Intravenous morphine for management of cancer pain

Behavioral video coding analysis of chronic morphine administration in rats

The present study assessed the behavior of morphine-addicted rats using behavioral video coding technology, to evaluate effective methods for identifying morphine addiction. Rats were divided into a control group (n=15) and a morphine addiction group (n=15). The morphine addiction model was established with a 14-day increasing dose scheme, confirmed using a conditional place preference (CPP) experiment. After successful modeling, the rats' behavior was recorded for 12 h, then coded and analyzed using Observer XT behavior analysis software. Compared with the control group, morphine-addicted rats showed increased heat pain tolerance time (P=0.039) and spent more time in the white box during the CPP experiment (P<0.001). Video coding analysis revealed significant behavioral changes in morphine-addicted rats compared to controls. In addition to being lighter, morphine-addicted rats showed decreased water intake, reduced licking of forelimbs and hind limbs, and altered sleeping posture (sleeping curled up) during the day (all P<0.05). In conclusion, chronic morphine administration in rats leads to distinctive behavioral changes, including decreased licking frequency, reduced water intake and altered sleep posture. Video coding analysis, as a safe and non-invasive method, may provide a convenient and efficient approach for studying morphine addiction in rats.

Upregulation of HCN2 in ventral tegmental area is involved in morphine-induced conditioned place preference in rats

Morphine is an opioid commonly used to treat pain in clinic, but it also has the potential to be highly addictive, which can lead to abuse. Despite these known risks, the cellular and molecular mechanism of morphine conditioned place preference (CPP) is still unclear. In this study, using a rat model of chronic morphine administration, we found that compared with the control group, the mRNA and protein expression of HCN2 channel in the ventral tegmental area (VTA) were upregulated. Further immunofluorescence analysis showed that the fluorescence intensity of HCN2 channel of VTA dopaminergic neurons in morphine group was significantly enhanced, while the patch clamp recording of brain slices showed that both the magnitude and the density of Ih (HCN channel current) of VTA neurons were significantly increased. Moreover, intra-VTA infusion of ZD7288, a selective inhibitor of HCN channel, into rats of the morphine group decreased morphine CPP. Taken together, our results show that chronic morphine administration induces an upregulation of HCN2 in VTA dopamine neurons, while HCN inhibition reduces morphine CPP, suggesting that HCN channel may be a potential target for the treatment of morphine addiction.

Opioid dose titration for cancer pain

BACKGROUND

Opioid dose titration is a fundamental process of opioid therapy in cancer pain.

AIMS

To assess data opioid dose titration.

METHODS

The principal opioid dose titration methods, outcomes, and modalities of administration regarding the different opioid preparations were examined in different clinical contexts.

RESULTS

Most studies suggested that opioid-naive patients should be started at doses of 15-30 mg/day of oral morphine equivalents. Opioid-tolerant patients may receive low or higher doses of oral morphine equivalents, depending on the level of opioid tolerance. Generally, dose increments of 30%-50% seem to be indicated to start dose titration. Some patients with severe excruciating cancer pain may present as an emergency requiring a rapid application of powerful analgesic strategies. The intravenous use of opioids may circumvent this problem providing a faster pain relief, due to the large availability and rapid achievement of effective plasma concentrations.

DISCUSSION

Opioid dose titration is a delicate passage in patients with cancer pain. This approach may be different according to different clinical conditions. Opioid dose titration requires expertise to optimize cancer pain management while minimizing the development of adverse effects.

CONCLUSION

While most approaches are meaningful and partially supported by existing literature, more studies are necessary to establish advantages and disadvantages in different clinical conditions. Optimization of opioid dose titration is of paramount importance.

SIGNIFICANCE

This review provides the most recent insights on the different modalities of opioid dose titration in cancer pain management.

An overview of the current drug treatment strategies for moderate to severe, chronic malignant tumor-related pain

INTRODUCTION

The pharmacological management of cancer pain is a complex issue that requires knowledge and experience in the use of analgesics. The aim of this expert review is to provide a panorama of the pharmacological strategies in cancer pain management.

AREAS COVERED

Opioid dose titration is a delicate process regarding the start of opioid treatment in different clinical conditions. How to improve the opioid response is a fundamental step, which includes different strategies when an initial treatment with opioids fails. The use of adjuvants is another relevant issue that should be considered in some specific circumstances to optimize the management of cancer pain management. Some clinical conditions, such as neuropathic pain and breakthrough pain, deserve a special attention. Relevant literature was selected to provide an overview of cancer pain management strategies.

EXPERT OPINION

Opioid therapy still remains the cornerstone of pharmacological management of cancer pain. Opioids should be used according to the level of tolerance, also personalizing the treatment (route, drug, and dosing). Adjuvant drugs may help in specific conditions, although their use should be balanced with the adverse effects. Breakthrough pain requires expertise in tailoring a treatment according to patient's profile and characteristics of episodes.

Comparison of two techniques (intermittent intravenous bolus morphine vs. morphine infusion) for analgesic titration in patients who had advanced cancer with severe pain: a prospective randomised study

OBJECTIVE

To compare the analgesic efficacy of two techniques of morphine titration (intermittent intravenous bolus vs infusion) by calculating rescue dosage in a day at 1 week after analgesic titration.

METHODS

One hundred and forty cancer patients were randomised into two groups. In group 1, intravenous morphine 1.5 mg bolus given every 10 min until Numerical Rating Scale (NRS) pain score <4 is achieved. Total intravenous dose converted to oral dose (1:1) and administered every 4 hours. In group 2, intravenous bolus morphine 0.05 mg/kg body weight administered followed by 0.025 mg/kg/hour intravenous infusion. The NRS pain score was recorded every 10 min but infusion rate was titrated every 30 min if required. The infusion rate of morphine was doubled if the pain score was unchanged and increased to 50% when NRS was between 4 and baseline. If NRS<4, then infusion at same rate was continued. Once the NRS<4 for two consecutive hours, total intravenous dose for 24 hours was calculated and converted to oral morphine in a ratio of 1:3 and divided into six doses given over 24 hours. For rescue (pain score ≥4) analgesia, one-sixth of the total daily oral dose was prescribed. The primary outcome of this study was to note the number of rescue doses of oral morphine in a day at 1 week.

RESULTS

The rescue dosage in a day at 1-week post discharge from the palliative care unit was significantly higher in group 1 as compared with group 2.

CONCLUSION

Intravenous infusion morphine may be a better analgesic titration technique for analgesia in patients with advanced cancer.

