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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.
The histamine receptors are a class of G protein–coupled receptors which bind histamine as their primary endogenous ligand. [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.
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. [1] Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides relief from nasal congestion, sneezing, or hives caused by pollen, dust mites, or animal allergy with few side effects. [1]
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 ...
Histamine H 1 receptors are activated by endogenous histamine, which is released by neurons that have their cell bodies in the tuberomammillary nucleus of the hypothalamus. The histaminergic neurons of the tuberomammillary nucleus become active during the 'wake' cycle, firing at approximately 2 Hz; during slow wave sleep , this firing rate ...
Doxylamine and other first-generation antihistamines are the most widely used sleep medications in the world. [6] Typical side effects of doxylamine (at recommended doses) include dizziness, drowsiness, grogginess, and dry mouth, among others. [7] [4] As an antihistamine, doxylamine is an inverse agonist of the histamine H 1 receptor.