Several studies showed a positive effect of the OPRM1 118G allele on NTX treatment response (for review see Sturgess et al. 2011). Healthy subjects expressing the 118G-allele showed greater cortisol response to opioid receptor blockade by NTX and naloxone (Wand et al. 2002). Since alcoholics seek activation of the HPA axis, we predicted that alcoholics with the 118G allele would respond better to NTX treatment. This prediction has been supported by several studies showing that AD subjects with the 118G allele have better clinical response (Anton et al. 2008; Oroszi et al. 2009; Oslin et al. 2003; Ray and Hutchison 2007). However, these results were not supported by two other studies (Gelernter et al. 2007; Tidey et al. 2008). NTX was also shown to increase the urge for alcohol in 118G allele carriers (McGeary et al. 2006) and to decrease the positive subjective effect of alcohol (Setiawan et al. 2011).
