Methadone for cancer pain

Opioid analgesics for nociceptive cancer pain: A comprehensive review

Pain is one of the most burdensome symptoms in people with cancer, and opioid analgesics are considered the mainstay of cancer pain management. For this review, the authors evaluated the efficacy and toxicities of opioid analgesics compared with placebo, other opioids, nonopioid analgesics, and nonpharmacologic treatments for background cancer pain (continuous and relatively constant pain present at rest), and breakthrough cancer pain (transient exacerbation of pain despite stable and adequately controlled background pain). They found a paucity of placebo-controlled trials for background cancer pain, although tapentadol or codeine may be more efficacious than placebo (moderate-certainty to low-certainty evidence). Nonsteroidal anti-inflammatory drugs including aspirin, piroxicam, diclofenac, ketorolac, and the antidepressant medicine imipramine, may be at least as efficacious as opioids for moderate-to-severe background cancer pain. For breakthrough cancer pain, oral transmucosal, buccal, sublingual, or intranasal fentanyl preparations were identified as more efficacious than placebo but were more commonly associated with toxicities, including constipation and nausea. Despite being recommended worldwide for the treatment of cancer pain, morphine was generally not superior to other opioids, nor did it have a more favorable toxicity profile. The interpretation of study results, however, was complicated by the heterogeneity in the study populations evaluated. Given the limited quality and quantity of research, there is a need to reappraise the clinical utility of opioids in people with cancer pain, particularly those who are not at the end of life, and to further explore the effects of opioids on immune system function and quality of life in these individuals.

The effects of OPRM1 118A>G on methadone response in pain management in advanced cancer at end of life

Cancer pain is the most feared symptom at end of life. Methadone has advantages over other opioids but is associated with significant variability in clinical response, making dosing challenging in practice. OPRM1 is the most studied pharmacogene associated with the pharmacodynamics of opioids, however reports on the association of the A118G polymorphism on opioid dose requirements are conflicting, with no reports including methadone as the primary intervention. This association study on OPRM1 A118G and response to methadone for pain management, includes a review of this genetic factor's role in inter-patient variability. Fifty-four adult patients with advanced cancer were recruited in a prospective, multi-centre, open label dose individualization study. Patient characteristics were not shown to influence methadone response, and no significant associations were observed for methadone dose or pain score. The findings of our review of association studies for OPRM1 A118G in advanced cancer pain demonstrate the importance of taking ancestry into account. While our sample size was small, our results were consistent with European populations, but in contrast to studies in Chinese patients, where carriers of the A118G polymorphism were associated with higher opioid dose requirements. Pharmacogenetic studies in palliative care are challenging, continued contribution will support future genotype-based drug dosing guidelines.

Methadone dose escalation in patients with opioid use disorder and cancer as a strategy for controlling cancer-related pain: A case series

OBJECTIVES

Opioid use disorder (OUD) and cancer gained attention as co-occurring diseases in the last 2 decades due to the possible relationship between opioid prescriptions for cancer pain and the risk of developing substance use disorder in cancer patients. However, little is known about patients previously diagnosed with OUD who develop cancer and how to manage both OUD symptoms and control pain.

METHODS

The present case series deals with this subpopulation and proposes a dose escalation of methadone to control both the cancer-related pain and drug addiction symptoms.

RESULTS

This approach is peculiar because methadone is not used as a first-line treatment in cancer pain management and is not often used as a second-line treatment as well. Our 4 patients experienced good clinical control of symptoms and no major adverse reactions.

SIGNIFICANCE OF RESULTS

The subgroup of patients with OUD who develop cancer could be the perfect population to reconsider the use of methadone as a first-line treatment for cancer pain. Prospective studies are needed to evaluate the efficacy and safety of increasing doses of methadone in these patients to validate our clinical approach.

Case report: The lesson from opioid withdrawal symptoms mimicking paraganglioma recurrence during opioid deprescribing in cancer pain

Pain is one of the predominant and troublesome symptoms that burden cancer patients during their whole disease trajectory: adequate pain management is a fundamental component of cancer care. Opioid are the cornerstone of cancer pain relief therapy and their skillful management must be owned by physicians approaching cancer pain patients. In light of the increased survival of cancer patients due to advances in therapy, deprescription should be considered as a part of the opioid prescribing regime, from therapy initiation, dose titration, and changing or adding drugs, to switching or ceasing. In clinical practice, opioid tapering after pain remission could be challenging due to withdrawal symptoms' onset. Animal models and observations in patients with opioid addiction suggested that somatic and motivational symptoms accompanying opioid withdrawal are secondary to the activation of stress-related process (mainly cortisol and catecholamines mediated). In this narrative review, we highlight how the lack of validated guidelines and tools for cancer patients can lead to a lower diagnostic awareness of opioid-related disorders, increasing the risk of developing withdrawal symptoms. We also described an experience-based approach to opioid withdrawal, starting from a case-report of a symptomatic patient with a history of metastatic pheochromocytoma-paraganglioma.

Clinical effectiveness and safety of intraoperative methadone in patients undergoing laparoscopic hysterectomy: a randomised, blinded clinical trial

Background

Laparoscopic hysterectomy is often carried out as day-stay surgery. Minimising postoperative pain is therefore of utmost importance to ensure timely discharge from hospital. Methadone has several desirable pharmacological features, including a long elimination half-life. Therefore, a single intraoperative dose could provide long-lasting pain relief.

Methods

Patients scheduled to undergo laparoscopic hysterectomy were randomly allocated to receive methadone (0.2 mg kg-1) or morphine (0.2 mg kg-1) intraoperatively, 60 min before tracheal extubation. Primary outcomes were opioid consumption (oral morphine equivalents in milligrams) at 6 and 24 h. Secondary outcomes included pain intensity at rest and during coughing, patient satisfaction, postoperative nausea and vomiting, and adverse events up to 72 h after completion of surgery.

Results

The postoperative median opioid consumption was reduced in the methadone group compared with the morphine group at 6 h (35.5 [0-61] mg vs 48 [31-74.5] mg; P=0.01) and 24 h (42 [10-67] mg vs 54.5 [31-83] mg; P=0.03). On arrival at the PACU, pain at rest was significantly lower in patients receiving methadone (numeric rating scale: 3 [2-5] vs 5 [3-6]), whereas pain scores at rest and coughing were not significantly different throughout the rest of the observation period. No differences in other secondary outcomes were found.

Conclusions

In this randomised, blinded, controlled trial, opioid consumption was reduced during the first 24 postoperative hours in patients receiving methadone without causing an increase in adverse events. The difference observed might be considered as small and of limited clinical relevance.

Clinical trial registration

NCT03908060; EudraCT no. 2018-004351-20.

Identification of Factors Contributing to Methadone-Induced Daytime Sleepiness in Cancer Patients and Proposal of the Conversion Ratio from Other Opioids to Oral Methadone: A Retrospective Cohort Study

Background

When methadone is used to treat cancer pain, the Japanese health insurance system recommends to determine the starting dose according to the equivalency conversion table based on the morphine-equivalent daily dose (MEDD) of prior opioids proposed by the National Comprehensive Cancer Network. Owing to the wide range in variability of the conversion table, methadone increases the incidence of daytime sleepiness.

