OPRM1 has also been evaluated as a moderator of the response to treatment with the opioid antagonist naltrexone. Ray and Hutchison (2007) used prospective genotyping to oversample individuals with the Asp40 allele for participation in a within-subject, double-blind, placebo-controlled laboratory study evaluating the effects of pre-treatment with naltrexone or placebo on the response to an intravenous alcohol challenge session. Individuals with one or two Asp40 alleles reported lower levels of alcohol craving and greater alcohol-induced “high” across rising breath alcohol concentrations. Further, naltrexone blunted the positive response to alcohol, an effect that was stronger among individuals with the Asp40 allele.
