Methadone is superior to fentanyl in treating neuropathic pain in patients with head-and-neck cancer

Shifting Views on Cancer Pain Management: A Systematic Review and Network Meta-Analysis

CONTEXT

Strong opioids are the cornerstone in the treatment of cancer-related pain.

OBJECTIVES

This study aims to compare analgesic effectiveness of different strong opioids for the treatment of cancer-related pain.

METHODS

PubMed and Embase were searched for RCTs that compared strong opioids for treatment of cancer-related pain against one another. A network meta-analysis was conducted and the related Surface Under the Cumulative RAnking (SUCRA)-based treatment ranks were calculated. Primary outcome was pain intensity (numerical rating scale (NRS)) and/or the percentage of patients with ≥50% pain reduction, after 1 and 2-4 weeks.

RESULTS

Sixteen RCTs (1813 patients) were included. Methadone showed, with a high certainty of evidence, increased ORs for treatment success at 1 week, compared with morphine, buprenorphine, fentanyl, and oxycodone, range 3.230-36.833. Methadone had the highest likelihood to be the treatment of preference (ToP) (SUCRA 0.9720). For fentanyl, ORs were lower, however significant and with high certainty. After 2-4 weeks, methadone again showed the highest likelihood for ToP, however, with moderate certainty and nonsignificant ORs. The combination of morphine/methadone, compared with morphine, buprenorphine, fentanyl, hydromorphone, methadone, and oxycodone achieved a treatment effect of mean NRS difference after 2-4 weeks between -1.100 and -1.528 and had the highest likelihood for ToP.

CONCLUSION

The results suggest that methadone possibly deserves further promotion as first-line treatment for the treatment of cancer-related 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.

Methadone and neuropathic cancer pain subcomponents: a prospective cohort pilot study

Forty per cent of cancer pain associate neuropathic and nociceptive pain simultaneously, and refractory pain affects 15% of cancer pain. Methadone is an effective opioid in treating nociceptive pain and could have an effect on neuropathic pain. Uncertainty remains on its effects on the different subcomponents of neuropathic pain.

OBJECTIVES

To identify which subcomponents of neuropathic cancer pain are addressed using methadone.

METHODS

An observational prospective cohort study of palliative care inpatients after rotation for refractory neuropathic cancer pain. Pain intensity was assessed weekly for 28 days, using a Visual Analogue Scale (VAS) and the Neuropathic Pain Symptom Inventory (NPSI).

RESULTS

Forty-eight patients were included and 17 completed the 28 days follow-up. VAS pain rating decreased by at least 20 mm in 47% of patients and the pain intensity was significantly lower at day 28 with 53% of patients with a VAS inferior to 4 (p<0.001). The pressure/squeezing component (NPSI score) decreased by more than 2 points in 50% of patients.A linear regression showed allodynia and pressure/squeezing were responsible for the largest part of the overall alleviation of pain (p=0.01).

CONCLUSIONS

Methadone could significantly improve neuropathic pain through a targeted effect of allodynia and its pressure/squeezing component.

Barriers to Adequate Pain Control and Opioid Use Among Cancer Survivors: Implications for Nursing Practice

BACKGROUND

Cancer survivors can experience long-term negative effects from cancer and its treatment. Pain is one of the most common and distressing symptoms that cancer survivors experience. Opioids are often prescribed for pain; however, cancer survivors who have completed active treatment may have unique challenges with regard to pain management.

OBJECTIVE

The aim of this study was to explore barriers to pain management and perceptions of opioid use among cancer survivors.

METHODS

This research was an exploratory pilot study using in-depth qualitative interviews with adult cancer survivors who were recruited from community-based survivorship organizations. Data were analyzed using applied thematic analysis techniques.

RESULTS

Participants (n = 25) were mostly women (96%), diagnosed with breast cancer (88%) and stages I to III disease (84%), with a mean age of 56.2 years. Three themes on barriers to adequate pain control emerged: (1) taking just enough to take the edge off: self-medicating behaviors and nonadherence to prescribed regimen; (2) lack of insurance coverage and costly alternative pain treatment options; and (3) chronicity of cancer-related pain not adequately addressed and often mismanaged.

CONCLUSIONS

Discussions with cancer survivors unveiled personal accounts of unmanaged pain resulting from limited pain management/opioid education, fear of opioid addiction, negative perceptions/experiences with opioids, lack of insurance coverage for alternative pain therapies, and regulatory policies limiting access to opioids.

IMPLICATIONS FOR PRACTICE

There is a clear need for improved access to multimodal pain management options and nonopioid alternatives for cancer survivors. Oncology nurses should endeavor to support policies and procedures aimed at opioid education, training, and legislation.

Differences in the Analgesic Effect of Opioids on Pain in Cancer Patients With Spinal Metastases

Background

Spinal metastasis pain includes both inflammatory and neuropathic pain, and opioids, which have only a μ-opioid receptor-stimulating effect, are generally less effective in neuropathic pain. However, no previous study has been conducted for the comparisons of the efficacy of opioids in treating spinal metastasis pain.

Objective

To compare the efficacy of tapentadol and methadone with other opioids for back pain caused by a metastatic spinal tumor.

Design

Retrospective cohort study.