TRIAL REGISTRATION NUMBER

CTRI/2018/04/013369.

The Use of Parenteral Opioids in Cancer Pain Management

Opioids should be offered to patients with moderate-to-severe pain related to cancer or active cancer treatment unless contraindicated. Although oral administration of opioids is generally preferable, a parenteral route may be advisable and mandatory in some clinical circumstances. Parenteral administration of opioids may accelerate the achievement of analgesia. The intravenous route fits the need of rapid achievement of analgesia in patients poorly responsive to other opioids and provides a fast analgesia in patients with breakthrough pain, that has a specific temporal pattern requiring a rapid analgesic effect. When the oral route is unavailable for the presence of nausea, vomiting, or dysphagia. the parenteral route is one of the principal options. Opioids have different pharmacokinetic and pharmacodynamic characteristics and should be chosen according to the individual needs. Thus, the knowledge and experience with these routes of administration are mandatory for anesthesiologists committed to cancer pain management.

Effects of Electroacupuncture for Opioid-Induced Constipation in Patients With Cancer in China: A Randomized Clinical Trial

IMPORTANCE

Opioid-induced constipation (OIC) is prevalent among patients treated with opioids for cancer pain. Safe and effective therapies for OIC in patients with cancer remain an unmet need.

OBJECTIVE

To determine the efficacy of electroacupuncture (EA) for OIC in patients with cancer.

DESIGN, SETTING, AND PARTICIPANTS

This randomized clinical trial was conducted at 6 tertiary hospitals in China among 100 adult patients with cancer who were screened for OIC and enrolled between May 1, 2019, and December 11, 2021.

INTERVENTIONS

Patients were randomized to receive 24 sessions of EA or sham electroacupuncture (SA) over 8 weeks and then were followed up for 8 weeks after treatment.

MAIN OUTCOMES AND MEASURES

The primary outcome was the proportion of overall responders, defined as patients who had at least 3 spontaneous bowel movements (SBMs) per week and an increase of at least 1 SBM from baseline in the same week for at least 6 of the 8 weeks of the treatment period. All statistical analyses were based on the intention-to-treat principle.

RESULTS

A total of 100 patients (mean [SD] age, 64.4 [10.5] years; 56 men [56.0%]) underwent randomization; 50 were randomly assigned to each group. Among them, 44 of 50 patients (88.0%) in the EA group and 42 of 50 patients (84.0%) in the SA group received at least 20 (≥83.3%) sessions of treatment. The proportion of overall responders at week 8 was 40.1% (95% CI, 26.1%-54.1%) in the EA group and 9.0% (95% CI, 0.5%-17.4%) in the SA group (difference between groups, 31.1 percentage points [95% CI, 14.8-47.6 percentage points]; P < .001). Compared with SA, EA provided greater relief for most OIC symptoms and improved quality of life among patients with OIC. Electroacupuncture had no effects on cancer pain and its opioid treatment dosage. Electroacupuncture-related adverse events were rare, and, if any, all were mild and transient.

CONCLUSIONS AND RELEVANCE

This randomized clinical trial found that 8-week EA treatment could increase weekly SBMs with a good safety profile and improve quality of life for the treatment of OIC. Electroacupuncture thus provided an alternative option for OIC in adult patients with cancer.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03797586.

CircNf1-mediated CXCL12 expression in the spinal cord contributes to morphine analgesic tolerance

BACKGROUND

Severe pain in patients can be alleviated by morphine treatment. However, long-term morphine treatment induces analgesic tolerance and the molecular mechanism of morphine analgesic intolerance is still not fully elucidated. Therefore, a novel target for improving morphine analgesic tolerance is required. Whole-genome sequencing showed that circNf1 is highly expressed in the dorsal horns of morphine-treated rats. Circular RNAs (circRNAs) are known to be unique and conserved cellular molecules that are mostly present in cytoplasm and participate in various biochemical processes with different functions. Therefore, we focused on exploring the molecular mechanism by which circNf1 contributes to morphine analgesic tolerance.

METHODS

CircRNA sequencing revealed differential expression of circRNAs after morphine treatment, and bioinformatics software programs (miRNAda, PicTar, and RNAhybrid) were used to predict possible mRNAs and binding sites. RNA binding protein immunoprecipitation (RIP), chromatin isolation by RNA purification (ChIRP), fluorescence in situ hybridization (FISH), western blotting, biotin-coupled probe pull-down assay, luciferase assay, and quantitative real-time polymerase chain reaction (qRT-PCR) were conducted to detect and measure the expression levels of circRNAs, mRNAs, and proteins. Intrathecal injections of small interfering RNAs (siRNAs), microRNA (miRNA) agomirs, and functional virus microinjections were administered to artificially mediate the expression of molecules. Tail immersion and hotplate tests were performed to evaluate morphine analgesic tolerance.

RESULTS

Morphine-induced circNf1 expression was high in the spinal cord. RIP-PCR and luciferase assay data showed that circNf1 could combine with both miR-330-3p and miR-665, and FISH showed that circNf1 co-localized with miR-330-3p and miR-665. qRT-PCR assay showed downregulation of miR-330-3p and miR-665 in morphine-treated rats; western blotting results showed that CXCL12 increased after morphine treatment, however, the upregulation of CXCL12 could be alleviated after the intrathecal injection of miR-330-3p as well as miR-665 agomir. qRT-PCR indicated that circNf1 can bind to CXCL12 promoter, the increased circNf1 can enhance CXCL12 mRNA in naïve rats, and inhibition of circNf1 can alleviate the upregulation of CXCL12 mRNA in morphine-treated rats. Behavioral tests revealed that inhibition of circNf1 and CXCL12 and the enhancement of miR-330-3p and miR-665 can alleviate morphine analgesic tolerance.

CONCLUSIONS

Our study indicates a novel pathway that can contribute to morphine analgesic tolerance, the circRNA to cytokine pathway, in which circNf1 functions as a sponge for miR-330-3p and miR-665 and induces the upregulation of CXCL12 at both transcriptional and translational levels in morphine-treated rats.

Rapid Titration With Intravenous Oxycodone for Severe Cancer Pain and Oral Conversion Ratio

CONTEXT

to assess a dose titration with intravenous oxycodone to achieve rapid pain relief of cancer pain of severe intensity. The second objective was to provide a conversion ratio with the oral route.

