Olopatadine (AL-4943A): ligand binding and functional studies on a novel, long acting H1-selective histamine antagonist and anti-allergic agent for use in allergic conjunctivitis

Progress of Research and Comparative Analysis on the Combination of Mast Cell Stabilizers and Antihistamines in Allergic Conjunctivitis Treatment

Allergic conjunctivitis (AC) is a common ophthalmological condition primarily associated with type I and IV allergic responses. Although AC typically does not cause visual impairments, it can significantly reduce the quality of life of individuals, regardless of age, with severe cases possibly affecting the cornea and potentially impairing vision. However, the mechanisms of action of primary therapeutic drugs-antihistamines, mast cell stabilizers, and their combination-remain unclear. This review introduces the pathogenesis of allergic conjunctivitis, including seasonal, perennial, and vernal keratoconjunctivitis. This study found that dual-acting drugs offer advantages over single-agent treatments. Compared to antihistamines or mast cell stabilizers used alone, dual-acting drugs have fewer adverse reactions, avoid side effects such as drowsiness, dizziness, and nausea, and do not cross the blood-brain barrier, thereby preventing potential impacts on learning and memory in both children and adults.

Sustained Delivery of Olopatadine from Vitamin-E Loaded Contact Lenses

Purpose: Topical antihistamines, such as olopatadine hydrochloride, an H1 receptor antagonist, are commonly prescribed for treating allergic conjunctivitis. Drug delivery via eye drops has many deficiencies including a short residence time due to tear drainage via the nasolacrimal duct, which results in a low bioavailability and potential for side effects. These deficiencies could be mitigated by a drug-eluting contact lens such as the recently approved ACUVUE® THERAVISION™ WITH KETOTIFEN which is a daily disposable etafilcon, a drug-eluting contact lens with ketotifen (19 μg per lens). Here, we investigate the feasibility of designing a drug-eluting lens with sustained release of olopatadine for treating allergies using an extended wear lens. Methods: Nanobarrier depots composed of vitamin-E (VE) are formed through direct entrapment by ethanol-driven swelling. The drug-loaded lenses are characterized for transparency and water content. In vitro release is measured under sink conditions and fitted to a diffusion control release model to determine diffusivity and partition coefficient. Results: In vitro studies indicate that ACUVUE OASYS® and ACUVUE TruEye™ lenses loaded with ∼0.3 g of VE/g of hydrogel effectively prolong olopatadine dynamics by 7-fold and 375-fold, respectively. Incorporation of VE into the lenses retains visible light transmission and other properties. Conclusion: The VE incorporation in commercial lenses significantly increases the release duration offering the possibility of antiallergy extended wear lenses.

PAF-induced inflammatory and immuno-allergic ophthalmic diseases and their mitigation with PAF receptor antagonists: Cell and nuclear effects

Ocular allergies are becoming more prevalent as more airborne pollutants, irritants and microbes pervade our environment. Inflammatory and allergic mediators released by dendritic and mast cells within the conjunctiva cause allergic conjunctivitis (AC), a prevalent ocular surface disorder that affects >40% of the world's human population on a seasonal or perennial basis. Even though histamine is a major culprit, platelet-activating factor (PAF) also contributes to AC, acting either directly or synergistically with histamine and other mediators. PAF receptor-meditated inflammatory reactions, via cell-membrane-bound and nuclear-membrane-bound and nuclear PAF receptors, are also implicated in the etiology of other eye diseases such as uveitis, diabetic retinopathy, corneal and choroidal neovascularization, and age-related macular degeneration which cause serious visual impairment and can lead to blindness. This review highlights the various deleterious elements implicated in the pathological aspects of ocular allergic reactions and inflammation and provides concepts and treatment options to mitigate these eye disorders with a special focus on PAF and PAF receptor antagonists.

Assessment of receptor affinities of ophthalmic and systemic agents in dry eye disease

PURPOSE OF REVIEW

To explore our current understanding of receptor profiles acted upon by medications used to treat dry eye disease (DED).

RECENT FINDINGS

Research into histaminic and muscarinic receptor affinities for drugs targeting the ocular surface has not kept up with bench research pertaining to the receptor profile of the ocular surface. These insights are necessary for better evaluation of medications used in DED and other allergic disorders.

SUMMARY

At the H1 receptor, Ketotifen (pKa = 9.2), pyrilamine (pKa = 9.0), and epinastine (pKa = 8.0) had the highest affinities, whereas ranitidine (pKa = 4.2) and cimetidine (pKa = 4.9) had the lowest. Ketotifen, a second-generation antihistamine, was found to have a pKa of 6.7 at muscarinic receptors which was higher than that of diphenhydramine (pKa = 6.4), a first-generation antihistamine. Additionally, second-generation antihistamines have higher affinity for H3 receptors, which have been linked to urticaria, compared to first-generation. Azelastine, a second-generation, demonstrated significant affinity (pKa = 7.1) at the H3 receptor compared to all other drugs. Antazoline (pKa = 4.4) and diphenhydramine (pKa = 4.6), both first-generation antihistamines, had the lowest affinities for the H3 receptor. These findings raise questions about the use of antihistamines in the treatment of DED and allergic disorders.

Combine therapy as a modern approach to treatment of allergic rhinitis

Allergic rhinitis (AR) is one the most common allergic diseases affecting from 10 to 40% of the population in different countries, including Russia. AR is a risk factor of bronchial asthma, other upper airway disease and may decrease patient quality of life, their productivity, increase probability of occupational traumatism, depression and anxiety. AR also presents a substantial economic burden. The rationale to use fixed dose combination of intranasal steroids and topical H1 antihistamines includes suboptimal control of symptoms by monotherapy, its complementary pharmacologic activity and the results of clinical trials. This review focused on fixed dose combination of intranasal mometasone furoate and olopataine. Double blind placebo-controlled and open clinical trials have confirmed that this combination decreased severity of nasal and ocular symptoms of seasonal and perennial AR, improved patient quality of life and had a good tolerability. Its efficacy was higher than those of monotherapy. Fast onset of action and sustainable effect on symptoms (during 1 yr) may improve adherence patients to the treatment and control of symptoms of AR.

The Nose as a Route for Therapy: Part 1. Pharmacotherapy

This article reviews nasal structure and function in the light of intranasal pharmacotherapy. The nose provides an accessible, fast route for local treatment of nose and sinus diseases, with lower doses than are necessary systemically and few adverse effects. It can also be used for other medications as it has sufficient surface area protected from local damage by mucociliary clearance, absence of digestive enzymes, responsive blood flow, and provides a rapid route to the central nervous system.

