Management of opioid side effects in cancer-related and chronic noncancer pain: a systematic review

Reorganization of synaptic inputs to spinal dorsal horn neurons in neuropathic pain

Peripheral nerve injuries produce a variety of negative structural and functional changes in the central terminal sites of damaged axons, as well as the injured primary afferents. Such changes have been shown to be involved in the development of neuropathic pain, which includes abnormal pain sensations such as allodynia and hyperalgesia. Since the spinal dorsal horn is the first central site where signals from peripheral sensory nerves are transmitted and shows a variety of changes after peripheral nerve injury or chronic inflammation of peripheral tissues, it is one of the most important sites contributing to the mechanisms underlying the development of neuropathic pain. The functional disruption of inhibitory interneurons and glial activation in the spinal dorsal horn after peripheral nerve injury cause reorganization of neuronal circuits and changes in the excitability of second-order neurons. These events are involved in the development or maintenance of neuropathic pain. Here, we describe the interactions of primary afferents, interneurons, and glial cells that may cause reorganization of synaptic inputs to spinal dorsal horn neurons after peripheral nerve injury.

Predictive Factors of Opioid-Induced Nausea in Cancer Patients

Approximately 30% of patients experience nausea after initiation of opioid therapy, which can lead to poor quality of life. We aimed to identify risk factors for opioid-induced nausea at the initiation of opioid therapy by conducting a retrospective review of medical records of patients diagnosed by palliative care specialists with solid cancer and pain at the lesion site at Showa University Hospital between June 2005 and June 2011. The primary endpoint was the development of nausea grade ≥1 according to the Common Terminology Criteria for Adverse Events version 4.0 within 48 hours of initiation of opioid therapy. The median age of the 134 enrolled patients was 67.7 (range 28-95) years. Fifty-three percent were male and 44% had gastrointestinal cancer. Furthermore, 22.4% had opioid-induced nausea. Age (odds ratio (OR) 1.74; 95% confidence interval (CI), 1.13-2.69), edema (OR 5.83; 95% CI, 1.22-28.19), and gastrointestinal cancer (OR 2.61, 95% CI 1.07-6.36) were significantly associated with opioid-induced nausea. Prophylactic antiemetics were found to be ineffective.

In Vivo, In Vitro and In Silico Studies of the Hybrid Compound AA3266, an Opioid Agonist/NK1R Antagonist with Selective Cytotoxicity

AA3266 is a hybrid compound consisting of opioid receptor agonist and neurokinin-1 receptor (NK1R) antagonist pharmacophores. It was designed with the desire to have an analgesic molecule with improved properties and auxiliary anticancer activity. Previously, the compound was found to exhibit high affinity for μ- and δ-opioid receptors, while moderate binding to NK1R. In the presented contribution, we report on a deeper investigation of this hybrid. In vivo, we have established that AA3266 has potent antinociceptive activity in acute pain model, comparable to that of morphine. Desirably, with prolonged administration, our hybrid induces less tolerance than morphine does. AA3266, contrary to morphine, does not cause development of constipation, which is one of the main undesirable effects of opioid use. In vitro, we have confirmed relatively strong cytotoxic activity on a few selected cancer cell lines, similar to or greater than that of a reference NK1R antagonist, aprepitant. Importantly, our compound affects normal cells to smaller extent what makes our compound more selective against cancer cells. In silico methods, including molecular docking, molecular dynamics simulations and fragment molecular orbital calculations, have been used to investigate the interactions of AA3266 with MOR and NK1R. Insights from these will guide structural optimization of opioid/antitachykinin hybrid compounds.

Opioid Analgesics Adverse Effects: The Other Side of the Coin

BACKGROUND

Opioids are the cornerstone of the management of cancer pain. However, the development of adverse effects may compromise the opioid response. They include nausea and vomiting, constipation, drowsiness, sleep disorders, cognitive dysfunction, myoclonus, pruritus, dysuria, dependence and the development of aberrant behaviors, respiratory depression, and some endocrine responses.

METHODS

The goal of this paper is to identify the most common opioid-related adverse effects, their pathophysiology, and proposing the possible treatments. This narrative review will describe how these adverse effects may develop and how to prevent or to treat.

CONCLUSION

Intensity of adverse effects tend to decrease with continuous use. However, they may be persistent and may require symptomatic treatment or more complex treatment including alternative strategies for pain management.

Incidence and risk factors for postoperative nausea and vomiting in orthognathic surgery: a 10-year retrospective study

Objectives

Postoperative nausea and vomiting (PONV) is considered as one of the most incessant and anguishing factors for patients who have surgery under general anesthesia. The occurrence of PONV after orthognathic surgery can lead to dehydration, infection, bleeding at the surgical site, and patient discomfort, all of which leave a patient with a negative impression of anesthesia and surgery. The purpose of this study is to assess the incidence of PONV after orthognathic surgery and to correlate it with factors related to patient, anesthesia, and surgery.

Materials and Methods

A 10-year retrospective survey was done for patients who underwent orthognathic surgery between January 2008 and March 2018. The incidence of PONV was evaluated, correlations with factors related to patient, anesthesia, and surgery were studied, and the duration between the end of surgery and the occurrence of the first episode of PONV was tabulated.

Results

The medical records of 109 patients were screened, out of which 101 satisfied the inclusion criteria. Amongst these patients, 60 patients (59.4%) suffered from PONV. Patient’s sex, induction agent used, intravenous fluids administered intraoperatively, duration and type of surgery, and the presence of a nasogastric tube were seen to have a significant influence on precipitating PONV. It was noted that among the patients who suffered from PONV, 61.7% of them experienced it 48-96 hours after the end of surgery.

Conclusion

Despite the improved anesthetic equipments, drugs, and surgical techniques currently used, the incidence of PONV was high in our study. Certain factors that were seen to influence PONV in this study need to be considered in order to develop an efficacious protocol to reduce PONV in orthognathic surgeries.

Indian Society for Study of Pain, Cancer Pain Special Interest Group Guidelines on Pharmacological Management of Cancer Pain (Part II)

The Indian Society for Study of Pain (ISSP), Cancer Pain Special Interest Group (SIG) guidelines on pharmacological management of cancer pain in adults provide a structured, stepwise approach, which will help to improve the management of cancer pain and to provide the patients with a minimally acceptable quality of life. The guidelines have been developed based on the available literature and evidence, to suit the needs, patient population, and situations in India. A questionnaire, based on the key elements of each sub draft addressing certain inconclusive areas where evidence was lacking, was made available on the ISSP website and circulated by e-mail to all the ISSP and Indian Association of Palliative Care members. We recommend that analgesics for cancer pain management should follow the World Health Organization 3-step analgesic ladder appropriate for the severity of pain. The use of paracetamol and nonsteroidal anti-inflammatory drugs alone or in combination with opioids for mild-to-moderate pain should be used. For mild-to-moderate pain, weak opioids such as tramadol, tapentadol, and codeine can be given in combination with nonopioid analgesics. We recommend morphine as the opioid of the first choice for moderate-to-severe cancer pain. Sustained-release formulations can be started 12 hourly, once the effective 24 h dose with immediate-release morphine is established. Opioid switch or rotation should be considered if there is inadequate analgesia or intolerable side effects. For opioid-induced respiratory depression, μ receptor antagonists (e.g. naloxone) must be used promptly. Antidepressants and/or anticonvulsants should be used to treat neuropathic cancer pain, and the dose should be titrated according to the clinical response and side effects. External beam radiotherapy should be offered to all patients with painful metastatic bone pain. There is evidence on use of ketamine in cancer neuropathic pain, but with no beneficial effect, thus, it is not recommended.

Intrathecal administration of SRT1720 relieves bone cancer pain by inhibiting the CREB/CRTC1 signalling pathway

Bone cancer pain (BCP) caused by primary or metastatic bone tumours significantly interferes with the quality of life of patients. However, the relief of BCP remains a major challenge. Our previous study demonstrated that intrathecal administration of the Sirtuin 1 (SIRT1) activator SRT1720 attenuated BCP in a murine model. Nevertheless, the underlying mechanisms have not been fully clarified. Previous studies demonstrated that the activation of the cAMP response element binding (CREB) protein played a critical role in BCP. Furthermore, SIRT1 can also regulate the balance between glucose and lipid metabolism through CREB deacetylation. In this study, we measured the analgesic effects of different intrathecal doses of SRT1720 on BCP in a murine model and further examined whether SRT1720 attenuated BCP by suppressing CREB/CREB-regulated transcription coactivator 1 (CRTC1) signalling pathway. Our results demonstrated that the BCP mice developed significant mechanical allodynia and spontaneous flinching, which were accompanied by the upregulation of phospho-Ser133 CREB (p-CREB) and CRTC1 expression in the spinal cord. SRT1720 treatment produced a dose-dependent analgesic effect on the BCP mice and downregulated the expression of p-CREB and CRTC1. These results suggest that intrathecal administration of SRT1720 reverses BCP likely by inhibiting the CREB/CRTC1 signalling pathway.

