Ocular metipranolol. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in glaucoma and ocular hypertension

Chemical Insights into Topical Agents in Intraocular Pressure Management: From Glaucoma Etiopathology to Therapeutic Approaches

Glaucoma encompasses a group of optic neuropathies characterized by complex and often elusive etiopathology, involvihttng neurodegeneration of the optic nerve in conjunction with abnormal intraocular pressure (IOP). Currently, there is no cure for glaucoma, and treatment strategies primarily aim to halt disease progression by managing IOP. This review delves into the etiopathology, diagnostic methods, and treatment approaches for glaucoma, with a special focus on IOP management. We discuss a range of active pharmaceutical ingredients used in glaucoma therapy, emphasizing their chemical structure, pharmacological action, therapeutic effectiveness, and safety/tolerability profiles. Notably, most of these therapeutic agents are administered as topical formulations, a critical aspect considering patient compliance and drug delivery efficiency. The classes of glaucoma therapeutics covered in this review include prostaglandin analogs, beta blockers, alpha agonists, carbonic anhydrase inhibitors, Rho kinase inhibitors, and miotic (cholinergic) agents. This comprehensive overview highlights the importance of topical administration in glaucoma treatment, offering insights into the current state and future directions of pharmacological management in glaucoma.

A Narrative Review of Ocular Surface Disease Related to Anti-Glaucomatous Medications

Topical anti-glaucomatous medications are still the most important measure to lower intraocular pressure. Large number of studies have confirmed that long-term use of anti-glaucomatous eye drops, especially containing benzalkonium chloride, a preservative, can cause or aggravate ocular surface injury. Ocular surface diseases damage the ocular microenvironmental health status, reduce the patients’ compliance with the treatment, and finally affect the treatment result. Therefore, the ocular surface management of patients with glaucoma is very important. This includes the selection of drugs that are better tolerated according to individual conditions, preservative-free formulations, drugs that protect against ocular surface disease, or selecting surgery and laser treatment, to prevent the damage to the ocular surface by topical anti-glaucomatous drugs.

Advances in the discovery of novel agents for the treatment of glaucoma

INTRODUCTION

Glaucoma, a neuropathy characterized by increased intraocular pressure (IOP), is the major cause of blindness worldwide and its treatment aims at reducing IOP.

AREAS COVERED

The authors review the design of the main classes of anti-glaucoma agents. Drugs which interfere with the aqueous humor secretion (adrenergic agonists/antagonists, carbonic anhydrase inhibitors) and with its outflow, by means of both conventional and non-conventional pathways (prostaglandin (PG) analogs, rho kinase inhibitors, nitric oxide (NO) donors) as well as new agents (adenosine receptors modulators, melatonin - fatty acid amide hydrolase hybrids, tyrosine kinase activators, natriuretic peptide analogs) are considered.

EXPERT OPINION

The anti-glaucoma drug field has undergone several developments in recent years with the approval of at least three new drugs belonging to novel pharmacological classes, the rho kinase inhibitors ripasudil and netarsudil, and the PG-NO donor hybrid latanoprostene bunod. Eye drops with combinations of two different drugs are also available, allowing for effective IOP control, with once daily administration for some of them, which assures a better patient compliance and ease of administration. Overall, after more than a decade without new anti-glaucoma drugs, the last year afforded interesting new pharmacological opportunities for the management of this disease.

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.

Ocular non-P450 oxidative, reductive, hydrolytic, and conjugative drug metabolizing enzymes

Metabolism in the eye for any species, laboratory animals or human, is gaining rapid interest as pharmaceutical scientists aim to treat a wide range of so-called incurable ocular diseases. Over a period of decades, reports of metabolic activity toward various drugs and biochemical markers have emerged in select ocular tissues of animals and humans. Ocular cytochrome P450 (P450) enzymes and transporters have been recently reviewed. However, there is a dearth of collated information on non-P450 drug metabolizing enzymes in eyes of various preclinical species and humans in health and disease. In an effort to complement ocular P450s and transporters, which have been well reviewed in the literature, this review is aimed at presenting collective information on non-P450 oxidative, hydrolytic, and conjugative ocular drug metabolizing enzymes. Herein, we also present a list of xenobiotics or drugs that have been reported to be metabolized in the eye.