Discovery to Launch of Anti-allergy (Emadine; Patanol/Pataday/Pazeo) and Anti-glaucoma (Travatan; Simbrinza) Ocular Drugs, and Generation of Novel Pharmacological Tools Such as AL-8810

The eye and eyesight are exquistly designed and are precious, and yet we often take them for granted. Good vision is critical for our long-term survival and for humanity's enduring progress. Unfortunately, since ocular diseases do not culminate in life-and-death scenarios, awareness of the plight of millions of people suffering from such eye ailments is not publicized as other diseases. However, losing eyesight or falling victim to visual impairment is a frightening outlook for most people. Glaucoma, a collection of chronic optic neuropathies, of which the most prevalent form, primary open-angle glaucoma (POAG), is the second leading cause of irreversible blindness. POAG currently afflicts >70 million people worldwide and is an insidious, progressive, silent thief of sight that is asymptomatic. On the other hand, allergic conjunctivitis (AC), and the associated rhinitis ("hay-fever"), frequently victimizes a huge number of people worldwide, especially during seasonal changes. While not life-threatening, sufferers of AC soon learn the value of drugs to treat their signs and symptoms of AC as they desire rapid relief to overcome the ocular itching/pain, redness, and tearing AC causes. Herein, I will describe the collective efforts of many researchers whose industrious, diligent, and dedicated team work resulted in the discovery, biochemical/pharmacological characterization, development and eventual launch of drugs to treat AC (e.g., olopatadine [Patanol/Pataday/Pazeo] and emedastine [Emedine]), and for treating ocular hypertension and POAG (e.g., travoprost [Travatan ] and Simbrinza). This represents a personal perspective.

Roles of Lys191 and Lys179 in regulating thermodynamic binding forces of ligands to determine their binding affinity for human histamine H1 receptors

Docking simulations based on the crystal structure of human histamine H₁ receptors have predicted crucial roles of Lys191^5.39 and Lys179^ECL2, which exist at the entrance of the ligand-binding pocket, in increasing the H₁-receptor selectivity for carboxylated second-generation antihistamines via electrostatic interaction. In this study, we evaluated the roles of Lys191^5.39 and Lys179^ECL2 in regulating the thermodynamic binding forces of non-carboxylated and carboxylated antihistamines that determine their binding affinity for human H₁ receptors. The binding enthalpy and entropy of the 3 sets of non-carboxylated and corresponding carboxylated antihistamines (doxepin and olopatadine, desloratadine and loratadine, and terfenadine and fexofenadine, respectively) were estimated using the van't Hoff equation with the dissociation constants obtained from the displacement curves of the non-carboxylated and carboxylated antihistamines against the binding of [³H]mepyramine to the membrane preparations of Chinese hamster ovary cells expressing human H₁ receptors at various temperatures, ranging from 4 °C to 37 °C. We found that the affinity for carboxylated antihistamines was lower than that for the corresponding non-carboxylated compounds due to lower enthalpy-dependent electrostatic binding forces and/or entropy-dependent hydrophobic binding forces. Mutations of Lys191^5.39 and/or Lys179^ECL2 to alanine mostly increased the binding affinity for antihistamines due to a variety of changes in both enthalpy- and entropy-dependent binding forces. These results suggest that Lys191^5.39 and Lys179^ECL2 may not contribute to selectively increasing the binding affinity for carboxylated antihistamines via electrostatic interaction, but that they can negatively modulate the binding affinity for non-carboxylated and carboxylated antihistamines non-selectively by affecting their electrostatic as well as hydrophobic binding forces.

Pupil Diameter, Corneal Thickness, and Anterior Chamber Alterations Following Topical Olopatadine Hydrochloride 0.1%: A Single-Masked Randomized Controlled Clinical Study

Purpose: Olopatadine hydrochloride 0.1% is one of the known primary topical treatments in ocular allergy. Although olopatadine is a worldwide used medication, the changes in pupil diameter, cornea, and anterior chamber associated with its use have not been studied in detail. In this prospective study, we aimed to determine the amount of mydriasis and explore the possible corneal and anterior chamber alterations after 0.1% topical olopatadine. Methods: A total of 77 eyes from 77 ocular-allergy diagnosed patients between 18 and 40 years were investigated in this prospective study. Thirty-nine eyes of 39 patients received topical olopatadine, and 38 eyes of 38 patients received sterile distilled water, randomly. Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) topography was used to assess the pupil and anterior chamber measurements at baseline and after 45 min of olopatadine or sterile distilled water instillation. Results: The differences between the baseline and 45th-min measurements for corneal thickness, anterior chamber depth, angle, and volume did not reach a statistical significance in the olopatadine or control groups. The pupil diameter significantly increased from 3.19 ± 0.62 to 3.36 ± 0.62 mm in the olopatadine group (P < 0.001), and remained relatively unchanged in the control group (P = 0.06). Conclusion: Olopatadine 0.1% does not lead to a significant change in corneal topography or anterior chamber parameters. However, it causes a slight but statistically significant increase in pupil diameter.

Comparison of cytotoxicities and anti-allergic effects of topical ocular dual-action anti-allergic agents

Background

To investigate the cytotoxicities of the topical ocular dual-action anti-allergic agents (alcaftadine 0.25%, bepotastine besilate 1.5%, and olopatadine HCL 0.1%) on human corneal epithelial cells (HCECs) and their anti-allergic effects on cultured conjunctival epithelial cells.

Methods

A Methylthiazolyltetrazolium(MTT)-based calorimetric assay was used to assess cytotoxicities using HCECs at concentrations of 10, 20 or 30% for exposure durations of 30 min, 1 h, 2 h, 12 h or 24 h. Cellular morphologies were evaluated by inverted phase-contrast and electron microscopy. Wound widths were measured 2 h, 18 h, or 24 h after confluent HCECs monolayers were scratched. Realtime PCR was used to quantify anti-allergic effects on cultured human conjunctival cells, in which allergic reactions were induced by treating them with Aspergillus antigen.

Results

Cell viabilities decreased in time- and concentration-dependent manners. Cells were detached from dishes and showed microvilli loss, cytoplasmic vacuoles, and nuclear condensation when exposed to antiallergic agents; alcaftadine was found to be least cytotoxic. Alcaftadine treated HCECs monolayers showed the best wound healing followed by bepotastine and olopatadine (p < 0.0001). All agents significantly reduced the gene expressions of allergic cytokines (IL-5, IL-25, eotaxin, thymus and activation-regulated chemokine, and thymic stromal lymphopoietin) and alcaftadine had the greatest effect (p < 0.0001 in all cases).

Conclusions

Alcaftadine seems to have less side effects and better therapeutic effects than the other two anti-allergic agents tested. It may be more beneficial to use less toxic agents for patients with ocular surface risk factors or presumed symptoms of toxicity.