Pharmacological characterization of 17-cyclopropylmethyl-3,14-dihydroxy-4,5-epoxy-6-[(3'-fluoro-4'-pyridyl)acetamido]morphinan (NFP) as a dual selective MOR/KOR ligand with potential applications in treating opioid use disorder

For thousands of years opioids have been the first-line treatment option for pain management. However, the tolerance and addiction potential of opioids limit their applications in clinic. NFP, a MOR/KOR dual-selective opioid antagonist, was identified as a ligand that significantly antagonized the antinociceptive effects of morphine with lesser withdrawal effects than naloxone at similar doses. To validate the potential application of NFP in opioid addiction treatment, a series of in vitro and in vivo assays were conducted to further characterize its pharmacological profile. In calcium mobilization assays and MOR internalization studies, NFP showed the apparent capacity to antagonize DAMGO-induced calcium flux and etorphine-induced MOR internalization. In contrast to the opioid agonists DAMGO and morphine, cells pretreated with NFP did not show apparent desensitization and down regulation of the MOR. Though in vitro bidirectional transport studies showed that NFP might be a P-gp substrate, in warm-water tail-withdrawal assays it was able to antagonize the antinociceptive effects of morphine indicating its potential central nervous system activity. Overall these results suggest that NFP is a promising dual selective opioid antagonist that may have the potential to be used therapeutically in opioid use disorder treatment.

Gender based differences, pharmacogenetics and adverse events in chronic pain management

Safety data in chronic non-cancer pain (CNCP) with long-term opioid therapy has been poorly studied and can be differently influenced by gender. Furthermore, pharmacogenetics (PGx) could possibly be used to tailor pain medication based on the individual's genetic background. The aim was to assess whether PGx applied to a pharmacovigilance system could help to improve a patient's security profile. A pharmacovigilance data recording system was conducted over 24 months, including genotyping of OPRM1 variants (opioid receptor, A118G) and COMT (enzyme that degrades catecholamines such as norepinephrine, G1947A). Pain intensity (visual analogue scale, VAS), morphine equivalent daily dose (MEDD), adverse events (AEs) and suspected adverse drug reactions (ADRs) were recorded and analysed by gender. The Ethics Committee approved the study and data were analysed with R 3.6.0 software. A total of 748 patients were recruited in the study (67% female, VAS 62 ± 29 mm, MEDD 119 ± 114 mg/day) reporting a median of 6 (3.5-9) AEs/patient. Women presented more nausea, headaches, insomnia, loss of appetite, weight change, depression and dizziness than men. Analysis by genotype demonstrated that PGx influenced the prevalence of vomiting and depression in men, dizziness in women and sexual dysfunction in both. Physicians notified 150 ADRs mostly in females (79%) related to nervous system disorders. PGx applied to a pharmacovigilance recording system provides important information to achieve a better knowledge about AEs in CNCP pharmacological therapy. OPRM1 and COMT polymorphisms were associated with AEs in CNCP patients that differed according to gender.

Use of the Rat Grimace Scale to Evaluate Visceral Pain in a Model of Chemotherapy-Induced Mucositis

Simple Summary

Mucositis is a painful and often debilitating condition associated with cancer treatment. Management of associated symptoms is an important clinical consideration. Animal models are used in mucositis research to model the condition in humans in order to develop novel therapeutic agents to relieve symptoms. Previous animal studies have focused on disease severity and outcomes, but often failed to measure pain. The rat grimace scale (RGS) is a validated observational measure used to gauge pain levels experienced by rats. The aim of this study was to assess the rat grimace scale in a rat model of mucositis, and to examine whether changes in clinical signs and anxiety reflected the grimace responses recorded. We also aimed to determine whether the responses were pain-specific by administering potent opioid painkilling agents. In the present study rat grimace scores did not change significantly between treatments. Development of reliable pain assessment methods in animal models is urgently required to improve model relevance to human clinical practice, in addition to safeguarding animal welfare.

Abstract

The rat grimace scale (RGS) is a measure of spontaneous pain that evaluates pain response. The ability to characterize pain through a non-invasive method has considerable utility for numerous animal models of disease, including mucositis, a painful, self-limiting side-effect of chemotherapy treatment. Preclinical studies investigating novel therapeutics for mucositis often focus on pathological outcomes and disease severity. These investigations fail to measure pain, in spite of reduction of pain being a key clinical therapeutic goal. This study assessed the utility of the RGS for pain assessment in a rat model of mucositis, and whether changes in disease activity index (DAI) and open field test (OFT) reflected the grimace responses recorded. Sixty tumor-bearing female Dark Agouti rats were injected with either saline or 5-Fluourouracil alone, or with co-administration of opioid analgesics. Whilst differences in DAI were observed between treatment groups, no difference in RGS scores or OFT were demonstrated. Significant increases in grimace scores were observed across time. However, whilst a statistically significant change may have been noted, the biological relevance is questionable in terms of practical usage, since an observer is only able to score whole numbers. Development of effective pain assessment methods in animal models is required to improve welfare, satisfy regulatory requirements, and increase translational validity of the model to human patients.

Intrathecal Therapy for Chronic Pain: A Review of Morphine and Ziconotide as Firstline Options

Objectives

To evaluate the evidence for morphine and ziconotide as firstline intrathecal (IT) analgesia agents for patients with chronic pain.

Methods

Medline was searched (through July 2017) for “ziconotide” or “morphine” AND “intrathecal” AND “chronic pain,” with results limited to studies in human populations.

Results

The literature supports the use of morphine (based primarily on noncontrolled, prospective, and retrospective studies) and ziconotide (based on randomized controlled trials and prospective observational studies) as first-choice IT therapies. The 2016 Polyanalgesic Consensus Conference (PACC) guidelines recommended both morphine and ziconotide as firstline IT monotherapy for localized and diffuse chronic pain of cancer-related and non–cancer-related etiologies; however, one consensus point emphasized ziconotide use, unless contraindicated, as firstline IT therapy in patients with chronic non–cancer-related pain. Initial IT therapy choice should take into consideration individual patient characteristics (e.g., pain location, response to previous therapies, comorbid medical conditions, psychiatric history). Trialing is recommended to assess medication efficacy and tolerability. For both morphine and ziconotide, the PACC guidelines recommend conservative initial dosing strategies. Due to its narrow therapeutic window, ziconotide requires careful dose titration. Ziconotide is contraindicated in patients with a history of psychosis. IT morphine administration may be associated with serious side effects (e.g., respiratory depression, catheter tip granuloma), require dose increases, and cause dependence over time.

Conclusion

Based on the available evidence, morphine and ziconotide are recommended as firstline IT monotherapy for cancer-related and non–cancer-related pain. The choice of first-in-pump therapy should take into consideration patient characteristics and the advantages and disadvantages of each medication.

Multimodal General Anesthesia: Theory and Practice

Balanced general anesthesia, the most common management strategy used in anesthesia care, entails the administration of different drugs together to create the anesthetic state. Anesthesiologists developed this approach to avoid sole reliance on ether for general anesthesia maintenance. Balanced general anesthesia uses less of each drug than if the drug were administered alone, thereby increasing the likelihood of its desired effects and reducing the likelihood of its side effects. To manage nociception intraoperatively and pain postoperatively, the current practice of balanced general anesthesia relies almost exclusively on opioids. While opioids are the most effective antinociceptive agents, they have undesirable side effects. Moreover, overreliance on opioids has contributed to the opioid epidemic in the United States. Spurred by concern of opioid overuse, balanced general anesthesia strategies are now using more agents to create the anesthetic state. Under these approaches, called “multimodal general anesthesia,” the additional drugs may include agents with specific central nervous system targets such as dexmedetomidine and ones with less specific targets, such as magnesium. It is postulated that use of more agents at smaller doses further maximizes desired effects while minimizing side effects. Although this approach appears to maximize the benefit-to-side effect ratio, no rational strategy has been provided for choosing the drug combinations. Nociception induced by surgery is the primary reason for placing a patient in a state of general anesthesia. Hence, any rational strategy should focus on nociception control intraoperatively and pain control postoperatively. In this Special Article, we review the anatomy and physiology of the nociceptive and arousal circuits, and the mechanisms through which commonly used anesthetics and anesthetic adjuncts act in these systems. We propose a rational strategy for multimodal general anesthesia predicated on choosing a combination of agents that act at different targets in the nociceptive system to control nociception intraoperatively and pain postoperatively. Because these agents also decrease arousal, the doses of hypnotics and/or inhaled ethers needed to control unconsciousness are reduced. Effective use of this strategy requires simultaneous monitoring of antinociception and level of unconsciousness. We illustrate the application of this strategy by summarizing anesthetic management for 4 representative surgeries.

