H1 antagonists, also called H1 blockers, are a class of medications that block the action of histamine at the H1 receptor, helping to relieve allergic reactions. Agents where the main therapeutic effect is mediated by negative modulation of histamine receptors are termed antihistamines; other agents may have antihistaminergic action but are not true antihistamines.
Phenylephrine is a medication used as a decongestant for uncomplicated nasal congestion, used to dilate the pupil, used to increase blood pressure, and used to relieve hemorrhoids. It can be taken by mouth, as a nasal spray, given by injection into a vein or muscle, or applied to the skin.
Cromoglicic acid (INN)—also referred to as cromolyn (USAN), cromoglycate, or cromoglicate—is traditionally described as a mast cell stabilizer, and is commonly marketed as the sodium salt sodium cromoglicate or cromolyn sodium. This drug prevents the release of inflammatory chemicals such as histamine from mast cells.
Allergic conjunctivitis (AC) is inflammation of the conjunctiva due to allergy. Although allergens differ among patients, the most common cause is hay fever. Symptoms consist of redness, edema (swelling) of the conjunctiva, itching, and increased lacrimation. If this is combined with rhinitis, the condition is termed allergic rhinoconjunctivitis (ARC).
Eye drops or eyedrops are liquid drops applied directly to the surface of the eye usually in small amounts such as a single drop or a few drops. Eye drops usually contain saline to match the salinity of the eye. Drops containing only saline and sometimes a lubricant are often used as artificial tears to treat dry eyes or simple eye irritation such as itching or redness. Eye drops may also contain one or more medications to treat a wide variety of eye diseases. Depending on the condition being treated, they may contain steroids, antihistamines, sympathomimetics, beta receptor blockers, parasympathomimetics, parasympatholytics, prostaglandins, nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics, antifungals, or topical anesthetics.
Olopatadine, sold under the brand name Patanol among others, is an antihistamine medication used to decrease the symptoms of allergic conjunctivitis and allergic rhinitis. It is used as eye drops or as a nasal spray. The eye drops generally result in an improvement within half an hour.
Ketotifen is an antihistamine medication and a mast cell stabilizer used to treat allergic conditions such as conjunctivitis, asthma, and urticaria (hives). Ketotifen is available in ophthalmic and oral forms: the ophthalmic form relieves eye itchiness and irritation associated with seasonal allergies, while the oral form helps prevent systemic conditions such as asthma attacks and allergic reactions. In addition to treating allergies, ketotifen has shown efficacy in managing systemic mast cell diseases such as mastocytosis and mast cell activation syndrome (MCAS), which involve abnormal accumulation or activation of mast cells throughout the body. Ketotifen is also used for other allergic-type conditions like atopic dermatitis (eczema) and food allergies.
Emedastine (trade name Emadine) is a second generation antihistamine used in eye drops to alleviate the symptoms of allergic conjunctivitis. It acts as a H1 receptor antagonist. It works by blocking the action of histamine that causes allergic symptoms. It is used in form of the difumarate. The emedastine difumarate is a white, crystalline, water-soluble fine powder. Emedastine eye drops is usually applied twice a day to the affected eye. When the patients with allergic conjunctivitis were treated with 0.05% emedastine difumarate ophthalmic solution for six weeks, the signs and symptoms such as redness, itching and swelling of the eyes were relieved. Emedastine appears to be devoid of effects on adrenergic, dopaminergic and serotonin receptors. This drug was developed by Alcon, which is global medical company specializing in eye care products.
Azelastine, sold under the brand name Astelin among others, is a H1 receptor-blocking medication primarily used as a nasal spray to treat allergic rhinitis (hay fever) and as eye drops for allergic conjunctivitis. Other uses may include asthma and skin rashes for which it is taken by mouth. Onset of effects is within minutes when used in the eyes and within an hour when used in the nose. Effects last for up to 12 hours.
Bimatoprost, sold under the brand name Lumigan among others, is a medication used to treat high pressure inside the eye including glaucoma. Specifically it is used for open angle glaucoma when other agents are not sufficient. It may also be used to increase the size of the eyelashes. It is used as an eye drop and effects generally occur within four hours.
Loteprednol is a topical corticosteroid used to treat inflammations of the eye. It is marketed by Bausch and Lomb as Lotemax and Loterex.
Naphazoline/pheniramine, sold under the brand name Naphcon-A among others, is a combination eye drop used to help the symptoms of allergic conjunctivitis such as from hay fever. It contains naphazoline and pheniramine. It is used as an eye drop. Use is not recommended for more than three days.
Bepotastine is a 2nd generation antihistamine. It was approved in Japan for use in the treatment of allergic rhinitis and urticaria/pruritus in July 2000, and January 2002, respectively. It is marketed in the United States as an eye drop under the brand name Bepreve, by ISTA Pharmaceuticals, a subsidiary of Bausch + Lomb.
Pemirolast (INN) is a mast cell stabilizer used as an anti-allergic drug therapy. It is marketed under the tradenames Alegysal and Alamast.
Besifloxacin (INN/USAN) is a fourth-generation fluoroquinolone antibiotic. The marketed compound is besifloxacin hydrochloride. It was developed by SSP Co. Ltd., Japan, and designated SS734. SSP licensed U.S. and European rights to SS734 for ophthalmic use to InSite Vision Incorporated in 2000. InSite Vision developed an eye drop formulation (ISV-403) and conducted preliminary clinical trials before selling the product and all rights to Bausch & Lomb in 2003.
Bilastine is an antihistamine medication used to treat hives (urticaria), allergic rhinitis and itchy inflamed eyes (allergic conjunctivitis) caused by an allergy. It is a second-generation antihistamine and takes effect by selectively inhibiting the histamine H1 receptor, preventing these allergic reactions. Bilastine has an effectiveness similar to cetirizine, fexofenadine, and desloratadine.
Dupilumab, sold under the brand name Dupixent, is a monoclonal antibody blocking interleukin 4 and interleukin 13, used for allergic diseases such as atopic dermatitis (eczema), asthma and nasal polyps which result in chronic sinusitis. It is also used for the treatment of eosinophilic esophagitis and prurigo nodularis.
Netarsudil, sold under the brand name Rhopressa among others, is a medication for the treatment of glaucoma. In the United States, in December 2017, the Food and Drug Administration (FDA) approved a 0.02% ophthalmic solution for the lowering of elevated intraocular pressure in people with open-angle glaucoma or ocular hypertension. The European Medicines Agency approved it in 2019 for the same uses under the brand name Rhokiinsa.
Netarsudil/latanoprost, sold under the brand name Rocklatan among others, is a fixed-dose combination medication use to treat elevated intraocular pressure (IOP) in people with open-angle glaucoma or ocular hypertension. It contains netarsudil mesylate and latanoprost. It is applied as eye drops to the eyes.
Anti-allergic agents are medications used to treat allergic reactions. Anti-allergic agents have existed since 3000 B.C in countries such as China and Egypt. It was not until 1933 when antihistamines, the first type of anti-allergic agents, were developed. Common allergic diseases include allergic rhinitis, allergic asthma and atopic dermatitis with varying symptoms, including runny nose, watery eyes, itchiness, coughing, and shortness of breath. More than one-third of the world's population is currently being affected by one or more allergic conditions.
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