Modulation of Allergic Inflammation in the Nasal Mucosa of Allergic Rhinitis Sufferers With Topical Pharmaceutical Agents

Allergic rhinitis (AR) is a chronic upper respiratory disease estimated to affect between 10 and 40% of the worldwide population. The mechanisms underlying AR are highly complex and involve multiple immune cells, mediators, and cytokines. As such, the development of a single drug to treat allergic inflammation and/or symptoms is confounded by the complexity of the disease pathophysiology. Complete avoidance of allergens that trigger AR symptoms is not possible and without a cure, the available therapeutic options are typically focused on achieving symptomatic relief. Topical therapies offer many advantages over oral therapies, such as delivering greater concentrations of drugs to the receptor sites at the source of the allergic inflammation and the reduced risk of systemic side effects. This review describes the complex pathophysiology of AR and identifies the mechanism(s) of action of topical treatments including antihistamines, steroids, anticholinergics, decongestants and chromones in relation to AR pathophysiology. Following the literature review a discussion on the future therapeutic strategies for AR treatment is provided.

Antihistamines suppress upregulation of histidine decarboxylase gene expression with potencies different from their binding affinities for histamine H1 receptor in toluene 2,4-diisocyanate-sensitized rats

Antihistamines inhibit histamine signaling by blocking histamine H1 receptor (H1R) or suppressing H1R signaling as inverse agonists. The H1R gene is upregulated in patients with pollinosis, and its expression level is correlated with the severity of nasal symptoms. Here, we show that antihistamine suppressed upregulation of histidine decarboxylase (HDC) mRNA expression in patients with pollinosis, and its expression level was correlated with that of H1R mRNA. Certain antihistamines, including mepyramine and diphenhydramine, suppress toluene-2,4-diisocyanate (TDI)-induced upregulation of HDC gene expression and increase HDC activity in TDI-sensitized rats. However, d-chlorpheniramine did not demonstrate any effect. The potencies of antihistamine suppressive effects on HDC mRNA elevation were different from their H1R receptor binding affinities. In TDI-sensitized rats, the potencies of antihistamine inhibitory effects on sneezing in the early phase were related to H1R binding. In contrast, the potencies of their inhibitory effects on sneezing in the late phase were correlated with those of suppressive effects on HDC mRNA elevation. Data suggest that in addition to the antihistaminic and inverse agonistic activities, certain antihistamines possess additional properties unrelated to receptor binding and alleviate nasal symptoms in the late phase by inhibiting synthesis and release of histamine by suppressing HDC gene transcription.

Ocular itch associated with allergic conjunctivitis: latest evidence and clinical management

Allergic conjunctivitis is one of the most common allergic conditions worldwide. Its incidence is increasing due to changing climate, pollution, increased pollen loads, and the subject's heightened immunological sensitivity in response to these environmental changes. The pathophysiology predominantly involves immunoglobulin E-related mast-cell activation, with release of histamine and other mediators contributing to the propagation of the response by calling in other immune cells and further inflammation. This article presents the evolution of ocular allergy treatments, from vasoconstrictors, to antihistamines and mast-cell stabilizers, to the dual-acting agents, as well as corticosteroid and immunomodulatory options. Future targets for allergy treatment are also discussed.

International Union of Basic and Clinical Pharmacology. XCVIII. Histamine Receptors

Histamine is a developmentally highly conserved autacoid found in most vertebrate tissues. Its physiological functions are mediated by four 7-transmembrane G protein-coupled receptors (H1R, H2R, H3R, H4R) that are all targets of pharmacological intervention. The receptors display molecular heterogeneity and constitutive activity. H1R antagonists are long known antiallergic and sedating drugs, whereas the H2R was identified in the 1970s and led to the development of H2R-antagonists that revolutionized stomach ulcer treatment. The crystal structure of ligand-bound H1R has rendered it possible to design new ligands with novel properties. The H3R is an autoreceptor and heteroreceptor providing negative feedback on histaminergic and inhibition on other neurons. A block of these actions promotes waking. The H4R occurs on immuncompetent cells and the development of anti-inflammatory drugs is anticipated.

Antihistamines and itch

Histamine is one of the best-characterized pruritogens in humans. It is known to play a role in pruritus associated with urticaria as well as ocular and nasal allergic reactions. Histamine mediates its effect via four receptors. Antihistamines that block the activation of the histamine H₁receptor, H₁R, have been shown to be effective therapeutics for the treatment of pruritus associated with urticaria, allergic rhinitis, and allergic conjunctivitis. However, their efficacy in other pruritic diseases such as atopic dermatitis and psoriasis is limited. The other histamine receptors may also play a role in pruritus, with the exception of the histamine H₂receptor, H₂R. Preclinical evidence indicates that local antagonism of the histamine H₃receptor, H₃R, can induce scratching perhaps via blocking inhibitory neuronal signals. The histamine H₄receptor, H₄R, has received a significant amount of attention as to its role in mediating pruritic signals. Indeed, it has now been shown that a selective H₄R antagonist can inhibit histamine-induced itch in humans. This clinical result, in conjunction with efficacy in various preclinical pruritus models, points to the therapeutic potential of H₄R antagonists for the treatment of pruritus not controlled by antihistamines that target the H₁R.

Transient receptor potentials (TRPs) and anaphylaxis

The transient receptor potential (TRP) superfamily consists of 28 members in mammals (27 in human) that act as polymodal sensors and ion channels. They regulate cellular calcium influx, generate depolarization thereby triggering voltage dependent cellular processes, and in turn they are critical in inducing the metabolic activities of cells. It is increasingly apparent that many of the inflammatory mediators released in allergic reactions involve at least two of these ion channels, the 'Vanilloid' TRPV1 and the 'Ankyrin" TRPA1. This review mainly focuses on TRPV1 and TRPA1 and the role they have in the allergic response and how these receptors may be influenced in exercise-induced anaphylaxis. The threshold to react to an allergen for mast cells and lymphocytes can be reduced by activating the melastatin channel TRPM4. This channel is briefly discussed in the context of allergy.

Recognition of allergic conjunctivitis in patients with allergic rhinitis

AIMS

To identify the incidence of allergic conjunctivitis in patients with allergic rhinitis.

METHODS

One hundred and eighty seven consecutive patients with allergic rhinitis (AR) were directly questioned if they have allergic conjunctivitis (AC) and this was clarified using standard screening questions relating to red, itchy and watery eyes recorded through a total ocular symptom score (TOSS). Patients were also asked about further symptoms that may be attributable to AC: eyelid dermatitis, frequent blinking; eye sensitivity and frontal headache from squinting or. blinking. All patients were given a drop of olopatadine hydrochloride 0.1% in each eye to help identify "silent" disease. 20 healthy non-atopic controls were also treated with olopatadine drops and questioned on ocular symptoms.

RESULTS

Fifty five percent of patients with AR were identified as having AC by direct questioning and the use of the TOSS questionaire. A further 41% were identifiable by asking additional questions and performing therapeutic challenge with olopadatine.

CONCLUSIONS

AC is a frequent comorbid condition occurring in 95% of our patients with AR. Only 55% of patients were able to identify that they had AC based on standard screening questions. Additional specific questioning and a therapeutic challenge in suspected patients can help identify patients who may benefit from treatment of AC.

