Chronic pain and opiates: a call for moderation

Noncoding RNAs: Novel Targets for Opioid Tolerance

As a global health problem, chronic pain is one of the leading causes of disability, and it imposes a huge economic and public health burden on families and society. Opioids represent the cornerstone of analgesic drugs. However, opioid tolerance caused by long-term application of opioids is a major factor leading to drug withdrawal, serious side effects caused by dose increases, and even the death of patients, placing an increasing burden on individuals, medicine, and society. Despite efforts to develop methods to prevent and treat opioid tolerance, no effective treatment has yet been found. Therefore, understanding the mechanism underlying opioid tolerance is crucial for finding new prevention and treatment strategies. Noncoding RNAs (ncRNAs) are important parts of mammalian gene transcriptomes, and there are thousands of unique noncoding RNA sequences in cells. With the rapid development of high-throughput genome technology, research on ncRNAs has become a hot topic in biomedical research. In recent years, studies have shown that ncRNAs mediate physiological and pathological processes, including chromatin remodeling, transcription, posttranscriptional modification and signal transduction, which are key regulators of physiological processes in developmental and disease environments and have become biomarkers and potential therapeutic targets for various diseases. An increasing number of studies have found that ncRNAs are closely related to the development of opioid tolerance. In this review, we have summarized the evidence that ncRNAs play an important role in opioid tolerance and that ncRNAs may be novel targets for opioid tolerance.

Retracted Article: Upregulation of miR-26b alleviates morphine tolerance by inhibiting BDNF via Wnt/β-catenin pathway in rats

Background: Morphine is a commonly used analgesic drug. However, long-term use of morphine will cause tolerance which limits its clinical application in pain treatment. MicroRNAs (miRNAs) have been reported to be involved in the morphine tolerance, but the underlying mechanism is still poorly understood. Methods: Tail flick test was used to measure the maximum possible effect (MPE). Quantitative real-time PCR was employed to detect miR-26b, BDNF, and Wnt5a expression in rat dorsal root ganglia (DRG). Luciferase report assay was introduced to verify the binding relationship between miR-26b and Wnt5a. BDNF, Wnt5a and β-catenin protein level were tested by western blotting. Results: MiR-26b was down-regulated during the development of morphine tolerance while BDNF was upregulated. Overexpression of miR-26b or BDNF inhibition alleviated morphine tolerance. Wnt5a was directly targeted and inhibited by miR-26b via binding to the 3'-UTR of Wnt5a. The Wnt/β-catenin pathway was active in morphine tolerant rats. Moreover, overexpression of Wnt5a could partially enhance miR-26 mimic-mediated morphine tolerance, while a Wnt5a inhibitor could attenuate the tolerance. Conclusion: The present study demonstrated that miR-26b overexpression alleviated morphine tolerance by inhibiting BDNF via the Wnt/β-catenin pathway in rats, highlighting a promising target for the treatment of morphine tolerance.

Interdisciplinary team-based care for patients with chronic pain on long-term opioid treatment in primary care (PPACT) - Protocol for a pragmatic cluster randomized trial

BACKGROUND

Chronic pain is one of the most common, disabling, and expensive public health problems in the United States. Interdisciplinary pain management treatments that employ behavioral approaches have been successful in helping patients with chronic pain reduce symptoms and regain functioning. However, most patients lack access to such treatments. We are conducting a pragmatic clinical trial to test the hypothesis that patients who receive an interdisciplinary biopsychosocial intervention, the Pain Program for Active Coping and Training (PPACT), at their primary care clinic will have a greater reduction in pain impact in the year following than patients receiving usual care.

METHODS/DESIGN

This is an effectiveness-implementation hybrid pragmatic clinical trial in which we randomize clusters of primary care providers and their patients with chronic pain who are on long-term opioid therapy to 1) receive an interdisciplinary behavioral intervention in conjunction with their current health care or 2) continue with current health care services. Our primary outcome is pain impact (a composite of pain intensity and pain-related interference) measured using the PEG, a validated three-item assessment. Secondary outcomes include pain-related disability, patient satisfaction, opioids dispensed and health care utilization. An economic evaluation assesses the resources and costs necessary to deliver the intervention and its cost-effectiveness compared with usual care. A formative evaluation employs mixed methods to understand the context for implementation in the participating health care systems.

