Complex Persistent Opioid Dependence-an Opioid-induced Chronic Pain Syndrome

Risk of infections among persons treated with opioids for chronic pain: a systematic review and meta-analysis protocol

INTRODUCTION

Millions of persons with chronic pain across North America and Europe use opioids. While the immunosuppressive properties of opioids are associated with risks of infections, these outcomes could be mitigated through careful patient selection and monitoring practices when appropriate. It is important to recognise that some patients do benefit from a carefully tailored opioid therapy. Enough primary studies have been published to date regarding the role of opioids in potential immunosuppression presenting as an increased rate of infection acquisition, infectious complications and mortality. There is thus a critical need for a consensus in this area.

METHODS AND ANALYSIS

The methodology is based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, the MOOSE Guidelines for Meta-Analyses and Systematic Reviews of Observational Studies and the Cochrane Handbook for Systematic Reviews of Interventions. We plan to systematically search Ovid MEDLINE, CINAHL, PsycINFO, EMB Review, EMBASE, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials and Google Scholar databases from their inception date to December 2023. Full-text primary studies that report measurable outcomes in adults with chronic pain, all routes of opioid use, all types of infections and all settings will be included. We will identify a scope of reported infections and the evidence on the association of opioid use (including specific opioid, dosage, formulation and duration of use) with the risk of negative infectious outcomes. Opioid use-associated outcomes, comparing opioid use with another opioid or a non-opioid medication, will be reported. The meta-analysis will incorporate individual risk factors. If data are insufficient, the results will be synthesised narratively. Publication bias and confounding evaluation will be performed. The Grading of Recommendations Assessment, Development and Evaluation framework will be used.

ETHICS AND DISSEMINATION

Approval for the use of published data is not required. The results will be published, presented at conferences and discussed in deliberative dialogue groups.

PROSPERO REGISTRATION NUMBER

CRD42023402812.

The cell-permeant antioxidant D-thiol ester D-cysteine ethyl ester overcomes physical dependence to morphine in male Sprague Dawley rats

The ability of morphine to decrease cysteine transport into neurons by inhibition of excitatory amino acid transporter 3 (EAA3) may be a key molecular mechanism underlying the acquisition of physical and psychological dependence to morphine. This study examined whether co-administration of the cell-penetrant antioxidant D-thiol ester, D-cysteine ethyl ester (D-CYSee), with morphine, would diminish the development of physical dependence to morphine in male Sprague Dawley rats. Systemic administration of the opioid receptor antagonist, naloxone (NLX), elicited pronounced withdrawal signs (e.g., wet-dog shakes, jumps, rears, circling) in rats that received a subcutaneous depot of morphine (150 mg/kg, SC) for 36 h and continuous intravenous infusion of vehicle (20 μL/h, IV). The NLX-precipitated withdrawal signs were reduced in rats that received an infusion of D-CYSee, but not D-cysteine, (both at 20.8 μmol/kg/h, IV) for the full 36 h. NLX elicited pronounced withdrawal signs in rats treated for 48 h with morphine (150 mg/kg, SC), plus continuous infusion of vehicle (20 μL/h, IV) that began at the 36 h timepoint of morphine treatment. The NLX-precipitated withdrawal signs were reduced in rats that received a 12 h infusion of D-CYSee, but not D-cysteine, (both at 20.8 μmol/kg/h, IV) that began at the 36 h timepoint of morphine treatment. These findings suggest that D-CYSee may attenuate the development of physical dependence to morphine and reverse established dependence to the opioid in male Sprague Dawley rats. Alternatively, D-CYSee may simply suppress the processes responsible for NLX-precipitated withdrawal. Nonetheless, D-CYSee and analogues may be novel therapeutics for the treatment of opioid use disorders.

Problems with opioids - beyond misuse

The U.S. is grappling with an opioid epidemic, with millions of adults on long-term opioid therapy (LTOT). Although patients often report pain relief and improved daily function with opioids, research shows no significant differences in short-term outcomes between opioid and non-opioid users, as well as no long-term opioid benefits. This scoping review aims to identify lesser-known side effects of long-term opioid use and increase awareness of them, allowing healthcare providers and patients to better assess the risks and benefits of opioid use. Our data search from PubMed and Google Scholar used keywords related to opioids, chronic pain, hypogonadism, endocrinopathies, cancer progression, cardiovascular events, renovascular events, sleep disturbances, mood disorders and others, narrowing down to English-language full articles published from January 2018 to April 2023. This review emphasizes the probable serious adverse consequences of long-term opioid use on various body systems in patients with chronic pain. Given the lack of long-term benefits and significant adverse effects, our review underscores the critical need for healthcare providers to include these risks in discussions with patients when considering the long-term use of opioid therapy.