Olopatadine ophthalmic solution suppresses substance P release in the conjunctivitis models

Background

Olopatadine hydrochloride ophthalmic solutions are treated for allergic conjunctival diseases that are a selective histamine H1 receptor antagonist and an inhibitor of the release of mediators including histamine from the human mast cells. Substance P (SP) levels are increased in tears of patients with allergic conjunctivitis. However, little is known about the regulation of SP release by anti-allergic ophthalmic solutions.

Objective

We investigated that the effect of olopatadine hydrochloride ophthalmic solutions (olopatadine 0.1% and olopatadine 0.2%) on rat conjunctivitis models compared with other anti-allergic ophthalmic solutions.

Methods

Conjunctivitis was induced by subconjunctival injection of histamine or intravenous injection of ovalbumin in rats passively sensitized with anti-ovalbumin anti-serum. The releases of SP were determined in the conjunctiva and tears using rat antigen-induced conjunctivitis models.

Results

Olopatadine 0.1% and 0.2% significantly inhibited the increased conjunctival dye leaked in the histamine- or antigen-induced hyperpermeability. The inhibitory effects by olopatadine were more potent than by other tested anti-allergic ophthalmic solutions. Moreover, olopatadine significantly inhibited the release of SP from the conjunctiva.

Conclusion

These results indicate that olopatadine ophthalmic solutions appear to exert additional SP release inhibition besides dual-action such as selective histamine H1 receptor antagonistic action and mast cell stabilization action.

Olopatadine hydrochloride and rupatadine fumarate in seasonal allergic rhinitis: A comparative study of efficacy and safety

Objective:

To compare the efficacy and safety of olopatadine and rupatadine in seasonal allergic rhinitis (SAR).

Materials and Methods:

A 2-week, single-centered, randomized, open, parallel group comparative clinical study was conducted on patients with SAR. Following inclusion and exclusion criteria, 70 patients were recruited and were randomized to two treatment groups and received the respective drugs for 2 weeks. At follow-up, clinical improvement was assessed in terms of change in total and differential count of leucocytes, serum Immunoglobulin E (IgE) level, Total Nasal Symptom Score (TNSS) and Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) scoring.

Results:

Both the drugs significantly reduced the differential count (P<0.001) and absolute eosinophil count (P<0.001), but olopatadine was found to be superior. In olopatadine group, there was significantly higher reduction in serum IgE (P=0.01), TNSS (P<0.001) and RQLQ score (P=0.015) than that of rupatadine. Incidence of adverse effects was found to be less in olopatadine group when compared with rupatadine group.

Conclusions:

Olopatadine is a better choice in SAR in comparison to rupatadine due to its better efficacy and safety profile.

Olopatadine 0.6% Nasal Spray Protects from Vasomotor Challenge in Patients with Severe Vasomotor Rhinitis

Background

Vasomotor rhinitis (VMR) is a hypersensitivity syndrome with heightened reactivity to environmental triggers.

Methods

Twenty-two patients with severe VMR were treated nasally with either normal saline or 0.6% olopatadine and challenged nasally with a hyperosmolar mannitol solution.

Results

Treatment with 0.6% olopatadine resulted in an improvement in instantaneous nasal symptom scores at 5 and 30 minutes (p < 0.01) compared with baseline and at 30 minutes after hyperosmolar challenge compared with saline-pretreated individuals (p < 0.01). There was also an improvement in nasal peak inspiratory flow rate at 30 minutes after hyperosmolar challenge compared with saline-pretreated individuals (p < 0.01.

Conclusion

In this patient population 0.6% olopatadine appears to be efficacious in symptom reduction in VMR and protects from hyperosmolar challenge.

Treatment of allergic conjunctivitis with olopatadine hydrochloride eye drops

Olopatadine hydrochloride exerts a wide range of pharmacological actions such as histamine H₁ receptor antagonist action, chemical mediator suppressive action, and eosinophil infiltration suppressive action. Olopatadine hydrochloride 0.1% ophthalmic solution (Patanol^®) was introduced to the market in Japan in October 2006. In a conjunctival allergen challenge (CAC) test, olopatadine hydrochloride 0.1% ophthalmic solution significantly suppressed ocular itching and hyperemia compared with levocabastine hydrochloride 0.05% ophthalmic solution, and the number of patients who complained of ocular discomfort was lower in the olopatadine group than in the levocabastine group. Conjunctival cell membrane disruption was observed in vitro in the ketotifen fumarate group, epinastine hydrochloride group, and azelastine hydrochloride group, but not in the olopatadine hydrochloride 0.1% ophthalmic solution group, which may potentially explain the lower discomfort felt by patients on instillation. Many other studies in humans have revealed the superiority of olopatadine 0.1% hydrochloride eye drops to several other anti-allergic eye drops. Overseas, olopatadine hydrochloride 0.2% ophthalmic solution for a once-daily regimen has been marketed under the brand name of Pataday^®. It is expected that olopatadine hydrochloride ophthalmic solutions may be used in patients with a more severe spectrum of allergic conjunctival diseases, such as vernal keratoconjunctivitis or atopic keratoconjunctivitis, in the near future.

Emedastine difumarate: a review of its potential ameliorating effect for tissue remodeling in allergic diseases

BACKGROUND

Emedastine difumarate, a selective histamine-H1 receptor antagonist and effective antiallergic agent, inhibits various clinical symptoms of allergic rhinitis, allergic conjunctivitis, urticaria, allergic dermatitis, pruritus cutaneous, and prurigo. In addition to greater efficacy than other antihistamines, emedastine difumarate produces no adverse cardiovascular effects and exhibits minimal anticholinergic activity. Moreover, a recent study revealed that the effect of emedastine difumarate on inhibition of histamine-induced collagen synthesis in vitro was greater in dermal fibroblasts than in nasal mucosa fibroblasts. This result indicates that there are tissue-specific effects of emedastine difumarate and that it may be more effective for treating fibrosis in skin than in nasal mucosa. However, the mechanism and role of tissue remodeling is less well established for allergic skin diseases and allergic conjunctivitis, in comparison to respiratory allergic diseases.

OBJECTIVE

This review outlines the involvement of histamine in the pathogenesis of tissue remodeling in a variety of organs, and presents the evidence for the effect of antihistamines on this process. Furthermore, this review also discusses antihistamines as an intervention strategy in tissue remodeling.

METHODS

The scientific literature, published abstracts, and selected textbooks were reviewed.

RESULTS/CONCLUSION

Although additional evidence is required, emerging evidence suggests that emedastine difumarate may be of value in the prevention of excess tissue remodeling in allergic skin inflammation.

The role of antihistamines in the treatment of vasomotor rhinitis

Background

The pathogenesis of vasomotor rhinitis is not understood. It is unlikely that antihistamines, based on their H1 antagonist activity alone, would be effective in this disorder.

Methods

Nonetheless, at least one double-blind, placebo-controlled multicenter trial has found that intranasal azelastine relieves symptoms of this disorder better than placebo. The mechanism responsible for its beneficial effect in nonallergic rhinitis is unclear but probably relates to "anti-inflammatory/antiallergic" activities.