Setting/Subjects

A total of 274 patients were enrolled, who started a tapentadol extended-release tablet, methadone tablet, hydromorphone extended-release tablet, oxycodone extended-release tablet, or transdermal fentanyl patch for cancer pain due to spinal metastasis in Japan from January 1, 2013 to October 31, 2021.

Measurements

The primary endpoint, the difference in the numerical rating scale (NRS) scores before and seven days after each opioid administration, was compared among the five groups.

Results

In patients with numbness, a decrease of the NRS score on day seven compared with before starting each opioid was significantly higher in the tapentadol group than those in the hydromorphone, oxycodone, and fentanyl groups and comparable to that in the methadone group. In patients without numbness, no significant differences were observed in decreases of the NRS scores on day seven among the five groups.

Conclusions

Tapentadol and methadone may be more effective than hydromorphone, oxycodone, and fentanyl for cancer pain due to spinal metastasis with numbness.

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.

Localized Drug Delivery Systems: An Update on Treatment Options for Head and Neck Squamous Cell Carcinomas

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers in the world, with surgery, radiotherapy, chemotherapy, and immunotherapy being the primary treatment modalities. The treatment for HNSCC has evolved over time, due to which the prognosis has improved drastically. Despite the varied treatment options, major challenges persist. HNSCC chemotherapeutic and immunotherapeutic drugs are usually administered systemically, which could affect the patient's quality of life due to the associated side effects. Moreover, the systemic administration of salivary stimulating agents for the treatment of radiation-induced xerostomia is associated with toxicities. Localized drug delivery systems (LDDS) are gaining importance, as they have the potential to provide non-invasive, patient-friendly alternatives to cancer therapy with reduced dose-limiting toxicities. LDDSs involve directly delivering a drug to the tissue or organ affected by the disease. Some of the common localized routes of administration include the transdermal and transmucosal drug delivery system (DDSs). This review will attempt to explore the different treatment options using LDDSs for the treatment of HNSCC and radiotherapy-induced damage and their potential to provide a better experience for patients, as well as the obstacles that need to be addressed to render them successful.

Levorphanol as a Second Line Opioid in Cancer Patients Presenting to an Outpatient Supportive Care Center: An Open-label Study

CONTEXT

Levorphanol is a potent opioid agonist and NMDA receptor blocker with minimal drug interactions, and there are few reports of its use in cancer patients.

OBJECTIVES

We aimed to determine the frequency of successful opioid rotation (OR) to levorphanol and the median opioid rotation ratio (ORR) from Morphine Equivalent Daily Dose (MEDD).

METHODS

This is a prospective, single-group, interventional study. Cancer outpatients requiring an OR and receiving a MEDD of 60-300 mg were rotated to levorphanol using a ratio of 10:1 and assessed daily for 10-day. Successful OR was defined as a 2-point improvement in the Edmonton Symptom Assessment System (ESAS) pain score on day 10 or achieving the personalized pain goal between days 3-10 in patients with uncontrolled pain or resolution of opioid side effects (OSE) in those undergoing OR for OSE alone. The ORR to levorphanol was calculated using net-MEDD (MEDD before OR minus the MEDD of the breakthrough opioid used along with levorphanol after OR).

RESULTS

Forty patients underwent OR to levorphanol, and uncontrolled pain 35/40 (87.5%) was the most common indication. The median net-MEDD and levorphanol doses were 95 and 10 mg, respectively, and 33/40 (82.5%) had a successful OR with a median (IQR) ORR of 8.56 (7.5-10). Successful OR was associated with significant improvement in ESAS and OSE scale scores. There was a strong association between MEDD and levorphanol dose.

CONCLUSION

This study provided preliminary data that cancer patients could be successfully rotated to levorphanol using an ORR of 8.5. Levorphanol was associated with improved pain and symptom control and was well- tolerated.

Glutamatergic systems in neuropathic pain and emerging non-opioid therapies

Neuropathic pain, a disease of the somatosensory nervous system, afflicts many individuals and adequate management with current pharmacotherapies remains elusive. The glutamatergic system of neurons, receptors and transporters are intimately involved in pain but, to date, there have been few drugs developed that therapeutically modulate this system. Glutamate transporters, or excitatory amino acid transporters (EAATs), remove excess glutamate around pain transmitting neurons to decrease nociception suggesting that the modulation of glutamate transporters may represent a novel approach to the treatment of pain. This review highlights and summarizes (1) the physiology of the glutamatergic system in neuropathic pain, (2) the preclinical evidence for dysregulation of glutamate transport in animal pain models, and (3) emerging novel therapies that modulate glutamate transporters. Successful drug discovery requires continuous focus on basic and translational methods to fully elucidate the etiologies of this disease to enable the development of targeted therapies. Increasing the efficacy of astrocytic EAATs may serve as a new way to successfully treat those suffering from this devastating disease.

