with either unilateral or bilateral OAG detected during the study period. Controls were a random sample of all other patients aged 30 or more, seen in the same department in the same period. Data on demographic, anthropometric and diet habits as well as medical characteristics were collected from 144 patients by medical examination and interview. The study took place at the University Department of Ophthalmology and general private practice of ophthalmology, both in the city of Kinshasa. Forty consecutive patients with OAG and 104 controls were chosen randomly between all consecutive non OAG patients. Odds ratio (OR) are presented for the relation between OAG and age, sex, ethnicity, family history of glaucoma, the length of stay in Kinshasa, body mass index, hypertension, diabetes mellitus, cigarette smoking, alcohol, diet habits. Adjusted odds ratio resulting from stepwise logistic regression was employed. Results indicate: family history of glaucoma (OR, 18; 95% CI, 5.80-59.00; P < 0.001), age (OR, 1.05; 95% CI, 1.01-1.09; P = 0.025), body mass index (OR, 1.09; 95% CI, 1.01-1.18; P = 0.05), hyperopia (OR, 2.9; 95% CI, 1.05-7.08; P = 0.03), Mongo ethnic group (OR, 3.5; 95% CI, 1.11-12.20; P = 0.03) and consumption of rice (OR, 4.6; 95% CI, 1.65-12.20; P = 0.004) conferred a significantly greater risk of OAG. This study seems confirm that Mongo ethnic group is associated with an increased risk of OAG.

Comparison of brimonidine with latanoprost in the adjunctive treatment of glaucoma. ALPHAGAN/XALATAN Study Group

OBJECTIVE

This study compared brimonidine with latanoprost as adjunctive therapy for the treatment of open-angle glaucoma and ocular hypertension.

BACKGROUND

Patients with open-angle glaucoma or ocular hypertension often require >1 medication to achieve control of intraocular pressure (IOP). Both brimonidine and latanoprost effectively lower IOP, but no previously reported clinical trials have directly compared these agents as adjunctive therapy.

METHODS

This was a prospective, randomized, investigator-masked, multicenter, parallel-design clinical trial. Forty patients (69 study eyes) with uncontrolled IOP of < or =34 mm Hg while using a topical beta-blocker plus dorzolamide or pilocarpine were randomly assigned to receive either brimonidine 0.2% BID or latanoprost 0.005% QD over 6 months as adjunctive therapy. Tolerability was assessed by reports of adverse events, and efficacy was determined by reduction in IOP from baseline. Clinical success was defined as the achievement of a > or =15% reduction in IOP from baseline.

RESULTS

There were no significant between-group differences in any demographic variable. Most patients in each group were white, had open-angle glaucoma, and were being treated with a nonselective beta-blocker and dorzolamide. When brimonidine or latanoprost was used as an adjunctive agent with a beta-blocker and dorzolamide or pilocarpine, the rates of clinical success at month 1 were 85% (17/20 patients) with brimonidine versus 65% (13/20 patients) with latanoprost (P = 0.144). Overall mean IOP reduction at month 1 was 4.60+/-0.62 mm Hg (22.8%; P < 0.001) with brimonidine and 3.43+/-0.62 mm Hg (17.2%; P < 0.001) with latanoprost, with no significant differences between groups (P = 0.219). Among the patients with an inadequate IOP-lowering response (<15% reduction from baseline), the mean IOP reduction was 0.36+/-0.66 mm Hg with latanoprost (n = 7) and 0.50+/-2.18 mm Hg with brimonidine (n = 3). Brimonidine and latanoprost had comparable IOP-lowering efficacy in patients receiving concomitant pilocarpine therapy (mean change in IOP of -4.23 mm Hg vs -3.75 mm Hg, P = 0.173). In patients concurrently treated with dorzolamide, brimonidine produced a mean change in IOP of -5.29 mm Hg, compared with a mean change of -3.21 mm Hg in the latanoprost group (P = 0.159). Both brimonidine and latanoprost were well tolerated. Few adverse events leading to discontinuation were observed with either drug regimen (n = 2 with brimonidine; n = 0 with latanoprost).

CONCLUSIONS

Both brimonidine 0.2% BID and latanoprost 0.005% QD were well-tolerated and reduced IOP in most patients when used as third-line adjunctive therapy. However, clinical success was achieved by 17 of 20 patients (85%) who received brimonidine, compared with 13 of 20 patients (65%) who received latanoprost (P = 0.144). These results suggest that brimonidine 0.2% BID may be more reliable than latanoprost 0.005% QD as adjunctive therapy for glaucoma and ocular hypertension.

