Effect of pregnancy on ethanol concentrations at onset of loss of righting reflex in rats.

To determine if the pharmacodynamics of ethanol are altered in advanced pregnancy, 20-days pregnant Lewis rats and nonpregnant rats of the same age received an i.v. infusion of ethanol, 96 mg/min/kg, until they lost their righting reflex. The concentrations of ethanol at that time in adult and fetal serum, and in the cerebrospinal fluid (CSF) and brain of the adult animals were determined. Ethanol concentrations in the pregnant rats were only slightly (less than 10%) but statistically significantly lower than in nonpregnant controls. Brain/serum, CSF/serum, and CSF/brain concentration ratios of ethanol were essentially identical in pregnant and nonpregnant rats, indicating no apparent effect of pregnancy on the distribution kinetics of ethanol. The serum concentrations of ethanol in mothers and their fetuses were similar and significantly correlated. The results of this investigation show that the central nervous system depressant effect of ethanol is not appreciably altered by pregnancy.