METHODS

Cancer patients admitted for severe pain were prospectively assessed. At admission (T0) previous opioid doses were recorded. Edmonton symptom assessment scale (ESAS) was collected from T0 until the conclusion of the observation. Intravenous boluses of oxycodone were given until the initial signs of significant analgesia were detected. The effective dose was multiplied for six and given as intravenous continuous infusion. When the patient was considered stabilized the intravenous daily dose was converted to oral oxycodone using an initial ratio of 1:2. Subsequently, doses of oral oxycodone were changed according to the clinical situation.

RESULTS

Twenty-nine patients were examined. A mean effective bolus dose of oxycodone was 9.5 mg (SD 8.0) allowed to achieve a meaningful pain relief in a mean of 10.4 minutes (SD 3.3). The mean initial and the final infusion doses were 51.0 mg/day (standard deviation 40.9) and 69.7 mg/day ( standard deviation76.6), respectively. A significant change in pain intensity was observed at the different time intervals (P<0.0005). Conversion to oral route occurred after a mean of 2.7 days (standard deviation1.2) of intravenous oxycodone. The final mean conversion ratio was 1:2,12 ( standard deviation0.36).

CONCLUSION

Rapid intravenous oxycodone dose titration resulted in rapid pain relief. The intravenous-oral conversion ratio of 1:2 is reliable. Further studies are necessary to confirm this preliminary observation.

Cancer Pain Treatment Strategies in Patients with Cancer

Management of cancer pain is challenging. Despite the poor evidence, opioid therapy still remains the cornerstone for the management of cancer-related pain. Opioids should be given according to the clinical presentation in the different stages of disease. There is no drug of choice, as most opioids are effective. Thus, the choice should be based on the individual characteristics of patients. Optimization of opioid therapy may allow individual treatment according to the patient's characteristics and pain syndromes, providing timely alternatives in the different stages of disease. While most patients respond to an appropriate treatment associated with a comprehensive assessment and symptom control, a high level of experience and knowledge is necessary in determining conditions to maximize the analgesic response, eventually adding adjuvants in some specific circumstances. Alternative opioids may improve the balance between analgesia and adverse effects in the presence of a poor response to the first opioid in a large number of patients. Finally, a selected population can benefit from some interventional procedures.

Effects of Electroacupuncture on Opioid-Induced Constipation in Patients With Cancer: Study Protocol for a Multicenter Randomized Controlled Trial

Background

Opioid-induced constipation (OIC) is one of the most prevalent adverse events associated with cancer patients who receive opioid analgesics for moderate to severe pain. Acupuncture may be an effective treatment for OIC. We designed this trial to assess the efficacy and safety of electroacupuncture for OIC in cancer patients.

Methods

This is a multicenter, sham-controlled, parallel-group, subject- and assessor-blinded randomized trial. A total of 100 cancer patients with OIC will be randomly assigned to either the electroacupuncture group or the sham electroacupuncture group at a ratio of 1:1. Patients in each group will receive a total of 24-session treatment over 8 weeks, three sessions a week and 30 min each session. Thereafter, patients will be followed up for another 8 weeks. The primary outcome will be the proportion of responders, defined as a patient who has ≥3 spontaneous bowel movements (SBMs)/wk and ≥ increase of 1 SBM from baseline simultaneously for at least 6 out of 8 weeks of the treatment period. The secondary outcomes will include the mean weekly SBMs and complete spontaneous bowel movements, the mean Bristol Stool Form Scale score for stool consistency, the mean score for straining of SBM, the total and subscale scores of Patient Assessment of Constipation-Symptom questionnaires, and the total and subscale scores of Patient Assessment of Constipation-Quality of Life questionnaire. Patients' global assessment of treatment effectiveness, patients' expectation toward the effectiveness of acupuncture and safety of acupuncture will also be assessed. All efficacy analyses will be performed in the intention-to-treat population.

Discussion

To improve the adherence to intervention protocols, the majority of the participants will be recruited from an inpatient setting. The results will help to determine the clinical effects and safety of electroacupuncture for the treatment of OIC among patients with cancer.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: NCT03797586, registered on 4 January 2019, https://clinicaltrials.gov/ct2/show/NCT03797586.

When the game is hard, more complex weapons are needed

OBJECTIVES

The aim of this paper is to illustrate how to manage a very difficult pain condition.

METHODS

This is a clinical note of a complex approach using multiple analgesic regimens to effectively afford challenging pain situations.

RESULTS

A man underwent an opioid dose titration, followed by dose stabilisation for some months. Then he underwent two opioid substitutions, unsuccessfully. A spinal analgesia provided good analgesia for a prolonged period of time, necessitating variable interventions to counteract the evolving, challenging clinical situation.

CONCLUSIONS

The description of this case illustrates the need of a high level of experience and knowledge to elaborate complex strategies step by step every time the pain syndrome was worsening. Recommendations are unlikely in these extreme circumstances, and treatment should be based on continuous clinical counteraction to the evolving clinical conditions.

Comparing Patient-Controlled Analgesia Versus Non-PCA Hydromorphone Titration for Severe Cancer Pain: A Randomized Phase III Trial

BACKGROUND

Opioid titration is necessary to achieve rapid, safe pain relief. Medication can be administered via patient-controlled analgesia (PCA) or by a healthcare provider (non-PCA). We evaluated the efficacy of intravenous PCA versus non-PCA hydromorphone titration for severe cancer pain (≥7 at rest on the 11-point numeric rating scale [NRS]).

PATIENTS AND METHODS

Patients with severe cancer pain were randomized 1:1 to PCA or non-PCA titration, stratified by opioid-tolerant or opioid-naïve status. The PCA pump was set to no continuous dose, with a hydromorphone bolus dose 10% to 20% of the total previous 24-hour equianalgesic (for opioid-tolerant patients) or 0.5 mg (for opioid-naïve patients). For the non-PCA group, the initial hydromorphone bolus dose was identical to that in the PCA group, with the subsequent dose increased by 50% to 100% (for NRS unchanged or increased) or repeated at the current dose (for NRS 4-6). Hydromorphone delivery was initiated every 15 minutes (for NRS ≥4) or as needed (for NRS ≤3). The primary endpoint was time to successful titration (TST; time from first hydromorphone dose to first occurrence of NRS ≤3 in 2 consecutive 15-minute intervals).