Pharmacological therapy for glaucoma: a review

For some time the medical treatment of glaucoma has consisted of topical beta-blockers, adrenergic agents, miotics and oral carbonic anhydrase inhibitors (CAIs). However, the therapeutic arsenal available for the medical treatment of glaucoma has recently extended with new classes of ocular hypotensive agents i.e. prostaglandins, local CAIs and alpha2-adrenergic agents. Beta-blockers are still the mainstay in glaucoma treatment and are first line drugs. However, even if they are applied once daily, as with timolol in gel forming solution and levobunolol, the possible cardiopulmonary adverse effects of beta-blockers remain a cause for concern. When monotherapy with beta-blockers is ineffective in reducing intraocular pressure (IOP) or is hampered by adverse effects, a change of monotherapy to prostaglandins, local CAIs, alpha2-adrenergic agonists (brimonidine) or to dipivalyl epinephrine is advised. Prostaglandins, local CAIs and alpha2-adrenergic agonists, such as brimonidine, may in time become first line drugs because they reduce IOP effectively and until now systemic adverse effects have rarely been reported with these agents. The development of a pro-drug of either a local CAI or an alpha2-adrenergic agonist with a sustained and continuous effect on IOP level, which could be applied once a day is suggested. Because of these new developments, miotics, i.e. pilocarpine and carbachol, are recommended as second or third line drugs. The cholinesterase inhibitors are considered third line drugs as better agents with fewer local and systemic adverse effects have become available. Oral CAIs may be used temporarily in patients with elevated IOPs e.g. postsurgery or post-laser, or continuously in patients with glaucoma resistant to other treatment. Combining ocular hypotensive drugs is indicated when the target pressure for an individual patient cannot be reached with monotherapy. Combination therapy of beta-blockers is additive with prostaglandins, topical CAIs and miotics. Prostaglandins such as latanoprost can be combined with beta-blockers, adrenergic agents, local CAIs and miotics. Combinations with brimonidine or local CAIs need further investigation. Treatment of glaucoma with the new ocular hypotensive agents, either in monotherapy or combination therapy, may provide lower IOPs and delay or postpone the need for surgery.

Ongoing clinical assessment of the safety profile and efficacy of brimonidine compared with timolol: year-three results. Brimonidine Study Group II

OBJECTIVE

We compared the safety profile and efficacy of brimonidine 0.2% BID with those of timolol 0.5% BID over 3 years in patients with ocular hypertension and glaucoma.

METHODS

Ninety-four eligible patients from an ongoing multicenter, interventional, double-masked clinical trial were followed through year 3, 48 receiving brimonidine 0.2% and 46 receiving timolol 0.5%. Study visits occurred at months 24, 27, 30, 33, and 36. The primary efficacy variable was mean reduction from baseline intraocular pressure (IOP) at trough. Visual acuity, visual fields, and safety variables (adverse events, ocular symptoms, heart rate, blood pressure, and laboratory test results) were monitored throughout the study.

RESULTS

The 2 treatment groups were well matched, with no significant differences in demographic or clinical characteristics. Both drug regimens caused significant mean reductions from baseline IOP at trough during year 3 (P < 0.001), with no significant differences between groups at any study visit. The overall mean reduction from baseline IOP at trough was 5.02 mm Hg with brimonidine and 5.57 mm Hg with timolol (P = 0.383). Brimonidine caused reductions in IOP at trough that were equivalent to those with timolol at months 30 and 36 (within the 95% CI). Visual fields were unchanged or improved in 95% of patients in both treatment groups. Both drug regimens appeared to be safe and were well tolerated. Ocular allergy occurred in 2 brimonidine-treated patients (4.2%). There were no statistically significant differences in adverse-event reports and no clinically significant effects on any ocular or systemic safety variable in either group.

CONCLUSIONS

Brimonidine 0.2% BID continues to appear to be safe, well tolerated, and effective in the long-term management of ocular hypertension and glaucoma. Over 3 years, it provided sustained IOP-lowering efficacy and visual-field preservation equal to those with timolol 0.5% BID.

Ocular hypotensive effect of pilocarpine before and after argon laser trabeculoplasty

PURPOSE

The purpose of this study was to compare the hypotensive response of human glaucomatous eyes to 1% pilocarpine solution before and after argon laser trabeculoplasty.

METHODS

We designed a prospective, 'repeated measures' study comparing the ocular hypotensive effect of acutely administered 1% pilocarpine solution in 30 medically uncontrolled glaucomatous eyes, before and after argon laser trabeculoplasty.

