Mechanisms of antihistamines and mast cell stabilizers in ocular allergic inflammation

Mast cells play a central role in allergic reactions and inflammation. Successful anti-allergic therapies have typically targeted mast cell mediators, particularly histamine. Antihistaminic compounds interact with the various histamine receptors found on many cells, whereas other compounds such as disodium cromoglycate, are referred to as mast cell stabilizers, as they inhibit degranulation. Some of the most successful compounds developed recently are dual-action, in that they have both anti-histaminic and mast cell stabilizing activities. Recent trends in pharmaceutical intervention, however, have been focused on the secondary effects of mast cell mediators on epithelial cell adhesion molecule expression and mediator release in the process of allergic inflammation. Since, the ocular mucosa is highly exposed to environmental allergens it is commonly involved in allergic reactions and, as such, has been a useful and accessible model in which to test new therapies in vivo. These ocular allergen provocation studies permit analysis of ocular surface cells and evaluation of tear film mediators. Furthermore, techniques to purify conjunctival mast cells have facilitated the study of the effects of mast cell stabilizing compounds on other mast cell mediators, such as cytokines, and the direct effects of mast cell mediators on epithelial cells in vitro. This review will discuss current understanding of how anti-histamines and mast cell stabilizers work, particularly in the context of molecular mechanisms of ocular allergic inflammation.     

Preliminary observations on the use of propionyl-L-carnitine in combination with sildenafil in patients with erectile dysfunction and diabetes

ABSTRACT

Background: Histamine receptor activation and degranulation of mast cells are the mechanisms by which the ocular itching, hyperemia, chemosis, eyelid swelling, and tearing of seasonal allergic conjunctivitis are induced. Some of the topical solutions available as anti-allergy therapies are intended to interfere with these mechanisms, and the body of research regarding the capabilities of these therapeutic molecules continues to expand.

Objective: To review the currently available literature regarding one topical ophthalmic anti-allergy agent, olopatadine (Patanol), and its anti-histaminic and mast cell stabilizing actions, both in pre-clinical and clinical settings.

Design and methods: Relevant research of laboratory, animal model, and clinical trial studies performed using olopatadine was reviewed. MEDLINE literature searches were conducted and supplemented by additional reports which furthered relevant discussion or were necessary to verify the information resulting from original searches.

Results: Olopatadine demonstrates unique properties both pre-clinically and clinically which differentiate it from other therapeutic molecules in its class of dual action mast cell stabilizer/anti-histamine. Its non-perturbation of cell membranes, human conjunctival mast cell stabilization in vivo and in vitro, and superior efficacy as compared to other topical anti-allergic medications including mast cell stabilizers, anti-histamines, and dual action agents, all contribute to olopatadine's profile.

Conclusions: Peer-reviewed literature suggests that olopatadine is clinically superior to the other anti-allergic molecules because of its strong anti-histaminic qualities and its unique ocular mast cell stabilizing properties.     

Evaluation of the effects of olopatadine ophthalmic solution, 0.2% on the ocular surface of patients with allergic conjunctivitis and dry eye*

ABSTRACT

Purpose: Olopatadine hydrochloride 0.2% (Pataday^?, Alcon, Fort Worth, USA) is a topical ocular anti-allergic agent that has shown high rates of efficacy in treating ocular itching, the primary symptom of allergic conjunctivitis, and allows for once-daily dosing. Since some patients suffer from signs or symptoms of dry eye in addition to ocular allergy, this study was designed to evaluate the safety of olopatadine 0.2% in a population of patients with both allergic conjunctivitis and dry eye.

Methods: This was a single-center, 3-visit, double-masked, randomized study. Fifty-two patients diagnosed with ocular allergy and mild-to-moderate dry eye were evaluated. After a run-in period, patients were randomized to receive either olopatadine hydrochloride 0.2% or a tear saline, and self-dosed once-daily for 1 week. Outcome measures included tear film break-up time, corneal and conjunctival staining, tear volume and flow as measured by fluorophotometry, Schirmer's test, injection, and symptom evaluations.