RESULTS

Among 214 patients (PCA, n=106; non-PCA, n=108), median TSTs (95% CI) were 0.50 hours (0.25-0.50) and 0.79 hours (0.50-1.42) for the PCA and non-PCA groups, respectively (hazard ratio [HR], 1.64; 95% CI, 1.23-2.17; P=.001). TSTs in opioid-tolerant patients were 0.50 hours (0.25-0.75) and 1.00 hours (0.50-2.00) for the PCA and non-PCA groups, respectively (HR, 1.92; 95% CI, 1.32-2.78; P=.003); in opioid-naive patients, TST was not significantly different for the PCA versus non-PCA groups (HR, 1.35; 95% CI, 0.88-2.04; P=.162). Pain score (median NRS; interquartile range) over 24 hours was significantly lower in the PCA group (2.80; 2.15-3.22) than in the non-PCA group (3.00; 2.47-3.53; P=.020). PCA administration produces significantly higher patient satisfaction with pain control than non-PCA administration (P<.001).

CONCLUSIONS

Intravenous hydromorphone titration for severe cancer pain was achieved more effectively with PCA than with non-PCA administration.

Understanding the Chameleonic Breakthrough Cancer Pain

Breakthrough cancer pain (BTcP) is a variegated phenomenon, that often presents in different ways in each individual, and may change its presentation in the same individual during the course of disease. An appropriate assessment is fundamental for depicting the pattern of BTcP in individuals. This information is determinant for a personalised management of BTcP. The use of opioids as needed, is recommended for the management of BTcP. There are several options which should be chosen according to the individual pattern of BTcP. In general, a drug with a short onset and offset should be preferred. Although oral opioids may still have specific indications, fentanyl products have been found to be more rapid and effective, providing analgesia in 5-15 min. The most controversial point regards the opioid dose to be used. The presence of tolerance suggests using a dose that is proportional to the dose used for background analgesia. In contrast, regulatory studies have suggested using the minimal available dose to be titrated until the effective dose. Further large studies should definitely settle this never-ending question.

The role of the M1/M2 microglia in the process from cancer pain to morphine tolerance

Cancer pain, especially bone cancer pain, is a pain state often caused by inflammation or dysfunctional nerves. Moreover, in the management of cancer pain, opioid especially morphine is widely used, however, it also brings severe side effects such as morphine tolerance to the patient (Deandrea et al., 2008). A growing body of literatures demonstrated that neuroinflammation is mediated by microglia. As the macrophages like immune cells, microglia play an important role in the pathogenesis of cancer pain and morphine tolerance. Microglia acquire different activation states to regulate the function of these cells. As to M1 phenotype, microglia release pro-inflammatory cytokines and neurotoxic molecules that promote inflammation and cytotoxic reactions. Conversely, when microglia represent M2 phenotypes secreting anti-inflammatory cytokines and nutrient factors that promote the function of repair, regeneration and restore homeostasis. A better understanding of microglia activation in cancer pain and morphine tolerance is crucial for the development of hypothesized neuroprotective drugs. Targeting microglia different polarization states by the inhibition of their deleterious pro-inflammatory neurotoxicity and/or enhancing their beneficial anti-inflammatory protective function seems to be an effective treatment for cancer pain and morphine tolerance.

The Endless Question of Opioid Doses for Breakthrough Pain

This letter to the editor responds to comments in the still open debate regarding the use of breakthrough pain medications in cancer patients.

Effects of periodic intake of drugs of abuse (morphine) on HIV dynamics: Mathematical model and analysis

Drugs of abuse, such as opiates, have been widely associated with diminishing host-immune responses, including suppression of HIV-specific antibody responses. In particular, periodic intake of the drugs of abuse can result in time-varying periodic antibody level within HIV-infected individuals, consequently altering the HIV dynamics. In this study, we develop a mathematical model to analyze the effects of periodic intake of morphine, a widely used opiate. We consider two routes of morphine intake, namely, intravenous morphine (IVM) and slow-release oral morphine (SROM), and integrate several morphine pharmacodynamic parameters into HIV dynamics model. Using our non-autonomous model system we formulate the infection threshold, R_i, for global stability of infection-free equilibrium, which provides a condition for avoiding viral infection in a host. We demonstrate that the infection threshold highly depends on the morphine pharmacodynamic parameters. Such information can be useful in the design of antibody-based vaccines. In addition, we also thoroughly evaluate how alteration of the antibody level due to periodic intake of morphine can affect the viral load and the CD4 count in HIV infected drug abusers.

Implications of the Parenteral Opioid Shortage for Prescription Patterns and Pain Control Among Hospitalized Patients With Cancer Referred to Palliative Care

Importance

The recent parenteral opioid shortage (POS) has potential implications for cancer-related pain management in hospitalized patients.

Objective

This study compared changes in opioid prescriptions and clinically improved pain (CIP) among patients treated by an inpatient palliative care (PC) team before and after our institution first reported the POS.

Design, Setting, and Participants

A cohort study of 386 eligible patients with cancer treated at a comprehensive cancer center 1 month before and after the announcement of the POS. We reviewed data from electronic health records, including patient demographics, opioid type, route of administration, and dose. Board-certified palliative care specialists assessed CIP at follow-up day 1.

Exposures

The announcement of the POS by the institution's pharmacy and therapeutics committee on February 8, 2018.

Main Outcomes and Measures

The primary outcome was to measure the change in opioid prescription patterns of physicians, and the secondary outcome was to measure the proportion of patients who achieved CIP before and after announcement of the POS.

Results

Of 386 eligible patients, 196 were men (51%), 270 were white (70%), and the median age was 58 years (interquartile range, 46-67 years). Parenteral opioids were prescribed less frequently by the referring oncology teams after the POS (56 of 314 [18%]) vs before the POS (109 of 311 [35%]) (P < .001). The PC team also prescribed fewer parenteral opioids after the POS (96 of 336 [29%]) vs before the POS (159 of 338 [47%]) (P < .001). After the POS (vs before the POS), significantly fewer patients achieved CIP on follow-up day 1 (119 [62%] vs 144 [75%] of 193; P = .01). Multivariate analysis showed that before the POS, patients had an 89% higher chance of achieving CIP on follow-up day 1 (odds ratio, 1.89; 95% CI, 1.22-2.94; P = .005).

Conclusions and Relevance

There was a significant change in opioid prescription patterns associated with the POS. Furthermore, after the POS, fewer patients achieved CIP. These factors have potential implications for patient satisfaction and hospital length of stay.

