H2-receptors in the human ocular surface

Brimonidine tartrate ophthalmic solution 0.025% for redness relief: an overview of safety and efficacy

INTRODUCTION

Ocular redness, or conjunctival hyperemia, is a common ophthalmic sign associated with reduced quality of life. For redness without apparent underlying pathology, topical ophthalmic decongestants have been widely used.

AREAS COVERED

Brimonidine tartrate was approved in 2017 as a topical vasoconstrictor at a 0.025% concentration for relief of ocular redness. Since then, investigators have reported on efficacy and safety findings from studies evaluating low-dose brimonidine for reducing ocular redness.

EXPERT OPINION

Brimonidine is highly selective for α₂-adrenergic receptors. Clinical trials have so far shown that the drug in low doses significantly reduces ocular redness in comparison to vehicle for up to 8 hours. Brimonidine-treated eyes did not present side effects of other vasoconstrictors, such as hypotension, cardiac arrhythmia or drowsiness. Ocular adverse events such as allergic reactions and redness rebound were also minimal. In this review, we examine in detail published literature on the mechanism of brimonidine tartrate and its efficacy and safety in relieving conjunctival hyperemia.

Ocular redness - I: Etiology, pathogenesis, and assessment of conjunctival hyperemia

The translucent appearance of the conjunctiva allows for immediate visualization of changes in the circulation of the conjunctival microvasculature consisting of extensive branching of superficial and deep arterial systems and corresponding drainage pathways, and the translucent appearance of the conjunctiva allows for immediate visualization of changes in the circulation. Conjunctival hyperemia is caused by a pathological vasodilatory response of the microvasculature in response to inflammation due to a myriad of infectious and non-infectious etiologies. It is one of the most common contributors of ocular complaints that prompts visits to medical centers. Our understanding of these neurogenic and immune-mediated pathways has progressed over time and has played a critical role in developing targeted novel therapies. Due to a multitude of underlying etiologies, patients must be accurately diagnosed for efficacious management of conjunctival hyperemia. The diagnostic techniques used for the grading of conjunctival hyperemia have also evolved from descriptive and subjective grading scales to more reliable computer-based objective grading scales.

Levocabastine Eye Drops: A New Approach for the Treatment of Acute Allergic Conjunctivitis

Acute allergic conjunctivitis (AAC) is a common ocular allergic disorder and incident rates as high as 20% have been reported. Although a wide range of therapeutic agents are available for the treatment of AAC, the ideal treatment seems to have remained elusive. Levocabastine, a highly potent specific H1-receptor, appears to offer a promising alternative as a topical single-agent therapy. Levocabastine eye drops have been found to be well tolerated with an adverse-effect profile comparable to placebo and sodium cromoglycate. In addition, ocular levocabastine has been shown to have a rapid onset and long duration of action. The efficacy of levocabastine has been extensively investigated in conjunctival provocation tests and environmental studies. The available data suggest that ocular levocabastine is an effective therapeutic agent. Statistically significant differences in favour of levocabastine have been observed in comparisons with sodium cromoglycate, antazoline/naphazoline and oral terfenadine.

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.

Advances in pharmacotherapy for allergic conjunctivitis

INTRODUCTION

Allergy is the fifth leading group of chronic diseases, affecting as much as 40% of the first-world population. Its pathophysiology has a genetic component, and is driven by the immune system's sensitized response to antigens and environmental factors. As research continues to uncover the mediators responsible for ocular allergy, the development of novel drugs should progress.

AREAS COVERED

A literature review of allergic conjunctivitis, ocular allergy and their treatment was performed using PubMed and Medline. Additional information is also included from clinicaltrials.gov and associated web sites for drugs currently in clinical trials.

EXPERT OPINION

The initial step of therapy remains identification and avoidance of allergic triggers. The mainstay of treatment is the new generation of dual-acting antihistamines. Drugs that improve the magnitude and duration of relief, with greater subject responder rates, are gradually making their way into the clinic. Allergic conjunctivitis is a relatively easy disease to study because of the availability of models such as the conjunctival allergen challenge. New classes of drugs that target inflammatory pathways or mediators involved in the early and late-phase allergic response are being screened in these models and we are making progress in identifying the next generation of anti-allergic therapy.

Effect of alcaftadine 0.25% on ocular itch associated with seasonal or perennial allergic conjunctivitis: a pooled analysis of two multicenter randomized clinical trials

PURPOSE

Seasonal and perennial allergic conjunctivitis represent the majority of cases of ocular allergy. This analysis was designed to evaluate the efficacy and safety of once-daily alcaftadine 0.25% in preventing ocular itching associated with seasonal or perennial allergic conjunctivitis.

SUBJECTS AND METHODS

Pooled data from two double-masked, multicenter, placebo-controlled studies using the conjunctival allergen challenge (CAC) model of allergic conjunctivitis were analyzed. Subjects randomized to receive treatment with alcaftadine 0.25% or placebo were challenged with seasonal (grass, ragweed, trees) or perennial (cat dander, cat hair, dog dander, dust mites, cockroach) allergens, 16 hours after treatment instillation. The primary efficacy measure was subject-evaluated mean ocular itching at 3 minutes post-CAC. Secondary measures included ocular itching at 5 and 7 minutes post-CAC. The proportion of subjects with minimal itch (itch score <1) and zero itch (itch score =0), and safety were also assessed.

RESULTS

A total of 189 subjects enrolled in the two studies were treated with alcaftadine or placebo. Overall, 129 subjects were challenged with seasonal allergens and 60 subjects were challenged with perennial allergens. Alcaftadine 0.25% achieved a statistically significant reduction in mean itch score at 3, 5, and 7 minutes post-CAC compared with placebo in subjects challenged with seasonal allergens (P<0.0001 at all time points) and those challenged with perennial allergens (P<0.0001 at all time points). A higher percentage of subjects treated with alcaftadine compared with placebo achieved minimal itch (P≤0.001 versus placebo at all time points) and zero itch (P<0.05 at all time points except 7 minutes for perennial) when challenged with either seasonal or perennial allergens. No treatment-related or serious adverse events were reported.

