Participants who passed all screening and eligibility criteria were urn-randomized (based on sex and smoking status) to receive 25 mg (2 days) and 50 mg (5 days) of naltrexone n=38 (19 asp40; 19 asn40) or identical placebo capsules n=45 (24 asp40; 21 asn40) for seven days in a blinded fashion. While subjects remained blind to their genotype, investigators attempted to select/match the more frequent asn40asn genotype subjects to the more rare asp40 subjects based on gender, smoking, alcohol problem severity (e.g. ADS scores) and alcoholism family history to minimize salient differences between the genetic sub-groups. All study medications were blister packed and administered in identical standard gel caps with 25 mg riboflavin added.