Pharmacological Management of Neuropathic Pain after Radiotherapy in Head and Neck Cancer Patients: A Systematic Review

Background: Neuropathic pain (NP) in head and neck cancer (HNC) patients represents a treatment challenge. Most studies investigating drugs against NP are conducted in patients suffering with diabetic neuropathy or postherpetic neuralgia, while data are limited in cancer pain management. Additionally, regarding cancer therapy-related NP, most of the studies do not focus on HNC patients. The aim of this review is to identify the studies on systematically administered medication for NP management that included HNC patients under radiotherapy. Methods: A systematic literature search was performed, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, in PubMed, Cochrane Library, Web of Science and ClinicalTrials.gov on 30 October 2021. The medical subject heading (MeSH) terms were (“head and neck cancer” OR “tumor”) AND “neuropathic pain” AND “medication” AND “radiotherapy.” The Cochrane Collaboration tool was used for quality assessment. Results: The search identified 432 articles. Three more articles were identified after searching the reference lists of the retrieved articles. A total of 10 articles met the eligibility inclusion criteria and were included in this review; 6 on gabapentin, 1 on pregabalin, 1 on nortriptyline, 1 on methadone, and 1 on ketamine. Statistically significant results in pain reduction compared to placebo or standard pain medication were found in the studies on pregabalin (p = 0.003), methadone (p = 0.03), ketamine (p = 0.012), and in two out of six gabapentin studies (p < 0.004). Two of the studies (both concerning gabapentin) had no comparison arm. Conclusions: Treatments including pregabalin, methadone, ketamine, and gabapentin were found to provide pain relief against HNC NP. While there is a plethora of pharmacological treatments available for the management of NP, only a few studies have been conducted regarding the pharmacological management of therapy-related NP in HNC patients. More studies should be conducted regarding the pharmacological approaches in HNC therapy-related NP so that specific treatment algorithms can be developed.

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.

Revision of Pharmacological Treatment Recommendations for Cancer Pain: Clinical Guidelines from the Japanese Society of Palliative Medicine

Background: Pain is one of the most common symptoms in cancer patients. The Japanese Society for Palliative Medicine (JSPM) first published its clinical guidelines for the management of cancer pain in 2010. Since then, more research on cancer pain management has been reported, and new drugs have become available in Japan. Thus, the JSPM has now revised the clinical guidelines using a validated methodology. Methods: This guideline was developed through a systematic review, discussion, and the Delphi method, following a formal guideline development process. Results: Thirty-five recommendations were created: 19 for the pharmacological management of cancer pain, 6 for the management of opioid-induced adverse effects, and 10 for pharmacological treatment procedures. Due to the lack of evidence that directly addressed our clinical questions, most of the recommendations had to be based on consensus among committee members and other guidelines. Discussion: It is critical to continue to build high-quality evidence in cancer pain management, and revise these guidelines accordingly.

Use of methadone as an alternative to morphine for chronic pain management: a noninferiority retrospective observational study

Methadone administration for outpatient was noninferior to morphine as analgesic on chronic pain. In addition, it was associated with lesser side effects.

Introduction:

Chronic pain causes disability and is prevalent in the general population. Opioids are a part of a multimodal strategy for pain management. Methadone, a cheap and long-acting synthetic opioid, may represent an option for those who have limited access to the aforementioned class of analgesics. We aimed to provide a real-world evidence for the analgesic use of methadone, compared with morphine.

Methods:

We conducted a noninferiority, retrospective observational single center study of patients with chronic pain, managed with either methadone or morphine at an outpatient specialized clinic. We extracted data from the electronic health records of patients who underwent an active treatment between August 2012 and January 2020 and were examined for at least 2 consecutive medical visits, after the administration of one of the aforementioned drugs. Data were analyzed using a generalized additive model with random-effects mixed linear method to account for the individual-related, time-related, and drug-related variations. The numeric verbal scale (0–10) was used to assess the pain severity.

Results:

From the database of 3373 patients, we included 262 patients (175 methadone and 87 morphine). In an unadjusted analysis, methadone was superior to morphine, and the mean worst pain was 0.86 points lower (95% confidence interval, −1.29 to −0.43). Moreover, methadone was superior to morphine in the adjusted analysis, with the worst pain mean being 1.24 points lower. This provided evidence for the noninferiority of methadone than morphine.

Conclusion:

Methadone was superior to morphine in a 20% noninferiority margin for reducing worst pain.

Assistance of a Palliative Care Certified Nurse in the Alleviation of Refractory Cancer Pain by Switching Opioids to Oral Methadone in a Japanese Outpatient Setting

Although methadone has the potential to improve the management of cancer pain, it has some serious problems, such as respiratory depression and QT interval prolongation. Therefore, patients who are prescribed methadone must be educated, monitored, and supported by specialized medical staff, especially in the outpatient setting. We assessed the effectiveness of support from the palliative care certified nurse who used the checklists in opioid switching to oral methadone for patients with refractory pain. Through the multidisciplinary palliative care team at our hospital, 15 outpatients with cancer pain were prescribed oral methadone between April 2013 and December 2020, and 14 cases were successful in switching to methadone. After taking medication, the certified nurse called the patient's home daily for 3 to 5 days and confirmed that the patient had taken the methadone, the degree of pain, the number of rescue medications, and the appearance of side effects, such as respiratory depression. Careful management by a multidisciplinary team is essential for opioid switching to oral methadone administration for outpatients. Certified nurses may play an important role in maintaining safety and resolving the patients' and families' anxieties with respect to the prescription of methadone.

