Hydroxyzine hydrochloride

Originator

Atarax,UCB,France,1956

Manufacturing Process

A mixture of 0.1 mol of N-mono-1-p-chlorobenzohydrylpiperazine and 0.1 mol of 1-chloro-2-(2-hydroxy-ethoxy)-ethane is heated for 3 hours to 150°C. The mass is then taken up in 100 ml of benzene and 100 ml of a 10% aqueous solution of NaOH; decanting takes place, and the benzene solution is washed with water and the solvent is evaporated. Vacuum distilling of the residue yields 1-p-chlorobenzohydryl-4-[2-(2-hydroxy-ethoxy)-ethyl]-piperazine, BP 220°C/0.5 mm Hg.
The corresponding dihydrochloride is prepared by dissolving this base in about twice its weight of alcohol, by treating it with excess of gaseous HCl and by precipitating it with ether. The solvent is decanted and the residue, dissolved in a minimum of alcohol, crystallizes on the addition of ether, MP 193°C.

Therapeutic Function

Tranquilizer

Clinical Use

Antihistamine:

Pruritus

Anxiety (short-term)

Drug interactions

Potentially hazardous interactions with other drugs
Analgesics: sedative effects possibly increased with opioid analgesics.

Metabolism

Hydroxyzine is extensively metabolised. The formation of the major metabolite cetirizine, a carboxylic acid metabolite (approximately 45% of the oral dose), is mediated by alcohol dehydrogenase. This metabolite has significant peripheral H1-antagonist properties. The other metabolites identified include a N-dealkylated metabolite, and an O-dealkylated metabolite with a plasma half-life of 59 hours. These pathways are mediated principally by CYP3A4/5. Only 0.8% of the dose is excreted unchanged in urine. The major metabolite cetirizine is excreted mainly unchanged in urine (25% and 16 % of the hydroxyzine oral and IM dose, respectively).