Objective

To identify the factors associated with daytime sleepiness and propose a conversion ratio from pretreatment MEDD to oral methadone that decreases the risk of daytime sleepiness.

Design

Retrospective cohort study.

Setting/Subjects

One hundred patients who started oral methadone to relieve cancer pain at Ashiya Municipal Hospital (Hyogo, Japan) from January 1, 2013, to August 31, 2022, were enrolled.

Measurements

The primary endpoint, the conversion ratio from pretreatment MEDD to oral methadone without daytime sleepiness, was determined using receiver operator characteristic (ROC) curve analysis.

Results

The incidence of daytime sleepiness within seven days of methadone initiation was 40.0%. The factors identified as contributing to daytime sleepiness were pretreatment MEDD (odds ratio [OR]: 0.941, 95% confidence interval [CI]: 0.916-0.966, p <0.001) and methadone dose (OR: 1.395, 95% CI: 1.178-1.652, p <0.001). The conversion ratio from pretreatment MEDD to oral methadone was 0.24, with an area under the ROC curve of 0.909 (p <0.001).

Conclusions

Daytime sleepiness developed when methadone dose is high relative to pretreatment MEDD. To the best of our knowledge, this is the first study to suggest the conversion ratio from pretreatment MEDD to oral methadone without causing daytime sleepiness.

Reply to "A better interpretation of data regarding the opioid switching to methadone"

In our article ?Methadone switching for refractory cancer pain' (BMC palliative care, 2022) we explore the efficacy, safety and economics of methadone in treatment of patients with refractory cancer pain in China. Professor Mercadante provided a better interpretation of data regarding the opioid switching to methadone in the Matters Arising. In this article, we answered the questions in Mercadante et al.'s comments one by one.

Oral Methadone versus Morphine IR for Patients with Cervical Cancer and Neuropathic Pain: A Prospective Randomised Controlled Trial

Objectives

In India, cervical cancer is the most common cancer among women and makes up for up to 29% of all registered cancer in females. Cancer-related pain is one of the major distressing symptoms for all cancer patients. Pain is characterised as somatic or neuropathic, and the total pain experience is often mixed. Conventional opioids are the backbone of analgesic treatment but are most often not sufficient in alleviating neuropathic pain, common in cervical cancer. Accumulating evidence of the advantage of methadone compared to conventional opioids, due to agonist action at both μ and q opioid receptors, N-methyl-D-aspartate (NMDA) antagonist activity and the ability to inhibit the reuptake of monoamines has been demonstrated. We hypothesised that, with these properties', methadone might be a good option for the treatment of neuropathic pain in patients with cervical cancer.

Material and Methods

Patients with cervical cancer stages ll-lll were enrolled in this randomized controlled trial. A comparison was made between methadone versus immediate release morphine (IR morphine), with increasing doses until pain was controlled. Inclusion-period was from October 3rd to December 31st 2020, and the total patient-study period was 12 weeks. Pain intensity was assessed according to the Numeric Rating Scale (NRS) and Douleur Neuropathique (DN4). The primary objective was to determine whether methadone was clinically superior versus noninferior to morphine as an analgesic for the treatment of cancer related neuropathic pain in women with cervical cancer.

Results

A total of 85 women were included; five withdrew and six died during the study period, leaving 74 patients completing the study. All participants showed a reduction in mean values of NRS and DN4 from the time of inclusion and to the end of the study period, for IR morphine and methadone 8.4-2.7 and 8.6-1.5, respectively (P < 0.001). The DN4 score mean reduction for Morphine and Methadone were 6.12-1.37 and 6.05-0, respectively (P < 0.001). Side effects were more common in the group of patients receiving IR morphine compared to the patients treated with methadone.

Conclusion

We found that Methadone had a superior analgesic effect with good overall tolerability compared with morphine as a first-line strong opioid for the management of cancer-related neuropathic pain.

High-dose opioids for chronic non-cancer pain: an overview of Cochrane Reviews

BACKGROUND

This overview was originally published in 2017, and is being updated in 2022.  Chronic pain is typically described as pain on most days for at least three months. Chronic non-cancer pain (CNCP) is any chronic pain that is not due to a malignancy. Chronic non-cancer pain in adults is a common and complex clinical issue, for which opioids are prescribed by some physicians for pain management. There are concerns that the use of high doses of opioids for CNCP lacks evidence of effectiveness, and may increase the risk of adverse events.

OBJECTIVES

To describe the evidence from Cochrane Reviews and overviews regarding the efficacy and safety of high-dose opioids (defined as 200 mg morphine equivalent or more per day) for CNCP.

METHODS

We identified Cochrane Reviews and overviews by searching the Cochrane Database of Systematic Reviews in The Cochrane Library. The date of the last search was 21 July 2022. Two overview authors independently assessed the search results. We planned to analyse data on any opioid agent used at a high dose for two weeks or more for the treatment of CNCP in adults.

MAIN RESULTS

We did not identify any reviews or overviews that met the inclusion criteria. The excluded reviews largely reflected low doses or titrated doses, where all doses were analysed as a single group; we were unable to extract any data for high-dose use only.

AUTHORS' CONCLUSIONS

There is a critical lack of high-quality evidence, in the form of Cochrane Reviews, about how well high-dose opioids work for the management of CNCP in adults, and regarding the presence and severity of adverse events.  No evidence-based argument can be made on the use of high-dose opioids, i.e. 200 mg morphine equivalent or more daily, in clinical practice. Considering that high-dose opioids have been, and are still being used in clinical practice to treat CNCP, knowing about the efficacy and safety of these higher doses is imperative.

[Pain management in German specialized outpatient palliative care : A cross-sectional study to present the current pain management of palliative patients in the home environment]

BACKGROUND

With the help of specialized outpatient palliative care teams (German abbreviation: SAPV), seriously ill and dying patients in Germany can be adequately cared for in their home environment until the end of their lives; however, there are no uniform standards or guidelines for well-executed pain management right now.

OBJECTIVE

This approach serves as basic research in the field of public health research. This is intended to present which methods (use of different professional groups, use of pain medications, alternative medical treatment etc.) the individual SAPV teams use for pain management. From this it can be deduced which procedures can be considered particularly effective.

MATERIAL AND METHODS

This cross-sectional study was conducted in May 2021. All German SAPV teams (n = 307) listed on the homepage of the German Association for Palliative Medicine (DGP) were contacted by post and invited to participate. A total of 175 teams (57%) responded to the request and were included in the evaluation. A descriptive data analysis was performed.

RESULTS

Pain management in the German outpatient care of palliative patients is based on several components. All common pain medications are used, but primarily metamizole (99.4%) as a non-opioid analgesic, morphine (98.3%) from the opiate series and pregabalin (96.6%) as a co-analgesic are mainly prescribed. If pain therapy fails, 22.5% of the SAPV teams perform palliative sedation for symptom control on a regular basis.

CONCLUSION

This cross-sectional study is the first of its kind to provide a general overview of the treatment options for pain management in German outpatient palliative care. In comparison with international studies, the question arises as to whether uniform therapy schemes and a reduction in the medication available in the individual SAPV teams could lead to an improvement in patient care.