Evaluation of Extended-Release Oxycodone Administered through Enteral Tubes for the Management of Pain in Patients with Head and Neck Cancer: A Case Series

An abuse-deterrent, microsphere-in-capsule extended-release formulation of oxycodone myristate (Xtampza® ER, Collegium Pharmaceutical Inc, Canton, Massachusetts), was approved by the FDA in 2016 for the management of pain. The advantage of this formulation of oxycodone is that the microspheres can be administered via enteral tubes without compromising the long-acting formulation. This case series characterizes the experiences of five head and neck cancer patients initiated on oxycodone myristate through enteral tube administration for control of cancer-related pain. The primary outcome of patient reported subjective improvement in pain within one week occurred in all five patients. The median time to pain control was 4 days. The safety profile of oxycodone myristate was consistent with the package insert with no new findings reported. Oxycodone myristate can be an appropriate long-acting opioid analgesic option for patients requiring enteral tube administration of medications to achieve adequate cancer-related pain control.

Tapentadol in Cancer Patients with Neuropathic Pain: A Comparison of Methadone, Oxycodone, Fentanyl, and Hydromorphone

Tapentadol has μ-opioid receptor stimulating and noradrenaline reuptake inhibiting properties, and should be effective for neuropathic pain (NP). However, the efficacy of tapentadol for NP in cancer patients is unclear. Ashiya Municipal Hospital (Hyogo, Japan) enrolled five groups of Japanese cancer patients between January 1, 2013, and December 31, 2019. Patients with NP were administered tapentadol (n = 29), methadone (n = 32), oxycodone (n = 20), fentanyl (n = 26), or hydromorphone (n = 20). The primary endpoint was the difference in the verbal rating scale (VRS) scores between days 0 and 7. The secondary endpoint was the tolerability of each opioid. Before administering opioids among the five groups, there was no significant difference in the VRS score (p = 0.99). The mean reduction in the VRS score on day 7 was significantly greater in the tapentadol group than in the oxycodone group (p = 0.0024) and was larger than that of the methadone, fentanyl, and hydromorphone groups. Regarding safety, the discontinuation rate in the tapentadol group was the lowest of all groups (tapentadol vs. methadone vs. oxycodone vs. fentanyl vs. hydromorphone, 0.0% vs. 6.3% vs. 5.0% vs. 3.8% vs. 10.0%, respectively). This study suggests that tapentadol could be efficacious for cancer patients with NP, and a preferred option in cases that require immediate dose adjustment or for those at high risk for adverse effects. However, the pain intensity was evaluated without pain assessment scales specific to NP. Thus, we think that it is desirable to validate our findings using assessment scales, such as the painDETECT questionnaire in future.

Oral Methadone for Patients With Neuropathic Pain Due to Neoplastic Brachial Plexopathy

INTRODUCTION

The brachial plexus nerves originate from the cervical (C5-C8) and first thoracic (T1) spinal nerves, and innervate muscles and skin of the chest, shoulder, arm and hand. Brachial plexus injuries can occur as a result of shoulder trauma and inflammation. Malignant tumors can also cause neoplastic brachial plexopathy (NBP), and refractory neuropathic pain is the most common symptom of NBP. Methadone is a synthetic opioid with high efficacy as an opioid-receptor agonist, and its inhibitory effects on N-methyl-D-aspartate (NMDA) may play a role in pain relief. However, there is a need to examine if oral methadone exhibits safety and efficacy against neuropathic pain due to NBP.

CASE PRESENTATIONS

NBP was diagnosed in 3 cases without brain or cervical spine metastasis. The clinical features of these patients were analyzed retrospectively. None of the cases had an indication for surgery because of advanced cancer and all had received radiation therapy that had an insufficient effect, prior to methadone treatment. All 3 patients had nociceptive and neuropathic pain. Methadone for refractory pain was initiated using the stop-and-go method. NRS pain scores decreased in all cases and there were no severe side effects.

DISCUSSION

For the purpose of pain relief, patients with NBP may receive surgery, radiation therapy and nerve block, but these are not always effective. Methadone was recently shown to be superior to fentanyl in treating neuropathic pain in patients with head-and-neck cancer in a RCT, and our findings suggest that methadone may also be effective for patients with NBP.

CONCLUSION

More studies are necessary, but results in 3 cases suggest that oral methadone may be a safe analgesic agent for patients with neuropathic pain due to NBP.

Narrative review of the management of oral mucositis during chemoradiation for head and neck cancer

Oral mucositis (OM) can be a significant problem for patients undergoing radiation or chemoradiation for head and neck cancer. In modern clinical trials, grade 3–4 OM can be seen in over 40% of patients and can cause a significant impact on their quality of life (QOL). Despite this fact, strategies for the prevention and treatment of OM vary widely, with options including both lifestyle modifications and pharmaceuticals. Here we evaluate and summarize the current clinical interventions for the management of radiation-induced OM. The majority of the current evidence focuses on reducing OM related pain. These agents are detailed over multiple clinical trials including treatment modalities such as: GC4419, doxepin mouthwash, diphenhydramine-lidocaine-antacid (DLA) mouthwash, gabapentin, and methadone. While several strategies have been employed to prevent radiation-induced OM, there is currently no strong evidence for the routine use of these agents in the clinic. After summarization of these treatments, we offer practical guidance for the treatment of OM in the clinic. We recommend a multiagent approach of pharmacological and non-pharmacological treatments including oral rinses, home humidification, escalating doses of gabapentin, doxepin or DLA mouthwash, over the counter analgesics, and lastly methadone. These interventions are tailored to address the expected increase of severity of symptoms during the course of head and neck radiotherapy.