DISCUSSION

This trial will inform the feasibility of implementing interdisciplinary behavioral approaches to pain management in the primary care setting, potentially providing a more effective, safer, and more satisfactory alternative to opioid-based chronic pain treatment. Clinical Trials Registration Number: NCT02113592.

miR-365 targets β-arrestin 2 to reverse morphine tolerance in rats

Morphine tolerance is a challenging clinical problem that limits its clinical application in pain treatment. Non-coding microRNAs (miRNAs) modulate gene expression in a post transcriptional manner, and their dysregulation causes various diseases. However, the significance of miRNAs in morphine tolerance is still poorly understood. In the present study, we hypothesized that microRNA-365 (miR-365) is a key functional small RNA that reverses morphine tolerance through regulation of β-arrestin 2 in rats. Here, microarray analysis and quantitative real-time PCR showed that miR-365 was robustly decreased in the spinal cord after chronic morphine administration. In situ hybridization and immunochemistry double staining showed that miR-365 was expressed in neurons of the spinal cord. We identified β-arrestin 2 as the target gene of miR-365 by bioinformatics analysis and luciferase reporter assay. The data showed that overexpression of miR-365 prevented and reversed established morphine tolerance, and increased expression of miR-365 caused a decrease in expression of β-arrestin 2 protein. miR-365 downregulation is involved in the development and maintenance of morphine tolerance through regulation of β-arrestin 2, and miR-365 upregulation provides a promising and novel approach for treatment of morphine tolerance.

Is Admission to the Intensive Care Unit Associated With Chronic Opioid Use? A 4-Year Follow-Up of Intensive Care Unit Survivors

PURPOSE

To describe opioid use before and after intensive care unit (ICU) admission and to identify factors associated with chronic opioid use upto 4 years after ICU discharge.

METHODS

Retrospective review of adult patients admitted to the ICU at a tertiary care center between January 1, 2005, to December 31, 2008. We defined "nonuser," "intermittent," and "chronic" opioid status by abstinence, use in <70%, and >70% of days for a given time period, respectively. We assessed opioid use at 3 months prior to ICU admission, at discharge, and annually for upto 4 years following ICU discharge.

RESULTS

A total of 2595 ICU patients were included for surgical (48.6%), medical (38.4%), and undetermined (13%) indications. The study population included both elective (26.9%) and emergent (73.1%) admissions. Three months prior to ICU admission, 76.9% were nonusers, 16.9% used opioids intermittently, and 6.2% used opioids chronically. We found an increase in nonuser patients from 87.8% in the early post-ICU period to 95.6% at 48-month follow-up. Consequently, intermittent and chronic opioid use dropped to 8.6% and 3.6% at discharge and 2.6% and 1.8% at 48-month follow-up, respectively. Prolonged hospital length of stay was associated with chronic opioid use.

CONCLUSION

Admission to ICU and duration of ICU stay were not associated with chronic opioid use.

A primary care-based interdisciplinary team approach to the treatment of chronic pain utilizing a pragmatic clinical trials framework

Chronic pain affects at least 116 million adults in the USA and exacts a tremendous cost in suffering and lost productivity. While health systems offer specialized pain services, the primary care setting is where most patients seek and receive care for pain. Primary care-based treatment of chronic pain by interdisciplinary teams (including behavioral specialists, nurse case managers, physical therapists, and pharmacists) is one of the most effective approaches for improving outcomes and managing costs. To ensure robust integration of such services into sustainable health-care programs, evaluations must be conducted by researchers well versed in the methodologies of clinical trials, mixed methods and implementation research, bioinformatics, health services, and cost-effectiveness. Recent national health policy changes, in addition to the increasing recognition of the high prevalence and cost of chronic pain conditions, present a unique opportunity to shift the care paradigm for patients with chronic pain.