RESULTS

The pilocarpine-induced IOP decrease was 3.6 +/- 0.59 mmHg before argon laser trabeculoplasty, and 1.8 +/- 0.53 mmHg after laser therapy. In both instances, the pilocarpine hypotensive effect was significantly correlated with pretreatment IOP (p = 0.02, r = 0.41 before argon laser trabeculoplasty, and p = 0.003, r = 0.52 after argon laser trabeculoplasty). We built a 'repeated measurements ANCOVA' model, and found no statistically significant difference between the pilocarpine IOP lowering effect before and after argon laser trabeculoplasty (p = 0.4).

CONCLUSION

Argon laser trabeculoplasty does not modify the IOP lowering effect of 1% pilocarpine solution.

The use of dorzolamide and pilocarpine as adjunctive therapy to timolol in patients with elevated intraocular pressure. The Dorzolamide Additivity Study Group

PURPOSE

To report the results of two studies on the use of dorzolamide as adjunctive therapy to timolol in patients with elevated intraocular pressure (IOP). In the larger study, the additive effect of dorzolamide administered twice daily also was compared with 2% pilocarpine.

METHODS

Both studies were parallel, randomized, double-masked, placebo-controlled comparisons. In the pilot study, 32 patients received 0.5% timolol twice daily plus either 2% dorzolamide twice daily or placebo twice daily for 8 days. In the Pilocarpine Comparison Study, 261 patients received 0.5% timolol twice daily plus 0.7% dorzolamide twice daily, 2% dorzolamide twice daily, 2% pilocarpine four times daily, or placebo (twice daily or 4 times daily) for 2 weeks. Patients then entered a 6-month extension period and received 0.5% timolol twice daily plus either 0.7% dorzolamide twice daily, 2% dorzolamide twice daily, or 2% pilocarpine four times daily.

RESULTS

In the pilot study, after 8 days, additional mean percent reductions in IOP for 2% dorzolamide and placebo were 17% and 3% at morning trough and 19% and 2% at peak, respectively. In the Pilocarpine Comparison Study, after 6 months, additional mean percent reductions in IOP (morning trough) were 9%, 13%, and 10% for 0.7% dorzolamide, 2% dorzolamide, and 2% pilocarpine, respectively. Patients receiving 2% pilocarpine had the highest rate of discontinuation due to a clinical adverse experience, and the use of dorzolamide was not associated with systemic side effects commonly observed with the use of oral carbonic anhydrase inhibitors.

CONCLUSION

Dorzolamide twice daily was effective and well tolerated by the patients in these studies as adjunctive therapy to timolol. The larger study demonstrated that both concentrations of dorzolamide produce similar IOP-lowering effects to 2% pilocarpine.

A comparison of the efficacy of various metipranolol-pilocarpine combinations in patients with ocular hypertension and primary open-angle glaucoma

We compared the ocular hypotensive effects of four fixed-dose metipranolol-pilocarpine combinations in nineteen ocular hypertensive subjects and glaucoma patients. Each patient was tested with all of the study medications: vehicle alone, 0.1% metipranolol HCl + 2% pilocarpine HCl, 0.1% metipranolol HCl + 4% pilocarpine HCl, 0.3% metipranolol HCl + 2% pilocarpine HCl, and 0.3% metipranolol HCl + 4% pilocarpine HCl, in a single dose, randomized, double-masked, cross-over placebo-controlled trial. In addition, another eight age and baseline intraocular pressure (IOP)-matched subjects received 0.1% or 0.3% metipranolol HCl, while a similar group of 14 volunteers received 2% or 4% pilocarpine HCl. A two week washout period was instituted between the various groups of treatments. All four metipranolol-pilocarpine combinations were more effective than placebo or either medication alone in reducing the average IOP for up to 8 hours (p < 0.05 for each treatment group). Metipranolol HCl 0.3%, regardless of the pilocarpine concentration, demonstrated the most significant IOP lowering effect, reducing the IOP by 4.9 mm Hg or about 20% from baseline. However, 0.1% metipranolol HCl in combination with 4% pilocarpine HCl was found almost as effective with a 18.5% reduction in IOP from baseline, but a shorter duration of action. In conclusion, all metipranolol-pilocarpine combinations were more efficacious than either medication alone in a single-dose trial. Additional multiple-dose studies are needed to determine the long-term effectiveness and tolerance of combining 0.3% metipranolol HCl with either 2% or 4% pilocarpine HCl.

