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Another type of antihistamines known as H2-antihistamines are used to treat gastrointestinal conditions caused by excessive stomach acid. [8] Mechanism. H-1 antihistamines work by inhibiting histamine from binding to H-1 receptors. Histamine receptors expressed in smooth muscles, vascular endothelial cells, the heart, and the central nervous ...
Normally, histamine acts on H 2 to stimulate acid secretion; drugs that inhibit H 2 signaling thus reduce the secretion of gastric acid. H 2-antihistamines are among first-line therapy to treat gastrointestinal conditions including peptic ulcers and gastroesophageal reflux disease. Some formulations are available over the counter.
The use of sedating drugs alongside hydroxyzine can cause oversedation and confusion if administered at high doses—any form of hydroxyzine treatment alongside sedatives should be done under the supervision of a doctor. [28] [25] Because of the potential for more severe side effects, this drug is on the list to avoid in the elderly. [29]
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.
Clemastine is an antihistamine with anticholinergic and sedative effects. Antihistamines competitively bind to histamine receptor sites, thus reducing the neurotransmitter's effects. [9] Effects of histamine (which are countered by antihistamines) include: Increased capillary permeability; Increased capillary dilatation; Edema (i.e., swelling ...
Cetirizine is a second-generation antihistamine used to treat allergic rhinitis (hay fever), dermatitis, and urticaria (hives). [5] It is taken by mouth. [6] Effects generally begin within thirty minutes and last for about a day. [6] The degree of benefit is similar to other antihistamines such as diphenhydramine, which is a first-generation ...
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.
An H 3 receptor antagonist is a type of antihistaminic drug used to block the action of histamine at H 3 receptors.. Unlike the H 1 and H 2 receptors which have primarily peripheral actions, but cause sedation if they are blocked in the brain, H 3 receptors are primarily found in the brain and are inhibitory autoreceptors located on histaminergic nerve terminals, which modulate the release of ...