Dichotomic effects of clinically used drugs on tumor growth, bone remodeling and pain management

Improvements in the survival of breast cancer patients have led to the emergence of bone health and pain management as key aspects of patient’s quality of life. Here, we used a female rat MRMT-1 model of breast cancer-induced bone pain to compare the effects of three drugs used clinically morphine, nabilone and zoledronate on tumor progression, bone remodeling and pain relief. We found that chronic morphine reduced the mechanical hypersensitivity induced by the proliferation of the luminal B aggressive breast cancer cells in the tumor-bearing femur and prevented spinal neuronal and astrocyte activation. Using MTT cell viability assay and MRI coupled to ¹⁸FDG PET imaging followed by ex vivo 3D µCT, we further demonstrated that morphine did not directly exert tumor growth promoting or inhibiting effects on MRMT-1 cancer cells but induced detrimental effects on bone healing by disturbing the balance between bone formation and breakdown. In sharp contrast, both the FDA-approved bisphosphonate zoledronate and the synthetic cannabinoid nabilone prescribed as antiemetics to patients receiving chemotherapy were effective in limiting the osteolytic bone destruction, thus preserving the bone architecture. The protective effect of nabilone on bone metabolism was further accompanied by a direct inhibition of tumor growth. As opposed to zoledronate, nabilone was however not able to manage bone tumor-induced pain and reactive gliosis. Altogether, our results revealed that morphine, nabilone and zoledronate exert disparate effects on tumor growth, bone metabolism and pain control. These findings also support the use of nabilone as an adjuvant therapy for bone metastases.

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.

The Regulatory Mechanisms and Therapeutic Potential of MicroRNAs: From Chronic Pain to Morphine Tolerance

Chronic pain, including cancer-related pain, is a pain condition often caused by inflammation or dysfunctional nerves. Chronic pain treatment poses a significant health care challenge, where opioids especially morphine are widely used and patients often develop tolerance over time with aggravated pain. microRNA (miRNA) is known to play important roles in regulating gene expressions in the nervous system to affect neuronal network plasticity related to algogenesis and the developing of morphine tolerance. In this article, we reviewed studies conducted in rodent animal models investigating the mechanisms of miRNAs regulation in chronic pain with different phenotypes and morphine tolerance. In addition, the potential of targeting miRNAs for chronic pain and morphine tolerance treatment is also reviewed. Finally, we point out the directions of the future research in chronic pain and morphine tolerance.

Non pharmacological interventions and non-fentanyl pharmacological treatments for breakthrough cancer pain: A systematic and critical review

BACKGROUND

Oral opioids or other pharmacological or non-pharmacological interventions are often suggested in the management of breakthrough cancer pain (BTcP). The aim of this systematic and critical review was to analyse and critically comment the evidence of any non-fentanyl therapies proposed for BTcP.

METHODS

A systematic literature search was carried out to find studies providing clinical data on any treatment excluding fentanyl products.

RESULTS

No data exist about the use of oral opioids. Some information is available on parenteral morphine in a large sample of patients and episodes of BTcP. For other treatments, including methadone, nitrous oxide, anti-inflammatory drugs, samarium, and gabapentin the existing data, observational and obtained in a small number of patients do not provide useful information to be generalized. Only ketamine, a drug difficult to use for many physicians, particularly in determined setting, provided some evidence according a randomized controlled double-blind study.

CONCLUSIONS

Recommendations suggesting the use of oral opioids or other pharmacological and non-pharmacologic interventions for BTcP, are not based on any, even minimal evidence. These treatments are worthwhile of further investigation, particularly in determined conditions that should fit the pharmacokinetics of oral opioids.

Neuron-restrictive silencer factor-mediated downregulation of μ-opioid receptor contributes to the reduced morphine analgesia in bone cancer pain

Neuron-restrictive silencer factor–induced downregulation of μ-opioid receptor is involved in the reduction of morphine analgesia in sarcoma-induced bone cancer pain.

Bone cancer pain has been reported to have unique mechanisms and is resistant to morphine treatment. Recent studies have indicated that neuron-restrictive silencer factor (NRSF) plays a crucial role in modulating the expression of the μ-opioid receptor (MOR) gene. The present study elucidates the regulatory mechanisms of MOR and its ability to affect bone cancer pain. Using a sarcoma-inoculated murine model, pain behaviors that represent continuous or breakthrough pain were evaluated. Expression of NRSF in the dorsal root ganglion (DRG) and spinal dorsal horn was quantified at the transcriptional and translational levels, respectively. Additionally, chromatin immunoprecipitation assays were used to detect NRSF binding to the promoter of MOR. Furthermore, NRSF was genetically knocked out by antisense oligodeoxynucleotide, and the expression of MOR and the effect of morphine were subsequently analyzed. Our results indicated that in a sarcoma murine model, NRSF expression is upregulated in dorsal root ganglion neurons, and the expression of NRSF mRNA is significantly negatively correlated with MOR mRNA expression. Additionally, chromatin immunoprecipitation analysis revealed that NRSF binding to the neuron-restrictive silencer element within the promoter area of the MOR gene is promoted with a hypoacetylation state of histone H3 and H4. Furthermore, genetically knocking down NRSF with antisense oligodeoxynucleotide rescued the expression of MOR and potentiated the systemic morphine analgesia. The present results suggest that in sarcoma-induced bone cancer pain, NRSF-induced downregulation of MOR is involved in the reduction of morphine analgesia. Epigenetically, up-regulation of MOR could substantially improve the effect of system delivery of morphine.

Recombinant protein transduction domain-Cu/Zn superoxide dismutase alleviates bone cancer pain via peroxiredoxin 4 modulation and antioxidation

Bone cancer pain (BCP) is a serious chronic clinical condition and reactive oxygen species (ROS) were considered to be involved in its development and persistency. Normally, superoxide dismutase (SOD) converts superoxide anions to hydrogen peroxide (H₂O₂) and H₂O₂ is then naturalized to be water by peroxiredoxin 4. We reported previously that recombinant protein transduction domain (PTD)-Cu/Zn SOD effectively scavenged excessive ROS and prevented cardiomyocytes from hypoxia-reoxygenation damage. However, whether PTD-Cu/Zn SOD would prevent BCP development is unknown. In the current study, we found that an implanted carcinoma in the rat tibia induced remarkable hyperalgesia, increased H₂O₂ levels and decreased SOD and peroxiredoxin 4 levels. After administration of recombinant PTD-Cu/Zn SOD to these tumor-burden rats, their hyperalgesia was significantly attenuated and peroxiredoxin 4 expression was significantly increased. In addition, an increased expression of N-methyl-d-aspartic acid (NMDA) receptors and a decreased expression of γ-aminobutyric acid (GABA) receptors in this cancer pain were prevented by PTD-Cu/Zn SOD administration or peroxiredoxin 4 overexpression. Our data suggested that reactive oxygen species, at least in part, play a role in cancer metastatic pain development and persistency which can be attenuated by the adminstration of recombinant PTD-Cu/Zn SOD via the peroxiredoxin 4 modulation from oxidative stress.

