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Fexofenadine, sold under the brand name Allegra among others, [10] is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria. [11] Therapeutically, fexofenadine is a selective peripheral H 1 blocker.
H 1 antagonists, also called H 1 blockers, are a class of medications that block the action of histamine at the H 1 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 ...
H 1-antihistamines work by binding to histamine H 1 receptors in mast cells, smooth muscle, and endothelium in the body as well as in the tuberomammillary nucleus in the brain. Antihistamines that target the histamine H 1 -receptor are used to treat allergic reactions in the nose (e.g., itching, runny nose, and sneezing).
[1] [2] Histamine receptors are proteins that bind with histamine, a neurotransmitter involved in various physiological processes. There are four main types: H1, H2, H3, and H4. H1 receptors are linked to allergic responses, H2 to gastric acid regulation, H3 to neurotransmitter release modulation, and H4 to immune system function.
The H 1 receptor is a histamine receptor belonging to the family of rhodopsin-like G-protein-coupled receptors. This receptor is activated by the biogenic amine histamine . It is expressed in smooth muscles , on vascular endothelial cells , in the heart, and in the central nervous system .
H 1-receptor antagonists are competitive inhibitor of histamine receptor H 1 and are used to treat allergies. This group is often referred simply as antihistamines . Wikimedia Commons has media related to H1 receptor antagonists .
Terfenadine acts as a peripherally-selective antihistamine, or antagonist of the histamine H 1 receptor. [3] It is a prodrug, generally completely metabolized to the active form fexofenadine in the liver by the enzyme cytochrome P450 3A4. Due to its near complete metabolism by the liver immediately after leaving the gut, terfenadine normally is ...
It contains fexofenadine, as the hydrochloride, an antihistamine; and pseudoephedrine, as the hydrochloride, a nasal decongestant. [ 2 ] In 2021, it was the 279th most commonly prescribed medication in the United States, with more than 800,000 prescriptions.