Results

Such mechanisms have been demonstrated for a number of different oral antihistamines, but often the concentrations required in vitro are higher than those that are normally achieved in vivo using recommended dosing. It has been postulated that intranasal administration, which can achieve high local levels, might be a factor responsible for enhancing the "anti-inflammatory/antiallergic" properties.

Conclusions

Interpreting this information allows one to conclude that antihistamines may be potentially effective agents in vasomotor rhinitis, and are more likely to be so when administered intranasally, despite the fact that data documenting this beneficial effect are sparse.

Management of allergic conjunctivitis: an evaluation of the perceived comfort and therapeutic efficacy of olopatadine 0.2% and azelastine 0.05% from two prospective studies

PURPOSE

Results from 2 patient-reported outcome studies of allergic conjunctivitis sufferers who used olopatadine 0.2% and azelastine 0.05% are analyzed.

METHODS

The PACE (Pataday Allergic Conjunctivitis Evaluation) multi-center, prospective, open-label study examined patient perceptions of olopatadine 0.2% once daily (qd) and previous twice daily (bid) allergic conjunctivitis medications via questionnaire in allergic conjunctivitis sufferers who had previously used bid medication and then initiated olopatadine. A second conjunctival antigen challenge (CAC) study evaluated comfort of 4 allergic conjunctivitis medications.

RESULTS

Forty-nine patients from the PACE study (N = 125) with prior azelastine use were examined. Significantly more patients rated themselves "very satisfied" with current olopatadine use compared with past azelastine use on drop comfort (p < 0.0001), speed of relief (p = 0.0004), and overall satisfaction (70% vs 16%, p < 0.0001). Significantly more patients reported olopatadine "very effective" against swelling compared with azelastine (47% vs 8%, p = 0.0404). In the CAC study (N = 36), data from olopatadine (n = 8), azelastine (n = 9) and placebo (N = 36) groups were reported. Olopatadine was rated significantly more comfortable than azelastine upon instillation (p = 0.0223), at 30 seconds (p = 0.0479), and at 1 minute after instillation (p = 0.0240).

CONCLUSION

In the reported studies, olopatadine 0.2% qd was more comfortable than azelastine 0.05% and preferred by patients with allergic conjunctivitis by a ratio of 4:1.

Allergic conjunctivitis

Allergic conjunctivitis is common, especially during the allergy season. Consultation with the allergist to perform skin tests or in vitro tests may be useful and confirmatory in the diagnosis of ocular allergy. If treatment is necessary, antihistamines, mast cell stabilizers, and nonsteroidal anti-inflammatory drugs are safe and reasonably effective. Corticosteroids are an order of magnitude more potent than noncorticosteroids; however, they have attendant side effects that are best monitored by the ophthalmologist. The development of "modified" corticosteroids has been a boon to the treatment of ocular allergy because these drugs may reduce potential side effects without sacrificing potency.

Perception and quality of life associated with the use of olopatadine 0.2% (Pataday) in patients with active allergic conjunctivitis

This 28-d, open-label, multicenter, single-arm clinical study was designed to evaluate perceptions of olopatadine 0.2% in patients with active ocular allergic signs and symptoms. The study enrolled 330 patients, 5 to 94 y of age, who had previously used olopatadine 0.1% for active allergic conjunctivitis. Most patients were white (n=230; 70.1%) and female (n=239; 72.9%). Of all enrolled patients, 328 were evaluable for analysis. Throughout the study, patients instilled 1 drop of olopatadine 0.2% into each eye once daily; adverse events were documented and ocular evaluations were conducted to ensure patient safety. Direct evaluations of efficacy were not performed. On days 1 and 7, patients completed the Rhinoconjunctivitis Quality of Life Questionnaire, recorded their perceptions of olopatadine 0.1% (day 1) or 0.2% (day 7), and had their ocular allergies assessed globally. On each of the first 6 d of treatment, patients also completed a telephone-based perception questionnaire. On day 28, patients returned to the study center, reported their treatment perceptions, had their ocular allergies assessed, and exited the trial. Overall, patients had a positive perception of olopatadine 0.2%. Patients were more satisfied with olopatadine 0.2% than they remembered being with olopatadine 0.1% (289 vs 257 patients; 87.6% vs 77.8%; P<.05). The majority of the 48 patients who wore contact lenses (n=42; 88%) believed that they could wear their contacts as desired. Significant improvement was noted in all categories of the Rhinoconjunctivitis Quality of Life Questionnaire (P<.0001). No unexpected safety findings were reported. Patients perceived olopatadine 0.2% to be effective and well tolerated.

Effect of Topical Ophthalmic Epinastine and Olopatadine on Tear Volume in Mice

PURPOSE

To investigate the effects of topical epinastine and olopatadine on tear volume by using a mouse model.

METHODS

Eighty-five C57BL6 mice (170 eyes) were treated twice daily with topical ophthalmic epinastine 0.05%, olopatadine 0.1%, or atropine 1% or served as untreated controls. A thread-wetting assay was used to measure tear volume at baseline and 15, 45, 90, 120, and 240 minutes after the last instillation of the drug on days 2 and 4 of treatment.

RESULTS

After 2 days of treatment, epinastine-treated mice showed greater mean tear volumes than olopatadine-treated mice did at 15, 45, 90, and 240 minutes, with statistical significance at 15 and 45 minutes (P<0.001). Olopatadine significantly reduced tear volume versus untreated controls at 15 and 45 minutes (P<0.001). After 4 days, tear volumes with epinastine treatment exceeded those with olopatadine treatment at all time points, with statistical significance at 45 minutes (P<0.05). Atropine rendered tears undetectable at 15, 45, and 90 minutes; tear volume returned to baseline levels at 240 minutes.

CONCLUSIONS

Topical epinastine did not inhibit tear secretion, whereas olopatadine caused a significant decrease in tear volume. Because of its neutral impact on the lacrimal functional unit, epinastine may be an especially good choice for the treatment of allergic conjunctivitis in patients with dry eye disease or in those who are at risk for developing dry eye.

A review of the use of olopatadine in allergic conjunctivitis

Ocular allergies are very common and range in intensity from mild, self-resolving, acute conditions to serious, chronic disease that can severely affect vision. The vast majority of sufferers experience relatively mild symptoms, which are often seasonal in nature. Treatments should be simple, comfortable and very safe. They should be able to respond to an ongoing attack but also provide long-term relief from symptoms. Mast cell degranulation is central to all forms of ocular allergic disease and so treatment has concentrated on preventing this process or antagonizing the effects of the primary mediator, histamine. Olopatadine is a relatively new selective H1 antagonist that has mast cell stabilizing properties and has been shown to affect release of TNFalpha and various cytokines from conjunctival epithelial cells. This paper reviews the local ocular use of olopatadine and discusses the place of the drug in the treatment of allergic eye disease.

