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Hydroxyzine (; sold as Vistaril, Atarax) is a first-generation antihistamine of the diphenylmethane and piperazine class. It was first synthesized by Union Chimique Belge in 1956 and was marketed by Pfizer in the United States later the same year, and is still in widespread use today. Due to its antagonistic effects on several receptor systems in the brain, hydroxyzine has strong anxiolytic and mild antiobsessive as well as antipsychotic properties. Today it is used primarily for the symptomatic relief of anxiety and tension associated with psychoneurosis and as an adjunct in organic disease states in which anxiety is manifested. Because of its antihistamine effects it can also be used for the treatment of severe cases of itching, hyperalgesia and motion sickness-induced nausea, it has also been used in some cases to relieve the effects of opioid withdrawal.〔FDA DrugInfo: http://dailymed.nlm.nih.gov/dailymed/archives/fdaDrugInfo.cfm?archiveid=51459〕〔(【引用サイトリンク】 Hydroxyzine Facts and Comparisons at Drugs.com )〕 Even though it is an effective sedative, hypnotic, and anxiolytic, it shares virtually none of the abuse, dependence, addiction, and toxicity potential of other drugs used for the same range of therapeutic reasons. Hydroxyzine has also been used to potentiate the analgesia of opioids and to alleviate some of their side effects, such as itching, nausea, and vomiting. Hydroxyzine preparations usually require a doctor's prescription. The drug is available in two formulations, the pamoate and the dihydrochloride or hydrochloride salts. Vistaril, Equipose, Masmoran, and Paxistil are preparations of the pamoate salt, while Atarax, Alamon, Aterax, Durrax, Tran-Q, Orgatrax, Quiess, and Tranquizine are of the hydrochloride salt. Other drugs related to hydroxyzine are cyclizine, buclizine, and meclizine, and they share all or most of the benefits, indications, contraindications, cautions, and side effects of hydroxyzine. The second-generation antihistamine cetirizine is in fact one of the metabolites of hydroxyzine produced in the human body. Unlike hydroxyzine, cetirizine is not reported to appreciably cross the blood-brain barrier, but it has been reported to be associated with dystonic reactions as well as sedation. Therefore, it has a narrower spectrum of effects, making it an effective antihistamine but removing some or all of the anxiolytic and other psychoactive properties, but it may cause dystonic reactions and drowsiness in some patients. ==Chemistry== Hydroxyzine is synthesized by the alkylation of 1-(4-chlorobenzohydril)piperazine with 2-(2-hydroxyethoxy)ethylchloride:〔H. Morren, (1959); H. Morren, (1954); H. Morren, (1954); H. Morren, (1954); H. Morren, (1954); H. Morren, (1954).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydroxyzine」の詳細全文を読む スポンサード リンク
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