Methadone for Pain Management in Children with Cancer

Methadone for Cancer Pain Management in Children: A Review of Literature

Pain associated with cancer is a common feature among children and adolescents. Among opioids, methadone is a unique drug for its multiple mechanisms of action. Methadone is currently underutilized in children. The use of methadone for cancer pain management in children was assessed in a systematic review. Altogether, 141 children receiving methadone were examined, and another 126 children were assessed for QT prolongation. In the clinical studies, modalities of use, dosing, and duration of assessment were highly variable. In general, methadone was effective and well tolerated with a limited tendency for dose increases. QT prolongation was reported in a percentage of patients independently of the dosages or other variables. The majority of studies considered the use of methadone to be safe and effective in children. Despite methadone possessing interesting properties that make this drug unique in a pediatric context, data is limited, and the literature available is based on retrospective studies. Methadone could be an effective, inexpensive, and versatile medication in children with cancer who have pain. This drug deserves more interest and should prompt studies of better quality with a larger number of patients.

The Pharmacological Treatment of Neuropathic Pain in Children

The International Association for the Study of Pain (IASP) defines neuropathic pain as pain caused by a lesion or disease of the somatosensory nervous system. It is characterized as a clinical condition in which diagnostic studies reveal an underlying cause of an abnormality in the peripheral or central nervous system. Many common causes of neuropathic pain in adults are rare in children. The purpose of this focused narrative review is, to 1) provide an overview of neuropathic pain in children, 2) highlight unique considerations related to the diagnosis and mechanisms of neuropathic pain in children, and 3) perform a comprehensive analysis of the pharmacological treatments available. We emphasize that data for routine use of pharmacological agents in children with neuropathic pain are largely inferred from adult literature with little research performed on pediatric populations, yet have clear evidence of harms to pediatric patients. Based on these findings, we propose risk mitigation strategies such as utilizing topical treatments whenever possible, assessing pain phenotyping to guide drug class choice, and considering pharmaceuticals in the broader context of the multidisciplinary treatment of pediatric pain. Furthermore, we highlight important directions for future research on pediatric neuropathic pain treatment.

Old Drug, New Pain. Roles and Challenges of Methadone Therapy in Pediatric Palliative Care: A Systematic Review

BACKGROUND

Pediatric palliative care (PPC) is defined as the prevention and relief from suffering of families and children with life-limiting (LLDs) or life-threatening diseases (LTDs). These patients often experience pain, with morphine being the most widely used drug to treat it. Few studies investigated the role of methadone in PPC patients, although it is considered among the most effective and underutilized drugs in PPC.

OBJECTIVES

Our aim was to evaluate the efficacy, safety, and dosage of methadone in PPC.

METHODS

Between August and October 2021 PubMed, Scopus and the Cochrane Library were searched for studies on the use of methadone in children with LLDs and LTDs. Articles were included if they met the following criteria: published in the last 10 years, English language, patients aged 0-23 years; children enrolled in a PPC center or receiving declared support from a PPC service; reporting of specific data on methadone in interventional trials, observational studies, or case series on >10 patients. The reporting of the article was guided by the PRISMA guidelines, and a critical appraisal of the included studies was performed using the JBI-tool.

RESULTS

After duplicates removal and full-text assessment, four studies were included and another one was added after checking the references of the retrieved papers. All were retrospective, and the literature is concordant in documenting the lack of evidence. A total of 116 children received methadone in PPC. From our review emerges the poor quality of data collection: in only one study pain was assessed with standardized scales. All studies documented the effectiveness of methadone in treating complex pain, either nociceptive or neuropathic. No serious adverse events were reported, with no cases of cardiac arrhythmias.

CONCLUSION

Our results suggest that methadone could represent a suitable strategy for treating pain in PPC. However, the evidence base is insufficient, and further research is warranted.