Adult Cancer Pain, Version 3.2019, NCCN Clinical Practice Guidelines in Oncology

In recent years, the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Adult Cancer Pain have undergone substantial revisions focusing on the appropriate and safe prescription of opioid analgesics, optimization of nonopioid analgesics and adjuvant medications, and integration of nonpharmacologic methods of cancer pain management. This selection highlights some of these changes, covering topics on management of adult cancer pain including pharmacologic interventions, nonpharmacologic interventions, and treatment of specific cancer pain syndromes. The complete version of the NCCN Guidelines for Adult Cancer Pain addresses additional aspects of this topic, including pathophysiologic classification of cancer pain syndromes, comprehensive pain assessment, management of pain crisis, ongoing care for cancer pain, pain in cancer survivors, and specialty consultations.

Balancing opioid analgesia with the risk of nonmedical opioid use in patients with cancer

The current opioid crisis has brought renewed attention and scrutiny to opioid prescriptions. When patients receiving opioid therapy for pain engage in nonmedical opioid use (NMOU) or diversion, untoward consequences can occur. New evidence suggests that patients with cancer might be at a higher risk of NMOU than was previously thought, but clinical evidence still supports the use of opioid analgesics as the gold standard to treat cancer-related pain, creating a dilemma in patient management. Clinicians are encouraged to adopt a universal precautions approach to patients with cancer receiving opioids, which includes screening all patients; discussing the risks, benefits, adverse effects and alternatives of opioid therapy; and providing education on safe use, storage and disposal. Use of urine drug tests, prescription drug monitoring programmes and close observation of behaviours related to opioid use help to ensure treatment adherence, detect NMOU and support therapeutic decision-making. These measures can optimize the risk-benefit ratio while supporting safe opioid use. In this Review, we examine the role of opioids in cancer pain, the risk of substance use disorder and methods to achieve the right balance between the two in order to ensure safe opioid use.

SIRT1 Activation Attenuates Bone Cancer Pain by Inhibiting mGluR1/5

Bone cancer pain (BCP), which is induced by primary or metastatic bone cancer, remains a clinically challenging problem due to the poor understanding of its mechanisms. Sirtuin 1 (SIRT1) plays an important role in various pain models. Intrathecal administration of SRT1720, a SIRT1 activator, attenuates BCP in a rat model. However, the expression and activity of SIRT1 during the development and maintenance of BCP remain unknown. Furthermore, the underlying mechanism of SIRT1 in BCP remains ambiguous. In this study, we detected the time course of SIRT1 expression and activity in the spinal cord of mice with BCP and examined whether SRT1720 alleviated BCP by inhibiting metabotropic glutamatergic receptor (mGluR) 1/5 expression. In addition, we downregulated spinal SIRT1 expression in normal mice through an intrathecal injection of AAV-SIRT1-shRNA and then assessed pain behavior and mGluR1/5 expression. Mice with BCP developed significant mechanical allodynia and spontaneous flinching, accompanied by decreased levels of the SIRT1 protein, mRNA, and activity in the spinal cord. The SRT1720 treatment produced an analgesic effect on tumor-bearing mice and decreased the spinal levels of the mGluR1/5 protein and mRNA. In contrast, the AAV-SIRT1-shRNA treatment induced pain behavior in normal mice and increased the spinal levels of the mGluR1/5 protein and mRNA. The results suggested a critical role for SIRT1 in the development and maintenance of BCP and further indicated that activation of SIRT1 in the spinal cord by SRT1720 functionally reverses BCP in mice by inhibiting mGluR1/5.

Dexmedetomidine Use in a Case of Severe Cancer Pain

A 58-year-old male with chronic pancreatitis was seen by the palliative care service for pain and agitation related to a recent diagnosis of disseminated abdominal cancer. Increasing symptom burden, including pain and nausea, in the face of escalating doses of multiple opioid and sedative medications resulted in the addition of dexmedetomidine to successfully control his symptoms. Visceral sensitization related to his chronic pancreatitis likely increased his pain perception and required a multimodal approach to control his symptoms.

Intrathecal morphine combined with ropivacaine induces spinal myoclonus in cancer patients with an implanted intrathecal drug delivery system: Three case reports

RATIONALE

Although intrathecal opioid infusion has been used for decades for the treatment of severe pain, myoclonus as one of the complications of this therapeutic modality is now beginning to be recognized more.

PATIENTS CONCERNS

Here, we report three patients who developed myoclonus after dose adjustment in intrathecal drug delivery system for the treatment of refractory cancer pain.

DIAGNOSIS

Spinal myoclonus is a sudden, brief, shock-like muscle contractions originating from the central nervous system. In our cases, it occurred after opioid administration via intrathecal delivery system with no abnormality found in laboratory or imaging examinations.

INTERVENTIONS

Spinal myoclonus can be treated effectively by reducing the dose or infusion rate as described in case 1, or changing from an intrathecal to systemic administration in case 2, or correcting infusion and bolus parameters mistakes in case 3.

OUTCOMES

All patients recovered quickly after stopping or decreasing the intrathecal drug infusion.

LESSONS

Prevention is more important than treatment as for spinal myoclonus. Pain management teams should be aware of this distressing complication. Dose of intrathecal drugs should not exceed the recommended maximal daily doses by guidelines and patient education is important for successful intrathecal analgesic therapy.

The δ-opioid receptor positive allosteric modulator BMS 986187 is a G-protein-biased allosteric agonist

BACKGROUND AND PURPOSE

The δ-opioid receptor is an emerging target for the management of chronic pain and depression. Biased signalling, the preferential activation of one signalling pathway over another downstream of δ-receptors, may generate better therapeutic profiles. BMS 986187 is a positive allosteric modulator of δ-receptors. Here, we ask if BMS 986187 can directly activate the receptor from an allosteric site, without an orthosteric ligand, and if a signalling bias is generated.

EXPERIMENTAL APPROACH

We used several clonal cell lines expressing δ-receptors, to assess effects of BMS 986187 on events downstream of δ-receptors by measuring G-protein activation, β-arrestin 2 recruitment, receptor phosphorylation, loss of surface receptor expression, ERK1/ERK2 phosphorylation, and receptor desensitization.

KEY RESULTS

BMS 986187 is a G protein biased allosteric agonist, relative to β-arrestin 2 recruitment. Despite showing direct and potent G protein activation, BMS 986187 has a low potency to recruit β-arrestin 2. This appears to reflect the inability of BMS 986187 to elicit any significant receptor phosphorylation, consistent with low receptor internalization and a slower onset of desensitization, compared with the full agonist SNC80.

CONCLUSIONS AND IMPLICATIONS

This is the first evidence of biased agonism mediated through direct binding to an allosteric site on an opioid receptor, without a ligand at the orthosteric site. Our data suggest that agonists targeting δ-receptors, or indeed any GPCR, through allosteric sites may be a novel way to promote signalling bias and thereby potentially produce a more specific pharmacology than can be observed by activation via the orthosteric site.

A parallel randomized controlled trial examining the effects of rhythmic sensory stimulation on fibromyalgia symptoms

This double-blind, two-arm parallel randomized controlled trial investigated the effects of gamma-frequency rhythmic sensory stimulation on fibromyalgia. We were interested in whether rhythmic sensory stimulation would promote significant changes in fibromyalgia and associated symptoms, and whether treatment effects would differ between two distinct treatment parameters. Fifty patients with a formal diagnosis of fibromyalgia were randomly assigned to two test groups. One group received vibrotactile stimulation from a continuous sine wave single-frequency stimulation (40 Hz) for 30 minutes, five days per week, over five weeks, concomitant with usual care. The second group completed the same treatment protocol but received a different stimulation, consisting of random and intermittent complex wave gamma-range vibrotactile stimulation. Fibromyalgia symptoms, pain severity and interference, depression symptoms, quality of life and sleep quality were assessed at baseline and post-intervention. Results indicated that there were statistically significant changes from baseline to post-treatment in measures of fibromyalgia symptom severity, pain interference, depression, and sleep quality. However, treatment outcomes did not differ significantly between groups. These findings provide preliminary evidence that gamma-frequency rhythmic vibroacoustic stimulation may decrease fibromyalgia symptoms and ease associated comorbidities, opening new avenues for further investigation of the effects of rhythmic sensory stimulation on chronic pain conditions.