Options for Treating Pain in Cancer Patients with Dysphagia

Patients with chronic pain often develop dysphagia during the course of an advanced disease such as cancer. Opioids are the cornerstone of the management of cancer pain and are commonly administered orally. However, the oral route does not suit patients with dysphagia, who require alternative methods to administer analgesic drugs. Opioids given by parenteral or transdermal routes provide adequate pain control, being at least as efficacious as the oral route, but knowledge and experience in conversion ratios are mandatory when using these routes of administration. For breakthrough pain, transmucosal fentanyl preparations should be the preferred option and these can be given as needed due to the route of absorption. In addition, a new class of opioid formulations has been developed for use in dysphagic patients that are administered via nasogastric or enteral tubes while maintaining their sustained-release properties.

Morphine versus methylprednisolone or aminophylline for relieving dyspnea in patients with advanced cancer in China: a retrospective study

Context

Dyspnea is one of the most common and distressing symptoms that occurs in terminal cancer patients. However, there are no existing treatment guidelines for this condition in China.

Objective

This single-center, retrospective, observational study aimed to compare the efficacy of using morphine, methylprednisolone, or aminophylline to relieve the symptom of breathlessness in patients with advanced malignant tumors and to investigate the safety of these regimens during the treatment of dyspnea.

Methods

Between August 2011 and January 2015 we retrospectively reviewed the medical records of 343 terminally ill cancer patients with dyspnea who received morphine, methylprednisolone, or aminophylline. The therapeutic effect of each treatment by means of visual analogue scale (VAS) scores was assessed and compared. Statistical methods included Chi square and analysis of variance tests. Differences were considered significant when P < 0.05.

Results

VAS scores after treatment were (16.82 ± 10.89), (25.72 ± 15.03), and (31.95 ± 16.00) points in the morphine, methylprednisolone, and aminophylline group, respectively. These differences were found to be significantly different (P < 0.05). The effectiveness ratings were 86.44, 62.16, and 49.12%, respectively (P < 0.05).

Conclusions

We found that morphine subcutaneous injection for advanced cancer patients with dyspnea was safe and typically more effective than methylprednisolone or aminophylline. Therefore, morphine treatment could significantly improve the quality of life in terminal cancer patients with short life expectancies who are experiencing shortness of breath.

Intravenous morphine titration as a rapid and efficient analgesia for adult patients with femoral shaft fractures after injury

This study aimed to compare the analgesic effects of intravenous ibuprofen and intravenous morphine titration for femoral shaft fractures in adult patients. In total, 293 participants were enrolled and randomly received intravenous ibuprofen or intravenous morphine titration. Their visual analogue scale (VAS) results were recorded every 5 minutes after the first administration. The VAS scores before and during transport were also measured. Meanwhile, the type and frequency of the adverse effects were also recorded in both groups. Patients treated with morphine showed a faster and greater reduction in the VAS than those in the ibuprofen group within 1 hour after the first administration. Interestingly, intravenous morphine titration provided consistent analgesia even during the further transport. No significant immediate adverse event was observed in all of the participants, except for sedation, which might be beneficial for keeping the patient quiet and might not be arbitrarily attributed to adverse effects. No addiction was noted in the morphine group. This study demonstrated that intravenous morphine titration is a faster and more efficient analgesia for femoral shaft fractures than ibuprofen in adult patients immediately after injury.

Breakthrough Cancer Pain: Ten Commandments

The term "breakthrough cancer pain" (BTcP) was introduced about 25 years ago. Peaks of pain intensity reported in patients with cancer had been invariably examined in the past years, providing relevant information for a better knowledge of this phenomenon and its treatment. The aim of this critical review was to provide the golden rules, namely, the 10 commandments, for a correct diagnostic pathway of BTcP and a consequent personalized pharmacological treatment. These are as follows: 1) assessment of background analgesia, 2) drugs used for background analgesia, 3) BTcP is a frequent phenomenon, 4) characteristics of BTcP, 5) diagnosis of BTcP, 6) continuous assessment, 7) tailored pharmacological treatment of BTcP, 8) selection of BTcP medication, 9) dosing BTcP medications, and 10) education. These steps may help clinicians to recognize and treat BTcP adequately.

Breakthrough pain in cancer patients: prevalence, mechanisms and treatment options

PURPOSE OF REVIEW

The aim of this article was to examine the definition, the characteristics, and the management of breakthrough cancer pain (BTP) in cancer patients by a critical review of recent literature.

RECENT FINDINGS

BTP should be more correctly defined as an episode of severe intensity in patients receiving an adequate treatment with opioids able to provide at least mild analgesia. BTP is a heterogeneous condition as episodes vary between individuals. BTP can be classified into two big distinct pictures: spontaneous-type and incident-type pain. The principal pharmacological treatment of BTP is represented by the administration of opioids as needed. Recent reviews revealed that transmucosal preparation of fentanyl provided superior and more rapid pain relief as compared with placebo in the first 30 min after dosing. Few comparison studies among fentanyl products have been performed.Finally, although dose titration was recommended for years, a meaningful dosing according to the level of opioid tolerance may enhance the advantages of such products.

SUMMARY

BTP represents a serious problem reported by many cancer patients despite receiving regular use of opioids. Subgroups of breakthrough pain have been identified. Different modalities of pharmacological interventions are available. Further studies are warranted to assess the net benefit of these drugs to assist decision-making by patients, clinicians, and payers according to individual clinical conditions.

Alternative routes to oral opioid administration in palliative care: a review and clinical summary

OBJECTIVE

A major goal of palliative care is to provide comfort, and pain is one of the most common causes of treatable suffering in patients with advanced disease. Opioids are indispensable for pain management in palliative care and can usually be provided by the oral route, which is safe, effective, and of lowest cost in most cases. As patients near the end of life, however, the need for alternate routes of medication increases with up to 70% of patients requiring a nonoral route for opioid administration. In order to optimize patient care, it is imperative that clinicians understand existing available options of opioid administration and their respective advantages and disadvantages.

METHODS

We performed a literature review to describe the most commonly used and available routes that can substitute for oral opioid therapy and to provide a summary of factors affecting choice of opioid for use in palliative care in terms of benefits, indications, cautions, and general considerations.

RESULTS

Clinical circumstances will largely dictate appropriateness of the route selected. When the oral route is unavailable, subcutaneous, intravenous, and enteral routes are preferred in the palliative care population. The evidence supporting sublingual, buccal, rectal, and transdermal gel routes is mixed.

