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Author(s): Ray, Lara A; Green, ReJoyce; Roche, Daniel J O; Bujarski, Spencer; Hartwell, Emily E; Lim, Aaron C; Rohrbaugh, Taylor; Ghahremani, Dara; Hutchison, Kent; Miotto, Karen | Abstract: Genetic variation in the endogenous opioid system has been identified as 1 potential source of individual variability in naltrexone treatment outcomes. The majority of naltrexone pharmacogenetic studies have focused on a particular single nucleotide polymorphism (SNP) of the mu-opioid receptor gene (OPRM1; rs1799971; commonly known as the Asn40Asp SNP) in Caucasian samples with decidedly mixed results. The goal of this study was to test the pharmacogenetic effects of naltrexone on subjective response to alcohol and self-administration of alcohol in individuals of East Asian descent. We hypothesized that naltrexone, compared with placebo, would potentiate the aversive and sedative effects of alcohol and reduce alcohol self-administration to a greater extent in Asp40 carriers.Participants (Nn=n77; Asn40Asn, nn=n29; Asn40Asp, nn=n34, and Asp40Asp, nn=n14) completed 2 double-blinded and counterbalanced experimental sessions: one after taking naltrexone (50nmg/d) for 5ndays and one after taking matched placebo for 5ndays. In each experimental session, participants received a priming dose of intravenous alcohol up to the breath alcohol concentration target of 0.06ng/dl which was immediately followed by an alcohol self-administration period (1nhour).There were no pharmacogenetic effects observed for alcohol-induced stimulation, sedation, craving for alcohol, or alcohol self-administration in the laboratory. During the self-administration period, Asp40 carriers consumed fewer drinks and had a longer latency to first drink as compared to Asn40 homozygotes.These findings in East Asians add to the mixed literature on naltrexone pharmacogenetics from predominantly Caucasian samples and highlight the complexity of these effects and their overall limited replicability. It is plausible that a consistent pharmacogenetic effect in tightly controlled preclinical and experimental medicine models "fades" in more complex and heterogeneous settings and samples.

Background Subjective response to alcohol has been examined as a marker of alcoholism risk. The A118G single-nucleotide polymorphism (SNP) of the mu-opioid receptor (OPRM1) gene has been previously associated with subjective response to alcohol in heavy drinkers. This study seeks to extend the literature by examining the effect of OPRM1 genotype on responses to alcohol in a sample of alcohol-dependent individuals. A secondary aim of this study is to examine alcoholism severity as a predictor of subjective responses to alcohol. Methods Nontreatment seeking problem drinkers (n = 295) were assessed in the laboratory for clinical dimensions of alcohol dependence. Following prospective genotyping, 43 alcohol-dependent individuals across the 2 genotype conditions (AA, n = 23 and AG/GG, n = 20) were randomized to 2 intravenous infusion sessions: 1 of alcohol (target breath alcohol concentration = 0.06 g/dl) and 1 of saline. Measures of subjective responses to alcohol were administered in both infusion sessions. Results Alcohol-dependent G-allele carriers reported greater alcohol-induced stimulation, vigor, and positive mood, as compared to A-allele homozygotes. There was no genotype effect on alcohol-induced sedation or craving. There was a statistical trend-level severity × alcohol interaction such that individuals at higher levels of severity reported greater alcohol-induced tension reduction. Conclusions These results support the hypothesis that OPRM1 genotype moderates the hedonic effects of alcohol, but not the sedative and unpleasant effects of alcohol, in a sample of alcohol-dependent patients. Results are discussed in light of a clinical neuroscience framework to alcoholism.