Pain Intensity in Patients with Opioid Use Disorder on Extended-Release Naltrexone or Opioid Agonists; The Role of COMT rs4680 and OPRM1 rs1799971: An Exploratory Study.

Purpose: To examine whether reported pain intensity over time is related to the single nucleotide polymorphisms of the catechol-O-methyltransferase (COMT rs4680) and mu-opioid receptor (OPRM1 rs1799971) in patients with opioid use disorder (OUD) choosing treatment with extended-release naltrexone (XR-NTX) or opioid agonist treatment (OAT).

Patients and methods: This exploratory study was part of a 24-week, open-label clinical prospective trial of patients with OUD who chose intramuscular XR-NTX, and patients receiving OAT. Men and women aged 18 to 65 years with OUD per the Diagnostic and Statistical Manual of Mental Disorders, fifth edition were included. Pain intensity was measured at baseline and at 24-week follow-up using the Numerical Pain Rating Scale-11 and genotyping was performed by TaqMan technology. Data were analyzed with ordinal logistic regression.

Results: Of 317 participants included at baseline, 210 samples were obtained and analyzed. In the OAT group, there was a negative significant association between pain intensity and having the Val/Val allele of COMT rs4680 (wild-type = most common type) and the rare allele G of OPRM1 rs1799971 at 24-week follow-up. No such effects were seen in the XR-NTX group.

Conclusion: The wild-type allele Val/Val of COMT rs4680 and the rare allele G of OPRM1 rs1799971 may have a possible protective effect regarding pain intensity in patients with OUD receiving OAT. Given relatively low sample size, particularly low number of female participants in the XR-NTX group and other possible confounders, our findings should be interpreted with caution.