Functional Mu Opioid Receptor Polymorphism (OPRM1 A118G) Associated With Heroin Use Outcomes in Caucasian Males: A Pilot Study

BackgroundHeroin's analgesic, euphoric and dependence-producing effects are primarily mediated by the mu opioid receptor (MOR). A single gene, OPRM1, encodes the MOR. The functional polymorphism A(118)G, located in exon 1 of the OPRM1 gene, results in anatomically-specific reductions in MOR expression, which may alter an individual's response to heroin. In prior studies (118)G (rare allele) carriers demonstrated significantly greater opioid tolerance, overdose vulnerability, and pain sensitivity than (118)AA homozygotes. Those findings suggest OPRM1 genotype may impact characteristics of heroin use. MethodsThe present pilot study characterized the impact of OPRM1 genotype (rs1799971, (118)G allele carriers vs. (118)AA homozygotes) on heroin-use phenotypes associated with heroin dependence severity in a sample of male, Caucasian chronic heroin users (n=86). ResultsResults indicate that (118)G allele carriers reported significantly more heroin use-related consequences and heroin-quit attempts, and were more likely to have sought treatment for their heroin use than (118)AA homozygotes. ConclusionsThese preliminary findings, consistent with extant data, illustrate a role for OPRM1 allelic variation on heroin use characteristics, and provide support for considering genotype in heroin treatment and relapse prevention. (Am J Addict 2015;XX:1-7).