First-line methadone for cancer pain: titration time analysis

BACKGROUND

Methadone is a low-cost, strong opioid that is increasingly used as a first-line treatment for pain in palliative care (PC). Its long and unpredictable half-life and slow elimination phase can make titration challenging. Evidence for titration modalities is scarce.

OBJECTIVE

To describe the titration phase of the treatment with low-dose first-line methadone and the use of methadone for breakthrough pain.

METHODS

Prospective study with strong opioid-naïve patients with moderate to severe cancer pain followed at a tertiary PC unit in Argentina. Starting methadone dose was 2.5-5 mg/day every 8, 12, or 24 h. Titration allowed daily dose increases from day 1, and prescription of oral methadone 2.5 mg every 2 h with a maximum of 3 rescue doses/day for breakthrough pain. Pain control, methadone stabilization dose, and adverse effects, among other variables, were daily assessed over the first 7 days (T0-T7).

RESULTS

Sixty-two patients were included. Initial median (IQR) methadone dose was 5 (2.5) mg/day. Pain intensity decreased from a median (IQR) of 8 (2.3) at T0 to 4 (2.3) at T1 and remained ≤ 4 until T7 (all p < 0.0001 compared to T0). Similar results were obtained through the categorical and tolerability scales for pain. Fifty patients (81%) reached pain control, 66% in the first 48 h. Methadone daily doses at T2 and T7 were higher than that at T0: 7.5 (3) and 6.7 (5.5) versus 5 (2.5), respectively (all p < 0.05). The opioid escalation index at T7 was 1.7%. The median (IQR) number of rescues, stabilization dose, and time for stabilization was 0 (1), 5(4.5) mg, and 3(2) days, respectively. Two patients were discontinued due to delirium. All other side effects were mild.

CONCLUSIONS

First-line, low-dose methadone using rescue methadone resulted in a pronounced and rapid decrease in pain, with minimal need for titration and for breakthrough doses, and no evidence of accumulation or sedation by the end of the week.

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.

The Adequateness of Methadone for Japanese Terminal Cancer Patients Can Be Determined Earlier than 7 Days: A Preliminary Retrospective Study

Introduction:

The Japanese packaging instructions for methadone prohibit dose escalation within 7 days of administration initiation as this may result in overdose and subsequent adverse events. However, for terminal cancer patients, evaluation of the effects of methadone may be desirable within 7 days because they have limited prognoses. We aimed to determine the possibility of estimating the adequateness of methadone earlier than the 7th day by investigating the onset timing of analgesic effects and adverse events of methadone in Japanese terminal cancer patients.

Methods:

Japanese terminal cancer patients who started taking methadone in Ashiya Municipal Hospital were enrolled from January 1, 2013 to February 28, 2019. Verbal rating scale (VRS) scores on pain and adverse events before and after methadone administration (on days 3, 5, and 7) were retrospectively investigated from medical records.

Results:

We enrolled 25 patients, of which 20 (80.0%) received methadone until day 7. The VRS score (mean ± standard deviation) on pain was significantly reduced to 0.90 ± 0.55 on day 3, compared with 1.65 ± 0.67 before the administration of methadone (p < 0.05). The mean VRS scores did not differ significantly on days 3, 5, and 7. Additionally, of the 23 patients who received methadone until day 3, 20 (87.0%) showed an analgesic effect on day 3 and 17 (85.0%) received methadone without experiencing serious adverse events until day 7.

Conclusions:

The adequateness of methadone in Japanese terminal cancer patients could be determined before day 7, considering the high analgesia incidence and few adverse events 3 days after the methadone administration under careful observation by a physician experienced in methadone administration. However, as this is a preliminary study, the relationship between pharmacokinetic parameters and analgesic effects was not evaluated. Further studies involving pharmacokinetics and multicenter prospective studies are required to support these findings.

Persistent and Chronic Postoperative Opioid Use in a Cohort of Patients with Oral Tongue Squamous Cell Carcinoma

BACKGROUND

Recently, the concept of persistent postsurgical opioid use has been described for patients undergoing cancer surgery. Our hypothesis was based on the premise that patients with oral tongue cancer require high dosages of opioids before, during, and after surgery, and thus a large percentage of patients might develop persistent postsurgical opioid use.

METHODS

After institutional review board approval, we conducted a retrospective study that included a cohort of patients with oral tongue cancers who underwent curative-intent surgery in our institution. Multivariable logistic regression models were fit to study the association of the characteristics of several patients with persistent (six months after surgery) and chronic (12 months after surgery) postoperative opioid use.