CONCLUSION

Once-daily alcaftadine 0.25% ophthalmic solution was well tolerated and demonstrated effective relief of ocular itching in subjects challenged with allergens classic for triggering either seasonal or perennial allergic conjunctivitis.

Ocular itch relief with alcaftadine 0.25% versus olopatadine 0.2% in allergic conjunctivitis: pooled analysis of two multicenter randomized clinical trials

Introduction

The efficacy and safety of the once-daily topical ophthalmic solutions, alcaftadine 0.25% and olopatadine 0.2%, in preventing ocular itching associated with allergic conjunctivitis were evaluated.

Methods

Pooled analysis was conducted of two double-masked, multicenter, active- and placebo-controlled studies using the conjunctival allergen challenge (CAC) model of allergic conjunctivitis. Subjects were randomized 1:1:1 to receive alcaftadine 0.25%, olopatadine 0.2%, or placebo. The primary efficacy measure was subject-evaluated mean ocular itching at 3 min post-CAC and 16 h after treatment instillation. Secondary measures included ocular itching at 5 and 7 min post-CAC. Ocular itch was determined over all time points measured (3, 5, and 7 min) post-CAC and the proportion of subjects with minimal itch (itch score <1) and zero itch (itch score = 0) was also assessed.

Results

A total of 284 subjects were enrolled in the two studies. At 3 min post-CAC and 16 h after treatment instillation, alcaftadine 0.25% achieved a significantly lower mean itch score compared with olopatadine 0.2% (0.50 vs. 0.87, respectively; P = 0.0006). Alcaftadine demonstrated a significantly lower mean itch score over all time points compared with olopatadine (0.68 vs. 0.92, respectively; P = 0.0390); both alcaftadine- and olopatadine-treated subjects achieved significantly lower overall mean ocular itching scores compared with placebo (2.10; P < 0.0001 for both actives). Minimal itch over all time points was reported by 76.1% of alcaftadine-treated subjects compared with 58.1% of olopatadine-treated subjects (P = 0.0121). Treatment with alcaftadine 0.25% and olopatadine 0.2% was safe and well tolerated; no serious adverse events were reported.

Conclusion

Once-daily alcaftadine 0.25% ophthalmic solution demonstrated greater efficacy in prevention of ocular itching compared with olopatadine 0.2% at 3 min post-CAC (primary endpoint), and over all time points, 16 h post-treatment instillation. Alcaftadine and olopatadine both provided effective relief compared with placebo and were generally well tolerated.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-014-0155-3) contains supplementary material, which is available to authorized users.

Treatment of allergic conjunctivitis with bepotastine besilate ophthalmic solution 1.5%

PURPOSE

To examine the pooled per-protocol ocular end points from two conjunctival allergen challenge (CAC) clinical trials of the dual-action antihistamine bepotastine besilate ophthalmic solution (BBOS) 1.5%.

METHODS

Two Phase III, placebo-controlled, double-masked, randomized clinical trials were conducted at a total of six separate centers using the CAC model of allergic conjunctivitis. The same study design was employed for both clinical trials, with subjects randomly assigned to either BBOS 1.5% (n=78) or placebo (n=79) treatment. Each subject received one eye drop of the test agent bilaterally at different study visits 15 minutes, 8 hours, or 16 hours prior to a CAC. Primary ocular end points included changes in ocular itching reported at 3, 5, and 7 minutes and conjunctival hyperemia assessed at 7, 15, and 20 minutes following each CAC. Secondary ocular end points included chemosis as well as episcleral and ciliary hyperemia judged by investigators, and tearing (scored as either absent or present) and eyelid swelling judged by subjects.

RESULTS

A statistically significant reduction in ocular itching was observed for BBOS 1.5% treatment compared to placebo at all time points (P<0.0001), while measures for onset and 8-hour persistence of action also reached clinical significance (ie, ≥1.0 unit difference) at a majority of time points. In addition, a significant reduction in conjunctival hyperemia was achieved at a majority of time points during the onset of action CAC test. Secondary end points were also significantly improved compared to placebo, most prominently for reduced tearing at all study visits and reduced eyelid swelling at the onset of action and 8-hour study visits. Adverse events were generally mild and transient.

CONCLUSION

BBOS 1.5% rapidly reduced CAC-induced ocular itching with duration of effectiveness of at least 8 hours after dosing. Certain secondary signs of inflammation were also significantly reduced.

Histamine H4 receptors in normal conjunctiva and in vernal keratoconjunctivitis

BACKGROUND

While it is known that histamine is the primary mediator of ocular allergy, the presence and distribution of histamine receptors are not well documented in the human eye. Our aim was to evaluate histamine receptor expression in normal and vernal keratoconjunctivitis conjunctiva.

METHODS

Mucosal biopsies were obtained from conjunctiva of healthy donors and from tarsal conjunctiva of vernal patients. Immunostaining and semi-quantitative reverse-transcriptase polymerase chain reaction for H(1), H(2), H(3), and H(4) receptors were performed. Histamine receptor expression was also evaluated in conjunctival cell cultures exposed to histamine, interleukin-4, interleukin-5, interferon-γ and tumor necrosis factor-α.

RESULTS

Immunostaining for H(1) and H(2) receptors was slightly positive in normal and over-expressed in vernal tissues. H(3) receptors were rarely present in normal and inflamed conjunctiva. In striking contrast to control tissues, H(4) receptors were highly expressed in all inflamed tissues, particularly by stromal inflammatory cells. Semi-quantitative reverse-transcriptase polymerase chain reaction demonstrated an over-expression of H(1), H(2), and H(4) receptors in vernal vs control tissues. Notably, H(4) receptors were five times more expressed in vernal vs control tissues. In cell cultures, H(2) receptor expression was stimulated eight times the normal levels by interleukin-4 and three times by histamine, but the H(4) receptor was only slightly affected by stimulation with these mediators.

