This study aimed to explore the potential association between the catechol-O-methyltransferase (COMT) rs4680 and mu-opioid receptor (OPRM<sub>1</sub>) rs1799971 genotypes and XR-NTX treatment outcomes in patients with opioid use disorder (OUD) specifically focusing on treatment retention, relapse to opioids, number of days of opioid use, and opioid cravings. Here, OPRM1 is linked to opioid use disorder.