Results: No significant differences between the treatment groups were observed (?p > 0.05). No serious adverse events occurred during the trial. Variability in the presentation of dry eye can hinder the observation of treatment effects. Although the study design facilitated the comparison of olopatadine 0.2% against an agent that was certain to not exacerbate dry eye, future comparison of olopatadine 0.2% against other agents in its drug class would provide useful information about relative drug tolerabilities.

Conclusion: As there were no significant changes in the signs and symptoms of dry eye, olopatadine hydrochloride 0.2% is safe to use in ocular allergy patients with mild-to-moderate dry eye.     

Efficacy and comfort of olopatadine 0.2% versus epinastine 0.05% ophthalmic solution for treating itching and redness induced by conjunctival allergen challenge

ABSTRACT

Background: Olopatadine 0.2% (Pataday, Alcon Laboratories Inc., Fort Worth, Texas, USA) and epinastine 0.05% (Elestat, Inspire Pharmaceuticals, Inc., Durham, NC, USA) are topical ocular anti-allergic agents. Both are H₁ antihistamine/mast cell stabilizers indicated for the treatment of ocular itching associated with allergic conjunctivitis.

Objective: To compare the efficacy and comfort of olopatadine 0.2% with epinastine 0.05%, in the prevention of ocular itching associated with allergic conjunctivitis following conjunctival allergen challenge (CAC).

Research design and methods: This was a 7 week, four visit, double-masked, randomized, placebo-controlled CAC study. Visit 1 screened subjects for positive ocular allergic responses and Visit 2 confirmed those responses. At Visit 3, 92 subjects were randomized into one of four treatment groups to receive one drop of study medication in each eye: (1) olopatadine 0.2%/placebo, (2) epinastine 0.05%/placebo, (3) olopatadine 0.2%/epinastine 0.05%, (4) placebo/placebo. Subjects were challenged 12?h after drop instillation to evaluate duration of action. At Visit 4, subjects were challenged 5?min after drop instillation to evaluate onset of action. Drop comfort was assessed at Visit 4.

Main outcome measures; results: This article focuses on the results of the onset-of-action challenge (Visit 4). At Visit 4, ocular itching was assessed at 3, 5, and 7?min and redness was assessed at 7, 15, and 20?min post-challenge. Drop comfort was assessed upon instillation, at 30?s, and at 1, 2, and 5?min post-instillation. Olopatadine 0.2%-treated eyes exhibited significantly lower mean ocular itching scores versus epinastine 0.05%-treated eyes at 5 (?p = 0.024) and 7?min (?p = 0.003) post-challenge. Olopatadine 0.2%-treated eyes exhibited significantly lower mean redness scores versus epinastine 0.05%-treated eyes at all time points post-challenge (ciliary: p ≤ 0.013, conjunctival: p ≤ 0.015, episcleral: p ≤ 0.006). Olopatadine 0.2% was rated as significantly more comfortable than epinastine 0.05% at 1?min post-drop instillation (?p = 0.003). All adverse events were non-serious and unrelated to study medication. Although the CAC model reproduces allergic responses that are not environmentally-induced, patients experience varying severities of responses as are seen in real-world situations.

Conclusion: Olopatadine 0.2% was superior to epinastine 0.05% in preventing ocular itching and redness at onset when induced by the CAC model.     