Health benefits of an adverse events reporting system for chronic pain patients using long-term opioids

BACKGROUND

Safety data from long-term opioid therapy in the real world has been poorly studied in chronic non-cancer pain (CNCP). The aim was to design a pharmacovigilance data recording system and assess whether participation in this recording system improves pain management, enhancing patient's health status.

METHODS

A pharmacovigilance data recording system was conducted during 24 months. Data were self-reported by patients (pain, adverse events [AEs] and healthcare resources use) and physicians (morphine equivalent daily dose [MEDD] prescribed and suspected adverse drug reaction [ADRs]). Outcomes from patients with (case) or without (controls) suspected ADRs and cases follow-up were also compared with Spanish Pharmacovigilance System data.

RESULTS

A total of 753 patients were recruited in 897 visits. Fentanyl and tramadol were the most prescribed opioids, 89% with concomitant drugs, pregabalin being the one with the most potential drug interactions. Cases presented significantly higher pain intensity (VAS 67 ± 26 vs 59 ± 30 mm, P < 0.05), number of AEs (8 ± 6 vs 5 ± 3 AEs/patient, P < 0.01), polypharmacy related to pain (65% vs 34%, P < 0.01) and MEDD (139 ± 130 vs 106 ± 99 mg/d, P < 0.01) than controls. Furthermore, cases presented significant higher changes in pharmacological pain therapy due to pain, unplanned emergency visits and hospital admission than controls. Physicians notified 168 suspected ADRs mostly related to neurological or psychiatric events and 8% of them were previously unknown.

CONCLUSIONS

This data recording system provided important information to achieve a better control of CNCP pharmacological pain therapy, improving patient's health status and reducing costs to the Health System.

An update on the safety of prescribing opioids in pediatrics

INTRODUCTION

The opioid abuse epidemic and its toll on the adolescent population have heightened awareness for safer opioid prescribing practices in pediatric pain management. Opioids remain the mainstay of therapy for severe pain, although there is an emphasis on multimodal therapy. Areas covered: In this update, the authors present information on parenteral/oral opioids commonly used in pediatrics. Recommendations for opioid use in special circumstances including neonates and developmental pharmacokinetic concerns are discussed. Due to noticeable interindividual variability, pharmacogenomics may be important for tailoring pain regimens. In particular, the role of CYP2D6 phenotypes on opioid selection/dosing and clinical implications are discussed. A summary of adverse effects and opioid safety data, and the role of regulations, risk assessment, Centers for Disease Control and Prevention guidelines, follow-up, and monitoring for compliance in opioid prescribing, are detailed. Expert opinion: 'One size does not fit all' describes the need for public policies focused on pediatric pain and opioid use, as children are not 'little adults.' Clinical trials to evaluate pharmacokinetics-pharmacodynamics of opioids are currently lacking. Development of novel biased opioid agonists, clinical integration of genetics in informed decision-making, and emphasis on top-down approaches to pain management will be key to decrease opioid reliance.

Design, Synthesis, and Biological Evaluation of the Third Generation 17-Cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6β-[(4'-pyridyl)carboxamido]morphinan (NAP) Derivatives as μ/κ Opioid Receptor Dual Selective Ligands

μ opioid receptor (MOR) agonists have been widely applied for treating moderate to severe pain. However, numerous adverse effects have been associated with their application, including opioid-induced constipation (OIC), respiratory depression, and addiction. On the basis of previous work in our laboratory, NAP, a 6β- N-4'-pyridyl substituted naltrexamine derivative, was identified as a peripheral MOR antagonist that may be used to treat OIC. To further explore its structure-activity relationship, a new series of NAP derivatives were designed, synthesized, and biologically evaluated. Among these derivatives, NFP and NYP significantly antagonized the antinociception effect of morphine. Whereas NAP acted mainly peripherally, its derivatives NFP and NYP actually can act centrally. Furthermore, NFP produced significantly lesser withdrawal symptoms than naloxone at similar doses. These results suggest that NFP has the potential to be a lead compound to treat opioid abuse and addiction.

Methylation Products of 6β- N-Heterocyclic Substituted Naltrexamine Derivatives as Potential Peripheral Opioid Receptor Modulators

Two 6β- N-heterocyclic naltrexamine derivatives, NAP and NMP, have been identified as peripherally selective mu opioid receptor (MOR) antagonists. To further enhance the peripheral selectivity of both compounds, the 17-amino group and the nitrogen atom of the pyridine ring in both NAP and NMP were methylated to obtain dMNAP and dMNMP, respectively. Compared with NAP and NMP, the binding affinities of dMNAP and dMNMP shifted to MOR and KOR (kappa opioid receptor) dual selective and they acted as moderate efficacy partial agonists. The results from radioligand binding studies were further confirmed by molecular docking studies. In vivo studies demonstrated that dMNAP and dMNMP did not produce antinociception nor did they antagonize morphine's antinociceptive activity, indicating that these compounds did not act on the central nervous system. Meanwhile, both dMNAP and dMNMP significantly slowed down fecal excretion, which indicated that they were peripherally acting opioid receptor agonists. All together, these results suggested that dMNAP and dMNMP acted as peripheral mu/kappa opioid receptor modulators and may be applicable in the treatment of diarrhea in patients with bowel dysfunction.

Effects of chronic fentanyl administration on behavioral characteristics of mice

Background

Fentanyl, a synthetic opioid categorized as a narcotic analgesic, has a 100‐ to 200‐fold stronger effect than most opioids, such as morphine. Fatal accidents due to chronic use and abuse of fentanyl are a worldwide social problem. One reason for the abuse of fentanyl is its psychostimulant effects that could induce behavioral changes. The effects of chronic fentanyl administration on behavior, however, are unclear.

Methods

Adult male C57BL/6J mice were chronically administered fentanyl (0.03 or 0.3 mg/kg/d i.p.), and various behaviors were assessed using a behavioral test battery.

Results

Mice chronically administered a high dose of fentanyl (0.3 mg/kg/d) exhibited decreased anxiety‐like behavior as assessed by the open field and elevated plus maze tests. On the other hand, interruption of fentanyl administration led to increased anxiety‐like behavior as observed in the light and dark transition test. The hot plate test revealed that chronic administration of fentanyl reduced pain sensitivity. High‐dose chronic fentanyl administration reduced the locomotor stimulatory effects of cocaine. The results, however, failed to reach the threshold for study‐wide statistical significance.

Conclusion

Chronic fentanyl administration induces some behavioral changes in mice. Although further studies are needed to clarify the underlying mechanisms of the behavioral effects of chronic fentanyl administration, our findings suggest that fentanyl is safe under properly controlled conditions.

To investigate the effects of long‐term fentanyl use on brain function, adult male C57BL/6J mice were chronically administered fentanyl (0.03 or 0.3 mg/kg/d ip) and analyzed in a behavioral test battery. Chronic fentanyl administration reduced anxiety‐like behavior, pain sensitivity, and the locomotor stimulatory effects of cocaine in mice. The results, however, failed to reach the threshold for study‐wide statistical significance.

