During the 5-day natural environment drinking period there was a three way interaction (F(1,75)=6.83, p=0.011) between medication group, ORPM1 genotype and DAT genotype on the number of drinks per day (figure 1). Decomposing this three-way interaction showed that when there was at least one DAT 9 VNTR present, naltrexone reduced alcohol consumption only when the subject also had the asn40asn genotype (p=0.006) but when there was no DAT 9 VNTR (i.e. 10/10 genotype) there was no medication by OPRM1 genotype interaction. The same three-way interaction was present with percent heavy drinking days but at a trend level (F(1,75)=3.43, p=0.068). The three-way interaction for number of drinks per day was similar but became even more significant for heavy drinking days when age, ADS score, and baseline drinking were used as covariates in the analyses (p=0.015 for drinks per day and p=0.039 for percent heavy drinking days).
