Implications of OPRM1 and CYP2B6 variants on treatment outcomes in methadone-maintained patients in Ontario: Exploring sex differences.

Genetic variants in the OPRM1 and CYP2B6 genes, respectively coding for an opioid receptor and methadone metabolizers, have been linked to negative treatment outcomes in patients undergoing methadone maintenance treatment, with little consensus on their effect. This study aims to test the associations between pre-selected SNPs of OPRM1 and CYP2B6 and outcomes of continued opioid use, relapse, and methadone dose. It also aims to observe differences in associations within the sexes. 1,172 participants treated with methadone (nMale = 666, nFemale = 506) were included in this study. SNPs rs73568641 and rs7451325 from OPRM1 and all the tested CYP2B6 SNPs were detected to be in high linkage disequilibrium. Though no associations were found to be significant, noteworthy differences were observed in associations of OPRM1 rs73568641 and CYP2B6 rs3745274 with treatment outcomes between males and females. Further research is needed to determine if sex-specific differences are present.