Naltrexone, an opioid receptor antagonist targeting particularly the mu‐opioid receptor (MOR) subtype (Verebey & Mule 1975; Schmidt et al.1985), has been shown in randomized controlled trials to be effective in alcohol dependence (AD) but may be more effective in some individuals or subgroups and not others (Streeton & Whelan 2001) (Anton 2008; Sturgess et al.2011). The gene discussed is OPRM1; the disease is alcohol dependence.