Let-7 microRNAs and Opioid Tolerance

This chapter will focus on the role of microRNAs (miRs) in regulating the actions of opioid drugs through the opioid receptors. Opioids, such as morphine, are analgesics that are used for treating many forms of acute and chronic pain. However, their chronic use is limited by undesirable effects such as opioid tolerance. The μ opioid receptor (MOR) is the primary receptor responsible for opioids' analgesia and antinociceptive tolerance. The long 3'-untranslated region (3'-UTR) of MOR mRNA is of great interest since this region may contain elements for the post-transcriptional regulation of receptor expression, such as altering the stability of mRNA, influencing translational efficiency, and controlling mRNA transport. MicroRNAs are small non-coding RNA molecules that exert their functions through base-pairing with partially complementary sequences in the 3'-UTR of target mRNAs, resulting in decreased polypeptide formation from those mRNAs. Since the discovery of the first miR, lin-4 in Caenorhabditis elegans, hundreds of miRs have been identified from humans to viruses, which have provided a crucial and pervasive layer of post-transcriptional gene regulation. The nervous system is a rich source of miR expression, with a diversity of miR functions in fundamental neurobiological processes including neuronal development, plasticity, metabolism, and apoptosis. Recently, the let-7 family of miRs is found to be a critical regulator of MOR function in opioid tolerance. Let-7 is the first identified human miR. Its family members are highly conserved across species in sequence and function. In the review, we will present a brief review of the opioid receptors, their regulation, and opioid tolerance as well as an overview of miRs and a perspective how miRs may interact with MOR and serve as a regulator of opioid tolerance.

Predictors of change in pain and physical functioning among post-menopausal women with recurrent pain conditions in the women's health initiative observational cohort

Pain complaints are commonly reported symptoms among postmenopausal women and can have significant effects on health-related quality of life. We sought to identify medical and psychosocial factors that predict changes in pain and overall physical functioning over a 3-year period among postmenopausal women with recurrent pain conditions. We examined data from postmenopausal women age 50 to 79 with recurrent pain conditions (low back pain, neck pain, headache or migraines, or joint pain or stiffness) over a 3-year period using the Women's Health Initiative Observational Study Cohort (N = 67,963). Multinomial logistic regression models controlling for demographic and clinical characteristics were used to identify baseline predictors of change in the SF-36 subscales for pain and physical functioning between baseline and 3-year follow-up. Body mass index (BMI) was associated with worsening of pain (OR [95% CI] 1.54 [1.45-1.63] for BMI ≥30) and physical functioning (1.83 [1.71-1.95] for BMI ≥30). A higher reported number of nonpain symptoms, higher medical comorbidity, and a positive screen for depression (1.13 [1.05-1.22] for worsened pain) were also associated with worsening of pain and physical functioning. Baseline prescription opioid use was also associated with lack of improvement in pain (OR .42, 95% CI .36-.49) and with worsened physical functioning (1.25 [1.04-1.51]).

PERSPECTIVE

This study presents prospective data on change in pain and physical functioning in postmenopausal women over a 3-year period. Our results suggest depression, nonpain physical symptoms, obesity, and possibly opioid treatment are associated with worse long-term pain outcomes in this population.

Negligible analgesic tolerance seen with extended release oxymorphone: a post hoc analysis of open-label longitudinal data

OBJECTIVE

To examine the development of analgesic tolerance in patients on oxymorphone extended-release (OxymER).

DESIGN

Post hoc analysis of data from a previously conducted prospective 1 year multi-center open-label extension study in which patients were able to titrate as needed.

PATIENTS

Sample of 153 hip and knee osteoarthritis (OA) subjects on OxymER. Primary analyses were limited to study completers (n = 62) due to the large amount of missing data for the noncompleters (n = 91).

OUTCOME MEASURES

Main outcome measures included OxymER doses (pill counts) and pain intensity ratings using a visual analog scale at monthly visits.