RESULTS

A total of 362 patients with oral tongue malignancies were included in the study. The rate of persistent use of opioids after surgery was 31%. Multivariate analysis showed that patients taking opioids before surgery and those receiving adjuvant therapy were 2.9 and 1.78 times more likely to use opioids six months after surgery. Fifteen percent of the patients were taking opioids 12 months after surgery. After adjusting for clinically relevant covariates, patients complaining of moderate tongue pain before surgery and those taking opioids preoperatively had at least three times higher risk of still using these analgesics one year after surgery.

CONCLUSIONS

Patients with oral tongue cancers have a high risk of developing persistent and chronic postsurgical opioid use.

MOP-dependent enhancement of methadone on the effectiveness of ALA-PDT for A172 cells by upregulating phosphorylated JNK and BCL2

BACKGROUND

Methadone, as a long-acting opioid analgesic, shows an ability to sensitize the treatment of ALA-PDT for glioblastoma cells (A172) in vitro by promoting apoptosis. However, the mechanisms how methadone enhances the effectiveness of ALA-PDT for tumor cells remains to be clarified.

METHODS

The expression of mu opioid receptor (MOP), apoptosis, phosphorylated c-Jun N-terminal kinase (JNK) and phosphorylated apoptosis regulator B cell lymphoma 2 (BCL2) were measured by flow cytometry. Cytotoxicity was determined using Cell Counting Kit-8 (CCK-8). A MOP antagonist, naloxone, was used to evaluate the role of MOP in the above process.

RESULTS

It was found that A172 cells show the expression of MOP and that naloxone inhibits the enhancement of the methadone effect on apoptosis following ALA-PDT (p < 0.05). Phosphorylated JNK and BCL2 induced by ALA-PDT were promoted in the presence of methadone (p < 0.05). These methadone effects were also inhibited by naloxone (p < 0.05).

CONCLUSIONS

The results suggest that apoptosis induced by ALA-PDT is enhanced by methadone, mostly MOP-mediated, through the upregulation of accumulation of phosphorylated JNK and BCL2, leading to a promotion of cytotoxicity of ALA-PDT for A172 cells.

A single-institution, randomized, pilot study evaluating the efficacy of gabapentin and methadone for patients undergoing chemoradiation for head and neck squamous cell cancer

BACKGROUND

The objective of the current study was to compare the safety and efficacy between 2 analgesic regimens for patients with head and neck cancer (HNC) undergoing definitive chemoradiation (CRT).

METHODS

The current study was a prospective, single-institution, 2-arm, randomized pilot study. Patients with American Joint Committee on Cancer seventh edition stage II to stage IV squamous cell carcinoma of the head and neck who were undergoing CRT were randomized to either arm 1, which entailed high-dose gabapentin (2700 mg daily) with the institutional standard of care (hydrocodone and/or acetaminophen progressing to fentanyl as needed), or arm 2, which comprised low-dose gabapentin (900 mg daily) with methadone. The primary endpoints were safety and toxicity. Secondary endpoints were pain, opioid requirement, and quality of life (QOL). Differences between the treatment arms at multiple time points were compared using a generalized linear mixed regression model with Sidak correction.

RESULTS

A total of 60 patients (31 in arm 1 and 29 in arm 2) were enrolled from April 2015 to August 2017. There was no difference between the treatment arms with regard to adverse events or serious adverse events. Pain was not found to be different between the treatment arms. More patients in arm 1 did not require an opioid during treatment (42% vs 7%; P = .002). Patients in arm 2 experienced significantly better QOL outcomes across multiple domains, including overall health (P = .05), physical functioning (P = .04), role functioning (P = .01), and social functioning (P = .01).

CONCLUSIONS

High-dose prophylactic gabapentin increased the percentage of patients who required no opioid during treatment. Methadone may improve QOL compared with a regimen of short-acting opioids and fentanyl. However, pain was found to significantly worsen throughout treatment regardless of treatment arm, necessitating further studies to identify a more optimal regimen.

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.

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.

A Systematic Review of NMDA Receptor Antagonists for Treatment of Neuropathic Pain in Clinical Practice

OBJECTIVE

To investigate the efficacy of N-methyl-D-aspartate receptor (NMDAR) antagonists for neuropathic pain (NeuP) and review literature to determine if specific pharmacologic agents provide adequate NeuP relief.

METHODS

Literature was reviewed on PubMed using a variety of key words for 8 NMDAR antagonists. These key words include: "Ketamine and Neuropathy," "Ketamine and Neuropathic Pain," "Methadone and Neuropathy," "Methadone and Neuropathic Pain," "Memantine and Neuropathic pain," "Memantine and Neuropathy," "Amantadine and Neuropathic Pain," "Amantadine and Neuropathy," "Dextromethorphan and Neuropathic Pain," "Dextromethorphan and Neuropathy," "Carbamazepine and Neuropathic Pain," "Carbamazepine and Neuropathy," "Valproic Acid and Neuropathy," "Valproic Acid and Neuropathic Pain," "Phenytoin and Neuropathy," and "Phenytoin and Neuropathic Pain." With the results, the papers were reviewed using the PRISMA (Preferred Reporting in Systematic and Meta-Analyses) guideline.