CONCLUSIONS

Increased expression of H1, and particularly of H(2) and H(4) receptors in vernal keratoconjunctival tissues indicate their important role in the pathogenesis of this disease. H(4) receptors may be a target in the treatment of allergic inflammation.

The safety and efficacy of alcaftadine 0.25% ophthalmic solution for the prevention of itching associated with allergic conjunctivitis

OBJECTIVE

The purpose of this study was to evaluate the safety and clinical efficacy of alcaftadine 0.25% ophthalmic solution, a new topical anti-allergic agent for the prevention of the signs and symptoms of allergic conjunctivitis induced by conjunctival allergen challenge (CAC).

STUDY DESIGN AND METHODS

This two-arm, double-masked, multi-center, placebo-controlled Phase III study (NCT00889330) enrolled healthy volunteers (N = 58) with a history of allergic conjunctivitis. Subjects ≥10 years of age with a reproducible, positive reaction to a CAC were randomized to receive either one drop of alcaftadine 0.25% ophthalmic solution bilaterally or vehicle bilaterally. After 16 hours (Visit 3) and 15 minutes (Visit 4), a CAC was performed and ocular and nasal symptoms of allergy were graded over a 20-minute period. Clinical and statistical significance were evaluated.

MAIN OUTCOME MEASURES

The primary endpoints were ocular itching and conjunctival redness. The secondary endpoints were all other signs and symptoms of allergic conjunctivitis. Visual acuity, slit lamp biomicroscopy and adverse event reporting were the predetermined safety measures.

RESULTS

Alcaftadine was effective in the prevention of ocular itching based on both clinically relevant and statistically significant differences compared with vehicle (placebo). Alcaftadine significantly reduced conjunctival redness, and almost all other allergic signs and symptoms at both 15 minutes and 16 hours after drug administration. No significant safety issues were reported. Between-group differences in ocular itching were higher 16 hours after drug administration than at 15 minutes after drug administration.

CONCLUSIONS

With an onset of action within 3 minutes and a duration of action of at least 16 hours, the statistically and clinically significant effect of alcaftadine 0.25% on itching make it an important addition to therapy for ocular allergy. Additional studies are warranted to better understand the mechanisms affording a fast onset and prolonged duration of action.

Evaluation of alcaftadine 0.25% ophthalmic solution in acute allergic conjunctivitis at 15 minutes and 16 hours after instillation versus placebo and olopatadine 0.1%

PURPOSE

To evaluate the effectiveness of alcaftadine 0.05%, 0.1%, and 0.25% ophthalmic solutions in treating the signs and symptoms of allergic conjunctivitis when compared with olopatadine hydrochloride 0.1% and placebo using the conjunctival allergen challenge (CAC) model.

METHODS

One hundred and seventy subjects were randomized and 164 subjects completed all visits. CAC was performed to determine and confirm subjects' eligibility at visits 1 and 2, respectively. The CAC was repeated at visit 3 (day 0 ± 3), 16 hours after study medication instillation, and at visit 4 (day 14 ± 3), 15 minutes after instillation. Ocular itching and conjunctival redness were evaluated after an allergen challenge, along with several secondary endpoints.

RESULTS

Alcaftadine 0.25% and olopatadine 0.1% treatments exhibited significantly lower mean scores compared with placebo for ocular itching and conjunctival redness at visits 3 and 4. Most adverse events were self-limiting and mild in severity. No serious treatment-related adverse events occurred.

CONCLUSION

Treatment with alcaftadine 0.25% ophthalmic solution resulted in mean differences of >1 unit (ocular itching) and approximately >1 unit (conjunctival redness), which was significant (P < 0.001) compared with placebo treatment. All doses of alcaftadine were safe and well tolerated in the population studied.

Allergic diseases of the eye

The prevalence of ocular allergy is clearly underappreciated; it has been an underdiagnosed and undertreated area in primary care medicine. The ocular symptoms associated with the most common ocular allergy conditions,such as seasonal and perennial AC, are twice as likely to affect the allergy sufferer as nasal symptoms alone. The emergence of new medications for the specific treatment of ocular symptoms over the course of the past 15 years offers a new field for improved patient care by the primary and sub-specialty health care providers.

Histamine receptors and the conjunctiva

PURPOSE OF REVIEW

The purpose of this review is to evaluate the effect of histamine on various receptors in the conjunctiva. A Medline search from 1980 was performed on the histamine receptor subtypes H1, H2 and H3 in the human conjunctiva.

RECENT FINDINGS

In the conjunctiva, histamine has been shown to induce various physiological and immunological changes through both H1 and H2 receptor stimulation. Histamine binding to conjunctival H1 receptors through the phospholipase C-dependent inositol phosphate pathway leads to the symptom of pruritus while histamine stimulation of the conjunctival H2 receptors has been indirectly shown to cause vasodilation.

SUMMARY

The effect of histamine on conjunctival H1 receptors appears to be the primary target for ocular allergy treatment as it is primarily involved in ocular pruritus. The exact interaction of the conjunctival H2 receptors appears to work in a complementary fashion to the H1 receptor in controlling other features of ocular allergy such as vasodilation and injection. Thus, oral and topical antihistamines with multiple histamine receptor binding activities may provide an improved treatment paradigm for the various signs and symptoms of ocular allergy. The histamine H1, H2 and H3 receptor affinities of ketotifen, pyrilamine, and epinastine appear to have the strongest H1 and H2 affinities.

Methodologies for the Study of Ocular Surface Disease

The ability to obtain reliable results from clinical trials of therapies for ocular allergic disease and dry eye disease is often limited because of inadequate control of variables, such as environment, patient life style, compliance, and individual fluctuations that occur from one assessment visit to another. The controlled allergen challenge (CAC) model of allergic conjunctivitis allows signs and symptoms of the disease to be elicited in a physiologically accurate and reproducible manner. The rigid criteria for subject selection, the controlled allergic reaction, and the standardized and quantified grading systems allow for a reproducible baseline from which statistically and clinically significant differences between formulations can be assessed. Similarly, the controlled adverse environment (CAE) model for dry eye mimics the environmental stimuli that lead to ocular surface drying. Preselected subjects have a reproducible, homogeneous baseline reaction from which the effects of various treatments can be significantly evaluated and compared. CAC and CAE provide accurate means to study highly variable and individual ocular surface disease.

