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Therapeutically, fexofenadine is a selective peripheral H 1 blocker. It is classified as a second-generation antihistamine because it is less able to pass the blood–brain barrier and cause sedation, compared to first-generation antihistamines. [12] [13] It was patented in 1979 and came into medical use in 1996. [14]
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).
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.
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.
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 .
Cimetidine was the prototypical histamine H 2 receptor antagonist from which later drugs were developed. Cimetidine was the culmination of a project at Smith, Kline & French (SK&F; now GlaxoSmithKline) by James W. Black, C. Robin Ganellin, and others to develop a histamine receptor antagonist that would suppress stomach acid secretion.
[2] [3] Apraxia of speech is the acquired form of this disorder caused by brain injury, stroke or dementia. Interventions are more effective when they occur individually at first, and between three and five times per week. With improvements, children with apraxia may be transitioned into group therapy settings.