Chronic pain is highly prevalent among patients with
opioid use disorder (OUD). However, little is known about how pharmacological treatments for OUD, for example, extended-release
naltrexone (XR-NTX) and
buprenorphine-naloxone (BUP-NX), affect
pain. To begin addressing this question, we performed a secondary analysis of
pain data on a large prospective 24-week, open-label, randomized-controlled comparative effectiveness trial of XR-NTX versus BUP-NX (X:BOT trial). Participants'
pain status was measured by the EuroQol (EQ-5D). Based on their responses to the
pain question at baseline, participants were dichotomized into "
Pain" versus "No
Pain" categories. Participant's
pain status was evaluated every 4 weeks. A mixed effects longitudinal logistic regression model was fitted to examine the differential effect of XR-NTX versus BUP-NX on
pain, modelling
pain at all available follow-up assessments, adjusted for age, sex, and baseline
pain. A total of 474 individuals who were successfully inducted onto their assigned medications were included in this analysis. Among participants endorsing
pain at baseline, substantial reductions in
pain were observed over the course of the study in both treatment groups. Howecver reduction in
pain was slightly greater in the group treated with XR-NTX than the one treated with BUP-NX (OR = 1.60 [95% CI: 1.07-2.40], P = 0.023). Future research using instruments and design specifically focused on
pain could extend the present observations and evaluate their clinical significance.