RESULTS

There were significant dose increases from weeks 1 to 2 and 2 to 6 (P < 0.05). Doses stabilized around week 6, suggesting the completion of what we defined as "titration." Both doses and pain ratings were stable when this titration phase was excluded from the analysis (P = 0.751; P = 0.056, respectively). Only 28% of the patients had any dose changes following this titration. While there was a significantly greater dose at week 52 compared with week 10 (P = 0.010), the increase in dose became insignificant after excluding four subjects who required two dose increases (P = 0.103).

CONCLUSIONS

The results showed that most of the titration/dose stabilization changes occurred within the first 10 weeks. A minority (28%) of subjects required dosage increases after this (defined) titration period. Pain reports stabilized statistically after 2 weeks. The findings of this post hoc analysis suggest a lack of opioid tolerance in the majority (72%) of these OA patients who completed this study following a defined titration period on OxymER.

SUMMARY

This post hoc analysis of oxymorphone ER consumption in osteoarthritis pain vs pain report showed that most dose changes occurred during an initial "titration period" as defined. Following this titration few subjects increased dose and analgesia remained stable. These findings suggest a lack of longitudinal opioid tolerance in the majority of those OA subjects who completed the trial.

Chronic opioid therapy and preventive services in rural primary care: an Oregon rural practice-based research network study

PURPOSE

For clinicians, using opioid therapy for chronic noncancer pain (CNCP) often gives rise to a conflict between treating their patients' pain and fears of addiction, diversion of medication, or legal action. Consequent stresses on clinical encounters might adversely affect some elements of clinical care. We evaluated a possible association between chronic opioid therapy (COT) for CNCP and receipt of various preventive services.

METHODS

We conducted a retrospective cohort study in 7 primary care clinics within the Oregon Rural Practice-based Research Network (ORPRN). Using medical records of 704 patients, aged 35 to 85 years, seen during a 3-year period, we compared the receipt of 4 preventive services between patients on COT for CNCP and patients not on chronic opioid therapy (non-COT). We used multivariate log-binomial regression analyses to estimate the relative risk of receipt of each preventive service.

RESULTS

After adjustment for plausible confounders, we found that patients using COT had a statistically significantly lower relative risk (RR) of receipt of cervical cancer screening (RR = 0.60; 95% confidence interval [CI], 0.47-0.76) and colorectal cancer screening (RR = 0.42; 95% CI, 0.22-0.80) when compared with non-COT patients. The RR was reduced, without statistical significance, for lipid screening (RR = 0.77; 95% CI, 0.54-1.10), and not notably reduced for smoking cessation counseling (RR = 0.95; 95% CI, 0.78-1.15).

CONCLUSIONS

Patients using COT for CNCP were less likely to receive some preventive services. Research is needed to better understand barriers to and improved methods for providing preventive services for these patients.

Understanding primary care physicians' treatment of chronic low back pain: the role of physician and practice factors

BACKGROUND

An increasing number of Operation Iraqi Freedom/Operation Enduring Freedom veterans experience chronic pain. Despite treatment guidelines, there is wide variation in physicians' approaches to pain treatment, and many physicians are unsure of the best treatment approach. Research has examined factors associated with opioid prescribing, but there is little information on physician characteristics that predict patterns of clinical responses to pain.

OBJECTIVES

To identify patterns in primary care physicians' treatment decisions for nonmalignant chronic pain, and identify physician and practice characteristics that predict treatment decision patterns.

METHODS

A national sample of 381 primary care physicians who responded to a mailed vignette involving a veteran with chronic low back pain (LBP) were categorized into latent classes by clinical actions taken to treat the pain. The associations between newly derived treatment patterns and physician and practice characteristics were examined with multivariate models.

RESULTS

Latent class analysis identified three treatment approaches: 1) Multimodal/Aggressive (14%); 2) Low Action (38%); and 3) Psychosocial/Non-Opioid (48%). In a multivariate model, treatment pattern was associated with demographic and personality factors; opioid-related attitudes, beliefs, and concerns; perceptions of the patient; availability of resources; and practice characteristics.

CONCLUSIONS

There may be distinct patterns in primary care physicians' responses to patients with chronic pain. Relatively few physicians use the multimodal approach endorsed by proponents of the biopsychosocial model of pain treatment. Several physician and practice characteristics predict patterns of clinical action.