Hydroxyzine is a first-generation antihistamine, of the piperazine class that is an H1 receptor antagonist. It was synthesised in the early 1950s and the medicinal formulation of this drug was announced in the 04. August 1956 issue of Chemistry Week. It is used primarily as an antihistamine for the treatment of itches and irritations, an antiemetic for the reduction of nausea, as a weak analgesic by itself and as an opioid potentiator, and as an anxiolytic for the treatment of anxiety. Its most common formulation is 25 mg small white, capsule-shaped and scored tablets of the hydrochloride salt made by UCB in the Netherlands. In the United States, a nearly-spherical dark green tablet is the most-commonly encountered version of it, with 25 and 100 mg capsules being available as well as a series of colour-coded round tablets from Mallinkrodt (25 mg white, 50 mg orange, 100 mg blue). Hydroxyzine preparations usually require a doctor's prescription as do other potent antihistamines in many countries whereas some countries allow hydroxyzine and all or most other antihistamines to be sold over the counter. Even though it is an effective sedative, hypnotic, and tranquilliser, it shares almost none of the abuse, dependence, addiction, and toxicity potential of other drugs used for the same range of therapeutic reasons. The drug is available in two formulations, the pamoate and the dihydrochloride or hydrochloride salts. Vistaril®, Equipose®, Masmoran®, Paxistil®, and Vistaril Pamoate® are preparations of the pamoate salt whilst Atarax®, Alamon®, Aterax®, Durrax®, Tran-Q®, Orgatrax®, Quiess®, Vistaril Parenteral®, and Tranquizine® are hydroxyzine hydrochloride. Other drugs related to hydroxyzine are cyclizine (Marezine®), buclizine, and meclizine (Dramamine II®) 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, therefore having a narrower spectrum of effects, making it an effective antihistamine but removing some or all of the anxiolytic and analgesic-sparing properties.