Treatment of painful calciphylaxis with methadone in a palliative care unit: A case report

A 72-year-old female was admitted with severe calciphylaxis-associated bilateral leg pain on a background of end-stage renal failure on hemodialysis. Palliative care input was requested, and following transfer to our unit she was commenced on low-dose methadone as adjunctive analgesic therapy. A remarkable and sustained analgesic response was observed. Calciphylaxis is associated with severe pain, and careful consideration of analgesic agents and their pharmacokinetics in patients with end-stage renal failure is required.

Association of KCNJ6 rs2070995 and methadone response for pain management in advanced cancer at end-of-life

Opioids are the therapeutic agents of choice to manage moderate to severe pain in patients with advanced cancer, however the unpredictable inter-individual response to opioid therapy remains a challenge for clinicians. While studies are few, the KCNJ6 gene is a promising target for investigating genetic factors that contribute to pain and analgesia response. This is the first association study on polymorphisms in KCNJ6 and response to methadone for pain management in advanced cancer. Fifty-four adult patients with advanced cancer were recruited across two study sites in a prospective, open label, dose individualisation study. Significant associations have been previously shown for rs2070995 and opioid response in opioid substitution therapy for heroin addiction and studies in chronic pain, with mixed results seen in postoperative pain. In this study, no associations were shown for rs2070995 and methadone dose or pain score, consistent with other studies conducted in patients receiving opioids for pain in advanced cancer. There are many challenges in conducting studies in advanced cancer with significant attrition and small sample sizes, however it is hoped that the results of our study will contribute to the evidence base and allow for continued development of gene-drug dosing guidelines for clinicians.

Time to initiate randomized controlled clinical trials with methadone in cancer patients

Public media coverage has fueled a demand for methadone as potential cure for cancer itself. Because patients have asked for respective prescriptions, clinical societies issued statements warning against the use of methadone as long as preclinical findings have not been supported by clinical evidence. In fact, not all preclinical data clearly support relevant effects. However, strong epidemiologic data suggest beneficial effects of methadone on cancer. Alternative explanations, namely better safety of methadone or hidden selection bias, seem less likely. This uncertainty can only be resolved by randomized controlled clinical trials. This review discusses all relevant data pertinent to methadone and cancer, uncovers supportive epidemiologic data, and suggests possible study designs.

The Use of Low-Dose Methadone as Add-On to Ongoing Opioid Treatment in Palliative Cancer Care—An Underrated Treatment?

The aim of this review is to summarize the current knowledge of low-dose methadone treatment in palliative cancer care. In Sweden, methadone is quite common in specialized palliative care, where almost a tenth of patients are prescribed this drug. Negative attitudes towards methadone do not seem to prevent it from being used for pain management, and by starting with low doses and then increasing slowly and gradually, methadone can apparently be introduced safely. It is still uncertain whether methadone has a better analgesic effect than other opioids. However, for pain relief in cancer patients with severe and complex cancer-related pain, NMDA receptor inhibition with methadone may, in selected cases, be an attractive alternative, especially in the form of low-dose supplements to other ongoing opioids. Due to long half-life and complex metabolism, the use of methadone requires an experienced physician and solid follow-up. Continuous administration of opioids, including low-dose methadone, has been proven effective and safe in reducing pain in dying patients without increasing the risk of confusion, regardless of age.

Managing Pain and Discomfort in Children with Cancer

PURPOSE OF REVIEW

Approximately 15,600 children are diagnosed with cancer annually. Many of these children have cancer-related pain that improves with cancer treatment, but some develop intractable pain from cancer progression or sequelae from treatment modalities. The purpose of this paper is to provide a critical evaluation of the literature relevant to pain management in children with cancer. We intend to emphasize important and up-to-date findings in pharmacology, interventional pain management, and complementary and alternative medicine.

RECENT FINDINGS

Alternative medications and routes of administration, complementary and alternative medicine techniques, and interventional pain procedures offer possible routes for a multi-pronged pediatric cancer pain management plan, although high-level data is often lacking. To improve pediatric cancer pain management, a multifaceted approach embracing the biopsychosocial model of pain is recommended, incorporating evidence-based pharmacology, complementary and alternative medicine techniques, and if needed, interventional pain procedures.

Depression and Long-Term Prescription Opioid Use and Opioid Use Disorder: Implications for Pain Management in Cancer

OPINION STATEMENT

Preventing depression in cancer patients on long-term opioid therapy should begin with depression screening before opioid initiation and repeated screening during treatment. In weighing the high morbidity of depression and opioid use disorder in patients with chronic cancer pain against a dearth of evidence-based therapies studied in this population, patients and clinicians are left to choose among imperfect but necessary treatment options. When possible, we advise engaging psychiatric and pain/palliative specialists through collaborative care models and recommending mindfulness and psychotherapy to all patients with significant depression alongside cancer pain. Medications for depression should be reserved for moderate to severe symptoms. We recommend escitalopram/citalopram or sertraline among selective serotonin reuptake inhibitors (SSRIs), or the serotonin and norepinephrine reuptake inhibitors (SNRIs) duloxetine, venlafaxine, or desvenlafaxine if patients have a significant component of neuropathic pain or fibromyalgia. Tricyclic antidepressants (TCAs) (consider nortriptyline or desipramine, which have better anticholinergic profiles) should be considered for patients who do not respond to or tolerate SSRI/SNRIs. Existing evidence is inadequate to definitively recommend methylphenidate or novel agents, such as ketamine or psilocybin, as adjunctive treatments for cancer-related depression and pain. Physicians who treat patients with cancer pain should utilize universal precautions to limit the risk of non-medical opioid use (non-medical opioid use). Patients should be screened for non-medical opioid use behaviors at initial consultation and at regular intervals during treatment using a non-judgmental approach that reduces stigma. Co-management with an addiction specialist may be indicated for patients at high risk of non-medical opioid use and opioid use disorder. Buprenorphine and methadone are indicated for the treatment of opioid use disorder, and while they have not been systematically studied for treatment of opioid use disorder in patients with cancer pain, they do provide analgesia for cancer pain. While an interdisciplinary team approach to manage psychological stress may be beneficial, this may not be possible for patients treated outside of comprehensive cancer centers.

The Introduction and Experiences of Methadone for Treatment of Cancer Pain at a Low-resource Governmental Cancer Center in India

Objectives

This study aimed to describe the clinical experience of the health-care professionals (HCPs) responsible for the introduction of methadone, for the treatment of complex cancer pain, at a low-resource hospital in India in a patient-group, burdened by illiteracy, and low socio-economic status.

Materials and Methods

Ten HCPs: Four medical doctors, four nurses, one pharmacist, and one hospital administrator were interviewed. The interviews are examined using a qualitative conventional content analysis.

Results

The interviews showed a confidence amongst the HCPs, responsible for the safe introduction of methadone in a stressful and low-resource surrounding, to patients with cancer pain and the different aspects of methadone, as initiation, titration, and maintenance of treatment.

Conclusion

Introduction of methadone for cancer pain management is safe and feasible although low resources in a challenging hospital setting and care environment.