Recent Patents on Emerging Therapeutics for the Treatment of Glaucoma, Age Related Macular Degeneration and Uveitis

Advancements in the field and rising interest among pharmaceutical researchers have led to the development of new molecules with enhanced therapeutic activity. Design of new drugs which can target a particular pathway and/or explore novel targets is of immense interest to ocular pharmacologists worldwide. Delivery of suitable pharmacologically active agents at proper dose (within the therapeutic window) to the target tissues without any toxicity to the healthy ocular tissues still remain an elusive task. Moreover, the presence of static and dynamic barriers to drug absorption including the corneal epithelium (lipophilic), corneal and scleral stroma (hydrophilic), conjunctival lymphatics, choroidal vasculature and the blood-ocular barriers also pose a significant challenge for achieving therapeutic drug concentrations at the target site. Although many agents are currently available, new compounds are being introduced for treating various ocular diseases. Deeper understanding of the etiology and complex mechanisms associated with the disease condition would aid in the development of potential therapeutic candidates. Novel small molecules as well as complex biotechnology derived macromolecules with superior efficacy, safety and tolerability are being developed. Therefore, this review article provides an overview of existing drugs, treatment options, advances in emerging therapeutics and related recent patents for the treatment of ocular disorders such as glaucoma, age related macular degeneration (AMD) and uveitis.

Effects of common topical antiglaucoma medications on the ocular surface, eyelids and periorbital tissue

Glaucoma affects millions of people around the world. With the baby boom generation aging, the number of people affected by primary open-angle glaucoma in the US is expected to reach 3.3 million by 2020, and about half may not know they have the disease. The treatment of most forms of glaucoma includes the use of topical agents that enhance aqueous humour outflow, reduce aqueous production, or both. Topical intraocular pressure-lowering drugs must penetrate across the tissues of the eye to reach their therapeutic targets. Often, these tissues show the first signs and symptoms of drug toxicity and adverse effects. These include eyelid dermatitis, malpositions, lacrimal system scarring, ocular discomfort upon instillation, tear film instability, conjunctival inflammation, subconjunctival fibrosis, conjunctival epithelium changes, and corneal surface and endothelial impairment. For these reasons, ophthalmologists should evaluate the risks and benefits of ophthalmic medications before initiating therapy, identify the minimum dosages necessary to achieve a therapeutic benefit, and monitor patients for local and systemic adverse effects. Adverse events may be reduced by changing to a different class of topical medication, using corticosteroids, lubricating the eyes frequently, and reducing exposure to preservatives. This in turn can lead to higher levels of adherence to antiglaucoma therapy, improved outcomes and a reduction in the costs associated with long-term glaucoma complications. This article reviews the ocular adverse effects associated with the various classes of topical antiglaucoma drugs, with a particular focus on the ocular surface, eyelids and periorbital tissue.

Pharmacotherapy of intraocular pressure: part I. Parasympathomimetic, sympathomimetic and sympatholytics

Elevated intraocular pressure (IOP) has been recognized as the major risk factor for the development of glaucoma and a wide range of options are now available to reduce it: medical treatment, laser, filtering, or cyclodestructive surgery (alone or in combination). All these modalities act by decreasing eye pressure and, thereby, protecting the optic nerve head from a mechanic direct and/or vascular indirect insult. Topical medical therapy represents the first-choice treatment and, in most cases, it effectively controls IOP, avoiding the occurrence of further optic nerve damage. All medications lower IOP in two main ways: decreasing the production of aqueous humour or by increasing its outflow from the eye. Consequently, antiglaucoma drugs either suppress aqueous humour formation (beta-adrenergic antagonists, carbonic anhydrase inhibitors, and alpha-2-adrenergic agonists) or raise aqueous humour outflow throughout the conventional (e.g., pilocarpine) or uveoscleral (prostaglandin FP receptor agonists, and prostamides) route. In addition, fixed and unfixed combinations of antiglaucoma compounds have also been available for patients requiring more than one type of medication. This review, which is part one of two (please see Expert Opinion on Pharmacotherapy 10 (17)) briefly considers the characteristics of sympathomimetic, sympatholytics and parasympathomimetic commonly employed in the medical treatment of glaucoma, mainly the primary open-angle form, focusing the discussion on the clinical evidence supporting the use of these three classes of compound.

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.

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.

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.

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.

