Antihistamines H1 Blockers

See also the following individual entries:

Astemizole

Brompheniramine maleate Cetirizine hydrochloride Chlorpheniramine maleate Dimenhydrinate

Diphenhydramine hydrochloride Fexofenadine hydrochloride Loratidine

Olopatadine hydrochloride Terfenadine Action/Kinetics: Compete with histamine at H1 histamine receptors (competitive inhibition), thus preventing or reversing the effects of histamine. First-generation antihista-mines bind to central and peripheral H1 receptors and can cause CNS depression or stimulation. Second-generation antihistamines are selective for peripheral H1 receptors and cause less sedation. Antihistamines prevent or reduce increased capillary permeability (i.e., decrease edema, itching) and bronchospasms. Allergic reactions unrelated to hista-mine release are not affected by antihistamines. Certain of the firstgeneration antihistamines also have anticholinergic, antiemetic, antipru-ritic, or antiserotonin effects. Clients unresponsive to a certain antihista-mine may regain sensitivity by switching to a different antihista-mine.

From a chemical point of view, the antihistamines can be divided into the following classes.

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