Hydroxyzine

Hydroxyzine is a piperazine derivative that is used as an antihistamine (especially for itches), anti-emetic (nausea reducing), and anxiolytic (anxiety reducing) drug. It can also be used as an adjunct to pre- and post-operative medication and it also possesses a weak analgesic effect. Hydroxyzine is sold under brand names such as Atarax, Serecid and Vistaril. more...

Mode of action

Hydroxyzine is not a cortical depressant, but its effects on the central nervous system may be due to suppression of certain regions of the subcortical areas. The antihistamine effect is due to one of its metabolites cetirizine, which is a potent H₁-antagonist.

Pharmacokinetics

Hydroxyzine can be administered orally as hydroxyzine hydrochloride or hydroxyzine embonate or as an intramuscular injection as hydroxyzine hydrochloride. When given orally, hydroxyzine is rapidly absorbed from the gastro-intestinal tract. The effect of hydroxyzine is notable in 30 minutes. Hydroxyzine is diffused throughout the body, but higher concentrations can be found in the skin than in the plasma. It is metabolised in the liver, and the main metabolite (45%), through oxidation of the alcohol moiety to a carboxylic acid, is cetirizine. Hydroxyzine's half-life is on average 14 hours for adults, but it can be as low as 5 hours for small children and over 30 hours for elderly people. Hydroxyzine is excreted into the urine almost wholly as metabolites.

Side effects

The side effects of hydroxyzine are usually mild, and include drowsiness and dry mouth, which is due to slight anticholinergic action. In rare cases muscle tremor and convulsions may occur.

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