CONCLUSIONS

This review is not designed to be a critical appraisal of the quality of current evidence; rather, it is a summation of that evidence and of current clinical practices regarding alternate routes of opioid administration. In doing so, the overarching goal of this review is to support more informed clinical decision making.

Direct effects of morphine but not of fentanyl-type opioids on human 5-HT3A receptors in outside-out patch-clamp studies

BACKGROUND

The alkaloid morphine is historically the oldest opiate, yet still today it has clinically important uses in analgesic therapies. The main analgesic effect of opioids, including synthetic opioids belonging to the family of 4-anilidopiperidines, is mediated via activation of opioid receptors spread throughout the peripheral and central nervous system. However, morphine acting as a 'dirty' drug also exhibits effects on other receptor systems, e.g., the serotonergic system and its 5-HT3 receptor. Therefore, this study focuses on the interaction of morphine and fentanyl-type opioids (alfentanil, remifentanil and sufentanil) with 5-HT3A receptors.

METHODS

Excised outside-out patches from human embryonic kidney-293 cells, stably transfected with the human 5-HT3A receptor cDNA, were used to determine the opioid effects using the patch-clamp technique.

RESULTS

Within clinical concentrations, the effects of morphine are concentration-dependent. Morphine reduced current amplitudes, as well as activation and decay time constants. These effects were not competitive. Contrary to these results, all fentanyl-type opioids only exerted effects far above their clinical concentration ranges. These effects were not homogenous but varying.

CONCLUSIONS

Morphine is an opioid compound exhibiting special antagonistic interaction with 5-HT3A receptors. This interaction is not shared by the newer synthetic derivatives of the fentanyl-type opioids in the clinical relevant concentration range.

A Prospective, Non-interventional Study of Assessment and Treatment Adequacy of Pain in the Emergency Department of a Tertiary Care Cancer Hospital

INTRODUCTION

Pain is the most common reason for emergency department (ED) visits by the cancer patients. Treatment inconsistency and inadequacy are reported worldwide in the management of ED pain. We conducted a non-interventional observational study of 100 patients visiting ED with moderate to severe pain in a tertiary care cancer center.

AIMS

The goal of this study was to describe the characteristics of pain and its treatment by oncologists in ED.

MATERIALS AND METHODS

Management of 100 adult patients with complaints of moderate to severe pain was observed by the investigator in ED. Treatment was provided by the doctors of respective oncological services. Later, patients were interviewed by the investigator to collect data about the details of their pain and treatment adequacy.

RESULTS

On arrival to ED, about 65% patients reported severe pain, however no formal pain assessment was performed and no patient received strong opioids. Poor compliance for prescribed analgesic medications was noted in a large number of patients (31%), primarily due to suboptimal pain relief and lack of awareness. Protocol based analgesic treatment was non-existent in ED. Majority of patients remained in significant pain after 30 min of analgesic administration and 24% patients could never achieve more than 50% pain relief at the time of discharge.

CONCLUSION

Due to lack of formal pain assessment and laid down protocols, suboptimal pain management is commonly prevalent in ED. Use of strong opioids continues to be scarce in management of severe pain. There is a need to formulate pain management protocols for ED pain.

Painful boney metastases

Boney metastasis may lead to terrible suffering from debilitating pain. The most likely malignancies that spread to bone are prostate, breast, and lung. Painful osseous metastases are typically associated with multiple episodes of breakthrough pain which may occur with activities of daily living, weight bearing, lifting, coughing, and sneezing. Almost half of these breakthrough pain episodes are rapid in onset and short in duration and 44% of episodes are unpredictable. Treatment strategies include: analgesic approaches with "triple opioid therapy", bisphosphonates, chemotherapeutic agents, hormonal therapy, interventional and surgical approaches, steroids, radiation (external beam radiation, radiopharmaceuticals), ablative techniques (radiofrequency ablation, cryoablation), and intrathecal analgesics.

Opioid use and effectiveness of its prescription at discharge in an acute pain relief and palliative care unit

The aim of this study was to present how opioids are used in an acute pain relief and palliative care unit (APRPCU), where many patients with difficult pain conditions are admitted from GPs, home palliative care programs, oncology departments, other hospitals or emergency units, and other regional places. From a consecutive sample of cancer patients admitted to an APRPCU for a period of 6 months, patients who had been administered opioids were included in this survey. Basic information was collected as well as opioid therapy prescribed at admission and, subsequently, during admission and at time of discharge. Patients were discharged once stabilization of pain and symptoms were obtained and the treatment was considered to be optimized. One week after being discharged, patients or relatives were contacted by phone to gather information about the availability of opioids at dosages prescribed at time of discharge. One hundred eighty six of 231 patients were specifically admitted for uncontrolled pain, with a mean pain intensity of 6.8 (SD 2.5). The mean dose of oral morphine equivalents in patients receiving opioids before admission was 45 mg/day (range 10-500 mg). One hundred seventy five patients (75.7 %) were prescribed around the clock opioids at admission. About one third of patients changed treatment (opioid or route). Forty two of 175 (24 %), 27/58 (46.5 %), 10/22 (45.4 %), and 2/4 (50 %) patients were receiving more than 200 mg of oral morphine equivalents, as maximum dose of the first, second, third, and fourth opioid prescriptions, respectively. The pattern of opioids changed, with the highest doses administered with subsequent line options. The mean final dose of opioids, expressed as oral morphine equivalents, for all patients was 318 mg/day (SD 798), that is more than six times the doses of pre-admission opioid doses. One hundred eighty six patients (80.5 %) were prescribed a breakthrough cancer pain (BTcP) medication at admission. Sixty five patients changed their BTcP prescription, and further 27 patients changed again. Finally, eight patients were prescribed a fourth BTcP medication. Of 46 patients available for interview, the majority of them (n = 39, 84 %) did not have problems with their GPs, who facilitated prescription and availability of opioids at the dosages prescribed at discharge. For patients with severe distress, APRPCUs may guarantee a high-level support to optimize pain and symptom intensities providing intensive approach and resolving highly distressing situations in a short time by optimizing the use of opioids.

