Pharmacological treatment of pain among persons with opioid addiction: A systematic review and meta-analysis with implications for drug development

Seven-membered N-heterocycles as approved drugs and promising leads in medicinal chemistry as well as the metal-free domino access to their scaffolds

Azepanes or azepines are structural motifs of many drugs, drug candidates and evaluated lead compounds. Even though compounds having N-heterocyclic 7-membered rings are often found in nature (e.g. alkaloids), the natural compounds of this group are rather rare as approved therapeutics. Thus, recently studied and approved azepane or azepine-congeners predominantly consist of semi-synthetically or synthetically-obtained scaffolds. In this review a comparison of approved drugs and recently investigated leads was proposed taking into regard their structural aspects (stereochemistry), biological activities, pharmacokinetic properties and confirmed molecular targets. The 7-membered N-heterocycles reveal a wide range of biological activities, not only against CNS diseases, but also as e.g. antibacterial, anticancer, antiviral, antiparasitic and against allergy agents. As most of the approved or investigated potential drugs or lead structures, belonging to 7-membered N-heterocycles, are synthetic scaffolds, this report also reveals different and efficient metal-free cascade approaches useful to synthesize both simple azepane or azepine-containing congeners and those of oligocyclic structures. Stereochemistry of azepane/azepine fused systems, in view of biological data and binding with the targets, is discussed. Apart from the approved drugs, we compare advances in SAR studies of 7-membered N-heterocycles (mainly from 2018 to 2023), whereas the related synthetic part concerning various domino strategies is focused on the last ten years.

The current state of knowledge on care for co-occurring chronic pain and opioid use disorder: A scoping review

BACKGROUND AND AIMS

Opioid use disorder often co-occurs with chronic pain but assessment and treatment of these co-occurring disorders is complex. This review aims to identify current treatments and delivery models for co-occurring chronic pain and opioid use disorder (OUD) documented in the scientific literature.

DESIGN

Scoping review.

METHODS

The review was conducted in six databases in June 2022 (no time limit): CINAHL, PsycINFO, Web of Science, Cochrane, PubMed and Embase. The PRISMA-ScR checklist was used to guide reporting.

RESULTS

Forty-seven publications addressing the issue of co-occurring chronic pain and OUD management were included. Randomized controlled trials provide evidence for the effectiveness of opioid agonist treatments (OAT) such as methadone or buprenorphine/naloxone, as well as for combining OAT with Mindfulness-Oriented Recovery Enhancement or cognitive behavioural therapy. A number of other pharmacological treatments (opioid and nonopioid), nonpharmacological treatments (e.g. physiotherapy) and service delivery models (e.g. simultaneous treatment of comorbidities, interdisciplinary and interprofessional collaboration) are also underlined. In most cases, authors recommend a combination of strategies to meet patient needs.

CONCLUSIONS

The scoping review reveals gaps in evidence-based knowledge to effectively care for co-occurring chronic pain and OUD, but several experts recommend the uptake of known 'best' practices such as integrated treatment of the multiple biopsychosocial dimensions of the co-occurring disorders as well as collaborative interdisciplinary work.

CLINICAL RELEVANCE

Improving services is dependent on alleviating barriers such as working in silos, the costs associated with nonpharmacological treatments, and the double stigma associated with pain in people with a substance use disorder.

Assessing pain in persons with opioid use disorder: Approaches, techniques and special considerations

Pain and opioid use disorder (OUD) are inextricably linked, as the former can be a risk factor for the development of the latter, and over a third of persons with OUD suffer concomitant chronic pain. Assessing pain among people with OUD is challenging, because ongoing opioid use brings changes in pain responses and most pain assessment tools have not been validated for this population. In this narrative review, we discuss the fundamentals of pain assessment for populations with OUD. First, we describe the biological, psychological and social aspects of the pain experience among people with OUD, as well as how opioid-related phenomena may contribute to the pain experience in this population. We then review methods to assess pain, including (1) traditional self-reported methods, such visual analogue scales and structured questionnaires; (2) behavioural observations and physiological indicators; (3) and laboratory-based approaches, such as quantitative sensory testing. These methods are considered from a perspective that encompasses both pain and OUD. Finally, we discuss strategies for improving pain assessment in persons with OUD and implications for future research, including educational strategies for multidisciplinary teams. We highlight the substantial gaps that persist in this literature, particularly regarding the applicability of current pain assessment methods to persons with OUD, as well as the generalizability of the existing results from adjacent populations on chronic opioid therapy but without OUD. As research linking pain and OUD evolves, considering the needs of diverse populations with complex psychosocial backgrounds, clinicians will be better equipped to reduce these gaps.