Review of LC techniques for determination of methadone and its metabolite in the biological samples

Methadone (MTD) is a synthetic analgesic drug used for treating opioid dependence and effectively used clinically for patients with severe pain. The abuse of MTD may lead to poisoning, disorder in the central nervous system and even death. The regular monitoring of MTD in biological matrices including serum, plasma and urine samples is an effective way to control abuse of MTD. In this manner, the selection of analytical monitoring of MTD in biological matrices is of paramount importance. This study was conducted to review high-performance liquid chromatography (HPLC) techniques carried out on MTD and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in the biological samples during 2015-June 2021.

Reducing pain in children with cancer at home: a feasibility study of the KLIK pain monitor app

PURPOSE

This study assessed adherence to, feasibility of, and barriers and facilitators of implementation of an app developed to monitor and follow-up with pain in children with cancer at home.

METHODS

Children (8-18 years) receiving cancer treatment (all diagnoses) or their parents (of children aged 0-7 years) used the KLIK Pain Monitor app for 3 weeks. Pain was assessed twice daily using an 11-point numeric rating scale (NRS-11) (ranging from 0 to 10). Healthcare professionals (HCP's) from the hospital's Pediatric Pain Service were instructed to follow-up with clinically significant pain scores (≥ 4) within 120 min (scores 4-6) or 30 min (scores 7-10). Adherence, feasibility, and implementation outcomes were assessed using questionnaires, app log data, and interviews.

RESULTS

Twenty-seven children (M age = 7.3 years, 51.8% male) and six HCP's participated. Sixty-three percent (N = 17) of families used the app on a daily basis during three weeks, and 18.5% (N = 5) reported pain scores twice daily during that time (family adherence). Twelve out of 27 children (44.4%) reported a clinically significant pain score at least once. In 70% (14/20) of clinically significant pain scores, HCP's followed-up with families within the set timeframe (HCP adherence). Outcomes reveal feasibility for the majority of app functions (i.e., positive evaluation by ≥ 70% families/HCP's), and non-feasible aspects could be resolved. Identified barriers and facilitators were used to improve future implementation efforts.

CONCLUSION

Use of the KLIK Pain Monitor app seems feasible. Future research will determine its effectiveness in reducing pain in children with cancer at home.

Alleviating Terminal Pediatric Cancer Pain

Terminal cancer pain remains one of the most distressing aspects of pediatric oncology practice. Opioids are the cornerstone of cancer pain management at end-of-life and fortunately, most pain at end-of-life can be managed successfully. This article presents a practical step-by-step approach to alleviating pediatric terminal cancer pain, which can be delivered across settings.

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.

Pain Management in Childhood Leukemia: Diagnosis and Available Analgesic Treatments

Pain is one of the most common symptoms in children suffering from leukemia, who are often misdiagnosed with other childhood painful diseases such as juvenile idiopathic arthritis. Corticosteroid-induced osteonecrosis (ON) and vincristine-induced peripheral neuropathy (VIPN) are the most common painful manifestations. Additionally, ongoing pain may continue to impact quality of life in survivorship. This narrative review focuses on the pathophysiological mechanisms of pain in childhood leukemia and current available indications for analgesic treatments. Pain management in children is often inadequate because of difficulties in pain assessment, different indications across countries, and the lack of specific pediatric trials. Analgesic drugs are often prescribed off-label to children by extrapolating information from adult guidelines, with possible increased risk of adverse events. Optimal pain management should involve a multidisciplinary team to ensure assessment and interventions tailored to the individual patient.

Pain at home during childhood cancer treatment: Severity, prevalence, analgesic use, and interference with daily life

BACKGROUND

Pain is a common symptom in childhood cancer. Since children spend more time at home, families are increasingly responsible for pain management. This study aimed at assessing pain at home.

PROCEDURE

In this longitudinal observational study (April 2016-January 2017), pain severity and prevalence, analgesic use, and pain interference with daily life (Brief Pain Inventory Short Form) were assessed for 4 consecutive days around the time of multiple chemotherapy appointments. Descriptive statistics (frequencies and percentages) were used to report pain severity (with clinically significant pain defined as: score ≥ 4 on "worst pain" or "average pain in the last 24 h"), pain prevalence, and analgesic use. Mixed models were estimated to assess whether patient characteristics were associated with pain severity, and whether pain severity was associated with interference with daily life.