Patient Motivation to Reduce or Discontinue Opioids for Chronic Pain: Self-efficacy, Barriers, and Readiness to Change

OBJECTIVES

This study aimed to assess levels and predictors of self-efficacy and motivation to change opioid use among a community sample of patients using opioids for chronic pain, as well as patient-reported barriers to pursuing opioid discontinuation.

METHODS

Participants with a variety of chronic pain conditions, recruited from ResearchMatch.org , completed a battery of electronic, self-report questionnaires assessing demographic and medical characteristics, pain treatment history, and levels of readiness, self-efficacy, and other attitudes toward reducing or discontinuing opioid use. Multiple regression analyses and analyses of variance were conducted to examine predictors of readiness and self-efficacy to change opioid use. A modified version of rapid qualitative analysis was utilized to analyze themes in participant responses to an open-ended item about "what it would take" to consider opioid discontinuation.

RESULTS

The final sample included N=119 participants, the majority of whom were female (78.2%), Caucasian (77.3%), and well-educated. Readiness and self-efficacy to decrease or stop opioid use were fairly low on a 0 to 10 Visual Analog Scale (2.6 to 3.8) and significantly higher to decrease than stop ( P <0.01). Higher readiness to change was predicted by lower pain severity and higher concern about opioids, whereas higher self-efficacy was predicted by shorter pain duration. Results from the qualitative analyses revealed that the availability of an alternative treatment option was the most commonly cited requirement to consider opioid discontinuation.

DISCUSSION

Patients with lower pain severity, shorter duration of pain, and higher concerns about opioids may be a prime target from a motivation standpoint for interventions addressing opioid tapering and discontinuation.

L-cysteine ethyl ester prevents and reverses acquired physical dependence on morphine in male Sprague Dawley rats

The molecular mechanisms underlying the acquisition of addiction/dependence on morphine may result from the ability of the opioid to diminish the transport of L-cysteine into neurons via inhibition of excitatory amino acid transporter 3 (EAA3). The objective of this study was to determine whether the co-administration of the cell-penetrant L-thiol ester, L-cysteine ethyl ester (L-CYSee), would reduce physical dependence on morphine in male Sprague Dawley rats. Injection of the opioid-receptor antagonist, naloxone HCl (NLX; 1.5 mg/kg, IP), elicited pronounced withdrawal phenomena in rats which received a subcutaneous depot of morphine (150 mg/kg) for 36 h and were receiving a continuous infusion of saline (20 μL/h, IV) via osmotic minipumps for the same 36 h period. The withdrawal phenomena included wet-dog shakes, jumping, rearing, fore-paw licking, 360° circling, writhing, apneas, cardiovascular (pressor and tachycardia) responses, hypothermia, and body weight loss. NLX elicited substantially reduced withdrawal syndrome in rats that received an infusion of L-CYSee (20.8 μmol/kg/h, IV) for 36 h. NLX precipitated a marked withdrawal syndrome in rats that had received subcutaneous depots of morphine (150 mg/kg) for 48 h) and a co-infusion of vehicle. However, the NLX-precipitated withdrawal signs were markedly reduced in morphine (150 mg/kg for 48 h)-treated rats that began receiving an infusion of L-CYSee (20.8 μmol/kg/h, IV) at 36 h. In similar studies to those described previously, neither L-cysteine nor L-serine ethyl ester (both at 20.8 μmol/kg/h, IV) mimicked the effects of L-CYSee. This study demonstrates that 1) L-CYSee attenuates the development of physical dependence on morphine in male rats and 2) prior administration of L-CYSee reverses morphine dependence, most likely by intracellular actions within the brain. The lack of the effect of L-serine ethyl ester (oxygen atom instead of sulfur atom) strongly implicates thiol biochemistry in the efficacy of L-CYSee. Accordingly, L-CYSee and analogs may be a novel class of therapeutics that ameliorate the development of physical dependence on opioids in humans.

Preclinical characterization of the efficacy and safety of biologic N-001 as a novel pain analgesic for post-operative acute pain treatment

Inhibition of actin remodeling in nerves modulates action potential propagation and therefore could be used to treat acute pain. N-001 is a novel protein analgesic engineered from several C. Botulinum toxins. N-001 targets sensory neurons through ganglioside GT1b binding and ADP-ribosylates G-actin reducing actin remodeling. The activity and efficacy of N-001 was evaluated previously in vitro and in a mouse inflammatory pain model. To assess the relevance of N-001 for treatment of acute post-surgical pain, the current study evaluated the efficacy of N-001 in a mouse hind-paw incision model by peri-incisional and popliteal nerve block administration combined with mechanical testing. N-001 provided relief of pain-like behavior over 3 days and 2 days longer than the conventional long-acting anesthetic bupivacaine. Preclinical safety studies of N-001 indicated the drug produced no toxic or adverse immunological reactions over multiple doses in mice. These results combined with past targeting results encourage further investigation of N-001 as an analgesic for post-operative pain management with the potential to function as a differential nociceptor-specific nerve block.