Delta-9-tetrahydrocannabinol modulates pain sensitivity among persons receiving opioid agonist therapy for opioid use disorder: A within-subject, randomized, placebo-controlled laboratory study

The opioid and cannabinoid receptor systems are inextricably linked-overlapping at the anatomical, functional and behavioural levels. Preclinical studies have reported that cannabinoid and opioid agonists produce synergistic antinociceptive effects. Still, there are no experimental data on the effects of cannabinoid agonists among humans who receive opioid agonist therapies for opioid use disorder (OUD). We conducted an experimental study to investigate the acute effects of the delta-9-tetrahydrocannabinol (THC) among persons receiving methadone therapy for OUD. Using a within-subject, crossover, human laboratory design, 25 persons on methadone therapy for OUD (24% women) were randomly assigned to receive single oral doses of THC (10 or 20 mg, administered as dronabinol) or placebo, during three separate 5-h test sessions. Measures of experimental and self-reported pain sensitivity, abuse potential, cognitive performance and physiological effects were collected. Mixed-effects models examined the main effects of THC dose and interactions between THC (10 and 20 mg) and methadone doses (low-dose methadone defined as <90 mg/day; high dose defined as >90 mg/day). Results demonstrated that, for self-reported rather than experimental pain sensitivity measures, 10 mg THC provided greater relief than 20 mg THC, with no substantial evidence of abuse potential, and inconsistent dose-dependent cognitive adverse effects. There was no indication of any interaction between THC and methadone doses. Collectively, these results provide valuable insights for future studies aiming to evaluate the risk-benefit profile of cannabinoids to relieve pain among individuals receiving opioid agonist therapy for OUD, a timely endeavour amidst the opioid crisis.

Prescription Opioid Misuse in Older Adult Surgical Patients: Epidemiology, Prevention, and Clinical Implications

ABSTRACT

The United States and many other developed nations are in the midst of an opioid crisis, with consequent pressure on prescribers to limit opioid prescribing and reduce prescription opioid misuse. This review addresses prescription opioid misuse for older adult surgical populations. We outline the epidemiology and risk factors for persistent opioid use and misuse in older adults undergoing surgery. We also address screening tools and prescription opioid misuse prevention among vulnerable older adult surgical patients (e.g., older adults with a history of an opioid use disorder), followed by clinical management and patient education recommendations. A significant plurality of older adults engaged in prescription opioid misuse obtain opioid medication for misuse from health providers. Thus, nurses can play a critical role in identifying those older adults at a higher risk for misuse and deliver quality care while balancing the need for adequate pain management against the risk for prescription opioid misuse.

Opioid-induced analgesia among persons with opioid use disorder receiving methadone or buprenorphine: A systematic review of experimental pain studies

BACKGROUND

Treating acute pain among persons with opioid use disorder (OUD) on opioid agonist therapy (OAT) is complex, and the therapeutic benefits of opioids remain unclear when weighted against their abuse potential and respiratory depressant effects.

METHODS

We conducted a systematic review of experimental pain studies examining opioid-induced analgesia among persons with OUD on OAT. We searched multiple databases from inception to July 30, 2021. Study quality was assessed by previously established validity measures.

RESULTS

Nine studies were identified, with a total of 225 participants, of whom 63% were male, and 37% were female. Six studies included methadone-maintained persons with OUD; four studies included buprenorphine-maintained persons with OUD; and three studies included healthy persons as comparison groups. Either additional doses of OAT or other opioids - morphine, oxycodone, hydromorphone, or remifentanil - were administered. In seven studies, persons with OUD on OAT did not experience analgesia, despite receiving opioid doses up to 20 times greater than those clinically used to treat severe pain among the opioid naïve. Conversely, in two studies, high-potency opioids did produce analgesia, albeit with greater abuse potential. Notably, persons with OUD on OAT remained vulnerable to respiratory depression.

CONCLUSIONS

Although persons with OUD on OAT can derive analgesic effects from opioids, high-potency compounds may be required to achieve clinically significant pain relief. Further, persons with OUD on OAT may remain vulnerable to opioid-induced abuse potential and respiratory depression. Together, these finding have clinical, methodological, and mechanistic implications for the treatment of acute pain in the context of OAT.