A review of olopatadine for the treatment of ocular allergy

Ocular allergy affects > 20% of the general population and many therapeutic preparations are available to individuals experiencing the most common forms – seasonal and perennial allergic conjunctivitis. 0.1% Olopatadine topical ophthalmic solution is currently approved for the treatment of allergic signs and symptoms in patients ≥ 3 years of age. Olopatadine is available in Europe as Opatanol^® and in > 30 other countries as Patanol^®. It inhibits mast cell degranulation and antagonises histamine receptors to manage the itching, redness, chemosis, tearing and lid swelling of the ocular allergic reaction, and its mast cell stabilising ability has been demonstrated both in vitro (using human conjunctival mast cells) and in vivo (human clinical experience). This article reviews both the laboratory and clinical information available on olopatadine, prefaced by a discussion of the current understanding of the ocular allergic reaction and followed by the future implications for this compound. Both laboratory and clinical studies have established the efficacy, safety and comfort of olopatadine in several study design models and comparisons to other antiallergy medications. The application of olopatadine, specifically in the management of lid swelling, an allergic sign recalcitrant to therapy and nasal allergic symptoms has also been established. In the future, a new formulation containing 0.2% olopatadine exhibits a duration of action up to 24 h, supporting once-daily dosing.     

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.     

Comparative efficacy of olopatadine 0.1% ophthalmic solution versus levocabastine 0.05% ophthalmic suspension using the conjunctival allergen challenge model

SUMMARY

Objective: To compare the efficacy of olopatadine and levocabastine in reducing ocular allergic itching and vascular hyperemia (redness) induced by conjunctival allergen challenge.

Research design and methods: The study was a randomized, double-masked, contralateral study using the conjunctival allergen challenge (CAC) model. At Visit 1, subjects with a positive allergen skin test and a history of allergic conjunctivitis were administered increasing concentrations of allergen until at least a moderate grade 2 ocular itching and conjunctival redness response was obtained in both eyes. Allergic signs were graded on standardized 0–4 scales. Subjects who reacted positively were re-challenged at Visit 2 with the pre-determined concentration of allergen. Subjects who again responded with at least a grade 2 bilateral ocular itching and conjunctival redness score at Visit 2 were eligible for drug evaluation. At Visit 3, subjects received olopatadine in one eye and levocabastine in the contralateral eye according to a computer-generated randomization scheme generated prior to commencement of the study. Ocular discomfort was then graded in both eyes. Subjects were bilaterally challenged with the predetermined concentration of allergen 27?min after topical drug administration, such that the first post-challenge assessment was made 30?min post-drug instillation. Allergic signs and symptoms were evaluated at 3?min, 10?min, and 20?min post-challenge and safety and efficacy analyses were performed.

Results: Sixty-eight subjects received study drug and were included in the safety and efficacy analyses. Ocular itching scores for olopatadine were significantly lower than levocabastine at 3?min and 10?min post-challenge (?p < 0.001). Ocular redness scores for olopatadine were significantly lower than levocabastine at all time points post-challenge (?p < 0.0001). Of all subjects, 4.41% reported ocular discomfort in the olopatadine eye and 26.5% in the levocabastine treated eye.

Conclusion: Olopatadine treated eyes had significantly less itching and redness than levocabastine treated eyes after conjunctival allergen challenge. Olopatadine was also associated with less discomfort upon instillation than levocabastine.     

A review of olopatadine for the treatment of ocular allergy

Ocular allergy affects > 20% of the general population and many therapeutic preparations are available to individuals experiencing the most common forms--seasonal and perennial allergic conjunctivitis. 0.1% Olopatadine topical ophthalmic solution is currently approved for the treatment of allergic signs and symptoms in patients > or = 3 years of age. Olopatadine is available in Europe as Opatanol) and in > 30 other countries as Patanol. It inhibits mast cell degranulation and antagonises histamine receptors to manage the itching, redness, chemosis, tearing and lid swelling of the ocular allergic reaction, and its mast cell stabilising ability has been demonstrated both in vitro (using human conjunctival mast cells) and in vivo (human clinical experience). This article reviews both the laboratory and clinical information available on olopatadine, prefaced by a discussion of the current understanding of the ocular allergic reaction and followed by the future implications for this compound. Both laboratory and clinical studies have established the efficacy, safety and comfort of olopatadine in several study design models and comparisons to other antiallergy medications. The application of olopatadine, specifically in the management of lid swelling, an allergic sign recalcitrant to therapy and nasal allergic symptoms has also been established. In the future, a new formulation containing 0.2% olopatadine exhibits a duration of action up to 24 h, supporting once-daily dosing.     