Fulranumab as Adjunctive Therapy for Cancer-Related Pain: A Phase 2, Randomized, Double-Blind, Placebo-Controlled, Multicenter Study

This randomized, double-blind (DB), placebo-controlled, phase 2 study assessed the efficacy and safety of fulranumab as a pain therapy adjunctive to opioids in terminally ill cancer patients. Ninety-eight patients were randomized (2:1) to receive one subcutaneous injection of fulranumab (9 mg) or placebo in the 4-week DB phase. Seventy-one (72%) patients entered the 48-week open-label extension phase and were administered 9 mg of fulranumab every 4 weeks. The study failed to demonstrated efficacy at the end of the DB phase (primary endpoint, mean [SD] change in average cancer-related pain intensity was -.8 (1.26) for fulranumab and -.7 (1.56) for placebo; P = .592). However, potential benefit is suggested based on secondary endpoints (30% responder rate [P = .020], Brief Pain Inventory-Short Form [BPI-SF] pain intensity subscale [P = .003], and pain interference subscale [P = .006]). The most commonly reported treatment-emergent adverse events were (fulranumab vs placebo): asthenia (16% vs 10%), decreased appetite (12% vs 6%), fatigue (10% vs 0%), and malignant neoplasm progression (10% vs 0%). Although no differences were seen between fulranumab and placebo groups on the primary endpoint, improvements in BPI-SF pain subscale scores and responder rates support further research of anti-nerve growth factor therapy in cancer-related pain. PERSPECTIVE: Efficacy and safety of fulranumab as adjunctive pain therapy in terminally ill cancer patients were assessed. Results suggest that anti-NGF agents may prove to be novel additions in helping to optimize pain relief in cancer patients who fail to respond adequately to opioids and other common co-analgesics.

A3 adenosine receptor agonist attenuates neuropathic pain by suppressing activation of microglia and convergence of nociceptive inputs in the spinal dorsal horn

Peripheral nerve injuries cause glial activation and neuronal hyperactivity in the spinal dorsal horn. These changes have been considered to be involved in the underlying mechanisms for the development and maintenance of neuropathic pain. Using double immunofluorescence labeling, we previously demonstrated that spinal microglial activation induced by nerve injury enhanced convergence of nociceptive inputs in the spinal dorsal horn from uninjured afferents. The adenosine A₃ receptor (A₃AR) agonists have been shown to have antinociceptive activities in several experimental neuropathic pain models. However, the mechanisms underlying these antinociceptive actions of the A₃AR agonist are still not fully explored. In this study, the effects of the A₃AR agonist (i.e., IB-MECA) on microglial activation, enhancement of convergent nociceptive inputs, and nocifensive behaviors were examined after tibial nerve injury. Injury to the tibial nerve initially caused hyposensitivity to touch stimulus at 3 days, and then resulted in tactile allodynia at 14-day post-injury. The daily systemic administration of IB-MECA (0.1 mg/kg/day) for 8 days in a row starting on the day of nerve injury or 7 days after nerve injury prevented the development of behaviorally assessed hypersensitivities, and spinal microglial activation induced by nerve injury. These treatments also suppressed anomalous convergence of nociceptive primary inputs in the spinal dorsal horn. The present findings indicate that the A₃AR agonist attenuates neuropathic pain states by suppressing enhanced microglial activation, and anomalous convergence of nociceptive inputs in the spinal dorsal horn from uninjured afferents after injury to the peripheral nerve.

Chinese herbal medicine for opioid induced constipation in cancer patients: Protocol for a systematic review

BACKGROUND

Opioid induced constipation (OIC) is a symptom that is commonly encountered in cancer pain management. Chinese herbal medicine (CHM) has been widely used to improve OIC in China. Many clinical trials indicate that CHM could improve OIC. In this systematic review, we aim to evaluate the effectiveness and safety of CHM for OIC in cancer patients.

METHODS

We will search the following electronic databases for randomized controlled trials to evaluate the effectiveness and safety of CHM for OIC in cancer patients: CENTRAL, EMBASE, MEDILINE, CINAHL and China National Knowledge Infrastructure. Each database will be searched from inception to June 2018. The entire process will include study selection, data extraction, risk of bias assessment and meta-analyses.

RESULTS

This proposed study will evaluate the effectiveness and safety of CHM for OIC. The outcomes will include change in bowel movements, quality of life and adverse events.

CONCLUSIONS

This proposed systematic review will evaluate the existing evidence on the effectiveness and safety of CHM for OIC in cancer patients.

DISSEMINATION AND ETHICS

The results of this review will be disseminated through peer-reviewed publication. Because all of the data used in this systematic review and meta-analysis has been published, this review does not require ethical approval. Furthermore, all data will be analyzed anonymously during the review process.

Analgesic Effect of 5-(3,4-Dihydroxyphenyl)-3-hydroxy-1-(2-hydroxyphenyl)penta-2,4-dien-1-one in Experimental Animal Models of Nociception

Curcuminoids derived from turmeric rhizome have been reported to exhibit antinociceptive, antioxidant and anti-inflammatory activities. We evaluated the peripheral and central antinociceptive activities of 5-(3,4-dihydroxyphenyl)-3-hydroxy-1-(2-hydroxyphenyl)penta-2,4-dien-1-one (DHHPD), a novel synthetic curcuminoid analogue at 0.1, 0.3, 1 and 3 mg/kg (intraperitoneal), through chemical and thermal models of nociception. The effects of DHHPD on the vanilloid and glutamatergic systems were evaluated through the capsaicin- and glutamate-induced paw licking tests. Results showed that DHHPD significantly (p < 0.05) attenuated the writhing response produced by the 0.8% acetic acid injection. In addition, 1 and 3 mg/kg of DHHPD significantly (p < 0.05) reduced the licking time spent by each mouse in both phases of the 2.5% formalin test and increased the response latency of mice on the hot-plate. However, the effect produced in the latter was not reversed by naloxone, a non-selective opioid receptor antagonist. Despite this, DHHPD decreased the licking latency of mice in the capsaicin- and glutamate-induced paw licking tests in a dose response manner. In conclusion, DHHPD showed excellent peripheral and central antinociceptive activities possibly by attenuation of the synthesis and/or release of pro-inflammatory mediators in addition to modulation of the vanilloid and glutamatergic systems without an apparent effect on the opioidergic system.

Oral methylnaltrexone does not negatively impact analgesia in patients with opioid-induced constipation and chronic noncancer pain

Purpose

An oral formulation of methylnaltrexone has been developed for treating opioid-induced constipation (OIC). This manuscript examines the impact of oral methylnaltrexone, a peripherally acting µ-opioid receptor antagonist, on opioid analgesia.

Methods

This Phase III, randomized, double-blind, placebo-controlled trial, evaluated changes in pain intensity scores (0= no pain to 10= worst possible pain) and opioid use in adults with chronic noncancer pain. Patients taking ≥50 mg/day oral morphine equivalent dose (MED) for ≥14 days before screening with less than three rescue-free bowel movements/week received oral methylnaltrexone 150 mg/day (n=201), 300 mg/day (n=201), 450 mg/day (n=200), or placebo (n=201) once daily for 4 weeks followed by 8 weeks of oral methylnaltrexone as needed.

Results

The primary condition requiring opioid use was back pain (68.2% of 803 patients). Baseline pain intensity scores were similar among treatment groups (mean range, 6.2–6.4) and remained stable throughout the 4-week double-blind (mean range, 6.1–6.5) and 8-week as needed (mean range, 6.3–6.5) periods. Baseline mean MED was comparable between oral methylnaltrexone 150 mg (200.0 mg/day), methylnaltrexone 450 mg (218.0 mg/day), and placebo (209.7 mg/day), but was slightly higher in the oral methylnaltrexone 300-mg group (252.6 mg/day). Nonsignificant, minimal changes in mean MED were observed after 4 weeks of treatment (214.5–235.6 mg/day) and at the end of the as needed phase (202.3–234.9 mg/day). The percentage of patients who initiated new opioid medications during the 4-week, once-daily dosing period was generally similar among the oral methylnaltrexone 150-mg, 300-mg, and 450-mg groups (44.8%, 43.3%, and 35.0%, respectively), the oral methylnaltrexone combined group (41.0%), and the placebo group (39.8%). The most common newly initiated opioid medications during this once-daily period were oxycodone (oral methylnaltrexone groups combined, 14.6%; placebo, 12.4%) and morphine (oral methylnaltrexone combined, 10.1%; placebo, 7.0%).

Conclusion

Oral methylnaltrexone does not elicit opioid withdrawal or interfere with opioid analgesia.