Efficacy and tolerability of newer antihistamines in the treatment of allergic conjunctivitis

Treatment for allergic conjunctivitis has markedly expanded in recent years, providing opportunities for more focused therapy, but often leaving both physicians and patients confused over the variety of options. As monotherapy, oral antihistamines are an excellent choice when attempting to control multiple early-phase, and some late-phase, allergic symptoms in the eyes, nose and pharynx. Unfortunately, despite their efficacy in relief of allergic symptoms, systemic antihistamines may result in unwanted adverse effects, such as drowsiness and dry mouth. Newer second-generation antihistamines (cetirizine, fexofenadine, loratadine and desloratadine) are preferred over older first-generation antihistamines in order to avoid the sedative and anticholinergic effects that are associated with first-generation agents. When the allergic symptom or complaint, such as ocular pruritus, is isolated, focused therapy with topical (ophthalmic) antihistamines is often efficacious and clearly superior to systemic antihistamines, either as monotherapy or in conjunction with an oral or intranasal agent. Topical antihistaminic agents not only provide faster and superior relief than systemic antihistamines, but they may also possess a longer duration of action than other classes including vasoconstrictors, pure mast cell stabilisers, NSAIDs and corticosteroids. Many antihistamines have anti-inflammatory properties as well. Some of this anti-inflammatory effect seen with 'pure' antihistamines (levocabastine and emedastine) may be directly attributed to the blocking of the histamine receptor that has been shown to downregulate intercellular adhesion molecule-1 expression and, in turn, limit chemotaxis of inflammatory cells. Some topical multiple-action histamine H(1)-receptor antagonists (olopatadine, ketotifen, azelastine and epinastine) have been shown to prevent activation of neutrophils, eosinophils and macrophages, or inhibit release of leukotrienes, platelet-activating factors and other inflammatory mediators. Topical vasoconstrictor agents provide rapid relief, especially for redness; however, the relief is often short-lived, and overuse of vasoconstrictors may lead to rebound hyperaemia and irritation. Another class of topical agents, mast cell stabilisers (sodium cromoglicate [cromolyn sodium], nedocromil and lodoxamide), may be considered; however, they generally have a much slower onset of action. The efficacy of mast cell stabilisers may be attributed to anti-inflammatory properties in addition to mast cell stabilisation. In the class of topical NSAIDs, ketorolac has been promoted for ocular itching but has been found to be inferior for relief of allergic conjunctivitis when compared with olopatadine and emedastine. Lastly, topical corticosteroids may be considered for severe seasonal ocular allergy symptoms, although long-term use should be avoided because of risks of ocular adverse effects, including glaucoma and cataract formation.

Drug therapy for ocular allergy

The spectrum of ocular allergy ranges from mild, non-sight threatening disease, such as hay fever, to disorders such as atopic keratoconjunctivitis (AKC) which cause permanent ocular surface changes and reduced vision. The ideal treatment is with topical preparations. Launched topical preparations include anti-histamines and mast cell (MC) stabilisers, which are safe, but only moderately potent, steroids, which are very potent, but carry very serious side-effects, and cyclosporin A, which is not widely available and difficult to tolerate. There are a number of anti-histamines, MC stabilisers (and combinations thereof) and steroids in development which are of potential interest. Other possibilities for therapeutic intervention include inhibition of tryptase, cyclooxygenase (COX), leukotrienes (LTs), bradykinins (BKs), platelet activating factor (PAF) and immunoglobulin E (IgE). Therapies based on cytokine antagonism and agonism, T-cell inhibition and adhesion molecule antagonism might be expected to provide safe, but potent new modes of treatment. The increasing interest in research into the pathogenesis of ocular allergic inflammation may lead to more relevant approaches, such as eosinophil inhibition. Success will be highly dependent on the ability to produce suitable topical ophthalmic preparations.

Clinical efficacy of olopatadine vs epinastine ophthalmic solution in the conjunctival allergen challenge model

BACKGROUND

Olopatadine hydrochloride 0.1% ophthalmic solution (Patanol) and epinastine hydrochloride 0.05% ophthalmic solution (Elestat) are two topical antiallergic agents. Olopatadine is indicated for the treatment of the signs and symptoms of allergic conjunctivitis that include itching, redness, tearing, lid swelling, and chemosis. Epinastine is indicated for the prevention of itching associated with allergic conjunctivitis.

OBJECTIVE

This study compared the clinical efficacy of olopatadine and epinastine in the prevention of itching and conjunctival redness in the conjunctival allergen challenge (CAC) model.

RESEARCH DESIGN AND METHODS

This was a prospective, randomized, double-masked, contralaterally-controlled, single center allergen challenge study. Ninety-six subjects with a history of allergic conjunctivitis were screened, and the 66 who responded to conjunctival allergen challenge at visits 1 and 2 were randomized into 1 of 3 treatment groups at visit 3 to receive one drop of study medication in each eye: (1) olopatadine in one eye and epinastine in the fellow eye, (2) olopatadine in one eye and placebo in the fellow eye, and (3) epinastine in one eye and placebo in the fellow eye. Five minutes after study drop instillation, subjects were bilaterally challenged with the allergen concentration that had elicited a positive conjunctival allergic response at Visits 1 and 2. Subjective itching assessments were given at 3 min, 5 min, and 7 min post challenge. Objective redness and chemosis assessments were made at 10 min, 15 min, and 20 min post challenge. Paired sample two-tailed t-tests were performed on the mean scores at each time point to assess statistical significance in the differences between treatments. MAIN OUTCOME MEASURES;

RESULTS

Fifty-three subjects were randomized into the olopatadine/epinastine treatment group, the primary analysis group. Olopatadine treated eyes exhibited significantly lower mean itching and conjunctival redness scores than the contralateral epinastine treated eyes, -0.19 (p = 0.003) and -0.52 (p < 0.001), respectively. Olopatadine treated eyes also exhibited significantly less chemosis -0.24 (p < 0.001), ciliary redness -0.55 (p < 0.001), and episcleral redness -0.58 (p < 0.001) than epinastine treated eyes.