Ocular allergy treatment comparisons: azelastine and olopatadine

Azelastine hydrochloride 0.05% and olopatadine hydrochloride 0.1% are topical ocular allergy treatments that have demonstrated multiple pharmacologic actions, including antihistamine, mast cell stabilization, and inhibition of proinflammatory mediators. In this article, the mechanisms of action, efficacy, and tolerability of these two agents on ocular signs and symptoms are examined. By studying the various target sites of drug action, an enhanced clinical response algorithm of these topical ocular agents can be implemented to maximize the response for patients suffering from ocular allergy.

Clinical efficacy of olopatadine hydrochloride ophthalmic solution 0.2% compared with placebo in patients with allergic conjunctivitis or rhinoconjunctivitis: a randomized, double-masked environmental study

BACKGROUND

Previous studies have suggested that olopatadine hydrochloride ophthalmic solution 0.2% administered once daily is effective for up to 24 hours after instillation and is well tolerated in adults and children aged > or =3 years.

OBJECTIVE

The goal of this study was to evaluate the efficacy and safety profile of olopatadine 0.2% compared with placebo in patients with seasonal allergic conjunctivitis or rhinoconjunctivitis.

METHODS

This was a 10-week, randomized, placebo-controlled, double-masked environmental study conducted during the spring allergy season (April-August) of 2003. Patients assessed their ocular signs and symptoms in terms of frequency (whole-unit scale from 0 to 5) and severity (half-unit scale from 0 to 4), and grass pollen counts were obtained daily for each investigative site. Responder analyses were conducted by pollen level (frequency based) and pollen period (severity based) to evaluate the clinical significance of differences in ocular itching and redness between treatment groups.

RESULTS

Two hundred sixty patients (137 females, 123 males) were enrolled in the study, including 28 children aged between 11 and 17 years; the overall population was 74% white, 11% black, 4% Hispanic, and 11% other. The frequency-based responder analyses of ocular itching and redness showed that when grass pollen counts were high (>20 gr/m(3) air), a respective 21% and 14% of patients in the olopatadine 0.2% group assessed the frequency of ocular itching and redness as >2, compared with 47% and 31% of patients in the placebo group (P < 0.001 for ocular itching; P < 0.003 for redness). The results of the severity-based responder analyses by peak pollen period were consistent with those of the frequency-based analyses. Compared with placebo, olopatadine 0.2% was associated with significant reductions in calculated mean scores for ocular itching and redness by pollen level and by pollen period. No patient was discontinued from the study because of a treatment-related adverse event, and no patient experienced a treatment-related serious adverse event.

CONCLUSION

In the patients studied, olopatadine 0.2% appeared to be effective and well tolerated when administered once daily for the treatment of the ocular signs and symptoms of allergic conjunctivitis or rhinoconjunctivitis.

Ketotifen fumarate and olopatadine hydrochloride in the treatment of allergic conjunctivitis: a real-world comparison of efficacy and ocular comfort

This 3-week prospective, randomized, double-masked, parallel-group study compared ketotifen fumarate 0.025% ophthalmic solution and olopatadine hydrochloride 0.1% ophthalmic solution in 66 patients with seasonal allergic conjunctivitis. The drugs were instilled twice daily. Signs and symptoms were assessed on days 5 (visit 2) and 21 (visit 3). Other efficacy variables were the responder rate (patients with excellent or good global efficacy on days 5 and 21) and patient and investigator ratings of global efficacy. Comfort was evaluated immediately after instillation of the first drop and at each follow-up visit. The frequency of adverse events was the safety assessment. The responder rate was higher with ketotifen than with olopatadine on day 5 (72% vs 54% for patient assessment, 88% vs 55% for investigator assessment) and day 21 (91% vs 55%, 94% vs 42%). Global efficacy ratings were higher with ketotifen, and severity scores for hyperemia and itching were significantly lower. Both drugs elicited comparable comfort ratings. The most common adverse events were burning/stinging and headache.

Topical immunopharmacology of ocular allergies

PURPOSE OF REVIEW

To review the histamine-1 receptor antagonists, mast cell blockers and natural agents with such actions that can be used for the topical treatment of ocular allergies.

RECENT FINDINGS

Increasing evidence indicates that some histamine-1 receptor antagonists have additional actions to inhibit secretion of inflammatory mediators, especially cytokines, from ocular mast cells and other cell types. Emerging information suggests that such actions may be through regulation of intracellular calcium ion levels of NF-kappaB activation.

SUMMARY

A number of available drugs and natural non-prescription agents may have anti-histaminic and anti-inflammatory actions.

Ocular allergy guidelines: a practical treatment algorithm

The treatment of ocular allergy requires a better understanding of the spectrum of clinical disorders involving various components of the immune system, and of interactions at the conjunctival surface. The immune response focuses primarily on the different levels of activity of Th2 lymphocytes and various other immune cells associated with allergic disorders, including mast cells, eosinophils, fibroblasts, and epithelial and endothelial cells. Ocular allergic disorders include seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), giant papillary conjunctivitis (GPC) and atopic keratoconjunctivitis (AKC), which, through immunopathological and molecular immunological techniques, can all be better appreciated as being part of a larger spectrum of an atopic disease state. In SAC, pathological changes, such as increased mast-cell activation, the presence of migratory inflammatory cells, and early signs of cellular activation at the molecular level, are minimal. In PAC, these changes are more pronounced in line with the increased duration of allergenic stimulation. In more chronic forms of allergic conjunctivitis, such as VKC in children and AKC in adults, the following changes are evident: a persistent state of mast cell, eosinophil and lymphocyte activation; noted switching from connective-tissue to mucosal-type mast cells; increased involvement of corneal pathology; and follicular development and fibrosis. The treatment of acute and more chronic forms of allergic conjunctivitis has focused in the past on symptomatic relief of symptoms, but with a better understanding of the mechanisms involved we can now provide interventional therapeutic strategies and symptomatic relief. Our advances in the basic understanding of these conditions are providing the foundation for guidelines that improve the ocular health of patients with ocular allergies.

Azelastine is more potent than olopatadine n inhibiting interleukin-6 and tryptase release from human umbilical cord blood-derived cultured mast cells

BACKGROUND

Mast cells are involved in early- and late-phase reactions by releasing vasoactive molecules, proteases, and cytokines. Certain histamine-1 receptor antagonists and other antiallergic drugs seem to inhibit the release of mediators from rat and human mast cells.

OBJECTIVE

Azelastine and olopatadine are antiallergic agents present in the ophthalmic solutions azelastine hydrochloride (Optivar, Asta Medica/Muro Pharmaceuticals, Tewksbury, MA), and olopatadine hydrochloride (Patanol, Alcon Laboratories, Fort Worth, TX), respectively. We investigated the effect of these drugs on interleukin-6 (IL-6), tryptase, and histamine release from cultured human mast cells (CHMCs).

