Rates of ethanol disappearance from blood and hypothermia following acute and prolonged ethanol inhalation

Abstract

An inhalation procedure was employed for the acute and prolonged administration of ethanol. The rate of ethanol clearance from blood of rats following 6 hr of inhalation was significantly faster than the rates of clearance associated with the ip or po routes of administration. Also, the blood clearances from ip and po ethanol differed significantly. However, the rates of ethanol disappearance were constant for a given route, such as inhalation or ip, regardless of the dose administered. Immediately after 10 days of ethanol inhalation, the rate of ethanol elimination was not accelerated when compared to the results obtained for 6 and 24 hr of inhalation. When the animals were again treated for 6 hr with ethanol vapor 48 hr post-10-day exposure, a significant enhancement of the rate of ethanol disappearance from the blood was observed. In another experiment, utilizing a 24-hr period of ethanol exposure, it was possible 48 hr later to separatethe accelerated rate of ethanol clearance from blood and the concomitant loss of hypothermia, which previously had been observed to occur 48 hr after prolonged ethanol inhalation. In addition, the data suggested that an increased rate of ethanol clearance is not a contributory factor to the loss of hypothermia, when these two events occur concurrently. Therefore, it appears that functional tolerance rather than metabolic tolerance was observed. Finally, when various ip doses of ethanol were administered to naive rats, it was found that a minimal peak blood ethanol concentration of 1.48 mg/ml had to be attained to produce hypothermia.