Effect of Adding Magnesium Sulphate to Epidural Bupivacaine and Morphine on Post-Thoracotomy Pain Management: A Randomized, Double-Blind, Clinical Trial

Post-thoracotomy pain is very severe and may cause pulmonary complications. Thoracic epidural analgesia can greatly decrease the pain experience and its consequences. However, finding new methods to decrease the amount of administered opioids is an important issue of research. We aimed to evaluate the effect of adding epidural magnesium sulphate to bupivacaine and morphine on pain control and the amount of opioid consumption after thoracotomy. Eighty patients undergoing thoracotomy at a tertiary cardiothoracic referral centre were enrolled in a randomized, double-blind trial. Patients were randomly allocated to two groups. Bupivacaine (12.5 mg) and morphine (2 mg) were administered epidurally to all patients at the end of operation. Patients in the magnesium (Mg) group received epidural magnesium sulphate (50 mg), and patients in the control (C) group received normal saline as an adjuvant. Visual analogue scale (VAS) score and the amount of morphine consumption were measured during 24 hr post-operation. Thirty-nine patients in the Mg group and 41 patients in the C group completed the study. Patients in the Mg group had significantly less VAS score at recovery time (p < 0.05), 2 hr (p < 0.01) and 4 hr (p < 0.05) after surgery. The patient-controlled analgesia pump was started earlier in the C group than in the Mg group (p < 0.05). The amount of morphine needed in the Mg group was significantly lower than in the C group (5.64 ± 1.69 mg/24 hr versus 8.44 ± 3.98 mg/24 hr; p < 0.001). Pruritus was seen in the C group (9.7%) and absent in the Mg group (p < 0.05). Co-administration of magnesium sulphate with bupivacaine and morphine for thoracic epidural analgesia after thoracotomy leads to a reduction in post-operative pain score and the need for opioid administration.

Nonpharmacologic Pain Interventions: A Review of Evidence-Based Practices for Reducing Chronic Cancer Pain

BACKGROUND

Pain is a common issue for patients with cancer and can be challenging to manage effectively. Healthcare professionals need to be knowledgeable about evidence-based nonpharmacologic interventions.
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OBJECTIVES

This systematic review critically appraises the strength and quality of the empirical evidence for nonpharmacologic interventions in reducing chronic cancer pain.
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METHODS

Intervention studies were critically appraised and summarized by an Oncology Nursing Society Putting Evidence Into Practice team of RNs, advanced practice nurses, and nurse scientists. A level of evidence and a practice recommendation was assigned to each intervention.
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FINDINGS

Based on evidence, recommended interventions to reduce chronic cancer pain are celiac plexus block for pain related to pancreatic and abdominal cancers and radiation therapy for bone pain. Although psychoeducational interventions are considered likely to be effective, the effective components of these interventions and their dose and duration need to be determined through additional research.

Effects of pain treatment on sleep in nursing home patients with dementia and depression: A multicenter placebo-controlled randomized clinical trial

OBJECTIVE

To investigate the effects of pain treatment on sleep in nursing home (NH) patients with dementia and depression.

METHODS

A multicenter, 2-armed, double-blinded, placebo-controlled, randomized clinical trial conducted between August 2014 and September 2016. One hundred six long-term patients from 47 NHs in Norway with dementia and depression according to the Mini-Mental State Examination and the Cornell Scale for Depression in Dementia were included. Patients received stepwise pain treatment in which those who did not use analgesics were randomized to receive either paracetamol (3 g/day) or placebo tablets; those who already used pain treatment were allocated to buprenorphine transdermal system (max. 10 μg/h/7 days) or placebo transdermal patches. Sleep was assessed continuously for 14 days by actigraphy, 1 week of baseline measurement, and 1 week of ongoing treatment. The following sleep parameters were evaluated: total sleep time, sleep efficiency (SE), sleep onset latency (SOL), wake after sleep onset, early morning awakening (EMA), and number of wake bouts.

RESULTS

In the intervention group (paracetamol/buprenorphine), SE (70%-72%), SOL (32-24 min), and EMA (50-40 min) improved compared with the control group (SE, 70%-67%; SOL, 47-60 min; EMA, 31-35 min). Treatment effects were significant (P < .01, P < .05, and P < .05, respectively).

CONCLUSION

Compared with placebo, pain treatment improved sleep as measured with actigraphy. This implies that sleep, pain, and depression in NH patients should be critically evaluated and that pain treatment should be considered to be a potentially beneficial treatment.

Long-Term Pain Treatment Did Not Improve Sleep in Nursing Home Patients with Comorbid Dementia and Depression: A 13-Week Randomized Placebo-Controlled Trial

Objective: Previous research indicates that pain treatment may improve sleep among nursing home patients. We aimed to investigate the long-term effect of pain treatment on 24-h sleep patterns in patients with comorbid depression and dementia.

Design: A 13-week, multicenter, parallel-group, double-blind, placebo-controlled randomized clinical trial conducted between August 2014 and September 2016.

Setting: Long-term patients from 47 nursing homes in Norway.

Participants: We included 106 patients with comorbid dementia and depression according to the Mini Mental Status Examination (MMSE) and the Cornell Scale for Depression in Dementia (CSDD).

Intervention: Patients who were not using analgesics were randomized to receive either paracetamol (3 g/day) or placebo tablets. Those who already received pain treatment were randomized to buprenorphine transdermal system (maximum 10 μg/h/7 days) or placebo transdermal patches.

Measurements: Sleep was assessed continuously for 7 days by actigraphy, at baseline and in week 13. Total sleep time (TST), sleep efficiency (SE), sleep onset latency (SOL), wake after sleep onset (WASO), early morning awakening (EMA), and number of wake bouts (NoW) were evaluated. In addition, daytime total sleep time (DTS) was estimated. Pain was assessed with Mobilization-Observation-Behavior-Intensity-Dementia-2 Pain Scale (MOBID-2).

Results: The linear mixed model analyses for TST, SE, SOL, WASO, EMA, NoW and DTS showed no statistically significant differences between patients who received active pain treatment and those who received placebo. Post hoc subgroup analyses showed that there were no statistically significant differences between active treatment and placebo from baseline to week 13 in patients who were in pain (MOBID-2 ≥ 3) at baseline, or in patients who had poor sleep (defined as SE < 85%) at baseline. Patients who received active buprenorphine showed an increase in TST and SE compared to those who received active paracetamol.

Conclusion: The main analyses showed that long-term pain treatment did not improve sleep as measured with actigraphy. Compared to paracetamol, TST and SE increased among patients who received buprenorphine. This could indicate that some patients had beneficial effects from the most potent pain treatment. However, based on the present findings, long-term pain treatment is not recommended as a strategy to improve sleep. Clinical Trial https://clinicaltrials.gov/ct2/show/NCT02267057.

To take or not to take: the association between perceived addiction risk, expected analgesic response and likelihood of trying novel pain relievers in self-identified chronic pain patients

BACKGROUND AND AIMS

Probability discounting refers to the effect of outcome uncertainty on decision making. Using probability discounting, we examined the degree to which self-identified chronic pain patients (CPP) were likely to try a novel analgesic medication given increasing addiction risk. We postulated that propensity for opioid misuse, trait impulsivity and previous opioid experience would be associated positively with likelihood of risky medication use.

DESIGN

This cross-sectional on-line study determined state/trait associations with addiction-related medication decisions in CPP.

SETTING

US-based CPP participated via Amazon Mechanical Turk; data were collected and analyzed in Baltimore, Maryland.

PARTICIPANTS

A total of 263 CPP (70.6% female) participated in the study from 12-13 December 2014.

MEASUREMENTS

CPP responded to the Benefit versus Addiction Risk Questionnaire (BARQ) assessing likelihood of taking a hypothetical once-daily oral analgesic medication as a function of two factors: risk of addiction (0-50%) and duration of expected complete pain relief (3, 30 or 365 days). The primary outcome was the BARQ, quantified as area under the curve (AUC). Grouping of CPP at high or low risk for opioid misuse was based on the Screener and Opioid Assessment for Patients with Pain-Revised (SOAPP-R). Predictors included previous experience with opioids, as well as various measures of chronic pain and mental health.

FINDINGS

Across hypothetical addiction risk assessed in the BARQ, the likelihood of taking a novel analgesic medication was elevated significantly in patients with high (≥18; n = 137) versus low (<18; n = 126) SOAPP-R scores [P < 0.001; 3-day: Cohen's d = 0.66, 95% confidence interval (CI) = 0.63, 0.69; 30-day: d = 0.74, 95% CI = 0.71, 0.78; 365-day: d = 0.75, 95% CI = 0.72, 0.79].

CONCLUSIONS

In the United States, self-identified chronic pain patients (CPP) at higher risk for opioid misuse were more likely to report willingness to try a novel analgesic despite increasing addiction risk than CPP with low risk of opioid misuse.