Long-term evaluation of timolol

Maintenance effect of the topical beta-blocker timolol on intraocular pressure (IOP) was investigated for a mean follow-up of 31.6 months in a group of 155 patients (275 eyes) with glaucoma or ocular hypertension. The mean IOP-value was calculated from 3 readings of the daytime IOP curve, and the mean eye pressure of the right and left eye in the respective individual was used. The medical therapy was carried out with our ranking order of drugs of choice: timolol, timolol combined with adjunctive drug therapy, laser trabeculoplasty and/or filtering surgery. Intraocular pressure was controlled with timolol alone in 98 of 155 patients (63.2%, Group 1). In 36 patients, timolol plus adjunctive medication was required to control IOP (23.2%, Group 2). Twenty-one (13.6%, Group 3) required either laser trabeculoplasty or filtering surgery in addition to timolol. Sufficient IOP-lowering effect was more frequently maintained in patients with ocular hypertension than those with glaucoma simplex or capsular glaucoma. Failures in timolol treatment occurred mostly within 6 months from the start of the therapy and correlated well with higher initial IOP. Transient adverse effects were observed in 11.2% of cases. In three cases (1.9%) local and systemic side effects were serious enough to require discontinuation of the drug therapy. One patient (0.7%) was a non-responder and was withdrawn from the study for that reason. Sixteen patients (10.3%) were lost to follow-up during the 4 year study.

Intraocular pressure effects of carbonic anhydrase inhibitors in primary open-angle glaucoma

We tested the effect on intraocular pressure of three commonly used oral carbonic anhydrase inhibitor preparations in a controlled, randomized, comparative study on patients with primary open-angle glaucoma. Preparations tested included acetazolamide tablets, acetazolamide Sequels, and methazolamide tablets. The effect of the three carbonic anhydrase inhibitors was assessed by using a statistical modeling approach as well as by evaluating the average maximum reduction in intraocular pressure for each preparation. Dosage and time effects were also determined. As expected, each drug preparation was more effective in reducing intraocular pressure when administered to a patient who had already been treated with the carbonic anhydrase inhibitor preparation. The amount of intraocular pressure lowering was directly related to dose for both acetazolamide preparations. Of particular interest was the finding that maximal rapid reduction of intraocular pressure was obtained with a 500-mg dosage of acetazolamide tablets.

Timolol inhibits adenylate cyclase activity in the iris-ciliary body and trabecular meshwork of the eye and blocks activation of the enzyme by salbutamol

The enzymatic activity of adenylate cyclase in homogenates and membrane-rich fractions prepared from rabbit iris-ciliary bodies and bovine trabecular meshwork was found to be inhibited by timolol. Treatment of iris-ciliary body homogenates with Triton X-305 resulted in abolition of the inhibitory effect of the drug on the activity of the enzyme. The stimulatory effect of salbutamol on the enzyme was also susceptible to blockade by timolol. It is suggested that the hypotensive action of timolol on intraocular pressure results from structural and functional changes induced on the plasma membranes of the iris-ciliary body and trabecular meshwork by the thiadiazole group of the molecule, and, also, from the occupation of the adrenergic receptors of the iris-ciliary body by the tert-butylamino-2-hydroxypropoxy part of the compound.

Comparison of two treatment schedules for combined timolol and dipivefrin therapy

In a prospective, randomized, single-masked, cross-over study, 18 patients with primary open-angle glaucoma were treated for one month with each of the following regimens: timolol 0.5% twice daily, timolol 0.5% plus dipivefrin 0.1% twice daily given ten minutes apart, and timolol 0.5% plus dipivefrin 0.1% given twice daily four hours apart. An eight-hour intraocular pressure curve was obtained before treatment and at the end of each monthly regimen. When added to timolol therapy, dipivefrin produced a small but statistically significant additional mean decrease in intraocular pressure. The difference in intraocular pressure reduction between the two regimens for combined timolol and dipivefrin therapy was not statistically significant.

Timolol and aceclidine. A clinical study of interaction in the eye

In the Netherlands timolol maleate, probably the drug of first choice in antiglaucoma therapy, is often combined with other intraocular pressure lowering drugs. The efficacy of most combinations have been discussed in the literature several times, except the one with aceclidine, a parasympathetic drug, that has a reasonable popularity in Western Europe. Unlike pilocarpine, aceclidine does not seem to give a clinically significant additional pressure lowering effect in timolol pre-treated eyes. The decrease in IOP in aceclidine pre-treated eyes after single dose timolol seems to be an effect of timolol alone. Our results suggest that co-administration of timolol and aceclidine is not a rational action in antiglaucomatous therapy.