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.
Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, itchy, and watery eyes, and swelling around the eyes. The fluid from the nose is usually clear. Symptom onset is often within minutes following allergen exposure, and can affect sleep and the ability to work or study. Some people may develop symptoms only during specific times of the year, often as a result of pollen exposure. Many people with allergic rhinitis also have asthma, allergic conjunctivitis, or atopic dermatitis.
Loratadine, sold under the brand name Claritin among others, is a medication used to treat allergies. This includes allergic rhinitis and hives. It is also available in drug combinations such as loratadine/pseudoephedrine, in which it is combined with pseudoephedrine, a nasal decongestant. It is taken orally.
Desloratadine (trade names Clarinex and Aerius) is a tricyclic H1 inverse agonist that is used to treat allergies. It is an active metabolite of loratadine.
Cetirizine is a second-generation antihistamine used to treat allergic rhinitis, dermatitis, and urticaria (hives). It is taken by mouth. Effects generally begin within thirty minutes and last for about a day. The degree of benefit is similar to other antihistamines such as diphenhydramine, which is a first-generation antihistamine.
Fexofenadine, sold under the brand name Allegra among others, is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.
Omalizumab, sold under the brand name Xolair, is an injectable medication to treat severe persistent allergic forms of asthma, nasal polyps, urticaria (hives), and immunoglobulin E-mediated food allergy.
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.
Montelukast, sold under the brand name Singulair among others, is a medication used in the maintenance treatment of asthma. It is generally less preferred for this use than inhaled corticosteroids. It is not useful for acute asthma attacks. Other uses include allergic rhinitis and hives of long duration. For allergic rhinitis it is a second-line treatment.
Allergen immunotherapy, also known as desensitization or hypo-sensitization, is a medical treatment for environmental allergies, such as insect bites, and asthma. Immunotherapy involves exposing people to larger and larger amounts of allergens in an attempt to change the immune system's response.
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.
Levocetirizine, sold under the brand name Xyzal, among others, is a second-generation antihistamine used for the treatment of allergic rhinitis and long-term hives of unclear cause. It is less sedating than older antihistamines. It is taken by mouth.
Terfenadine is an antihistamine formerly used for the treatment of allergic conditions. It was brought to market by Hoechst Marion Roussel and was marketed under various brand names, including Seldane in the United States, Triludan in the United Kingdom, and Teldane in Australia. It was superseded by fexofenadine in the 1990s due to the risk of a particular type of disruption of the electrical rhythms of the heart and has been withdrawn from markets worldwide.
Chloropyramine is a classical first-generation antihistamine drug approved in Eastern European countries for the treatment of allergic conjunctivitis, allergic rhinitis, bronchial asthma, and other atopic (allergic) conditions. Related indications for clinical use include angioedema, allergic reactions to insect bites, food and drug allergies, and anaphylactic shock.
Azelastine, sold under the brand name Optivar 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.
Acrivastine is a medication used for the treatment of allergies and hay fever. It is a second-generation H1-receptor antagonist antihistamine and works by blocking histamine H1 receptors.
Paramethadione is an anticonvulsant drug of the chemical class called oxazolidinediones developed by the Illinois-based pharmaceutical company Abbott Laboratories, and approved by the Food and Drug Administration in 1949 for the treatment of absence seizures, also called partial seizures.
Ebastine is a H1 antihistamine with low potential for causing drowsiness.
Rupatadine is a second generation antihistamine and platelet-activating factor antagonist used to treat allergies. It was discovered and developed by Uriach and is marketed as Rupafin and under several other trade names.
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.