Methadone Switching for Cancer Pain: A New Classification of Initiation Protocols, Based on a Critical Literature Review

Background: The initiation of methadone, a known effective analgesic for cancer pain, is complex. The existing protocols are often inadequately described; therefore, a classification of literature is needed. We reviewed and classified the recent literature on methadone initiation protocols in cancer patients experiencing severe pain. Objective: To provide a new classification of initiation protocols, based on a critical literature review. Data Sources: The MEDLINE database was searched for articles published until March 25, 2021, using the terms "cancer pain," "methadone," "methadone introduction," or "methadone initiation." The search was limited to human studies, randomized controlled trials (RCTs), other clinical trials, meta-analyses, and case reports. Selected articles were assessed for initiation details (rapid or progressive), administered dose (fixed rescue dose or ad libitum), and dose calculation (fixed or progressive ratios using morphine equivalent daily dose [MEDD] for daily or unitary dose). Results: Twenty-four publications that met our inclusion criteria were analyzed. No large-scale prospective double-blind RCTs with robust design were identified. Most studies assessed relatively small numbers of patients. Eight initiation types were identified, of which three involved seven "high quality" studies: "rapid switch-fixed doses and rescue dose-progressive daily ratio," "progressive switch-fixed dose and rescue dose-progressive daily ratio," and "rapid switch-ad libitum-fixed ratio for unitary dose" protocols. This classification provides the latest information on methadone initiation protocols. The total daily dose of methadone varied largely across protocols. Conclusion: We recommend a maximal daily methadone dose of 100 mg (3 doses of 30 mg or 5 doses of 20 mg) for MEDD <500 mg, when the two "ad libitum" protocols are used. Further clinical research on this topic is warranted.

Multifarious Targets and Recent Developments in the Therapeutics for the Management of Bone Cancer Pain

Bone cancer pain (BCP) is a distinct pain state showing characteristics of both neuropathic and inflammatory pain. On average, almost 46% of cancer patients exhibit BCP with numbers flaring up to as high as 76% for terminally ill patients. Patients suffering from BCP experience a compromised quality of life, and the unavailability of effective therapeutics makes this a more devastating condition. In every individual cancer patient, the pain is driven by different mechanisms at different sites. The mechanisms behind the manifestation of BCP are very complex and poorly understood, which creates a substantial barrier to drug development. Nevertheless, some of the key mechanisms involved have been identified and are being explored further to develop targeted molecules. Developing a multitarget approach might be beneficial in this case as the underlying mechanism is not fixed and usually a number of these pathways are simultaneously dysregulated. In this review, we have discussed the role of recently identified novel modulators and mechanisms involved in the development of BCP. They include ion channels and receptors involved in sensing alteration of temperature and acidic microenvironment, immune system activation, sodium channels, endothelins, protease-activated receptors, neurotrophins, motor proteins mediated trafficking of glutamate receptor, and some bone-specific mechanisms. Apart from this, we have also discussed some of the novel approaches under preclinical and clinical development for the treatment of bone cancer pain.

Effect of Methadone and Tramadol Opioids on Stem Cells Based on Integrated Plasmonic-Ellipsometry Technique

Introduction: Plasmonic biosensors provide high sensitivity in detecting the low amount of biomarkers and pharmaceutical drugs. We studied the mesenchyme cell activity under the treatment of common sedative drugs of methadone and tramadol using the integrated plasmonic-ellipsometry technique. Methods: Mesenchymal stem cells were cultured on patterned plasmonic chips under the treatment of methadone and tramadol drugs. Three cultured chips were kept non-treated as the control ones. The plasmonic-ellipsometry technique was applied to study the signaling characteristic of the cells affected by these two drugs. In this technique, optical information regarding the amplitude ratio and phase change between p- and s-polarized light was recorded. Results: This drug treatment could affect the spectral plasmonic resonance and subsequently the phase shift (Δ) and the amplitude ratio (Ψ) values under p- and s-polarized impinging light. A more significant Δ value for tramadol treatment meant that the phase split was larger between p- and s-polarized light. Tramadol also had more prominent absolute Δ eff and Ψ eff values in comparison with methadone. Conclusion: We showed that tramadol caused more contrast in phase shift (Δ) and amplitude ratio (Ψ) between p- and s-polarized impinging light for cultured stem cells in comparison with methadone. It means that tramadol differentiated more the optical responses for p- and s-polarized lights compared to methadone. Our proposed technique possesses the potential of quantitative and qualitative analysis of drugs on humans even on a cell scale.

The American Society of Pain and Neuroscience (ASPN) Best Practices and Guidelines for the Interventional Management of Cancer-Associated Pain

Moderate to severe pain occurs in many cancer patients during their clinical course and may stem from the primary pathology, metastasis, or as treatment side effects. Uncontrolled pain using conservative medical therapy can often lead to patient distress, loss of productivity, shorter life expectancy, longer hospital stays, and increase in healthcare utilization. Various publications shed light on strategies for conservative medical management for cancer pain and a few international publications have reviewed limited interventional data. Our multi-institutional working group was assembled to review and highlight the body of evidence that exists for opioid utilization for cancer pain, adjunct medication such as ketamine and methadone and interventional therapies. We discuss neurolysis via injections, neuromodulation including targeted drug delivery and spinal cord stimulation, vertebral tumor ablation and augmentation, radiotherapy and surgical techniques. In the United States, there is a significant variance in the interventional treatment of cancer pain based on fellowship training. As a first of its kind, this best practices and interventional guideline will offer evidenced-based recommendations for reducing pain and suffering associated with malignancy.

Prescription Opioid Misuse Motives in US Older Adults

OBJECTIVES

To evaluate age-based differences in prescription opioid misuse (POM) motives and to evaluate substance use and mental and physical health correlates of POM motive categories in older adults.

DESIGN

Data were from the National Survey on Drug Use and Health (NSDUH), a nationally representative US survey.

SETTING

The NSDUH is a household survey.

SUBJECTS

A total of 5,826 US residents with past-year POM; 415 were 50 years and older (7.1%).

METHODS

Nine POM motives were assessed among those engaged in past-year POM, grouped into three categories: solely physical pain relief, solely non-pain relief, or mixed motives. Prevalence of POM motives were calculated by age group, with logistic models examining age-based differences. Finally, odds of substance use and mental and physical health correlates by motive category were calculated via logistic models in older adults.

RESULTS

POM motivated solely by physical pain relief increased from 35.1% in young adults to 65.4% in older adults; in older adults, 84.7% of POM episodes involved pain relief as a motive. POM for solely non-pain relief or mixed motives was associated with greater odds, vs pain relief only, of past-year benzodiazepine misuse (odds ratio [OR] = 4.43 and 6.15, respectively), any substance use disorder (OR = 5.57 and 5.60, respectively), and suicidal ideation (OR = 4.05 and 3.56, respectively) in older adults.

CONCLUSIONS

. POM motives change over the lifespan, with increasing POM for pain relief with aging. Comprehensive nonopioid pain management is needed for those engaged in POM for pain relief, and substance use and mental health treatment are needed for those with non-pain relief motives.