Effect of Rhizoma Paridis saponin on the pain behavior in a mouse model of cancer pain

Rhizoma Paridis saponins (RPS) as active parts of P. polyphylla Smith var. yunnanensis has been used as an anti-cancer drug in traditional Chinese medicine. In this study, RPS was first found to demonstrate a potent effect on markedly reducing the pain induced by cancer. Therefore, the aim of this study was to further explore the analgesic effect of RPS and its possible reaction pathway on H22 hepatocarcinoma cells inoculated in the hind right paw of mice. Cancer-induced pain model mice were randomly divided into 5 groups (n = 10) and orally administered with RPS (50–200 mg kg⁻¹) for 2 weeks. On the last day of treatment, the pain behavior of mice was measured using hot-plate test and open field test, and brain tissues were sampled for detection of biochemical indices, malondialdehyde (MDA), superoxide dismutase (SOD), prostaglandin E2 (PGE2), serotonin (5-HT) and β-endorphin (β-EP). Moreover, the concentrations of NF-κB and IL-1β in the blood serum were measured by ELISA reagent kits. In addition, naloxone, the non-selective antagonist of opioid receptors, was used to identify the opioid receptors involved in RPS's action. It has been found that RPS alleviates cancer pain mainly via the suppression of inflammatory pain induced by oxidative damage, such as decreasing MDA and PGE2 levels, renewing activity of SOD, as well as increasing 5-HT and β-EP in the brain and suppressing the expression of NF-κB and IL-1β in the serum in a concentration-dependent manner. Overall, the current study highlights that RPS has widespread potential antinociceptive effects on a mouse model of chronic cancer pain, which may be associated with the peripheral nervous system and the central nervous system.

Rhizoma Paridis saponins (RPS) as active parts of P. polyphylla Smith var. yunnanensis has been used as an anti-cancer drug in traditional Chinese medicine.

The influence of AMN082, metabotropic glutamate receptor 7 (mGlu7) allosteric agonist on the acute and chronic antinociceptive effects of morphine in the tail-immersion test in mice: Comparison with mGlu5 and mGlu2/3 ligands

Preclinical data indicated that the metabotropic glutamate receptors 5 (mGlu5) and glutamate receptors 2/3 (mGlu2/3) are involved in modulating morphine antinociception. However, little is known about the role of metabotropic glutamate receptors 7 (mGlu7) in this phenomenon. We compared the effects of AMN082 (0.1, 1 or 5mg/kg, ip), a selective mGlu7 allosteric agonist, LY354740 (0.1, 1 or 5mg/kg, ip), an mGlu2/3 agonist and MTEP (0.1, 1 or 5mg/kg, ip), a selective mGlu5 antagonist, on the acute antinociceptive effect of morphine (5mg/kg, sc) and also on the development and expression of tolerance to morphine analgesia in the tail-immersion test in mice. To determine the role of mGlu7 in morphine tolerance, and the association of the mGlu7 effect with the N-methyl-d-aspartate (NMDA) receptors regulation, we used MMPIP (10mg/kg, ip), a selective mGlu7 antagonist and MK-801, a NMDA antagonist. Herein, the acute administration of AMN082, MTEP or LY354740 alone failed to evoked antinociception, and did not affect morphine (5mg/kg, sc) antinociception. However, these ligands inhibited the development of morphine tolerance, and we indicated that MMPIP reversed the inhibitory effect of AMN082. When given together, the non-effective doses of AMN082 and MK-801 did not alter the tolerance to morphine. Thus, mGlu7, similarly to mGlu2/3 and mGlu5, are involved in the development of tolerance to the antinociceptive effects of morphine, but not in the acute morphine antinociception. Furthermore, while mGlu7 are engaged in the development of morphine tolerance, no interaction exists between mGlu7 and NMDA receptors in this phenomenon.

Prolonged release oxycodone and naloxone treatment counteracts opioid-induced constipation in patients with severe pain compared to previous analgesic treatment

OBJECTIVE

Treatment with prolonged-release oxycodone/naloxone (PR OXN) has been shown to improve opioid induced constipation (OIC) in constipated patients. This publication reports on a real-life observational study investigating the efficacy of PR OXN with regard to bowel function in patients switching to PR OXN from WHO step 1, step 2 and step 3 opioids.

METHODS

Patients with chronic pain experiencing insufficient pain relief and/or unacceptable side effects were switched to PR OXN and monitored in this observational study with respect to efficacy regarding bowel function and efficacy regarding pain relief in comparison with previous analgesic therapy. A patient was considered a responder with respect to efficacy if this assessment was "slightly better", "better" or "much better" compared with previous therapy. Bowel function index, pain intensity, quality of life, laxative medication use, and safety analgesic were also evaluated.

RESULTS

A total of 1338 patients (mean [SD] age 64.3 [14.9], 63% female) were observed for 43 [3-166] days (median [range]) during treatment with PR OXN. Overall response rate regarding bowel function efficacy was 82.5%. Patients with symptoms of constipation at study entry obtained a clinically relevant improvement of the bowel function index (BFI) within the first 2 weeks of PR OXN treatment. Non-constipated patients at study entry maintained normal bowel function despite switching to treatment with the opioid PR OXN.

CONCLUSION

In conclusion, treatment with PR OXN results in a significant and clinically relevant improvement of bowel function. During the observation of the treatment with PR OXN patients reported an improvement of quality of life (QoL). More interestingly, non-constipated patients maintained a normal bowel function, showing prevention of constipation despite the use of an opioid.

Efficacy of Prophylactic Treatment for Oxycodone-Induced Nausea and Vomiting Among Patients with Cancer Pain (POINT): A Randomized, Placebo-Controlled, Double-Blind Trial

BACKGROUND

Although opioid-induced nausea and vomiting (OINV) often result in analgesic undertreatment in patients with cancer, no randomized controlled trials have evaluated the efficacy of prophylactic antiemetics for preventing OINV. We conducted this randomized, placebo-controlled, double-blind trial to evaluate the efficacy and safety of prophylactic treatment with prochlorperazine for preventing OINV.

MATERIALS AND METHODS

Cancer patients who started to receive oral oxycodone were randomly assigned in a 1:1 ratio to receive either prochlorperazine 5 mg or placebo prophylactically, given three times daily for 5 days. The primary endpoint was the proportion of patients who had a complete response (CR) during the 120 hours of oxycodone treatment. CR was defined as no emetic episode and no use of rescue medication for nausea and vomiting during 5 days. Key secondary endpoints were the proportion of patients with emetic episodes, proportion of patients with moderate or severe nausea, quality of life, and proportion of treatment withdrawal.

RESULTS

From November 2013 through February 2016, a total of 120 patients were assigned to receive prochlorperazine (n = 60) or placebo (n = 60). There was no significant difference in CR rates (69.5% vs. 63.3%; p = .47) or any secondary endpoint between the groups. Patients who received prochlorperazine were more likely to experience severe somnolence (p = .048).

CONCLUSION

Routine use of prochlorperazine as a prophylactic antiemetic at the initiation of treatment with opioids is not recommended. Further research is needed to evaluate whether other antiemetics would be effective in preventing OINV in specific patient populations.

IMPLICATIONS FOR PRACTICE

Prophylactic prochlorperazine seems to be ineffective in preventing opioid-induced nausea and vomiting (OINV) and may cause adverse events such as somnolence. Routine use of prophylactic prochlorperazine at the initiation of treatment with opioids is not recommended. Further research is needed to evaluate whether other antiemetics would be effective in preventing OINV in specific patient populations.

Opioid-Induced Constipation and Bowel Dysfunction: A Clinical Guideline

OBJECTIVE

To formulate timely evidence-based guidelines for the management of opioid-induced bowel dysfunction.

SETTING

Constipation is a major untoward effect of opioids. Increasing prescription of opioids has correlated to increased incidence of opioid-induced constipation. However, the inhibitory effects of opioids are not confined to the colon, but also affect higher segments of the gastrointestinal tract, leading to the coining of the term "opioid-induced bowel dysfunction."

METHODS

A literature search was conducted using Medline, EMBASE, and EMBASE Classic, and the Cochrane Central Register of Controlled Trials. Predefined search terms and inclusion/exclusion criteria were used to identify and categorize relevant papers. A series of statements were formulated and justified by a comment, then labeled with the degree of agreement and their level of evidence as judged by the Strength of Recommendation Taxonomy (SORT) system.

RESULTS

From a list of 10,832 potentially relevant studies, 33 citations were identified for review. Screening the reference lists of the pertinent papers identified additional publications. Current definitions, prevalence, and mechanism of opioid-induced bowel dysfunction were reviewed, and a treatment algorithm and statements regarding patient management were developed to provide guidance on clinical best practice in the management of patients with opioid-induced constipation and opioid-induced bowel dysfunction.