RESULTS

A total of 58 randomized controlled trials were reviewed among 8 pharmacologic agents, which are organized by date and alphabetical order. Of the trials for ketamine, 15 showed some benefit for analgesia. Methadone had 3 positive trials, while amantadine and memantine each only had 2 trials showing NeuP analgesic properties. Dextromethorphan and valproic acid both had 4 randomized controlled trials that showed some NeuP treatment benefit while carbamazepine had over 8 trials showing efficacy. Finally, phenytoin only had 1 trial that showed clinical response in treatment.

CONCLUSIONS

There are a variety of NMDAR antagonist agents that should be considered for treatment of NeuP. Nevertheless, continued and further investigation of the 8 pharmacologic agents is needed to continue to evaluate their efficacy for treatment of NeuP.

Treatment of Pain in Cancer: Towards Personalised Medicine

Despite increased attention to cancer pain, pain prevalence in patients with cancer has not improved over the last decade and one third of cancer patients on anticancer therapy and half of patients with advanced disease still suffer from moderate to severe pain. In this review, we explore the possible reasons for the ongoing high prevalence of cancer pain and discuss possible future directions for improvement in personalised pain management. Among possible reasons for the lack of improvement are: Barriers for patients to discuss pain with clinicians spontaneously; pain measurement instruments are not routinely used in daily practice; limited knowledge concerning the assessment of undertreatment; changes in patients’ characteristics, including the ageing of the population; lack of significant improvement in the treatment of neuropathic pain; limitations of pharmacological treatment and lack of evidence-based nonpharmacological treatment strategies. In order to improve cancer pain treatment, we recommend: (1) Physicians proactively ask about pain and measure pain using assessment instruments; (2) the development of an optimal tool measuring undertreatment; (3) educational interventions to improve health care workers’ skills in pain management; (4) the development of more effective and personalised pharmacological and nonpharmacological pain treatment.

The Association between Patient Characteristics and Opioid Treatment Response in Neuropathic and Nociceptive Pain due to Cancer

BACKGROUND

Cancer pain remains a difficult problem, for which opioids are often necessary. At present it is difficult to predict the effectiveness of opioid therapy.

OBJECTIVES

We aim to assess the association between patient characteristics and opioid treatment response in cancer patients, and develop a model to predict probability of response.

SUBJECTS

We used data from two previously published randomized clinical trials, in which patients with head and neck cancer were treated with fentanyl or methadone (total N = 134).

MEASUREMENTS

Treatment success was defined as ≥50% pain reduction at one and five weeks. We analyzed patient characteristics (age, sex, depression, and anxiety), treatment characteristics (having had chemotherapy, radiotherapy, surgery, methadone, or fentanyl) and pain characteristics (neuropathic and nociceptive).

DESIGN

Based on univariable and multivariable regression analyses determinants of therapy success were assessed. Based on these analyses a prediction model was developed.

RESULTS

Our analyses show that one-week therapy success was associated with methadone (odds ratio [OR] = 5.21), duration of pain in months (OR = 1.12), neuropathic pain (OR = 3.36), and age of the patient in years (OR = 0.95). Inclusion of these four characteristics into our prediction model resulted in an area under the curve of 81.6%.

CONCLUSIONS

Careful analyses of patient attributes, treatment, and pain type of patients with head and neck cancer resulted in a prediction model that allowed to predict short-term pain relief and the opioid treatment response in neuropathic and nociceptive pain owing to cancer.

Methadone as a First-Line Opioid in Cancer Pain Management: A Systematic Review

AIM

The objective of this review was to assess the existent evidence for the use of methadone as a first-line therapy in cancer pain management.

METHODS

A systematic literature search on MEDLINE and Embase databases was carried out from each database, setting up the date to August 30, 2017. Studies were included if methadone was a first-line drug as a Step 3 of World Health Organization analgesic ladder, or at low doses (Step 2), if they were conducted in adult patients with cancer pain, and if they contained outcomes on pain- and opioid-related adverse effects.

RESULTS

The initial search yielded 219 records. Ten articles were considered after the initial screening according to inclusion and exclusion criteria. They included three longitudinal open-label studies. In two studies methadone was initiated at low doses (≤10 mg/day). These studies suggested that methadone was effective in providing analgesia and well tolerated as first opioid at different starting doses and in different conditions and settings. Five additional studies were randomized controlled studies with morphine in patients who had received opioids for moderate pain. Methadone, compared with oral morphine, or transdermal fentanyl, either at low (Step 2 level) or relatively higher doses (Step 3 level), provided similar analgesia with similar adverse effects profile with limited dose escalation in time.

CONCLUSION

Available data are not sufficient to draw net conclusion. However, open-label and controlled studies have shown that methadone may be effective as first-line drug in the management of cancer pain, providing analgesia and adverse effect profiles similar to those produced by other opioids. The finding that methadone doses tend to remain stable suggests that metabolic characteristics and extraopioid analgesic effects, as its well antihyperalgesic properties may be interesting potential advantages. Further studies should provide information regarding the long-term use of methadone or the need to switch from methadone to other opioids when a loss of analgesic response occurs.