The Use of Methadone in Adult Patients with Cancer Pain at a Governmental Cancer Center in India

Background:

Management of cancer-related pain relies on the access to opioids. When regular opioids as morphine are not tolerated or are insufficient, adjuvant opioids as methadone are an affordable and effective analgesic.

Aim:

The aim of the project was to describe the pattern of use and clinical experiences of methadone in patients with cancer-related pain at a low-resource hospital in Hyderabad, one of few Indian cancer centers with permission to prescribe methadone.

Methods:

Medical records of all patients who had been prescribed methadone, September 9, 2017 and November 19, 2019 were studied retrospectively. Data on analgesic treatment and opioid side effects were analyzed.

Results:

A total of 93 adult cancer patients were included in the study. A majority of patients (79%) were prescribed opioid analgesic, mainly morphine, before methadone introduction. The initial daily dose of methadone ranged between 5 and 22.5 years and in the vast majority of the patients 5 mg, divided in two daily administrations. A good analgesic effect, with decreased pain, was reported in 60% of the patients. No severe side effects were reported.

Conclusions:

In this study, methadone as a primary opioid was used with a good analgesic effect for cancer pain in a low-resource setting. Indication for methadone was mainly uncontrolled pain with a regular opioid treatment. No severe adverse effects were reported. Further research and prospective studies are needed on methadone treatment in low-resource settings to establish the robust guidelines to support prescribing physicians.

The Use of Methadone in Pediatric Cancer Pain - A Retrospective Study from a Governmental Cancer Center in India

Background:

The management of cancer-related pain relies on access to opioids. When regular opioids are not tolerated, or are insufficient, methadone is an affordable and effective analgesic.

Aim:

The aim of the project was to describe the pattern of use and clinical experience of methadone in pediatric cancer pain at a governmental cancer hospital in Hyderabad, one of the four Indian cancer centers with permission to prescribe methadone.

Methods:

This was a retrospective study of medical records of all children, under the age of 18, who had been prescribed methadone from September 9, 2017, to November 19, 2019. Data on analgesic effect, prior and concomitant analgesic treatment, opioid side effects, and the handling of methadone were analyzed.

Results:

A total of 11 children were identified and studied. Methadone was introduced mainly when pain was uncontrolled by regular opioids. Initial daily doses ranged from 1 to 15 mg. The duration of treatment ranged from 7 to 307, with a median of 50 days in the nine patients where treatment exceeded one single dosage. Good analgesic effect was reported in 5/9 children, unchanged from previous analgesic treatment in three patients and without any effect in one child. No severe side effects were reported.

Conclusion:

Low-dose methadone in the treatment of pediatric cancer pain at a low-resource cancer center was safe and well tolerated by the patients, with long treatment durations. It was safely managed, administered with single to double daily dosages, hence easy for patients and family to handle, and an affordable treatment option.

Methadone for Pain Management: A Pharmacotherapeutic Review

Methadone is increasingly being used for its analgesic properties. Despite the increasing popularity, many healthcare providers are not familiar with methadone's complex pharmacology and best practices surrounding its use. The purpose of this narrative review article is to discuss the pharmacology of methadone, the evidence surrounding methadone's use in acute pain management and both chronic cancer and non-cancer pain settings, as well as highlight pertinent safety, monitoring, and opioid rotation considerations. Methadone has a unique mechanism of action when compared with all other opioids and for this reason methadone has come to hold a niche role in the management of opioid-induced hyperalgesia and central sensitization. Understanding of the mechanisms of variability in methadone disposition and drug interactions has evolved over the years, with the latest evidence revealing that CYP 2B6 is the major determinant of methadone elimination and plays a key role in methadone-related drug interactions. From an acute pain perspective, most studies evaluating the use of intraoperative intravenous methadone have reported lower pain scores and post-operative opioid requirements. Oral methadone is predominantly used as a second-line opioid treatment for select chronic pain conditions. As a result, several oral morphine to oral methadone conversion ratios have been proposed, as have methods in which to rotate to methadone. From an efficacy standpoint, limited literature exists regarding the effectiveness of methadone in the chronic pain setting with most of the available efficacy data pertaining to methadone's use in the treatment of cancer pain. Many of the prospective studies that exist feature low participant numbers. Few clinical trials investigating the role of methadone as an analgesic treatment are currently underway. The complicated pharmacokinetic properties of methadone and risks of harm associated with this drug highlight how critically important it is that healthcare providers understand these features before prescribing/dispensing methadone. Particular caution is required when converting patients from other opioids to methadone and for this reason only experienced healthcare providers should undertake such a task. Further randomized trials with larger sample sizes are needed to better define the effective and safe use of methadone for pain management.

How to Use Methadone in an Era of an Opioid Epidemic

OPINION STATEMENT

The opioid epidemic is one of the most important public health crises as opioid-related deaths have become a leading cause of accidental death in the USA. Various efforts have been made to understand how to safely and appropriately prescribe opioids for patients with chronic pain, including those with cancer-related pain. We find the guidelines proposed by the Expert Consensus White Paper on the use of methadone to be current, comprehensive, and practical. While methadone is a complex medication with unique pharmacokinetics and pharmacodynamics, it remains a superior choice for many patients with cancer pain given its cost and applicability in a variety of situations. Methadone should be prescribed in the context of experienced clinicians as well as an interdisciplinary team. At a critical time when preventing opioid-related deaths is a priority, we recommend implementing additional precautions for monitoring including universal screening for risk of non-medical opioid use, education on proper storage and disposal, as well as discussing a plan with patients and caregivers in the case of serious complications such as opioid overdose.

Methadone in Cancer Pain

Methadone has been an unique, versatile, cost effective, synthetic opioid utilized in nociceptive as well as neuropathic pain. Pain and palliative care physicians started accepting methadone in treatment of complex pain associated with advanced cancer and neuropathic pain syndromes in which conventional opioids were no longer effective. The challenge is in accepting methadone as a main stream first line opioid, from being considered as a second line replacement/substitution drug all these years. Methadone has a significant role as opioid rotation in refractory cancer pain, especially when started early leading to successful conversion. Advantages of methadone in paediatric patients with advanced cancer were its safety and efficacy as a first-choice opioid, availability as a liquid formulation and its infrequent dose requirements. Methadone is neither recommended nor justified to be used as an anti-cancer drug and its role as an anti-cancer agent is a misconception. Many guidelines were proposed after 2008 to address methadone safety. Most of them emphasized on prevention of cardiac arrhythmia and association of methadone with QTc prolongation rather than address the real issue. Methadone has been established to be safe when used in opioid naïve patients with careful titration instituted in an ambulatory setting and has equal success in opioid rotation in outpatient setup. Methadone prescription should be carried out by experienced pain and palliative care providers with careful dose titration and clinical monitoring.

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

The Indian Society for Study of Pain (ISSP), Cancer Pain Special Interest Group guidelines on pharmacological management of cancer pain in adults provides a structured, step-wise 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 drafts 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 (IAPC) members. We recommend that analgesics for cancer pain management should follow the World Health Organization three-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 first choice for moderate-to-severe cancer pain.