CONCLUSION

Olopatadine is significantly more effective than epinastine in controlling itching, redness and chemosis associated with allergic conjunctivitis in the CAC model.

Long-term Safety of Loteprednol Etabonate 0.2% in the Treatment of Seasonal and Perennial Allergic Conjunctivitis

PURPOSE

To determine the long-term safety of the topical steroid, loteprednol etabonate 0.2%, in the treatment of seasonal and perennial allergic conjunctivitis.

METHODS

A retrospective review of 397 patients from three private ophthalmologic practices treating seasonal and perennial allergic conjunctivitis with long-term loteprednol etabonate 0.2% was performed. Chart review of slitlamp findings and intraocular pressure measurements during follow-up visits was performed to determine the incidence of adverse effects, such as steroid-induced intraocular pressure increase, cataract formation, and any other possible topical steroid-induced adverse event. One hundred fifty-nine of the 397 patients had been continuously using loteprednol for more than 12 months.

RESULTS

There were no reported adverse effects of long-term loteprednol etabonate 0.2% use in any of the 159 patients, whose continuous use ranged from a cumulative total of 120 drops per eye to 3,741 drops per eye.

CONCLUSIONS

Loteprednol etabonate 0.2% is a safe topical steroid when used on a long-term basis for the treatment of seasonal and perennial allergic conjunctivitis.

One-visit, randomized, placebo-controlled, conjunctival allergen challenge study of scanning and imaging technology for objective quantification of eyelid swelling in the allergic reaction with contralateral use of olopatadine and artificial tears

BACKGROUND

The eyelids are more susceptible than other tissues to swelling, acute inflammation, and resultant long-term damage. However, no precise, objective means of measuring eyelid swelling in the clinical setting has been developed.

OBJECTIVES

The aims of this study were to assess the novel use of scanning and imaging technology for quantifying eyelid swelling and to use positive and negative controls to assess this new method for potential use in future clinical studies of eyelid swelling and pharmaceutical agents' effects on it.

METHODS

This was a 1-visit, single-center, prospective, randomized, double-masked, placebo-controlled study using the conjunctival allergen challenge (CAC). After baseline examinations and eyelid scanning, medication was instilled as follows: olopatadine hydrochloride 0.1% ophthalmic solution in 1 eye and placebo in the other. An allergen solution to which patients had a history of reaction was instilled in each eye 15 minutes after instillation of medication. Evaluations were performed for itching (3, 5, and 7 minutes after CAC), redness and chemosis (10, 15, 20, and 30 minutes), subjective eyelid evaluation (15 and 30 minutes), and 3-dimensional (3D) objective eyelid scan (15 and 30 minutes).

RESULTS

One hundred seven patients were randomized. Fifty-six patients (35 women, 21 men; mean age, 44.7 years) were evaluable for efficacy. Results of the objective and subjective evaluations of eyelid swelling were consistent, indicating significantly less eyelid swelling in olopatadine-treated eyes than in those that received placebo (objective evaluation, P < 0.001 at 15 minutes, P < 0.017 at 30 minutes; subjective evaluation, P < 0.001 at 15 and 30 minutes). Patients rated eyelid swelling in the placebo eye as 2.31 times and 2.40 times greater than that in the olopatadine-treated eye at 15 and 30 minutes, respectively. However, the digitally scanned eyelid swelling was calculated to be 5.65 times and 1.76 times greater in the placebo eye at the same respective time points. Reduction of ocular chemosis was observed in olopatadine-treated eyes at all time points (P < 0.001).

CONCLUSIONS

In this study, eyelid swelling was quantifiably measured with 3D imaging technology. In this model, the standard antiallergy medication olopatadine, used as a positive control, significantly modulated eyelid swelling when used prophylactically. A negative control, artificial tears, did not significantly affect the allergic eyelid-swelling reaction. These results concurred with subjective grading but offered a more precise assessment of eyelid swelling.

Ocular Allergic Disease: Mechanisms, Disease Sub-types, Treatment

Ocular allergy refers to a variety of hypersensitivity disorders that affect the lid, conjunctiva, and/or cornea. Its incidence is estimated at over 20% of the general population in the United States. This review will discuss the various forms of ocular allergy, their pathophysiology, clinical presentation, and treatment. New frontiers in mechanisms, therapy, and management in the office are emphasized throughout.

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.

Advances in ocular allergy: basic mechanisms, clinical patterns and new therapies

Ocular allergy presents unsolved mysteries in molecular and cellular mechanisms, and at the same time continues to challenge ophthalmologists daily in a wide array of disease forms. The recent understanding of the key role of the T helper type 2 cytokines, adhesion molecules and chemokines may provide future avenues for pharmacological targeting of releasable inflammatory mediators. More potent topical mast cell stabilizers and H1 receptor antagonists have become commercially available for the management of the prevalent and benign forms of allergic conjunctivitis. Immunostimulatory DNA sequences present an innovative and promising route for the treatment of ocular allergy, but clinical studies are needed to demonstrate their efficacy in humans. Surgical methods are suggested to reconstruct the ocular surface in the sight-threatening diseases vernal keratoconjunctivitis and atopic keratoconjunctivitis. This review presents an update of the major advances in both the basic mechanisms and clinical and therapeutic aspects of ocular allergic diseases that were reported during the past year.

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.

