Given the known minor allele frequency imbalance across ethnic groups, extension of these findings to diverse samples is warranted. To that end, a placebo-controlled study of naltrexone among Korean alcohol-dependent patients found that, among treatment adherent individuals, Asp40 carriers reported longer time to relapse, compared to Asn40 homozygotes (Kim et al., 2009). These results were not statistically significant in the intent-to-treat analysis and only reached statistical significance when medication noncompliant patients were excluded from the analysis. As with the preclinical literature discussed later, there is evidence of sex-specific effects of this polymorphism in a Korean sample, such that the Asp40 allele was overrepresented in women with alcohol dependence versus controls, but not in men (Kim, 2009). This is relevant as some clinical trials have reported sex-specific effects, with men showing a better clinical response to naltrexone (Garbutt et al., 2005; Kranzler et al., 2009), although these differences may be a function of reduced sample size and/or the endpoint drinking variable selection (Baros et al., 2008).