Emerging Challenges to the Safe and Effective Use of Methadone for Cancer-Related Pain in Paediatric and Adult Patient Populations

Methadone continues to be an important medication for the treatment of paediatric and adult cancer-related pain. Appropriate patient selection to ensure safe and effective treatment by a team of clinicians who appreciate and are familiar with methadone and its unique pharmacology is crucial. Unlike morphine and other more common opioids, methadone is purported to have involvement with delta-opioid receptor and higher affinity as an N-methyl-D-aspartate-receptor antagonist. Clinically this gives it the advantage of being effective for both nociceptive and neuropathic pain, but also may be useful in the setting of tolerance to other opioids. Methadone also comes in multiple available formulations that can be administrated through a variety of routes beyond the oral route. Challenges with methadone in treating cancer-related pain include drug interactions specifically as it relates to new targeted cancer therapies. Recent guidelines recommend electrocardiogram monitoring with methadone and there is potential for additive cardiac toxicity in the oncology setting. Appropriate dosing of methadone for pain management given age, organ dysfunction, and patients who are on methadone maintenance therapy are also key factors. This article aims to provide clinicians with evidence and clinical practice guidelines for safe and appropriate use of methadone including indication, initiation, and monitoring given its complexity for management of pain in the dynamic oncology setting.

Opioid Rotation to Methadone for Refractory Cancer Pain: A Case Series

Methadone has been increasingly used in the treatment of refractory cancer pain with different conversion methods and ratios described.A retrospective chart review of patients on methadone for cancer pain was conducted to assess its use as the primary opioid, focusing on pain characteristics, opioid rotation indication, previous analgesics, adverse effects and final methadone dose in comparison with the pre-rotation Morphine Equivalent Daily Dose (MEDD).Eight patients were rotated to methadone due to refractory moderate-severe cancer pain and achieved good pain relief. Three developed adverse effects (2 mild, 1 serious). None required withdrawal of methadone. The final methadone dose required varied significantly from predictions made based on equianalgesic conversion tables.Methadone is effective for the treatment of refractory cancer pain. The eventual required methadone doses for these patients were significantly different from predicted doses suggested by equianalgesic conversion tables and guidelines. This highlights the importance of individualized titration and careful clinical assessment during the rotation and in the days after, to prevent serious adverse effects.

Risk Factors and Prevention Strategies for Postoperative Opioid Abuse

Worldwide, 80% of patients who undergo surgery receive opioid analgesics as the fundamental agent for pain relief. However, the irrational use of opioids leads to excessive drug dependence and drug abuse, resulting in an increased mortality rate and huge economic loss. The crisis of opioid overuse remains a great challenge. In this review, we summarize several key factors in opioid abuse, including race, region, income, genetic factors, age and gender, smoking and alcohol abuse, history of chronic pain and analgesic drug abuse, surgery, neuropsychiatric illness, depression and antidepressant use, human factors, national policies, hospital regulations, and health insurance under treatment of pain. Furthermore, we present several prevention strategies, such as perioperative measures, opioid substitutes, treatment of the primary illness, emotional regulation, use of opioid antagonists, efforts of the state, hospitals, doctors and pharmacy benefit managers, gene therapy, and vaccines. Greater understanding and better assessment are required of the risks associated with opioid abuse to ensure the safety and analgesic effects of pain treatment after surgery.

Palliative care in gynecologic oncology

PURPOSE OF REVIEW

Patients with gynecologic malignancies face many difficult issues in the course of their diseases, ranging from physical symptoms to advance care planning in light of a poor prognosis. This review examines the evidence supporting integration of palliative care early in the course of disease and symptom management, and provides a framework for difficult conversations.

RECENT FINDINGS

Palliative care has been demonstrated to improve quality of life and promote survival if integrated early in the course of disease. An evidence-based approach should guide symptom management, such as pain and nausea. Advance care planning and goals of care discussions are enhanced by a framework guiding discussion and the incorporation of empathetic responses.

SUMMARY

Palliative care is a diverse multidisciplinary field that can provide significant benefit for patients with gynecologic malignancies.

Challenges of Using Methadone in the Indian Pain and Palliative Care Practice

Palliative care providers across India lobbied to gain access to methadone for pain relief and this has finally been achieved. Palliative care activists will count on the numerous strengths for introducing methadone in India, including the various national and state government initiatives that have been introduced recognizing the importance of palliative care as a specialty in addition to improving opioid accessibility and training. Adding to the support are the Non-Governmental Organizations (NGOs), the medical fraternity and the international interactive and innovative programs such as the Project Extension for Community Health Outcome. As compelling as the need for methadone is, many challenges await. This article outlines the challenges of procuring methadone and also discusses the challenges specific to methadone. Balancing the availability and diversion in a setting of opioid phobia, implementing the amended laws to improve availability and accessibility in a country with diverse health-care practices are the major challenges in implementing methadone for relief of pain. The unique pharmacology of the drug requires meticulous patient selection, vigilant monitoring, and excellent communication and collaboration with a multidisciplinary team and caregivers. The psychological acceptance of the patient, the professional training of the team and the place where care is provided are also challenges which need to be overcome. These challenges could well be the catalyst for a more diligent and vigilant approach to opioid prescribing practices. Start low, go slow could well be the way forward with caregiver education to prescribe methadone safely in the Indian palliative care setting.

SEOM clinical guideline for treatment of cancer pain (2017)

Pain is a highly prevalent symptom in patients with cancer. Despite therapeutic advances and well-accepted treatment guidelines, a percentage of patients with pain are under-treated. Currently, it has been recognized that several barriers in pain management still exist and, in addition, there are new challenges surrounding complex subtypes of pain, such as breakthrough and neuropathic pain, requiring further reviews and recommendations. This is an update of the guide our society previously published and represents the continued commitment of SEOM to move forward and improve supportive care of cancer patients.

Methadone as a "Tumor Theralgesic" against Cancer

Methadone has beneficial characteristics as an analgesic against cancer pain, including high bioavailability, multiple receptor affinities, and lack of active metabolites that might induce adverse side effects. However, methadone has an own pharmacological profile that should be considered in the treatment of cancer patients. There is evidence from preclinical studies that methadone could also elicit antitumor activity by downregulating the threshold of apoptosis and to enhance the effects of different chemotherapeutic agents. This confirms the concept of using methadone as a chemosensitizer in the future treatment of cancer. Our article discusses major issues about the role of methadone as a possible “tumor theralgesic,” combining tumor therapeutic and analgesic activities.

High-dose opioids for chronic non-cancer pain: an overview of Cochrane Reviews

BACKGROUND

Chronic pain is typically described as pain on most days for at least three months. Chronic non-cancer pain (CNCP) is any chronic pain that is not due to a malignancy. Chronic non-cancer pain in adults is a common and complex clinical issue where opioids are routinely used for pain management. There are concerns that the use of high doses of opioids for chronic non-cancer pain lacks evidence of effectiveness and may increase the risk of adverse events.

OBJECTIVES

To describe the evidence from Cochrane Reviews and Overviews regarding the efficacy and safety of high-dose opioids (here defined as 200 mg morphine equivalent or more per day) for chronic non-cancer pain.