Allergic and immunologic disorders of the eye. Part II: ocular allergy

Allergy affects more than 15% of the world population, and some studies have shown that up 30% of the US population has some form of allergy. Most of these patients have various target organs for their allergies, and most have ocular involvement. The ocular component may be the most prominent and sometimes disabling feature of their allergy. Some are affected for only a few weeks to months, whereas others have symptoms that last throughout the year. The seasonal forms may present to clinical allergists, whereas the more chronic forms may present to ophthalmologists. Thus, in the second of this 2-part review series (Part I: Ocular Immunology appeared in the November issue of the Journal), an overview is provided of the spectrum of ocular allergy that ranges from acute seasonal allergic conjunctivitis to chronic variants of atopic keratoconjunctivitis. With a better understanding of the immunologic mechanisms, we now can develop better treatment approaches and design further research in intervention of allergic eye diseases.

Histamine effects on conjunctival fibroblasts from patients with vernal conjunctivitis

Histamine, an important mast cell mediator in allergic disorders, may affect extracellular matrix production and cell growth in vernal keratoconjunctivitis (VKC). In the present study, the histamine reactivity of conjunctival fibroblasts derived from VKC patients was investigated in vitro. Conjunctival fibroblast cultures were derived from biopses of 8 tarsal VKC patients and 5 normal subjects. These cells were maintained in vitro and stimulated with different concentrations of histamine with and without H1 (clorpheniramine) and H2 (cimetidine) receptor antagonists. Comparisons were made to fibroblasts grown in the same media without histamine and to fibroblasts stimulated with just antihistamine. The effects of histamine were evaluated by: (1) the MTT test to assess cell proliferation; (2) an in vitro wound model for cell migration and (3) the measurement of procollagen I (PIP) and procollagen III (PIIIP) in supernatants for collagen production. Results showed: (1) While VKC-derived fibroblasts proliferated at a faster rate than normal cells in unstimulated media, after histamine stimulation, VKC and normal cells grew at a similar rate. Both H1 and H2 antagonists significantly inhibited (P<0.05) histamine-induced cell proliferation. (2) Histamine enhanced cell migration after wounding; this effect was inhibited only by H2 antagonism. (3) When stimulated with histamine, VKC fibroblasts produced significantly more PIP than those in control media. Furthermore, VKC-derived fibroblasts were more sensitive to histamine challenge, producing significantly more PIP than normal fibroblasts. H1 and H2 antagonists did not modify histamine-stimulated PIP production. The enhanced proliferative and productive capacity of VKC fibroblasts may be the result of a selective overgrowth of one or more fibroblast subpopulations in a chronically inflamed tissue. Histamine increased proliferation, migration and collagen production in both normal and VKC fibroblasts. Since H2 antagonism modulated both cell growth and migration, but not histamine-induced collagen production, the latter may be mediated by a different receptor. These results showed that histamine is at least partially responsible for fibroblast stimulation.

Evaluation of olopatadine, a new ophthalmic antiallergic agent with dual activity, using the conjunctival allergen challenge model

BACKGROUND

An ophthalmic antiallergic agent with selective H1 antihistaminic and mast cell stabilizing properties has been developed.

OBJECTIVES

To evaluate efficacy and safety, determine optimal concentration, and demonstrate onset and duration of action of this new drug, olopatadine.

METHODS

This was a placebo-controlled, randomized, double-masked, parallel-group, single-center study with five outpatient visits at least 7 days apart. Ninety-eight healthy, allergy-positive, subjects with a recent history of active allergic conjunctivitis not receiving current treatment participated. Conjunctival allergen challenge (CAC) tests were performed on visits 1 and 2 to identify an allergen and concentration that consistently elicited signs and symptoms of allergic conjunctivitis. On visits 3, 4, and 5, CAC was performed 27 minutes, 8 hours, and 6 hours, respectively, after instillation of one drop of olopatadine (0.01%, 0.05%, 0.1%, or 0.15%) in one eye and placebo in the other. Both eyes were scored for the intensity of itching and redness at 3, 10, and 20 minutes after the CAC.

RESULTS

All four concentrations of olopatadine were clinically and statistically superior to placebo in preventing ocular itching at all evaluations and preventing redness at most evaluations from immediately and 8 hours after drug administration. No drug-related adverse events were reported. The 0.1% concentration was found to be most effective.

CONCLUSIONS

The results indicate that olopatadine ophthalmic solution is safe and effective in the treatment of allergic conjunctivitis, with the 0.1% concentration of olopatadine being optimal. The rapid onset and at least 8 hour duration of action of olopatadine indicates that the drug can be used twice daily.

Combined analysis of two studies using the conjunctival allergen challenge model to evaluate olopatadine hydrochloride, a new ophthalmic antiallergic agent with dual activity

PURPOSE

To evaluate the effectiveness and safety of olopatadine hydrochloride and to determine its optimal concentration and the onset and duration of action for treating allergic conjunctivitis. Olopatadine is a new topical ophthalmic antiallergic agent that demonstrates activity as both an antihistamine and a mast cell stabilizer. Two double-masked, randomized, placebo-controlled, contralateral eye comparison studies were conducted using the conjunctival allergen challenge model.

METHODS

A total of 169 subjects received 0.05% or 0.1% olopatadine. Study subjects were healthy adult men and women with a history of active allergic conjunctivitis within the previous two seasons but not receiving current treatment. With an allergen dose that produced signs and symptoms of allergic conjunctivitis at visits 1 and 2, the conjunctival allergen challenge was performed 27 minutes after study drug administration at the third visit (onset-of-action challenge) and at 8 hours after study drug administration at the fourth visit (duration-of-action challenge). Olopatadine was administered in one eye and placebo in the opposite eye. Itching and redness were scored for both eyes at 3, 10, and 20 minutes after the conjunctival allergen challenge.

RESULTS

Both 0.05% and 0.1% concentrations of olopatadine were significantly (P < .05) more effective than placebo in inhibiting itching and redness at all evaluations when administered 27 minutes or 8 hours before the conjunctival allergen challenge. There were no serious or drug-related ocular or nonocular adverse events in either study.

CONCLUSION

These findings demonstrate the rapid and prolonged (at least 8 hours) ocular antiallergic action of olopatadine.

