Medication (naltrexone 50 mg or matched placebo) was administered in a double-blind and crossover fashion such that each participant completed two infusion visits: one after taking naltrexone and another after taking matched placebo. Participants were asked to take a single dose of medication (either naltrexone or placebo) on each of the two days preceding the infusion visit, with a last dose occurring on the morning of the infusion, totaling three days on the active medication (or placebo). To assess medication compliance, naltrexone and placebo were packed into capsules with 50 mg of riboflavin, which becomes visible in urine samples held under ultraviolet light (Del Boca et al., 1996). Urine samples were collected prior to each infusion session and all samples tested positive for riboflavin content. To assess for the integrity of the medication blind, participants were asked to guess which medication they were currently receiving during each alcohol infusion visit. A total of 79% of the participants correctly guessed in the placebo condition, while 72% guessed correctly while in the naltrexone condition. While higher than chance levels (50%), these percent correct medication guesses did not differ by medication condition in a chi-square test [χ2 (1)= 1.33; p = .25].