METHODS

We identified Cochrane Reviews and Overviews through a search of the Cochrane Database of Systematic Reviews (The Cochrane Library). The date of the last search was 18 April 2017. Two review authors independently assessed the search results. We planned to analyse data on any opioid agent used at high dose for two weeks or more for the treatment of chronic non-cancer pain in adults.

MAIN RESULTS

We did not identify any reviews or overviews meeting the inclusion criteria. The excluded reviews largely reflected low doses or titrated doses where all doses were analysed as a single group; no data for high dose only could be extracted.

AUTHORS' CONCLUSIONS

There is a critical lack of high-quality evidence regarding how well high-dose opioids work for the management of chronic non-cancer pain in adults, and regarding the presence and severity of adverse events. No evidence-based argument can be made on the use of high-dose opioids, i.e. 200 mg morphine equivalent or more daily, in clinical practice. Trials typically used doses below our cut-off; we need to know the efficacy and harm of higher doses, which are often used in clinical practice.

Individual variability in clinical effect and tolerability of opioid analgesics – Importance of drug interactions and pharmacogenetics

Background

As pain is often a comorbid condition, many patients use opioid analgesics in combination with several other drugs. This implies a generally increased risk of drug interactions, which along with inherent pharmacogenetic variability and other factors may cause differences in therapeutic response of opioids.

Aim

To provide an overview of interactions and pharmacogenetic variability of relevance for individual differences in effect and tolerability of opioid analgesics, which physicians and other healthcare professionals should be aware of in clinical practice.

Methods

The article was based on unsystematic searches in PubMed to identify literature highlighting the clinical impact of drug interactions and pharmacogenetics as sources of variable response of opioid analgesics.

Results

Cytochrome P450 (CYP)-mediated metabolism is an important process for both clinically relevant interactions and pharmacogenetic variability of several opioids. Concomitant use of CYP inhibitors (e.g. paroxetine, fluoxetine and bupropion) or inducers (e.g. carbamazepine, phenobarbital and phenytoin) could counteract the clinical effect or trigger side effects of analgesics in the same manner as genetically determined differences in CYP2D6-mediated metabolism of many opioids. Moreover, combination treatment with drugs that inhibit or induce P-glycoprotein (ABCB1), a blood-brain barrier efflux transporter, may alter the amount (‘dose’) of opioids distributed to the brain. At the pharmacodynamic level, it is crucial to be aware of the potential risk of interaction causing serotonergic syndrome when combining opioids and serotonergic drugs, in particular antidepressants inhibiting serotonin reuptake (SSRIs and SNRIs). Regarding pharmacogenetics at the receptor level of pain treatment, the knowledge is currently scarce, but an allelic variant of the μ1 opioid receptor (OPRM1) gene has been associated with higher dosage requirement to achieve analgesia.

Conclusions and implications

Drug interactions and pharmacogenetic differences may lead to therapeutic failure or serious side effects of opioid analgesics. Many interactions involve combinations with antidepressants and antiepileptics, which are highly relevant drugs in patients suffering from pain. To prevent unfavourable drug interactions it is important that clinicians pay close attention and use electronic drug interaction checkers when treatments are initiated or discontinued. For the management of issues related to pharmacogenetic differences, blood-based CYP genotyping is available as routine test at many laboratories, and provide a valuable tool for proper choice of drugs and doses for treatment of pain and other diseases.

Opioids for cancer pain - an overview of Cochrane reviews

BACKGROUND

Pain is a common symptom with cancer, and 30% to 50% of all people with cancer will experience moderate to severe pain that can have a major negative impact on their quality of life. Opioid (morphine-like) drugs are commonly used to treat moderate or severe cancer pain, and are recommended for this purpose in the World Health Organization (WHO) pain treatment ladder. The most commonly-used opioid drugs are buprenorphine, codeine, fentanyl, hydrocodone, hydromorphone, methadone, morphine, oxycodone, tramadol, and tapentadol.

OBJECTIVES

To provide an overview of the analgesic efficacy of opioids in cancer pain, and to report on adverse events associated with their use.

METHODS

We identified systematic reviews examining any opioid for cancer pain published to 4 May 2017 in the Cochrane Database of Systematic Reviews in the Cochrane Library. The primary outcomes were no or mild pain within 14 days of starting treatment, withdrawals due to adverse events, and serious adverse events.

MAIN RESULTS

We included nine reviews with 152 included studies and 13,524 participants, but because some studies appeared in more than one review the number of unique studies and participants was smaller than this. Most participants had moderate or severe pain associated with a range of different types of cancer. Studies in the reviews typically compared one type of opioid or formulation with either a different formulation of the same opioid, or a different opioid; few included a placebo control. Typically the reviews titrated dose to effect, a balance between pain relief and adverse events. Various routes of administration of opioids were considered in the reviews; oral with most opioids, but transdermal administration with fentanyl, and buprenorphine. No review included studies of subcutaneous opioid administration. Pain outcomes reported were varied and inconsistent. The average size of included studies varied considerably between reviews: studies of older opioids, such as codeine, morphine, and methadone, had low average study sizes while those involving newer drugs tended to have larger study sizes.Six reviews reported a GRADE assessment (buprenorphine, codeine, hydromorphone, methadone, oxycodone, and tramadol), but not necessarily for all comparisons or outcomes. No comparative analyses were possible because there was no consistent placebo or active control. Cohort outcomes for opioids are therefore reported, as absolute numbers or percentages, or both.Reviews on buprenorphine, codeine with or without paracetamol, hydromorphone, methadone, tramadol with or without paracetamol, tapentadol, and oxycodone did not have information about the primary outcome of mild or no pain at 14 days, although that on oxycodone indicated that average pain scores were within that range. Two reviews, on oral morphine and transdermal fentanyl, reported that 96% of 850 participants achieved that goal.Adverse event withdrawal was reported by five reviews, at rates of between 6% and 19%. Participants with at least one adverse event were reported by three reviews, at rates of between 11% and 77%.Our GRADE assessment of evidence quality was very low for all outcomes, because many studies in the reviews were at high risk of bias from several sources, including small study size.

AUTHORS' CONCLUSIONS

The amount and quality of evidence around the use of opioids for treating cancer pain is disappointingly low, although the evidence we have indicates that around 19 out of 20 people with moderate or severe pain who are given opioids and can tolerate them should have that pain reduced to mild or no pain within 14 days. This accords with the clinical experience in treating many people with cancer pain, but overstates to some extent the effectiveness found for the WHO pain ladder. Most people will experience adverse events, and help may be needed to manage the more common undesirable adverse effects such as constipation and nausea. Perhaps between 1 in 10 and 2 in 10 people treated with opioids will find these adverse events intolerable, leading to a change in treatment.

Methadone for neuropathic pain in adults

BACKGROUND

This review replaces an earlier review, "Methadone for chronic non-cancer pain in adults". This review serves to update the original and includes only studies of neuropathic pain. Methadone belongs to a class of analgesics known as opioids, that are considered the cornerstone of therapy for moderate-to-severe postsurgical pain and pain due to life-threatening illnesses; however, their use in neuropathic pain is controversial. Methadone has many characteristics that differentiate it from other opioids, which suggests that it may have a different efficacy and safety profile.