Evaluation of 0.05% levocabastine versus 4% sodium cromolyn in the allergen challenge model

PURPOSE

This study was conducted to evaluate the efficacy of 0.05% levocabastine compared with 4% cromolyn for treating allergic conjunctivitis induced by ocular allergen challenge.

METHODS

Subjects who met all entry criteria and reacted positively to ocular allergen challenge at two previous visits (n = 50) received placebo in one eye and cromolyn in the fellow eye, four times daily for 2 weeks. On day 18, subjects received the final dose of cromolyn in the pretreated eye and one drop of levocabastine in the fellow eye. Subjects were challenged and evaluated after 3, 5, and 10 minutes. Four hours after drug administration, subjects were rechallenged and evaluated after 3, 5, and 10 minutes.

RESULTS

Levocabastine was significantly more effective than cromolyn in inhibiting itching, hyperemia, eyelid swelling, chemosis, and tearing after the initial challenge and 4-hour rechallenge (P < 0.05).

CONCLUSION

These results suggest that levocabastine is superior to cromolyn for treating allergen-induced conjunctivitis and has a duration of action of at least 4 hours.

Evaluation of the new ophthalmic antihistamine, 0.05% levocabastine, in the clinical allergen challenge model of allergic conjunctivitis

The objective of this study was to evaluate the efficacy of 0.05% levocabastine, a new antihistamine formulated for ophthalmic use, compared with the placebo vehicle for the treatment of allergic conjunctivitis induced by ocular allergen challenge. Subjects who reacted. positively in both eyes on two separate occasions to ocular allergen challenge with grass, ragweed, or cat dander (N = 47) received one dose of 1 to 2 drops of 0.05% levocabastine in one eye and its vehicle in the other eye. After 10 minutes, the predetermined dose of allergen was instilled in both eyes. Signs and symptoms of allergic conjunctivitis were evaluated with biomicroscopy and subjective evaluation of itching after 3, 5, and 10 minutes. Four hours after drug administration, subjects were rechallenged and reevaluated to determine levocabastine's duration of action. Results showed that levocabastine was significantly more effective than placebo in inhibiting itching, hyperemia, eyelid swelling, chemosis, and tearing after the initial challenge and in inhibiting all parameters except eyelid swelling after the rechallenge 4 hours later (p < 0.05). These results demonstrate that levocabastine, currently the only ophthalmic antihistamine available that is not combined with a vasoconstrictor, is efficacious in the inhibition of itching, as well as all of the allergic signs of a vascular origin, with a duration of action of at least 4 hours. Because of its strong effects on itching and hyperemia, chemosis, lid swelling, and tearing, levocabastine would be a valuable therapeutic agent to add to the heterogeneous family of antiallergic compounds presently available for the treatment of seasonal allergic conjunctivitis.

Levocabastine eye drops in the treatment of vernal conjunctivitis

The efficacy and tolerability of levocabastine eye drops in vernal conjunctivitis (VC) were evaluated in a double-blind, placebo-controlled trial involving 46 patients over a period of 4 weeks. After 1 week of treatment, therapeutic efficacy was considered to be excellent or good for 70% of the levocabastine-treated patients compared with only 33% of patients in the placebo group (p < 0.009). Levocabastine patients experienced significantly greater relief of their individually severest symptom than placebo-treated patients both after 1 week and at the end of the trial (p < 0.04). The reduction in symptom severity was significantly greater in the levocabastine group than in the control group for photophobia (p < 0.003) after 1 week, and for photophobia (p < 0.008), irritation (p = 0.05) and itchy eyes (p = 0.05) at the end of the trial. The percentage of days on which patients were completely symptom-free was significantly higher in the levocabastine group than in the placebo group (28% versus 4%; p < 0.02). Eight placebo-treated patients withdrew from the trial due to treatment inefficacy compared with only four levocabastine-treated patients (p = 0.013). Two of the three levocabastine, and all five placebo patients who elected to continue on open-label levocabastine had an excellent or good overall response after 1 to 3 weeks of treatment. All reported adverse reactions were mild and their incidence was equal in the two treatment groups. Levocabastine eye drops are effective and well tolerated in the treatment of VC.

Conjunctivitis of allergic origin: immunologic mechanisms and current approaches to therapy

The pathogenesis of ocular allergy involves multiple mechanisms, which lead to mast cell degranulation and the release of chemical mediators. Mast cell mediators that have been implicated in allergic ocular disease include histamine, eosinophil chemotactic factors, eosinophil granule major basic protein, platelet-activating factor, prostaglandin D2, and several other less well-defined preformed or newly synthesized mediators. The release of these chemical mediators ultimately results in conjunctival vasodilation, increased vascular permeability, leukocyte chemotaxis, and, rarely, ocular surface destruction. Current therapy of ocular allergy involves elimination of the offending allergen, modulation of the immune system, and pharmacologic inhibition of the chemical mediators. The purpose of this article is to provide a better understanding of the pathogenesis and current therapy of ocular allergic disorders and to review the central role of the mast cell and chemical mediators involved in ocular allergy.

Efficacy of levocabastine in conjunctival provocation studies

Levocabastine is a new topical histamine H1 antagonist. The antihistaminic and antiallergic effects of levocabastine eye drops have been evaluated in eight conjuctival provocation studies (n = 238). Two studies used a histamine challenge; five studies used allergen challenge; one study used both and in one study allergic provocation was with compound 48/80. In all but one study, only one single dose of levocabastine (one or two drops) was given. Six studies were against placebo only; one was against cromoglycate and one study used both placebo and cromoglycate as reference drugs. Single instillation of levocabastine eye drops protected against histamine and allergen-induced ocular symptoms within a period of 10 minutes. Levocabastine eye drops significantly alleviated conjunctival itching, redness, chemosis, eyelid swelling and tearing induced by histamine or allergen challenge (p < or = 0.05). Four hours after administration levocabastine was still active. With levocabastine, but not with cromoglycate, a significant increase was observed in the allergen threshold. Even when compared to cromoglycate given as a pre-treatment four times daily for two weeks before the allergen challenge, a single dose of levocabastine was significantly more effective in inhibiting hyperaemia, eyelid swelling, chemosis and tearing (all p < 0.05). In conclusion, conjunctival provocation studies have established that levocabastine has a rapid and long-lasting effect in protecting against histamine or allergen-induced conjunctival symptoms.

