Editorial for the themed issue: Addressing the dual challenges of opioid use disorder and chronic pain in the context of the opioid crisis

Abstract

Opioid overdose deaths have reached alarming levels, particularly in North America with over 100 000 deaths annually in the United States alone. Opioid use disorder (OUD) is closely linked to chronic pain, with two thirds of individuals with OUD also experience chronic pain. Notably, the majority of these individuals reported experiencing chronic pain prior to the diagnosis of OUD.¹ Further, chronic pain often persists even after the individuals initiate evidence-based opioid agonist treatment for OUD. Rates of chronic pain among individuals receiving such treatment range from 23% to 80%.² The presence of chronic pain may be a significant barrier for seeking OUD treatment, staying in treatment and reducing the likelihood of relapse.³ This special issue explores the impact of the opioid epidemic on pain management and the role of clinical pharmacology in addressing the crisis. The manuscripts in this special issue will be of particular interest to researchers and clinicians working with patients with OUD and chronic pain, as they provide valuable insights into the complex interplay between these two conditions and offer potential strategies for both assessing and improving treatment outcomes.

Despite a strong theoretical association, the temporal relationship between pain and opioid craving remains unclear.⁴ MacLean and colleagues examined this relationship in individuals who are on methadone maintenance treatment for OUD.⁵ Using a within-participant design, participants completed measures of pain and craving after taking methadone as scheduled or delaying methadone for 4 h. They found a strong association between pain and craving, demonstrating that even brief delays in methadone treatment can lower pain threshold, thereby increasing the risk to relapse.

The long-term use of opioids to treat chronic pain remains controversial. Manhapra and colleagues critically examined the underlying assumptions regarding long-term opioid use for chronic pain and provided clinical guidelines for the practitioners managing such patients.⁴ The authors proposed guidelines with clinical examples, to evaluate the risks and functional benefits of long-term opioid therapy. To aid in the assessment of maladaptive long-term opioid therapy dependence, the authors propose diagnostic criteria for opioid-induced chronic pain (OICP) syndrome.

Nunes and colleagues provided a thorough review of the challenges in assessing pain among individuals with OUD, highlighting the lack of validated tools for this population.⁶ They examined a range of assessment methods, from self-report measures and behavioural observations to advanced laboratory techniques like quantitative sensory testing. The review emphasized the need for tailored pain assessment strategies that account for the unique complexities of OUD and identifies significant gaps in current research, particularly regarding the applicability of existing tools. The authors called for further research and educational strategies to improve pain assessment in this underserved group.

Two articles examined the pharmacological management of acute pain in individuals with OUD. Rostamipoor and colleagues investigated the efficacy of clonidine, an alpha adrenergic agonist, for the management of orthopaedic fracture pain in patients with OUD.⁷ They found that pain scores and the dose of morphine required were lower in the clonidine group than those in the placebo group. These findings supported the potential utility of clonidine in these patients. Management of peri-operative pain in individuals who are on opioid agonist treatment remains a significant challenge, and many patients face discontinuation of treatment despite evidence supporting continuation of treatment. Their chart review supports the feasibility of tapering of opioids prescribed for pain among individuals following surgery.⁸

For patients who require long-term opioid therapy, new interventions are essential to manage both OUD and chronic pain effectively.⁹ Garland's review of Mindfulness-Oriented Recovery Enhancement (MORE) offered detailed insights into this innovative intervention, which integrates mindfulness training, cognitive-behavioural therapy and positive psychology. The review highlighted MORE's proven benefits in reducing opioid misuse, managing chronic pain and improving overall patient outcomes, making it a promising approach for broader implementation in clinical settings.

The resurgence of interest in psychedelic medications presents promising avenues for treating multiple psychiatric disorders, including OUD and chronic pain. Weleff and colleagues explored the emerging potential of psychedelics, particularly psilocybin and lysergic acid diethylamide (LSD), in treating OUD and chronic pain.¹⁰ While current studies are limited and based on small sample sizes, the preliminary evidence is promising. The authors highlighted the need for further research and provide critical considerations for designing future clinical trials to explore these innovative therapeutic avenues amidst the ongoing opioid crisis.

The potential utility of glial modulators in treating comorbid chronic pain and OUD was thoroughly examined in an article by Schwartz and colleagues.¹¹ The review synthesized existing clinical studies, highlighting the emerging role of glial activation in both chronic pain and substance use disorders, including OUD. Despite the preliminary nature of the evidence and limitations such as small sample sizes and methodological variability, the findings point to significant therapeutic promise. As research advances, these agents may become key in improving pain management and reducing addiction-related outcomes, underscoring their potential as innovative therapeutics in the face of these persistent public health problems.

Both preclinical and clinical studies on OUD and chronic pain have significant sex/gender biases. A scoping review by DeVito et al.¹² identified both quantitative and qualitative sex/gender differences in development and treatment of these co-occurring disorders across a range of biological and psychological factors. The authors identified gaps in the literature and emphasized the important of sex and gender in the development and treatment of OUD and chronic pain.

The special issue underscores the urgent need for effective pain management strategies for individuals with OUD. While significant progress has been made, further research is necessary to develop and validate innovative approaches to treat these conditions. Repeated and rigorous evaluation of pain and OUD outcomes (e.g., opioid use) is an important first step that can be immediately integrated into OUD clinical care. Addressing the impact of individual differences (e.g., sex/gender) is also crucial to ensure that treatments are tailored to the specific needs of individuals presenting for care. By advancing our understanding of the relationship between OUD and chronic pain, we can develop novel treatments and improve outcomes for individuals suffering from these debilitating conditions.

The authors disclose no conflicts of interest. J.P.D. has been supported in clinical trials by Jazz Pharmaceuticals, specifically through medication provisions. Additionally, J.P.D. has been a compensated consultant for Boehriger Inhelheim.

[Correction added on 7 October 2024, after first online publication: Liu et al. 2024 has been added as reference number 8, and the subsequent references and their citations have been renumbered accordingly in this version.]