Practical Pharmacology of Methadone: A Long-acting Opioid

Methadone is a naturally long-acting analgesic with unique pharmacodynamic and pharmacokinetic properties compared to other opioids, available now in India, to treat severe pain. It has the potential to dramatically relieve suffering among patients with serious illness who are living with persistent physical pain. However, clinicians must appreciate its unique pharmacologic properties and its use in clinical practice safely and effectively. The available formulation in India is a racemic mixture of the S- and R-enantiomers, and as such, it will have a propensity for drug-drug and drug-genetic interactions that can increase the risk of Torsades de Point and respiratory depression. Appropriate patient selection, careful dosing and thorough monitoring of methadone will mitigate these risks.

When to Use Methadone for pain: A Case-Based Approach

The case studies are written in this article to illustrate how methadone might be used for pain in the Indian context. These cases might be used for discussion in a multidisciplinary team, or for individual study. It is important to understand that pain requires a multidisciplinary approach as opioids will assist only with physical, i.e. neuropathic and nociceptive pain, but not emotional, spiritual, or relational pain or the pain of immobility. The social determinants of pain were included to demonstrate how emotional, relational, and psychological dimensions of pain amplify the physical aspects of pain. The case studies follow a practical step-wise approach to pain while undergoing cancer treatment, pain toward the end-of-life and needing longer acting opioid. Methadone in children, and methadone in conditions of opioid toxicity or where there is a need for absorption in the proximal intestine cases are included.

The use of fentanyl in pain management in head and neck cancer patients: a narrative review

Background

Head and neck (H&N) cancers account for about 5% of all malignant tumours. Pain is one of the most feared consequences of H&N neoplasms and is experienced by up to 80% of patients and worsens their quality of life inhibiting speaking, eating, drinking or swallowing. Nevertheless, pain is still often underestimated and undertreated.

Objectives

The role of opioids in cancer pain has been well established but evidences about the role and the relative effectiveness of opioids such as fentanyl in the context of H&N cancer pain remains unclear.

Methods

A literature review based on the guidance of the Centre for Reviews and Dissemination was conducted. An iterative approach was used starting with an electronic search in the MEDLINE database. The search terms (('Neoplasms'[Mesh]) AND 'Head and Neck Neoplasms'[Mesh]) AND 'Fentanyl'[Mesh] were used.

Results

A total of 18 publications were found by the first performed search on PubMed. Other publications concordant with our aim were found by cross-reference. Considering inclusion and exclusion criteria for our review, eight papers resulted eligible for analysis.

Conclusion

Fentanyl transdermal therapeutic system (TTS) seems to be an important option, thanks to the way of administration, the good safety and tolerability profiles to control baseline pain. For breakthrough cancer pain (BTcP), several formulations of transmucosal fentanyl are available. All the formulations seem to be active and safety but we lack head-to-head studies of fentanyl versus other strong opioids, as well as with different formulation of fentanyl, particularly for BTcP where H&N cancer population is very poorly represented.

Methadone versus Fentanyl in Patients with Radiation-Induced Nociceptive Pain with Head and Neck Cancer: A Randomized Controlled Noninferiority Trial

BACKGROUND

Pain is still a burden for many patients with cancer. A recent trial showed the superiority of methadone over fentanyl in neuropathic pain, and we expect that this finding could influence the number of patients treated with methadone.

METHODS

We performed a randomized controlled noninferiority trial in patients with nociceptive pain. Eighty-two strong-opioid-naïve patients with head and neck cancer with substantial pain (pain numeric rating scale [NRS] score ≥ 4) due to radiation therapy were included. Forty-two patients were treated with methadone, and 40 with fentanyl. Patients were evaluated at 1, 3, and 5 weeks. The primary outcomes were reduction in average pain and clinical success (50% pain decrease). We set the predefined noninferiority margin at 1 on the NRS and 10% clinical success. Secondary outcomes were pain interference, global perceived effect (GPE), side effects, and opioid escalation index.

RESULTS

Noninferiority was shown for decrease in NRS for maximum and mean pain scores at 1 and 3 weeks. Noninferiority was shown for clinical success at 1 week only. The opioid escalation index was lower in the methadone group at 3 and 5 weeks as compared to fentanyl (1.44 vs. 1.99, P = 0.004; and 1.50 vs. 2.32, P = 0.013). The pain interference in the methadone group was significantly decreased at 3 weeks only. GPE and side effects were not different.

CONCLUSION

This is the first study to show noninferiority of methadone compared to fentanyl at 1 and 3 weeks in the treatment of radiation-induced nociceptive pain in patients with head and neck cancer.

Survivorship: Morbidity, Mortality, Malignancy

Survivorship encompasses the entire therapeutic, psychosocial, functional, and financial experience of living with and through a cancer diagnosis. The period of survivorship starts on the day of the cancer diagnosis and lasts until the end of the survivor's life, regardless of the cause of death. The National Cancer Institute's Office of Cancer Survivorship expands the term "survivor" to include, importantly, caregivers, family, and friends close to the survivor who also live through this period.

Head and Neck Cancer Pain

Pain is a significant morbidity resulting from head and neck cancer. Pain may also be the result of the treatments directed against head and neck cancer. An experienced practitioner may manage this pain by understanding the multifactorial mechanisms of pain and the various pharmacotherapies available. Pain should be managed with multiple medications in a multimodal approach, and nonpharmacologic therapies should be considered as well.

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.