New trends in the treatment of allergic conjunctivitis

Histamine is the key mediator producing itching, redness and chemosis in allergic conjunctivitis. Histamine levels in tears are increased ten-fold in patients with this allergic condition. Levocabastine is a newly synthesized histamine H1 antagonist which has been formulated as both eye drops and nasal spray. In well established assays of antihistamine activity, levocabastine was found to be the most potent antihistamine compound available, being 15,000 times more potent than chlorpheniramine. Ocular provocation studies in man have shown that levocabastine protects against the symptoms of allergen-induced conjunctivitis. Ophthalmological examinations, including slit lamp and ophthalmoscopy showed no adverse effects. Data from therapeutic studies are available for more than 1700 patients with allergic conjunctivitis treated for 2-16 weeks. One drop of levocabastine (0.5 mg/ml) per eye given two to four times daily provided significantly better symptom control than placebo, with good to excellent results in 71% of patients on levocabastine compared to 55% on placebo (p < 0.001). Levocabastine has a fast onset of action. In one study 94% of patients experienced symptom relief within 15 minutes after the first instillation. The effects observed with levocabastine were at least as good as those with ocular cromoglycate or oral terfenadine. The incidence of adverse experiences was not different from placebo. Levocabastine promises to be a valuable treatment for patients with allergic conjunctivitis.

Twice daily 4% Sodium Cromoglycate vs. 2% Sodium Cromoglycate used four times daily in seasonal (grass pollen) allergic conjunctivitis

It is well established that 2% Sodium Cromoglycate is an effective treatment for a number of allergic eye diseases. It has been shown to be non-toxic. It can be used longterm and in serious allergic problems it is a useful adjunctive therapy to steroids. The main problem with Sodium Cromoglycate is that the recommended dosage is a four times daily application and patient non-compliance is common. One of the main objectives of any therapy is to reduce the frequency of dosage and the current study has been designed to investigate the efficacy of a 4% solution of Sodium Cromoglycate, used twice daily, versus a 2% solution used four times daily in seasonal allergic conjunctivitis. A multicentre study, therefore, was carried out to assess the efficacy of both drugs and to assess any possibility of side effects. In addition, a unit dose was used, thus eliminating preservatives and it was used specifically in seasonal allergic conjunctivitis in the pollen season. This study showed that 4% Sodium Cromoglycate used twice daily was at least as affective as 2% Sodium Cromoglycate used four times daily.

Double-blind comparison of levocabastine eye drops with sodium cromoglycate and placebo in the treatment of seasonal allergic conjunctivitis

The efficacy and tolerance of topical administration (one drop in each eye q.i.d.) of levocabastine (0.5 mg/ml) was compared with that of sodium cromoglycate (20 mg/ml) and placebo in a 4-week double-blind trial in patients with seasonal allergic conjunctivitis. The investigator rated the treatment as globally good or excellent in significantly more patients treated with levocabastine (89%) than with cromoglycate (67%, P = 0.03) or placebo (48%, P = 0.007). The patients felt that the treatment was more efficacious in 95% (levocabastine), 35% (cromoglycate) and 36% (placebo) of the cases in which they had taken previous antiallergic medication. Total symptom severity according to the patients' diary data was consistently lower with levocabastine than with cromoglycate or placebo for all ocular symptoms. The difference was mainly apparent at the beginning of treatment. The percentage of symptom-free days was higher in the levocabastine group (53%) than in the cromoglycate (31%, P = 0.02) and the placebo group (34%, P = 0.08). Particularly at high-pollen days, levocabastine was superior to cromoglycate in eliminating moderate or severe symptoms. Adverse effects did not occur more frequently with levocabastine or cromoglycate than with placebo. It is concluded that levocabastine is an efficacious, fast-acting and well-tolerated drug in the management of seasonal allergic conjunctivitis.

Allergic conjunctivitis: a survey of new antihistamines

The objective of this study was to determine the therapeutic value of a wide variety of H1 antihistamines for potential ophthalmic use by performing ocular toxicity and efficacy tests in rabbits and humans. Fourteen antihistamines were formulated into ophthalmic preparations and were screened in the rabbit model; of these, thirteen were preliminary evaluated for toxicity and efficacy in humans. Based on comfort and efficacy, four (pheniramine, chlorpheniramine, dexbrompheniramine and pyrilamine) were selected for more extensive dose response and efficacy testing. 0.3% chlorpheniramine, dexbrompheniramine, pyrilamine and pheniramine significantly reduced histamine-induced itching (p less than or equal to 0.01 for each drug) and conjunctival injection (p less than or equal to 0.02 for each drug), when compared to contralateral eyes receiving PBS. When compared to 0.3% pheniramine in the fellow eye (mean difference score = 0.79 +/- 0.21), 0.3% chlorpheniramine (1.5 +/- 0.22; p = 0.04) and 0.3% dexbrompheniramine (1.71 +/- 0.18; p = 0.01) were superior in decreasing histamine-induced itching. Dose-response curves demonstrated that 0.4% and 0.5% pheniramine were statistically superior to 0.3% in relieving itching and redness. Compared to 0.3% pheniramine, 0.1% and 0.2% chlorpheniramine and 0.2% pyrilamine were statistically superior in inhibiting redness and itching. The results of this study suggest that 0.1%, 0.2% and 0.3% chlorpheniramine, 0.3% dexbrompheniramine, 0.2% pyrilamine, and 0.4% and 0.5% pheniramine were effective in relieving the itching and conjunctival injection associated with topically applied histamine. These seven formulations should be considered as possible new preparations for use as ophthalmic antihistamines and may warrant further evaluation.