Astemizole (marketed under the brand name Hismanal) is a second generation antihistamine drug which has a long duration of action. It has been withdrawn from the market in most countries because of rare but potentially fatal interactions with CYP34A enzyme inhibitors.

Pharmacology

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Astemizole is an histamine H1-receptor antagonist. It is structurally similar to terfenadine and haloperidol (a butyrophenone antipsychotic). It has anticholinergic and antipruritic effects.

Astemizole competitively binds to histamine H1-receptor sites in the gastrointestinal tract, uterus, blood vessels, and bronchial muscle. This suppresses the formation of edema and pruritus (caused by histamine).

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