Mast cell stabilization and anti-histamine effects of olopatadine ophthalmic solution: a review of pre-clinical and clinical research

BACKGROUND: Histamine receptor activation and degranulation of mast cells are the mechanisms by which the ocular itching, hyperemia, chemosis, eyelid swelling, and tearing of seasonal allergic conjunctivitis are induced. Some of the topical solutions available as anti-allergy therapies are intended to interfere with these mechanisms, and the body of research regarding the capabilities of these therapeutic molecules continues to expand. OBJECTIVE: To review the currently available literature regarding one topical ophthalmic anti-allergy agent, olopatadine (Patanol), and its anti-histaminic and mast cell stabilizing actions, both in pre-clinical and clinical settings. DESIGN AND METHODS: Relevant research of laboratory, animal model, and clinical trial studies performed using olopatadine was reviewed. MEDLINE literature searches were conducted and supplemented by additional reports which furthered relevant discussion or were necessary to verify the information resulting from original searches. RESULTS: Olopatadine demonstrates unique properties both pre-clinically and clinically which differentiate it from other therapeutic molecules in its class of dual action mast cell stabilizer/anti-histamine. Its non-perturbation of cell membranes, human conjunctival mast cell stabilization in vivo and in vitro, and superior efficacy as compared to other topical anti-allergic medications including mast cell stabilizers, anti-histamines, and dual action agents, all contribute to olopatadine's profile. CONCLUSIONS: Peer-reviewed literature suggests that olopatadine is clinically superior to the other anti-allergic molecules because of its strong anti-histaminic qualities and its unique ocular mast cell stabilizing properties.     

The role of inflammation and allergy in acute coronary syndromes

It is well known that inflammatory mechanisms play a crucial role in the pathogenesis of atherosclerosis and coronary artery disease. In recent years, allergic episodes have been shown to be associated with acute coronary syndromes. Mast cells release certain inflammatory mediators including histamine and neutral proteases during an allergic episode and these inflammatory mediators are implied to induce coronary artery spasm and/or atheromatous plaque erosion or rupture. As the inflammatory component of acute coronary syndromes is a potential therapeutic target, drugs that stabilize mast cell membrane and monoclonal antibodies that protect mast cell surface may be effective in preventing allergy associated acute coronary syndromes. In this review, we will mention the role of inflammation and allergy and anti-inflammatory therapeutic modalities in acute coronary syndromes.     

Targeting CD44 in mast cell regulation

Importance of the field: Accumulating evidence suggests that mast cells are involved in a wide variety of immune responses including chronic inflammation, immune tolerance and tumor immunity. Mast cells originate from hematopoietic stem cells and undergo terminal differentiation in the tissues, in which they are ultimately resident. Heterogeneity of tissue mast cells is, therefore, one of the key concepts for a better understanding of various immune responses.

Areas covered in this review: This review describes the candidate genes involved in regulation of cutaneous mast cell differentiation, with a particular attention to CD44, which is the primary receptor for hyaluronan.

What the reader will gain: CD44 is involved in various aspects of cutaneous inflammation. Regarding mast cells, CD44 is upregulated upon differentiation and maturation of mast cells, and plays a critical role in regulation of cutaneous mast cell number. Since both degradation and decrease of hyaluronan are often observed upon chronic inflammation, CD44 might be involved in modulation of local immune responses through regulation of cutaneous mast cell functions.

Take home message: Understanding of cutaneous immune responses should require clarification of local mast cell functions, a part of which is regulated by extracellular matrix components and their membrane receptors.     