METHODS

CHMCs were grown from human umbilical cord blood-derived CD34+ cells in the presence of stem cell factor and IL-6 for 14 to 16 weeks. Sensitized CHMCs were pretreated with various concentrations of azelastine or olopatadine for 5 minutes. CHMCs were then challenged with anti-immunoglobulin E, and the released mediators were quantitated.

RESULTS

The greatest inhibition of mediator release was seen with 24 microM azelastine; this level of inhibition was matched with the use of 133 microM olopatadine. At this concentration, these drugs inhibited IL-6 release by 83% and 74%, tryptase release by 55% and 79%, and histamine release by 41% and 45%, respectively. Activated CHMCs were characterized by numerous filopodia that were inhibited by both drugs as shown by electron microscopy.

CONCLUSIONS

These results indicate that azelastine and olopatadine can inhibit CHMCs activation and release of IL-6, tryptase, and histamine. On an equimolar basis, azelastine was a more potent inhibitor than olopatadine.

Update on ocular allergy treatment

Allergy affects > 15% of the world population with a higher prevalence of 30% in westernised industrialised countries, such as the US. Allergy commonly affects various target organs including the eyes, nose, sinuses, ears, lungs and skin. However, the ocular component may be the most common and initially the most prominent disabling feature. Some patients are affected for only a few weeks to months while others have symptoms that last throughout the year. The associated healthcare costs related to allergic conjunctivitis has been commonly nestled with allergic rhinitis and has been reported to be as high as US$5.9 billion in the US, with 25% (US$1.5 billion) of it related to medication use. The expenditures related to ocular prescription medication has only recently risen in the past decade from US$6 million in early 1990s to > US$200 million in the new millennium with a projected continuous expansion of 25% per year. This appears to be due to improved prescription medications and their clear benefit over the less efficacious over-the-counter products. The actual cost of the medications and their relative price increases over the past year have ranged from 0 - 49% with an average cost of < US$ day. The newer topical medications (multiple acting agents) are focusing on multiple actions that include an antihistaminic effect to provide an immediate relief and additional delayed effects to act on the mediators of the late phase reaction without steroid side effects (glaucoma, cataracts). The paradigm for the treatment of ocular allergy ranges from primary measures (avoidance measures, cold compresses and lubrication), to secondary measures (various combination of topical agents) and tertiary measures that would include topical steroids and immunotherapy. The increased interest in advancing ocular treatment will lead to the development of additional therapies, novel pharmacokinetic delivery systems and, thus, improved healthcare outcomes for patients with allergic conjunctivitis.

Pharmacological, pharmacokinetic and clinical properties of olopatadine hydrochloride, a new antiallergic drug

Olopatadine hydrochloride (olopatadine, 11-[(Z)-3-(dimethylamino)propylidene]-6,11-dihydrodibenz[b,e]oxepin-2-acetic acid monohydrochloride) is a novel antiallergic/histamine H1-receptor antagonistic drug that was synthesized and evaluated in our laboratories. Oral administration of olopatadine at doses of 0.03 mg/kg or higher inhibited the symptoms of experimental allergic skin responses, rhinoconjunctivitis and bronchial asthma in sensitized guinea pigs and rats. Olopatadine is a selective histamine H1-receptor antagonist possessing inhibitory effects on the release of inflammatory lipid mediators such as leukotriene and thromboxane from human polymorphonuclear leukocytes and eosinophils. Olopatadine also inhibited the tachykininergic contraction in the guinea pig bronchi by prejunctional inhibition of peripheral sensory nerves. Olopatadine exerted no significant effects on action potential duration in isolated guinea pig ventricular myocytes, myocardium and human ether-a-go-go-related gene channel. Olopatadine was highly and rapidly absorbed in healthy human volunteers. The urinary excretion of olopatadine accounted for not less than 58% and the contribution of metabolism was considerably low in the clearance of olopatadine in humans. Olopatadine is one of the few renal clearance drugs in antiallergic drugs. Olopatadine was shown to be useful for the treatment of allergic rhinitis and chronic urticaria in double-blind clinical trials. Olopatadine was approved in Japan for the treatment of allergic rhinitis, chronic urticaria, eczema dermatitis, prurigo, pruritus cutaneous, psoriasis vulgaris and erythema exsudativum multiforme in December, 2000. Ophthalmic solution of olopatadine was also approved in the United States for the treatment of seasonal allergic conjunctivitis in December, 1996 (Appendix: also in the European Union, it was approved in February 2002).

Preclinical efficacy of travoprost, a potent and selective FP prostaglandin receptor agonist

Travoprost is the isopropyl ester prodrug of a high affinity, selective FP prostaglandin full receptor agonist. In contrast to travoprost acid's high affinity and efficacy at the FP receptor, there is only sub-micromolar affinity for the DP, EP1, EP3, EP4, IP, and TP receptors. Travoprost produced a lower incidence of ocular irritation than PGF20 isopropyl ester at a dose of 1 microg in the New Zealand albino (NZA) rabbit. Topical ocular application of travoprost produced a marked miotic effect in cats following doses of 0.01, 0.03 and 0.1 microg. In the ocular hypertensive monkey, b.i.d. application of 0.1 and 0.3 microg of travoprost afforded peak reduction in intraocular pressure (IOP) of 22.7% and 28.6%, respectively. Topical application of travoprost was well tolerated in rabbits, cats and monkeys, causing no ocular irritation or discomfort at doses up to 1 microg. Travoprost is a promising ocular hypotensive prostaglandin FP derivative that has the ocular hypotensive efficacy of PGF2alpha isopropyl ester but with less severe ocular side effects.

Comparison of the clinical efficacy and comfort of olopatadine hydrochloride 0.1% ophthalmic solution and nedocromil sodium 2% ophthalmic solution in the human conjunctival allergen challenge model

BACKGROUND

Mast cell stabilizers, such as the ocular antiallergic agent nedocromil sodium 2% ophthalmic solution, are not rapid acting and often require a loading period of > or =2 weeks for maximal efficacy. Olopatadine hydrochloride 0.1% ophthalmic solution is a member of a new class of topical antiallergic agents that have combined antihistaminic and mast cell-stabilizing properties.

OBJECTIVE

The purpose of this study was to compare the clinical efficacy and comfort of olopatadine with those of nedocromil in the conjunctival allergen challenge model.

METHODS

This was a single-center, 3-visit, randomized, double-masked, contralaterally controlled study. Seventy-five subjects with a history of allergic conjunctivitis were screened, and the 52 who responded to conjunctival allergen challenge at visits I and 2 were randomized by eye to receive olopatadine, nedocromil, or placebo (a "natural tears" lubricant eye drop). Because nedocromil may require a 2-week loading period for maximal efficacy, the eyes assigned to that agent received nedocromil for 14 days (between visits 2 and 3), whereas the eyes assigned to olopatadine or placebo received placebo during this period. Throughout the loading phase, subjects instilled 1 drop of the assigned masked medication in each eye twice daily. At the assessment visit (visit 3), subjects received I drop of masked olopatadine, nedocromil, or placebo in each eye and were asked to rate the comfort of each drop on a scale from 0 to 8. Fifteen minutes after instillation of medication, subjects were challenged with the allergen concentration that had elicited a positive conjunctival allergic response at the previous visits. Subjects then scored their itching on a scale from 0 to 4 at 3, 5, and 10 minutes after challenge. Mean itching scores for all eyes were compared by treatment. Paired t tests were performed on the mean itching and ocular comfort scores at each time point. At the end of the study, subjects were asked which treatment they preferred in terms of comfort and efficacy.