Effects of beta-blockers association with pilocarpine on rabbit intraocular pressure and heart rate

The effect of 7-days BID (twice in a day) or TID (three times in a day) administration of the eye-drop combinations of timolol and pilocarpine (0.5% and 2%, respectively), metipranolol and pilocarpine (0.1% and 2%, respectively) or placebo on intraocular pressure (IOP) and heart rate (HR) of conscious rabbits were studied in order to assess the pharmacological potency of the combinations and their heart side effects. TID administration of both pharmacological combinations was followed by similar decrease of IOP as measured over 24 h (at 4.00 and 20.00 h). After the BID administration, a reduction in IOP was observed only twice with the timolol-pilocarpine combination. In contrast, a constant reduction in IOP was seen with the metipranolol-pilocarpine combination. Furthermore, the TID administration of the timolol-pilocarpine combination exerted a decrease of IOP that appeared to be more pronounced than that observed after the BID administration of the same combination, while no difference was found between the TID and BID administration of the metipranolol-pilocarpine treatment. Heart rate, when measured after 7 days of treatment, appeared to be constantly decreased only in the group of animals which received the TID administration of timolol-pilocarpine combination. The present results suggest that the BID or TID administration of metipranolol-pilocarpine combination was fully effective in reducing IOP without influencing HR. The timolol-pilocarpine association appeared to be fully active in reducing IOP only under the TID administration schedule. However, this rate of administration was followed by a constant reduction of HR. Thus, on a dose basis the metipranolol-pilocarpine combination appeared to be more effective in reducing IOP and less effective in inducing bradycardia than the timolol-pilocarpine association.

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.

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.

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.

Ocular carteolol. A review of its pharmacological properties, and therapeutic use in glaucoma and ocular hypertension

Carteolol is a relatively potent nonselective beta-adrenoceptor antagonist with partial agonist activity. It is used topically to reduce elevated intraocular pressure (IOP) in patients with glaucoma or ocular hypertension. Twice-daily ocular administration of carteolol 1 or 2% lowers IOP by approximately 32% on average in patients with these conditions, an efficacy equivalent to that of timolol 0.25 or 0.5%. Carteolol eyedrops lack local anaesthetic activity, appear to cause less local irritation than timolol, and produce less pronounced decreases in heart rate or dyspnoea, possibly due to partial agonist activity. The latter activity may also improve retinal perfusion. Thus, although additional comparative trials are needed to accurately assess the precise place of carteolol in therapy, this drug offers a useful alternative to timolol in the management of conditions associated with a raised IOP, and may have advantages in older patients with regard to its tolerability profile, although careful monitoring is still wise.

A clinical trial of metipranolol, a noncardioselective beta-adrenergic antagonist, in ocular hypertension

In randomized, double-masked fashion, 24 volunteers with ocular hypertension received 0.3% or 0.6% metipranolol, a noncardioselective beta blocker; or placebo twice daily to both eyes for six weeks. Intraocular pressure (mean +/- SEM) was reduced (P = .01) in the metipranolol-treated patients (baseline measurement, 25.9 +/- 0.5 mm Hg to 18.1 +/- 1.2 mm Hg at six weeks, 0.6% concentration; baseline measurement, 27.1 +/- 0.4 mm Hg to 21.6 +/- 1.5 mm Hg at six weeks, 0.3% concentration). Intraocular pressure was not markedly changed in placebo-treated patients. Outflow facility was unaltered two hours after instillation of metipranolol at study week 2 compared to baseline measurement. Aqueous humor flow rates were reduced (P = .02) 20% after 0.6% or 0.3% metipranolol instillation and were unchanged after placebo administration compared to baseline measurement. Mean systolic blood pressure, diastolic blood pressure, and pulse rate were not markedly altered. Metipranolol reduces intraocular pressure by suppressing aqueous humor flow rates.

Metipranolol-associated granulomatous anterior uveitis

This paper presents for the first time documented evidence, clinical details, and photographic illustrations of metipranolol-associated granulomatous anterior uveitis in 26 eyes of 15 patients being treated for glaucoma. There were 56 episodes of granulomatous anterior uveitis, all associated with large (mutton-fat) keratic precipitates, flare, cells, and 'white eyes' (except in seven episodes). In 30 (53.6%) of these episodes there was loss of control of intraocular pressure. Metipranolol 0.6% was implicated in 54 of the 56 episodes and metipranolol 0.3% in the remaining two. Fifty-one other cases of metipranolol-associated granulomatous anterior uveitis have so far been reported from other parts of the country to the Committee on Safety of Medicines. As a result multidose metipranolol in 0.1%, 0.3%, and 0.6% strengths has been withdrawn from clinical use in the United Kingdom. The pathogenesis of this adverse drug reaction is uncertain.