In vitro anti-allergic activity of the fungal metabolite pyridovericin

Mast cells play a critical role during the development of an allergic response. Upon activation by an antigen and IgE, via FcεRI receptors, mast cells release histamine and other mediators that initiate and propagate immediate hypersensitivity reactions. Mast cells also secrete cytokines that regulate the immune responses. In this way, inhibitors of mast cell activity could work as promising therapeutics for allergic disorders. In the present work, we investigated the capacity of pyridovericin, a natural product isolated from the entomopathogenic fungus Beauveria bassiana, to inhibit mast cell degranulation and cytokine secretion. It was found that pyridovericin strongly decreased the release of β-hexosaminidase, a marker for mast cell degranulation, when mast cells were stimulated by both FcεRI-dependent and independent pathways. In addition, pyridovericin strongly abrogated secretion of interleukin-4. Pyridovericin-mediated suppression of stimulated increase in intracellular Ca^2 + levels, a crucial signal for mounting of both degranulation and cytokine production responses, was ascribed as one of the inhibition targets of pyridovericin. Those initial studies identify pyridovericin as a potential new candidate for the development of new anti-allergic drugs.     

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

SUMMARY

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.

* Patanol is a registered tradename of Alcon Laboratories Inc, Forth Worth, TX, USA     

Ocular allergic disease

Ocular allergy is a common condition that usually affects the conjunctiva of the eye and is therefore often referred to as allergic conjunctivitis. The severity of the disease can range from mild itching and redness, as seen in seasonal allergic conjunctivitis, to the more serious vision threatening forms of ocular allergy which affect the cornea, such as atopic keratoconjunctivitis. The pathogenesis of allergic conjunctivitis involves a complex mechanism which centers around IgE-mediated mast cell degranulation and release of multiple preformed and newly formed inflammatory mediators. The diagnosis of allergic conjunctivitis is usually a clinical one which can be made based on a thorough history and careful examination. Treatment of ocular allergy should begin with conservative measures including allergen avoidance, environmental control, ocular irrigation and cold compresses. Pharmacotherapy of allergic conjunctivitis consists of several classes of drugs. Antihistamines are widely used to treat mild conditions such as seasonal and perennial conjunctivitis and potent new agents such as levocabastine and emedastine are now available. Mast cell stabilizers such as sodium cromoglycate are both safe and effective and are commonly used in ocular allergy. More effective mast cell stabilizers such as nedocromil, lodoxamide and olopatadine are now being used. Nonsteroidal antiinflammatory drugs have demonstrated only limited efficacy and, as such, are not widely used. Topical steroids are very effective in treating signs and symptoms but are reserved for only refractory cases due to their serious side effects. Loteprednol and rimexelone are newer corticosteroids which reportedly have less of an effect on intraocular pressure. Cyclosporine has recently been shown to be highly effective in cases of vernal keratoconjunctivitis and atopic keratoconjunctivitis while producing no adverse effects.     

牛樟芝水提取物抗过敏作用及其机制研究

目的 研究牛樟芝水提物的抗过敏作用并初步探讨其作用机制。方法 采用大鼠被动皮肤过敏模型、小鼠迟发型超敏模型、小鼠全身皮肤瘙痒模型、小鼠腹腔毛细血管通透性模型,观察牛樟芝水提物在体抗过敏作用。采用体外培养的RBL-2H3肥大细胞,观察牛樟芝水提物对细胞增殖及凋亡的影响,初步探讨其抗过敏反应的作用机制。结果 体内试验中,牛樟芝水提物显著降低大鼠被动皮肤过敏反应,明显降低小鼠耳肿胀度、胸腺指数及脾指数,提高右旋糖酐所致皮肤瘙痒阈值,减少小鼠瘙痒次数,抑制组胺所致血管通透性上升;体外试验中,其剂量相关性的抑制RBL-2H3细胞增殖,促进细胞凋亡。结论 牛樟芝水提取物有一定的抗过敏作用,其机制与促进RBL-2H3细胞凋亡有关。     