Continuous morphine infusion for end-stage lung cancer patients

End-stage cancer patients frequently receive continuous morphine infusion (CMI) to alleviate the various symptoms associated with cancer progression or adverse events; however, there have been a limited number of studies concerning such patients. We conducted a retrospective analysis of 79 end-stage lung cancer patients who received CMI at the Kyoto University Hospital, Kyoto, Japan between 2008 and 2010. Thirty-one patients (39%) received CMI intravenously and 48 (61%) received it subcutaneously. The patients were divided into four groups based on the indications for CMI: group A (uncontrolled pain; n=9), group B (dyspnea; n=44), group C (both dyspnea and pain; n=13) and group D (an inability to take oral medicine; n=13). The median maximum dose of morphine in groups A-D was 60.0, 25.0, 50.0 and 15.0 mg/day, respectively. The median survival time from the start of CMI was 4 days (range 0-136). In our limited experience, pain, dyspnea and the inability to take oral medicine were identified as indications for CMI in end-stage lung cancer patients, with dyspnea being the major indication for CMI. Patients in group B (dyspnea) required a lower dose of morphine for alleviation compared with those in groups A (uncontrolled pain) and C (both dyspnea and pain). The survival time from the initiation of CMI was markedly shorter in patients with dyspnea (groups B and C) than in patients without dyspnea (group A). Further studies are required to facilitate the effective and appropriate use of CMI in end-stage lung cancer patients. Dyspnea was the major indication for CMI in end-stage lung cancer patients, and the survival time was extensively limited in such patients.

Pain in blood cancers

Patients with blood-related cancers (BRC) suffer from a substantial symptom burden, including several pain syndromes sustained by different causes and pathogenetic mechanisms. So, with regard to pain, a multifaceted clinical scenario may be observed in this setting. Indeed, pain may be correlated to disease itself, to disease-associated complications, to iatrogenic causes or may be due to unrelated clinical conditions. A close diagnostic procedure for the assessment of the underlying causes of the pain and of its pathogenetic mechanisms may direct the treatment approach which should be based on a multidisciplinary management and requires the integration of etiology-targeted interventions and painkilling drugs. The World Health Organization's three-step analgesic ladder for cancer pain relief can provide adequate pain control using oral drugs in most patients with BRC on pain, although more complex interventions may be necessary for many difficult-to-treat pain syndromes which are not infrequently encountered in this setting.

Activation of spinal TDAG8 and its downstream PKA signaling pathway contribute to bone cancer pain in rats

Bone cancer pain is difficult to treat and has a strong impact on the quality of life of patients. Few therapies have emerged because the molecular mechanisms underlying bone cancer pain are poorly understood. Recently, T-cell death-associated gene 8 (TDAG8) has been shown to participate in complete Freund's adjuvant-induced chronic inflammatory pain. In this study, we aimed to examine whether TDAG8 and its downstream protein kinase A (PKA) pathway are involved in bone cancer pain. A bone cancer pain model was made by inoculation of Walker 256 cells into the intramedullary space of rat tibia. Spinal TDAG8 expression was increased after inoculation with tumor cells. Intrathecal TDAG8 siRNA attenuated bone cancer pain behaviors during the initiation and maintenance phases; there were also concomitant decreases in TDAG8 mRNA and protein levels in spinal cord. Moreover, we found spinal PKA and phosphorylated cAMP response element-binding (pCREB) protein levels were up-regulated in the rat model of bone cancer pain. Knockdown of TDAG8 resulted in reduced bone cancer pain-induced spinal PKA and pCREB protein expression in two procedures. Furthermore, intrathecal H-89 (a PKA inhibitor) significantly attenuated bone cancer pain behaviors in rats. Our results suggest a causal relationship between TDAG8 expression and the initiation and maintenance of bone cancer pain. Activation of spinal TDAG8 contributes to bone cancer pain through the PKA signaling pathway in rats. These findings may lead to novel strategies for the treatment of bone cancer pain.

[Neuropathic and tumour-induced headache: Therapeutic options]

Cancer pain in the field of otolaryngology can be effectively alleviated. Only very few questions regarding the patient's history of pain are required to understand the type of pain being dealt with and to be able to make the correct selection of analgetic agents. It is particularly important to treat tumor breakthrough pain appropriately, for which a sufficient number of therapeutic agents are available. The present article comments on the various possibilities of specific drugs and interventional therapeutic approaches, as well as their specific characteristics within the field of otolaryngology, supplemented with various tricks for their practical application. Using these basic rules, most problems can be identified and specific treatments optimized. The progression of cancer pain may show wide dynamic ranges, and the therapeutic approach should always be adjusted to the current situation. Palliative care of a cancer patient may be particularly challenging in that, not only the treatment of pain, but also the treatment of respiratory distress is of key importance.

Spinal activation of delta opioid receptors alleviates cancer-related bone pain

Over the past few years, significant progress has been made in cancer therapy. Indeed, the lifespan of cancer patients has significantly increased. Although patients live longer, cancer-related pain remains a daily problem affecting their quality of life, especially when metastases reach the bone. In patients coping with cancer-induced bone pain, morphine and NSAIDs, often used in combination with other medications, are the most commonly used drugs to alleviate pain. However, these drugs have dose-limiting side effects. Morphine and other routinely used opioids are mu opioid receptor (MOPR) agonists. The MOPR is responsible for most opioid-related adverse effects. In the present study, we revealed potent analgesic effects of an intrathecally-administered selective delta opioid receptor (DOPR) agonist, deltorphin II, in a recently developed rat bone cancer model. Indeed, we found that deltorphin II dose-dependently reversed mechanical allodynia 14 days post-surgery in this cancer pain model, which is based on the implantation of mammary MRMT-1 cells in the femur. This effect was DOPR-mediated as it was completely blocked by naltrindole, a selective DOPR antagonist. Using the complete Freund's adjuvant model of inflammatory pain, we further demonstrated that deltorphin II was equipotent at alleviating inflammatory and cancer pain (i.e. similar ED50 values). Altogether, the present results show, for the first time, that activation of spinal DOPRs causes significant analgesia at doses sufficient to reduce inflammatory pain in a rat bone cancer pain model. Our results further suggest that DOPR represents a potential target for the development of novel analgesic therapies to be used in the treatment of cancer-related pain.

The management of cancer pain

The experience of pain in cancer is widely accepted as a major threat to quality of life, and the relief of pain has emerged as a priority in oncology care. Pain is associated with both the disease as well as treatment, and management is essential from the onset of early disease through long-term survivorship or end-of-life care. Effective relief of pain is contingent upon a comprehensive assessment to identify physical, psychological, social, and spiritual aspects and as a foundation for multidisciplinary interventions. Fortunately, advances in pain treatment and in the field of palliative care have provided effective treatments encompassing pharmacological, cognitive-behavioral, and other approaches. The field of palliative care has emphasized that attention to symptoms such as pain is integral to quality cancer care.