RESULTS

Forty-nine subjects completed the study. Forty eyes received olopatadine, 36 received nedocromil, and 22 received placebo. Olopatadine was clinically and statistically superior to nedocromil at reducing itching in the conjunctival allergen challenge model (mean unit difference: -1.60 at 3 minutes, -1.68 at 5 minutes, -1.19 at 10 minutes; P < 0.001). One drop of olopatadine was more efficacious than 29 drops of nedocromil. Olopatadine-treated eyes were rated as being significantly more comfortable than nedocromil-treated eyes (0.73 vs 1.55; P = 0.034). Of the 14 subjects treated with olopatadine and nedocromil who stated a preference, 10 (71%) were more satisfied with olopatadine than with nedocromil.

CONCLUSION

In the conjunctival allergen challenge model, olopatadine was more efficacious and comfortable than nedocromil in reducing the itching associated with allergic conjunctivitis.

Comparative evaluation of olopatadine ophthalmic solution (0.1%) versus ketorolac ophthalmic solution (0.5%) using the provocative antigen challenge model

OBJECTIVE

This study was conducted to compare the efficacy and safety of olopatadine ophthalmic solution (0.1%) with ketorolac ophthalmic solution (0.5%) in a clinical model of acute allergic conjunctivitis. Olopatadine is a dual acting H1 histamine receptor antagonist and a mast cell stabilizer, shown to be effective in treating allergic conjunctivitis. Ketorolac is a non-steroidal anti-inflammatory drug approved in the United States for the relief of ocular itching associated with seasonal allergic conjunctivitis.

METHODS

The provocative antigen challenge model was used in this randomized, double-blind, single-center, crossover study. The allergen and concentration that consistently elicited a positive allergic reaction was used for challenge. After at least 14 days, subjects were randomized to receive either olopatadine in one eye and placebo in the contralateral eye, or ketorolac in one eye and placebo in the contralateral eye. Twenty-seven minutes after drug instillation subjects were challenged with allergen. At 3, 10, and 20 minutes following allergen challenge, subjects graded ocular itching and were assessed for hyperemia in conjunctival, ciliary, and episcleral vessel beds. Approximately 14 days later, subjects received the alternate treatment in one eye and placebo in the contralateral eye. They were again challenged with allergen and their responses were rated in the same manner.

RESULTS

Olopatadine significantly (p < 0.0001) reduced both ocular itching and hyperemia in all three vessel beds compared to placebo at all time points tested following allergen challenge. Ketorolac did not significantly reduce itching and showed a trend of increased hyperemia compared to placebo. Olopatadine was significantly (p < 0.001) more effective than ketorolac in reducing hyperemia and ocular itching at all time points and was also significantly (p < 0.05) more comfortable than ketorolac as reported by subjects immediately following drug instillation.

CONCLUSION

The study demonstrated that olopatadine is effective and safe in preventing and treating ocular itching and hyperemia associated with acute allergic conjunctivitis and is more effective and more comfortable than ketorolac.

Human retina contains polyamine sensitive [3H]-ifenprodil binding sites: implications for neuroprotection?

AIMS

This study characterised the pharmacology of [3H]-ifenprodil binding to the polyamine binding sites (PBS) on the N-methyl-D-aspartate (NMDA) receptor channel complex on human retinas. These data were correlated with the known neuroprotective effects of ifenprodil and eliprodil.

METHODS

Specific binding of [3H]-ifenprodil (under sigma site blockade) was investigated using human retinal homogenates and radioligand binding techniques. Scatchard and competition analyses were utilised to define the pharmacology of the [3H]-ifenprodil binding sites.

RESULTS

Specific binding of [3H]-ifenprodil comprised 73% (SEM 3%) of total and reflected interaction with two affinity sites (Kds = 0.39 and 4.3 microM) of different densities (Bmax = 14.4 and 105 pmol/mg protein) (n = 5). The rank order of affinity of compounds competing for [3H]-ifenprodil binding to the high affinity PBS was: ifenprodil > eliprodil > arcaine > spermine > diaminodecane > spermidine > putrescine >> MK-801 (n = 3-7). However, [3H]-ifenprodil binding was minimally inhibited by glutamate, NMDA, and kainate.

CONCLUSION

These studies have shown, for the first time, the presence of specific [3H]-ifenprodil binding sites in the human retina with pharmacological characteristics of PBS associated with the NMDA receptor ionophore complex. The neuroprotective effects of eliprodil and ifenprodil may, in part, be mediated via these [3H]-ifenprodil labelled sites.

Comparative effects of topical ocular anti-allergy drugs on human conjunctival mast cells

BACKGROUND

The concept of mast cell heterogeneity is well established. Recent data indicate that human conjunctival tissue mast cells and human connective tissue mast cells respond to various secretagogues in similar fashion. It is now recognized that different mast cell populations respond differently to anti-allergic drugs.

OBJECTIVE

The purpose of the study is to compare the effects of three new ocular anti-allergic drugs (nedocromil, olopatadine, and pemirolast) on mediator release from the target human conjunctival mast cell population with those of cromolyn sodium. The affinity of the compounds for the histamine H1 receptor was also compared.

METHODS

A monodispersed suspension of partially purified human conjunctival mast cells was prepared from cadaver conjunctival tissue. Mast cells (5 x 10(3)) were challenged with anti-human IgE in the presence or absence of test drugs, and histamine content of the cell supernatants was determined using a specific radioimmunoassay. H1 receptor binding activity was assessed using a radioligand binding assay.

RESULTS

Cromolyn and pemirolast (100 nM to 1 mM) failed to significantly inhibit histamine release from human conjunctival mast cells using exposure times of 1 and 15 minutes prior to challenge. Using identical nedocromil concentrations and exposure times, statistically significant (P < .05) inhibition (28%) of histamine release was observed at only the 100 microM concentration and 1-minute exposure time. In contrast, olopatadine inhibited histamine release in a concentration-dependent fashion (r = 0.891, n = 59, IC50 = 653 microM). Only olopatadine exhibited significant H1 receptor binding activity at relevant concentrations (Ki = 36 nM, n = 13).

CONCLUSIONS

These data indicate that olopatadine possesses anti-allergic activity in the appropriate targets for topical ocular anti-allergic drug therapy, human conjunctival mast cells. Coupled with the compound's antihistaminic activity, this suggests that olopatadine will have efficacy advantages in allergic conjunctivitis patients over the other drugs tested.