CONCLUSIONS

In recent years, more insight has been gained in the pathophysiology of this "entity"; new treatment approaches have been developed, but guidelines on clinical best practice are still lacking. Current knowledge is insufficient regarding management of the opioid side effects on the upper gastrointestinal tract, but recommendations can be derived from what we know at present.

Use of strong opioids for chronic pain in osteoarthritis: an insight into the Latin American reality

INTRODUCTION

Osteoarthritis is the most common cause of arthritis and one of the main causes of chronic pain. Although opioids are frequently employed for chronic pain treatment, their usage for osteoarthritis pain remains controversial due to the associated adverse effects. Most guidelines reserve their use for refractory pain in patients with hip and knee osteoarthritis. The situation is even more complex in Latin America, where the prevalence of insufficient pain treatment is high because of the limited availability and use of strong opioids. Areas covered: In this article we review the epidemiology of osteoarthritis, its socioeconomic burden, its impact as a chronic pain cause and the pharmacological treatment options, giving emphasis to the role of strong opioids, their safety and efficacy, especially in Latin American countries, where restrictions regulate their usage. Expert commentary: Usage of strong opioids is safe and effective in the short-term management of osteoarthritis with moderate to severe pain, when other pharmacological treatments are inadequate and surgery is contraindicated, provided their use adheres to existing guidelines. Educational programs for patients and physicians and further research on treating chronic pain with opioids should be implemented to reduce adverse effects and improve care quality.

Colonic Perforation: A Medical Complication

Hypothyroidism is a common comorbidity that on acute presentation is often overlooked. It can be an easily managed condition; however non-compliance can have severe consequences. In the presented case it was requirement for emergency surgery that resulted in stoma formation. This case is a first example of the need to include patient's decision making process with regards to medication adherence in the setting of chronic disease.

The effects of food on opioid-induced nausea and vomiting and pharmacological parameters: a systematic review

Opioids remain the standard of care for treating moderate to severe pain resulting from surgery or injury in cases of acute pain, and are recommended for patients who have not responded to nonopioid analgesics. Effective management of pain has an impact on clinical course and often depends on achieving an acceptable balance between opioid efficacy, safety, and tolerability. Common opioid-related adverse events such as nausea and vomiting are associated with an overall lower achievement of effective pain management and patient satisfaction. However, in practice, clinicians employ various strategies to maximize efficacy, minimize these adverse effects, and ensure the careful, judicious, and evidence-based use of opioids for patients who require them. Typical strategies for management and minimization of these types of adverse events include dose reduction, dose titration, opioid rotation, prescription for an antiemetic, and recommending the patient take opioids with food. Overall, the most straightforward approach that clinicians tend to employ that does not require additional visits or adjustment of prescriptions, is to recommend patients take opioids with food. However, given the current climate with opioids, it is critical and imperative that decisions for use of opioids be grounded in a solid and thorough evidence-base. In fact, several opioids are recommended to be taken explicitly with or without food because of interactions with abuse-deterrent technologies that can cause increased adverse events or inadequate analgesia. Therefore, we sought to review, synthesize, and summarize the literature for randomized, controlled trials and other studies to support the hypothesis that taking opioids with food reduces opioid-related events such as nausea and vomiting. Based on the current evidence we surveyed, the recommendation to take opioids with food does not appear to consistently and unequivocally reduce nausea and vomiting and, in many cases, increases the frequency of these adverse events in the studies we examined.

Recent Advances in the Realm of Allosteric Modulators for Opioid Receptors for Future Therapeutics

Opioids, and more specifically μ-opioid receptor (MOR) agonists such as morphine, have long been clinically used as therapeutics for severe pain states but often come with serious side effects such as addiction and tolerance. Many studies have focused on bringing about analgesia from the MOR with attenuated side effects, but its underlying mechanism is not fully understood. Recently, focus has been geared toward the design and elucidation of the orthosteric site with ligands of various biological profiles and mixed subtype opioid activities and selectivities, but targeting the allosteric site is an area of increasing interest. It has been shown that allosteric modulators play key roles in influencing receptor function such as its tolerance to a ligand and affect downstream pathways. There has been a high variance of chemical structures that provide allosteric modulation at a given receptor, but recent studies and reviews tend to focus on the altered cellular mechanisms instead of providing a more rigorous description of the allosteric ligand's structure-function relationship. In this review, we aim to explore recent developments in the structural motifs that potentiate orthosteric binding and their influences on cellular pathways in an effort to present novel approaches to opioid therapeutic design.

Spinal Metastatic Disease: A Review of the Role of the Multidisciplinary Team

Historically, a simple approach centered on palliation was applicable to the majority of patients with metastatic spinal disease. With advances in diagnosis and treatment, a more complicated algorithm has devolved requiring a multidisciplinary approach with institutional commitment and support. We performed a database review including pertinent articles exploring the multidisciplinary management of spinal metastatic disease. The wide variation in clinical presentation and tumor response to treatment necessitates a multidisciplinary approach that integrates the diagnosis and treatment of the cancer, symptom management, and rehabilitation for optimal care of patients with spinal metastases. Advances in the field of radiology have led to earlier and more focused diagnosis of spinal metastasis and acts to guide therapy. Advances in surgical techniques, neurophysiologic monitoring, and anesthetic expertise have allowed surgeons to perform more extensive procedures leading to improved outcomes and reduced morbidity. Radiation oncology input that is essential as external beam radiation therapy can provide significant pain relief. Non-operative measures may include bisphosphonate infusions, management of complications (e.g. hypercalcemia of malignancy), monoclonal antibody infusions, and chemotherapy if indicated in the treatment of the primary malignancy. Input from psychology services is necessary to address the biopsychosocial ramifications of spinal metastasis. Allied health professionals in the form of physiotherapists, social workers, and dieticians also contribute in maximizing patients' quality of life and well-being.

Mashiningan Improves Opioid-Induced Constipation in Rats by Activating Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel

Opioid receptor stimulants are analgesics used in patients with and without cancer; however, they often cause constipation, resulting in poor adherence and deterioration of the quality of life. Hence, suitable treatments for constipation are required. In this study, we investigated the pharmacological mechanisms of action of mashiningan (MNG), a Kampo medicine used to treat constipation, and evaluated the effect of MNG on opioid-induced constipation in rats. MNG (100 or 300 mg/kg) was orally administered to normal or codeine phosphate (CPH)-induced constipation in rats, and its effect was evaluated on the basis of fecal counts, characteristics, and weight. Small intestinal fluid secretion was measured after treatment with MNG alone or coadministration with a cystic fibrosis transmembrane conductance regulator (CFTR)-specific inhibitor (CFTRinh-172). The effects of MNG on the CFTR and type-2 chloride channel were determined using patch-clamp or short-circuit current experiments, respectively. MNG increased the fecal weight and proportion of soft feces in normal rats. CPH-induced constipation in rats decreased fecal counts and weight, whereas MNG prevented these effects and increased the proportion of soft feces. MNG increased the electronic chloride current, and this effect was inhibited by the CFTRinh-172 in the CFTR assay. Furthermore, MNG increased small intestinal fluid secretion, and this effect was abolished by coadministration with the CFTRinh-172. MNG improved opioid-induced constipation in rats, and this improvement may have been mediated by increasing intestinal fluid secretion via CFTR chloride channel activation. Therefore, MNG is expected as a medicine of the treatment of constipation in patients taking opioids.

Binding mode analyses of NAP derivatives as mu opioid receptor selective ligands through docking studies and molecular dynamics simulation

Mu opioid receptor selective antagonists are highly desirable because of their utility as pharmacological probes for receptor characterization and functional studies. Furthermore, the mu opioid receptors act as an important target in drug abuse and addiction treatment. Previously, we reported NAP as a novel lead compound with high selectivity and affinity towards the mu opioid receptor. Based on NAP, we have synthesized its derivatives and further characterized their binding affinities and selectivity towards the receptor. NMP and NGP were identified as the two most selective MOR ligands among NAP derivatives. In the present study, molecular modeling methods were applied to assess the dual binding modes of NAP derivatives, particularly on NMP and NGP, in three opioid receptors, in order to analyze the effects of structural modifications on the pyridyl ring of NAP on the binding affinity and selectivity. The results indicated that the steric hindrance, electrostatic, and hydrophobic effects caused by the substituents on the pyridyl ring of NAP contributed complimentarily on the binding affinity and selectivity of NAP derivatives to three opioid receptors. Analyses of these contributions provided insights on future design of more potent and selective mu opioid receptor ligands.