Influence of the A118G polymorphism of the OPRM1 gene and exon 3 VNTR polymorphism of the DRD4 gene on cigarette craving after alcohol administration.

INTRODUCTION: The current study examined whether the presence of the G allele of the A118G polymorphism of the OPRM1 gene (rs1799971) and the long allele of exon 3 VNTR polymorphism of the DRD4 gene moderate the effect of alcohol administration on urge to smoke. These polymorphisms have been associated with greater alcohol induced-urge to drink. Urge to drink and alcohol consumption increase urge to smoke. Therefore, these polymorphisms may also sensitize urge to smoke after alcohol consumption. METHODS: Individuals smoking 10-30 cigarettes per day and reporting heavy drinking were recruited from the community. Caucasians (n = 62), 57.3% male, mean age 39.2, took part in a three-session, within-subjects, repeated-measures design study. Participants were administered a placebo, 0.4 g/kg, or 0.8 g/kg dose of alcohol. A118G genotype, exon 3 VNTR genotype, and urge to smoke (baseline and three times after receiving alcohol) were assessed. RESULTS: G allele carriers showed greater urge to smoke across all assessments. Additionally, a significant interaction indicated that G carriers, compared to homozygotes (AA), evinced a significantly greater increase in urge to smoke after high dose alcohol relative to placebo. The interaction between condition, DRD4 polymorphism, and time was not significant. CONCLUSIONS: Presence of G allele of the A118G polymorphism of the OPRM1 gene may lead to greater increases in urge to smoke after a high dose of alcohol. Pharmacotherapies targeted to opiate receptors (eg, naltrexone) may be especially helpful in aiding smoking cessation among G carriers who are heavy drinkers.