Obstetric pain management for pregnant women with opioid use disorder: A qualitative and quantitative comparison of patient and provider perspectives (QUEST study)

BACKGROUND AND AIM

Patients with opioid use disorder (OUD) may experience inadequate pain management especially during childbirth. This study assessed and compared patient and provider perspectives on analgesia during and after delivery in women with OUD.

DESIGN

Prospective cohort, mixed method design including semi-structured interviews and structured surveys with pregnant or recently pregnant patients (n = 17) and provider (n = 15) groups.

SETTING

Prenatal clinics and hospital postpartum units.

PARTICIPANTS

Patients were pregnant women with OUD currently treated with methadone (n = 1) or buprenorphine (n = 16). Providers were obstetricians (n = 5), obstetric nurses (n = 5) and anesthesiologists (n = 5).

MEASUREMENTS

Validated questionnaires were completed by both groups; patient interviews were conducted during the third trimester and at 5 days post-delivery. Patient topics included pain management preferences, analgesia satisfaction and attitudes toward pain. Provider topics included labor and postpartum pain management perspectives. Interviews were independently coded and qualitatively analyzed for major themes.

FINDINGS

Five major themes emerged from patient interviews: (1) neuraxial blockade was endorsed for labor pain; (2) otherwise, limited pain control options were perceived; (3) no consensus around use of opioids for pain; (4) non-opioid options should be available; and (5) provider communication and health-care system issues act as barriers to adequate pain management. Provider perspective themes included the following: (1) unique challenges in pain management for patients with OUD; (2) confusion on how to plan for and make perinatal adjustments to medication for OUD; (3) discrepant views on use of opioids for pain management; (4) endorsement of non-pharmacological and non-opioid options; and (5) need for improved provider collaboration in developing pain management plans.

CONCLUSIONS

Patients with opioid use disorder and health-care providers prioritize pain management during and after childbirth, but have discrepant views on use of opioids and other pain management options. Inadequate care coordination and discrepancies in opinions need to be addressed both within care teams and between patients and providers. Clinicians would benefit from better evidence to guide clinical care of patients with OUD for patient-centered pain management.

Effect of music intervention on subjective scores, heart rate variability, and prefrontal hemodynamics in patients with chronic pain

INTRODUCTION

Music interventions have been proposed in recent years as a treatment for chronic pain. However, the mechanisms by which music relieves pain are unclear, and the effects of music intervention on physiological indicators in patients with chronic pain remain to be explored. This study aimed to explore whether a music intervention would have effects on subjective pain ratings, heart rate variability, and functional connectivity of the cerebral cortex in patients with chronic pain.

METHODS

A randomized controlled study was conducted on 37 pain patients aged 18-65 years, with the control group receiving usual care, and the intervention group receiving music intervention (8-150 Hz, 50-70 dB) for 30 min before bedtime for 7 days on top of usual care. Pain visual analog scale and heart rate variability were used as subjective and objective physiological indices before and after the music intervention, respectively. Changes in oxyhemoglobin and deoxyhemoglobin concentrations in the cerebral cortex were measured by functional near-infrared spectroscopy, and whole-brain correlation analysis was used to quantify the connectivity of prefrontal brain regions associated with the pain response.

RESULTS

Results showed that patients with chronic pain in the intervention group had significantly lower visual assessment scale scores, as well as significantly lower overall voluntary mobility during pain episodes, resulting in relatively higher vagal innervation compared to the control group. In addition, connections between the bilateral dorsolateral prefrontal cortex (BA9, BA46) and frontal areas (BA10) were significantly higher in the intervention group.

DISCUSSION

This study demonstrates the effectiveness of the combined application of music interventions with usual care in reducing pain levels in patients with chronic pain and provides insight into the pathological mechanisms of music interventions for analgesia, providing direction for new baseline indicators for quantitative clinical assessment of pain. The study was registered in the Chinese Clinical Trial Registry (No. ChiCTR2100052993).

CLINICAL TRIAL REGISTRATION

[https://www.chictr.org.cn/showproj.aspx?proj=136268], identifier [ChiCTR2100052993].