A comparison of the effects of 6-β naltrexol and naltrexone on the consumption of ethanol or sucrose using a limited-access procedure in rats

Abstract

We recently reported that 6-β naltrexol, the major metabolite of naltrexone in humans, reduced ethanol consumption in rats. Two new experiments were designed to compare 6-β naltrexol and naltrexone across three dose levels on an ethanol or sucrose baseline using a limited-access procedure in Wistar rats. The results of Experiment 1 showed that both 6-β naltrexol and naltrexone reduced ethanol consumption across a range of doses. An in vivo assay showed that naltrexone was approximately 25 times more potent than 6-β naltrexol at comparable ED 50 doses. In addition, there was no indication of systematic development of tolerance to the effect of either drug across the 4 days of drug administration. In Experiment 2, both 6-β naltrexol and naltrexone reduced the consumption of a sucrose solution using a limited-access procedure. The implications of these data for the development of pharmacotherapeutic agents capable of reducing drinking in recovering alcoholics are discussed.