This MedLibrary.org supplementary page on Histamine antagonist is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
 |
This article may be too technical for a general audience. Please help improve this article by providing more context and better explanations of technical details to make it more accessible, without removing technical details. |
A histamine antagonist is an agent which serves to inhibit the release or action of histamine. Antihistamine can be used to describe any histamine antagonist, but it is usually reserved for the classical antihistamines that act upon the H1 histamine receptor.
Many people suffer from allergies. These are caused by an excessive response of the body to allergens, materials that are sometimes omnipresent, such as the pollen released by grasses and trees. An allergic reaction indicates an excessive release, by the body, of histamines.
Contents |
Clinical: H1- and H2-receptor antagonists
H1-receptor antagonists
In common use, the term antihistamine refers only to H1 antagonists, also known as H1 antihistamines. It has been discovered that these H1-antihistamines are actually inverse agonists at the histamine H1-receptor, rather than antagonists per se.[1] Clinically, H1 antagonists are used to treat allergic reactions.
Examples:
- Diphenhydramine
- Loratadine
- Desloratadine
- Meclizine
- Quetiapine (this is a side-effect of a drug usually used as an antipsychotic)
- Fexofenadine
- Pheniramine
- Cetirizine
H2-receptor antagonists
H2 antagonists, like H1 antagonists, are also inverse agonists and not true antagonists. H2 histamine receptors are found principally in the parietal cells of the gastric mucosa. H2 antagonists are used to reduce the secretion of gastric acid, treating gastrointestinal conditions including peptic ulcers and gastroesophageal reflux disease.
Examples:
Experimental: H3- and H4-receptor antagonists
These are experimental agents and do not yet have a defined clinical use. H3-antagonists have a stimulant effect, and are being investigated for the treatment of conditions such as ADHD, Alzheimer's Disease and schizophrenia, while H4-antagonists appear to have an immunomodulatory role.
H3-receptor antagonists
Examples:
H4-receptor antagonists
Examples:
Others
Inhibitors of histamine release
These agents (mast cell stabilizers) appear to stabilize the mast cells to prevent degranulation and mediator release.
Examples:
- Cromoglicate (cromolyn)
- Nedocromil
Other agents with antihistaminergic activity
Many drugs, used for other indications, possess unwanted antihistaminergic activity. These include tricyclic antidepressants and antipsychotics. One drug initially developed as an antipsychotic, but now commonly used for its antihistaminic effect, is promethazine.
Large doses of vitamin C are known to alleviate shock by inhibiting deaminizing proteins which release histamine. [2]
References
- ^ Leurs R, Church MK, Taglialatela M (2002). "H1-antihistamines: inverse agonism, anti-inflammatory actions and cardiac effects". Clin Exp Allergy 32 (4): 489–98. doi:. PMID 11972592.
- ^ Klenner, Frederick R. Observations On the Dose and Administration of Ascorbic Acid.... Section "Ascorbic acid to the rescue."
External links
|
|||||||||||||||||||||||
|
|||||||||||||||||||||||||||||
Wikipedia content modification information:
- This page was last modified on 2 July 2008, at 04:40.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Histamine antagonist".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.