Antihistamine

An antihistamine is a drug which serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions, through action at the histamine receptor. Only 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.

Other agents

Inhibitors of histamine release

These agents appear to stabilise the mast cells to prevent degranulation and mediator release.

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• cromoglicate (cromolyn)
• nedocromil

H₂-receptor antagonists

Main article: H2-receptor antagonist

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Clinically-relevant histamine H2-receptors are found principally in the parietal cells of the gastric mucosa. H2-receptor "antagonists" are also inverse agonists, rather than true antagonists; and are used to reduce the secretion of gastric acid. Examples include cimetidine, ranitidine, and famotidine.

Related Topics:
Parietal cell - Gastric - Inverse agonist - Antagonists - Gastric acid - Cimetidine - Ranitidine - Famotidine

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H₃- and H₄-receptor antagonists

These are experimental agents and do not yet have a defined clinical use.

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Other agents with antihistaminergic activity

Many drugs, used for other indications, possess unwanted antihistaminergic activity. These include tricyclic antidepressants, antipsychotics, etc.

Related Topics:
Tricyclic antidepressants - Antipsychotic

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