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.
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Diphenhydramine (DPH), is an antihistamine mainly used to treat allergies. It can also be used for insomnia, symptoms of the common cold, tremor in parkinsonism, and nausea. It is used by mouth, injection into a vein, injection into a muscle, or applied to the skin. Maximal effect is typically around two hours after a dose, and effects can last for up to seven hours.
Allergic rhinitis, also known as hay fever, is a type of inflammation in the nose which 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 combination with pseudoephedrine, a decongestant, known as loratadine/pseudoephedrine. It is taken by mouth.
Brompheniramine, sold under the brand name Dimetapp among others, is an antihistamine drug of the propylamine (alkylamine) class. It is indicated for the treatment of the symptoms of the common cold and allergic rhinitis, such as runny nose, itchy eyes, watery eyes, and sneezing. It is a first-generation antihistamine and one of the drugs of highest anticholinergic activity.
Desloratadine (trade name Clarinex and Aerius) is a tricyclic H1 antagonist that is used to treat allergies. It is an active metabolite of loratadine.
Cetirizine, sold under the brand name Zyrtec among others, is a second-generation antihistamine used to treat allergic rhinitis, dermatitis, and urticaria. It is taken by mouth. Effects generally begin within an hour and last for about a day. The degree of benefit is similar to other antihistamines such as diphenhydramine.
Promethazine is a first-generation antihistamine. It is used to treat allergies, trouble sleeping, and nausea. It may help with some symptoms associated with the common cold. It may also be used for sedating people who are agitated or anxious. It is available by mouth in syrup or tablet dosage forms, as a rectal suppository, or by injection into a muscle.
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).
Olopatadine, sold under the brand name Opatanol among others, is a 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 general result in an improvement within half an hour.
Levocetirizine, sold under the brand name Xyzal among others, is an 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.
Ketotifen, sold under the brand name Zaditor among others, is a second-generation noncompetitive H1-antihistamine and mast cell stabilizer. It is most commonly sold as a salt with fumaric acid, ketotifen fumarate, and is available in two forms. In its ophthalmic form, it is used to treat allergic conjunctivitis. In its oral form, it is used to prevent asthma attacks or anaphylaxis, as well as various mast cell, allergic-type disorders.
Azelastine, sold under the brand name Optivar among others, is a medication primarily used as a nasal spray to treat allergic rhinitis 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.
Skin allergy testing comprises a range of methods for medical diagnosis of allergies that attempts to provoke a small, controlled, allergic response.
Maraviroc, sold under the brand names Selzentry (US) and Celsentri (EU), is an antiretroviral drug in the CCR5 receptor antagonist class used in the treatment of HIV infection. It is also classed as an entry inhibitor. It also appeared to reduce graft-versus-host disease in patients treated with allogeneic bone marrow transplantation for leukemia, in a Phase I/II study.
Antihistamines are drugs which treat allergic rhinitis and other allergies. Typically people take antihistamines as an inexpensive, generic, over-the-counter drug that can provide relief from nasal congestion, sneezing, or hives caused by pollen, dust mites, or animal allergy with few side effects. Antihistamines are usually for short-term treatment. Chronic allergies increase the risk of health problems which antihistamines might not treat, including asthma, sinusitis, and lower respiratory tract infection. Consultation of a medical professional is recommended for those who intend to take antihistamines for longer-term use.
Talastine is an antihistamine.
Meclizine, sold under the brand names Bonine among others, is an antihistamine used to treat motion sickness and dizziness (vertigo). It is taken by mouth. Effects generally begin in an hour and last for up to a day.
RxNorm is US-specific terminology in medicine that contains all medications available on the US market. It can also be used in personal health records applications. RxNorm is part of Unified Medical Language System (UMLS) terminology and is maintained by the United States National Library of Medicine (NLM).