OBJECTIVES

To assess the analgesic efficacy and adverse events of methadone for chronic neuropathic pain in adults.

SEARCH METHODS

We searched the following databases: CENTRAL (CRSO), MEDLINE (Ovid), and Embase (Ovid), and two clinical trial registries. We also searched the reference lists of retrieved articles. The date of the most recent search was 30 November 2016.

SELECTION CRITERIA

We included randomised, double-blind studies of two weeks' duration or longer, comparing methadone (in any dose, administered by any route, and in any formulation) with placebo or another active treatment in chronic neuropathic pain.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently considered trials for inclusion in the review, assessed risk of bias, and extracted data. There were insufficient data to perform pooled analyses. We assessed the overall quality of the evidence for each outcome using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

We included three studies, involving 105 participants. All were cross-over studies, one involving 19 participants with diverse neuropathic pain syndromes, the other two involving 86 participants with postherpetic neuralgia. Study phases ranged from 20 days to approximately eight weeks. All administered methadone orally, in doses ranging from 10 mg to 80 mg daily. Comparators were primarily placebo, but one study also included morphine and tricyclic antidepressants.The included studies had several limitations related to risk of bias, particularly incomplete reporting, selective outcome reporting, and small sample sizes.There were very limited data for our primary outcomes of participants with at least 30% or at least 50% pain relief. Two studies reported that 11/29 participants receiving methadone achieved 30% pain relief versus 7/29 participants receiving placebo. Only one study presented data in a manner that allowed us to calculate the number of participants with at least 50% pain relief. None of the 19 participants achieved a 50% reduction in pain intensity, either when receiving methadone or when receiving placebo. No study provided data for our other primary outcomes of Patient Global Impression of Change scale (PGIC) much or very much improved (equivalent to at least 30% pain relief) and PGIC very much improved (equivalent to at least 50% pain relief).For secondary efficacy outcomes, one study reported maximum and mean pain intensity and pain relief, and reported statistically significant improvements versus placebo for all outcomes with 20 mg daily doses of methadone, but not with 10 mg daily doses. The second study reported differences in pain reduction between methadone (n = 26) and morphine (n = 38) and found morphine to be statistically superior. The third study reported the number of responders (variously defined) for several pain and functional outcomes and found methadone to be statistically superior to placebo for the outcomes of categorical pain intensity and evoked pain. In the two studies that reported data, 0/29 participants withdrew due to lack of efficacy, whereas 4/29 participants withdrew due to adverse events while taking methadone versus 3/29 while taking placebo.One study reported incidences for several individual adverse events, but found a statistically significant increased incidence for methadone over placebo for only one event, dizziness. The other studies did not report data in a manner that enabled us to analyze adverse events. There were no serious adverse events or deaths reported.We assessed the quality of the evidence as very low for all efficacy and safety outcomes using GRADE, primarily because of the heterogeneity of study designs and populations, short durations, cross-over methodology, and few participants and events.

AUTHORS' CONCLUSIONS

The three studies provide very limited, very low quality evidence of the efficacy and safety of methadone for chronic neuropathic pain, and there were too few data for pooled analysis of efficacy or harm, or to have confidence in the results of the individual studies. No conclusions can be made regarding differences in efficacy or safety between methadone and placebo, other opioids, or other treatments.

Tramadol with or without paracetamol (acetaminophen) for cancer pain

BACKGROUND

Tramadol is an opioid analgesic licensed for use in moderate to severe pain. It is considered as a low risk for abuse, so control regulations are not as stringent as for 'strong' opioids such as morphine. It has a potential role as a step 2 option of the World Health Organization (WHO) analgesic ladder.

OBJECTIVES

To assess the benefits and adverse effects of tramadol with or without paracetamol (acetaminophen) for cancer-related pain.

SEARCH METHODS

We searched the following databases using a wide range of search terms: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and LILACS. We also searched three clinical trials registry databases. The date of the last search was 2 November 2016.

SELECTION CRITERIA

We selected studies that were randomised, with placebo or active controls, or both, and included a minimum of 10 participants per treatment arm. We were interested particularly in blinded studies, but also included open studies.We excluded non-randomised studies, studies of experimental pain, case reports, and clinical observations.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data using a standard form and checked for agreement before entry into Review Manager 5. We included information about the number of participants treated and demographic details, type of cancer, drug and dosing regimen, study design (placebo or active control) and methods, study duration and follow-up, analgesic outcome measures and results, withdrawals, and adverse events. We collated multiple reports of the same study, so that each study, rather than each report, was the unit of interest in the review. We assessed the evidence using GRADE and created a 'Summary of findings' table.The main outcomes of interest for benefit were pain reduction of 30% or greater and 50% or greater from baseline, participants with pain no worse than mild, and participants feeling much improved or very much improved.

MAIN RESULTS

We included 10 studies (12 reports) with 958 adult participants. All the studies enrolled participants with chronic malignant tumour-related pain who were experiencing pain intensities described as moderate to severe, with most experiencing at least 4/10 with current treatment. The mean ages were 59 to 70 years, with participants aged between 24 and 87 years. Study length ranged from one day to six months. Five studies used a cross-over design. Tramadol doses ranged from 50 mg as single dose to 600 mg per day; doses of 300 mg per day to 400 mg per day were most common.Nine studies were at high risk of bias for one to four criteria (only one high risk of bias for size). We judged all the results to be very low quality evidence because of widespread lack of blinding of outcome assessment, inadequately described sequence generation, allocation concealment, and small numbers of participants and events. Important outcomes were poorly reported. There were eight different active comparators and one comparison with placebo. There was little information available for any comparison and no firm conclusions could be drawn for any outcome.Single comparisons of oral tramadol with codeine plus paracetamol, of dihydrocodeine, and of rectal versus oral tramadol provided no data for key outcomes. One study used tramadol combined with paracetamol; four participants received this intervention. One study compared tramadol with flupirtine - a drug that is no longer available. One study compared tramadol with placebo and a combination of cobrotoxin, tramadol, and ibuprofen, but the dosing schedule poorly explained.Two studies (191 participants) compared tramadol with buprenorphine. One study (131 participants) reported a similar proportion of no or mild pain at 14 days.Three studies (300 participants) compared tramadol with morphine. Only one study, combining tramadol, tramadol plus paracetamol, and paracetamol plus codeine as a single weak-opioid group reported results. Weak opioid produced reduction in pain of at least 30% from baseline in 55/117 (47%) participants, compared with 91/110 (82%) participants with morphine. Weak opioid produced reduction in pain of at least 50% in 49/117 (42%) participants, compared with 83/110 (75%) participants with morphine.There was no useful information for any other outcome of benefit or harm.

AUTHORS' CONCLUSIONS

There is limited, very low quality, evidence from randomised controlled trials that tramadol produced pain relief in some adults with pain due to cancer and no evidence at all for children. There is very low quality evidence that it is not as effective as morphine. This review does not provide a reliable indication of the likely effect. The likelihood that the effect will be substantially different is very high. The place of tramadol in managing cancer pain and its role as step 2 of the WHO analgesic ladder is unclear.