Interactive effect of ethanol administration on blood hydroxyzine levels in rabbits

Mechanism of a rise of blood hydroxyzine concentrations (BHC) due to ethanol administration was investigated used rabbits. When 10 mg/kg hydroxyzine dihydrochloride were orally administered together with 10 ml/kg of 1 to 15% ethanol solution, BHC raised in all rabbits given ethanol solution more than 10%. When 10 ml/kg of 15% ethanol solution were orally administered at 1, 2 or 3 hours before oral administration of hydroxyzine, BHC raised markedly in all cases. BHC raised little or a little when hydroxyzine were orally administered immediately after intravenous administration of 5 ml/kg of 20% ethanol solution. It was considered that the main mechanism of a rise of BHC was not metabolic interaction between hydroxyzine and ethanol, but an enhancement of intestinal absorption of hydroxyzine due to ethanol. It was also found that hydroxyzine in blood distributed rapidly into bodily tissues.