Effects of naltrexone pretreatment on the subjective and performance effects of ethanol in social drinkers

Clinical trials suggest that opioid antagonists may be effective in the treatment of alcoholism. For example, two recent clinical trials reported that alcoholics treated with the opioid antagonist naltrexone exhibited higher abstinence rates, decreased craving and a decrease in the amount of alcohol consumed if drinking occurred. The present study examined the hypothesis that naltrexone pretreatment would attenuate the behavioral responses to an acute dose of ethanol in normal, healthy social drinkers. Thirteen healthy male and female social drinkers participated in a six-session, double-blind, placebo-controlled, crossover design study. On each session, subjects ingested a capsule containing naltrexone (25 or 50mg) or placebo and one hour later consumed a beverage containing ethanol (0.5g/kg) or placebo. For three hours after the beverage was consumed, breath alcohol levels were measured and subjects completed standardized subjective effects questionnaires and performance tasks at regular intervals. Ethanol alone produced its prototypic effects, including positive subjective responses such as euphoria and increased ratings of overall liking, as well as increased ratings of confusion. Ethanol also impaired performance on a verbal recall task. Naltrexone alone produced few subjective effects and did not impair psychomotor or verbal recall performance. Contrary to our hypothesis, pretreatment with naltrexone did not alter the positive subjective effects, or any other effects, of ethanol. Further research is needed to determine the influence of factors such as baseline level of ethanol consumption or duration of naltrexone treatment on the interaction between ethanol and the endogenous opioid system.