Targeting mast cells

Mast cells play a key role in the induction of allergic disorders, such as asthma and rhinitis, through the release of mediators including histamine, arachidonate products, proteases and several cytokines, which are found in relatively high quantities in these cells. A significant number of therapeutic approaches for allergies have been designed based on antagonising specific mediators released from mast cells and on selectively inhibiting the activation of these cells. Classical mast cell stabilisers, such as sodium cromoglycate, continue to attract new developments based on improved formulation and delivery systems, while efforts to identify new pathway (e.g., tyrosine kinase Syk) inhibitors or mediator (e.g., prostaglandin D₂, β-tryptase) antagonists may bring new successes to this field.     

Anti-allergic effects of Teucrium japonicum on mast cell-mediated allergy model

The mast cell-mediated immediate-type allergic reaction is involved in many allergic diseases such as asthma, allergic rhinitis, and sinusitis. Stimulation of mast cells starts the process of degranulation resulting in release of mediators such as histamine and an array of inflammatory cytokines. In this report, we investigated the effect of aqueous extract of Teucrium japonicum Houttuyn (Labiatae) (AXTJ) on the mast cell-mediated allergy model and studied its possible mechanisms of action. AXTJ inhibited compound 48/80-induced systemic reactions and serum histamine release in mice. AXTJ decreased immunoglobulin E-mediated passive cutaneous anaphylaxis reaction. AXTJ reduced histamine release and intracellular calcium from rat peritoneal mast cells activated by compound 48/80. In addition, AXTJ attenuated activation of nuclear factor (NF)-κB, and downstream tumor necrosis factor (TNF)-α expression in phorbol 12-myristate 13-acetate and calcium ionophore A23187-stimulated human mast cells. Our findings provide evidence that AXTJ inhibits mast cell-derived allergic reactions and involvement of intracellular calcium, TNF-α, and NF-κB in these effects.     

Olopatadine nasal spray for the treatment of seasonal allergic rhinitis in patients aged 6 years and older

Importance of the field: Allergic rhinitis is an IgE-mediated condition that produces inflammation of the mucosa of the nose, paranasal sinuses and, frequently, of the ocular conjunctiva. Allergic rhinitis causes a significant disease burden in terms of quality of life, lost productivity and medical treatment costs. One of the newest treatments approved by the FDA is Patanase^® (olopatadine hydrochloride) Nasal Spray, 665 μg/spray (OLO). Olopatadine is an antihistamine with selective H₁-receptor antagonist activity.

Areas covered in this review: This review details the basic and clinical research on the olopatadine molecule and OLO nasal spray from 1996 to the present day.

What the reader will gain: The reader will gain a better understanding of the pharmacology of OLO nasal spray, the clinical trial data that have established the efficacy of OLO nasal spray and the overall role of OLO nasal spray in the management of allergic rhinitis.

Take home message: Olopatadine nasal spray is one of the newest treatments approved by the FDA for the management of allergic rhinitis. OLO has a rapid onset of action, efficacy comparable to intranasal steroid sprays and is approved for seasonal allergic rhinitis in patients aged ≥ 6 years.     

Olopatadine hydrochloride ophthalmic solution for the treatment of allergic conjunctivitis

Introduction: Olopatadine hydrochloride is an antihistamine and mast cell stabilizer available as oral, intranasal and ocular preparations. Most of the practical applications of olopatadine therapy focus on the treatment of allergic rhinoconjunctivitis via intranasal and ocular routes.

Areas covered: This article was created from a comprehensive literature search with information taken from meta-analyses, systematic reviews, and clinical trials of children and adults. The articles that have been selected, evaluate the use of intranasal and ocular antihistamines and their role in allergic rhinoconjunctivitis.

Expert opinion: Olopatadine is significantly more effective than placebos in relieving the symptoms of allergic rhinoconjunctivitis. It can function both as a viable alternative or addition to first line therapies such as intranasal steroids and oral antihistamines.     

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.