275: Characteristics of Chronic Pain in Patients on Different Medications for Opioid Use Disorder

Topic: Clinical Science
Subtopic: Non-specific to any diagnosis, Psychology, Pharmacological treatments, Pain in Special Populations

Background and Aims: Chronic pain is common in individuals with opioid use disorder. Because the opioid antagonist naltrexone blocks opioid receptors, fear of inadequate pain management can cause reluctance among patients to enter treatment for opioid use disorder with this medication. A considerable number of patients with co-occurring chronic pain nevertheless begin naltrexone treatment for their opioid use disorder[1]. Here, we explored observational data from a work package in the Norwegian NaltRec study (NCT03647774)[2] to identify potential differences in the pain experiences of extended-release naltrexone- (XR-NTX) and opioid agonist-treated (OAT) patients with co-occurring opioid use disorder and chronic pain.

Methods: Thirty-eight patients (17 on XR-NTX and 21 on OAT; age mean±SD = 43±11 years; 13 women) provided detailed information about their pain by completing the McGill Pain Questionnaire Short Form affective and sensory subscales, rating items from Brief Pain Inventory and Oslo University Hospital pain registry covering pain intensity, bothersomeness and interference, and coloring a digital body map assessing bodily pain distribution. We used non-parametric (Wilcoxon-Mann-Whitney) tests to compare these pain characteristics between the two groups. Non-significant and significant results were followed up with equivalence tests and tests for clinical significance, respectively, using a threshold of 15 percentage points difference.

Results: Pain was distributed to an equivalent degree in both groups (median [IQR] = 6% [3-11%], p < 0.0001). The groups did not significantly differ in the intensity (6 [4-7]) or the sensory (11 [5-17]) or affective load (3 [0-6]) of their pain (all ps ≥ 0.11), and equivalence tests were inconclusive (all ps ≥ 0.11). Patients on XR-NTX reported being significantly less bothered (5 [4-6] vs. 7 [6-8], p = 0.03) and disrupted (3 [3-6] vs. 7 [6-7], p < 0.01) by their pain compared to patients on OAT, but not to a clinically significant degree (all ps ≥ 0.06).

Conclusions: Major differences in pain characteristics between patients on XR-NTX and patients on OAT with co-occurring chronic pain seem unlikely based on the current results. The lower pain interference and bothersomeness could indicate that those on XR-NTX have pain that is either slightly more manageable before starting XR-NTX treatment or that becomes so with this treatment. However, data from more and larger samples are needed to verify these findings and determine the impact of XR-NTX on experiences of pain in individuals with co-occurring opioid use disorder and chronic pain.

References: [1] Trøstheim M, Leknes S, Hama LM, Roland MN, Solli KK, Weimand BM, Tanum L, Eikemo M. Experimental Pain Responses and Clinical Pain Symptoms in Patients Receiving Opioid Agonist and Antagonist Treatment for Opioid Use Disorder: An Observational Study. PsyArXiv Prepr 2025.
[2] Weimand BM, Solli KK, Reichelt WH, Tanum L. Enablers and hindrances for longer-term abstinence in opioid dependent individuals receiving treatment with extended-release naltrexone: A Norwegian longitudinal recovery trial (NaltRec study). Contemp Clin Trials Commun 2021;21:100728.

Presenting Author: Martin Trøstheim
Submitting Author: Martin Trøstheim

Senior Author: Marie Eikemo

IASP 2026 Global Year theme of Neuropathic Pain: No

• Siri Leknes: PhD - University of Oslo
• Lennja Majid Hama: MS - OptiMedis AG
• Mathias Nikolai Roland: MS - University of Oslo
• Kristin Klemmetsby Solli: PhD - Vestfold Hospital Trust
• Bente M. Weimand: PhD - University of South-Eastern Norway
• Lars Tanum: PhD - Akershus University Hospital