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Fexofenadine should not be taken with a high-fat meal, as mean concentrations of fexofenadine in the bloodstream are seen to be reduced by 20–60% depending on the form of medication (tablet, ODT, or suspension). [5] Distribution: Fexofenadine is 60–70% bound to plasma proteins, mostly albumin. [5]
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 not true antihistamines.
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.
Clinically, H 1-antihistamines are used to treat allergic reactions and mast cell-related disorders. Sedation is a common side effect of H 1 -antihistamines that readily cross the blood–brain barrier ; some of these drugs, such as diphenhydramine and doxylamine , may therefore be used to treat insomnia .
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.
At chemical equilibrium, the reaction quotient Q r of the product activity (a Red) by the reagent activity (a Ox) is equal to the equilibrium constant (K) of the half-reaction and in the absence of driving force (ΔG = 0) the potential (E red) also becomes nul. The numerically simplified form of the Nernst equation is expressed as:
Clemastine, also known as meclastin, is a first-generation H1 histamine antagonist (antihistamine) with anticholinergic properties (drying) and sedative side effects. [1] Like all first-generation antihistamines, it is sedating. [2] [3] Patented in 1960, it came into medical use in 1967. [4]
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.