RESULTS

Seventy-three children (50.7% male) participated (1-18 years). A majority (N = 57, 78%) experienced clinically significant pain at least once, and 30% reported clinically significant pain at least half the time. In 33.6% of scores ≥ 4, no medication was used. We found an association between pain severity and interference with daily life: the higher the pain, the bigger the interference (estimated regression coefficient = 1.01 [95% CI 0.98-1.13]).

CONCLUSIONS

The majority of children experienced clinically significant pain at home, and families frequently indicated no medication use. A stronger focus on education and coaching of families seems essential, as well as routine screening for pain in the home setting.

Methadone for Cancer Pain in Pediatric End-of-Life Care

BACKGROUND

The goal of adequate pain control becomes increasingly salient for children with cancer and their families as the patients approach the end of life. Methadone is one option that is particularly desirable in end-of-life care given its long duration of action and NMDA antagonism that may help in controlling pain refractory to conventional opioids. The purpose of this study was to describe a single institution's experience with methadone for the treatment of cancer pain in pediatric end-of-life care.

METHODS

This retrospective, observational, single-center study included all patients during a 9-year period who died in the inpatient setting and were receiving methadone in their last 30 days of life.

RESULTS

Twenty patients were identified, 18 (90%) of whom received methadone for nociceptive pain. The median duration of methadone use was 32 days (range 2-323 days). Methadone doses ranged from 0.09 to 7.76 mg/kg per day. There were no instances of discontinuing methadone due to an increased QTc interval. No episodes of torsades de pointes were observed.

CONCLUSION

In patients with pediatric cancer who are nearing the end of life, methadone is a valuable adjunctive therapy to treat nociceptive and neuropathic pain and to prevent opioid-induced hyperalgesia and opioid tolerance. An individualized approach to dosage and route should be considered based on specific clinical circumstances.

Stability of Methadone Hydrochloride for Injection in Saline Solution

BACKGROUND

Until October 2014, methadone hydrochloride for injection (10 mg/mL) was available in Canada through Health Canada's Special Access Programme. Diluted to 5 mg/mL in saline, it was used in pediatrics for acute and cancer-related pain. More recently, the department of pharmacy of the Centre hospitalier universitaire Sainte-Justine in Montréal, Quebec, proposed compounding a solution of methadone hydrochloride for injection (5 mg/mL) from bulk powder and saline solution for pediatric administration.

OBJECTIVE

To assess the stability of the proposed compounded preparation.

METHODS

Solutions of methadone hydrochloride in saline were prepared from bulk powder and stored in clear glass vials for up to 180 days at room temperature (25 °C) or with refrigeration (5 °C), with testing on days 0, 7, 14, 30, 60, 90, and 180. The appearance of the solutions and presence of particulate matter were assessed. A stability-indicating high-performance liquid chromatography (HPLC) method was developed to assay the concentration of methadone over time.

RESULTS

No notable changes in appearance of the methadone solution were observed, particle counts did not exceed limits specified by the United States Pharmacopeia, and no microbial growth was observed. The HPLC analysis showed that the concentration of methadone remained above 90% on all study days.

CONCLUSIONS

Methadone hydrochloride for injection prepared from bulk powder in saline solution at a concentration of 5 mg/mL remained chemically stable for at least 180 days when stored in clear glass vials at 5 °C and at 25 °C.

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.

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.

Corrected QT Interval Prolongation in Pediatric and Young Adult Patients on Methadone for Cancer-Related Pain

CONTEXT

Methadone has been reported to prolong the corrected QT (QTc) interval and increase the risk of torsades de pointes.

OBJECTIVES

Our study examined the frequency of QTc prolongation among pediatric and young adult patients starting methadone for cancer pain.

METHODS

All patients followed a standardized protocol. Electrocardiograms (ECGs) were obtained at baseline (methadone starting day to 14 days prior), 1-2 weeks, and 4-6 weeks later. QTc values were manually calculated using the Bazett formula. QTc prolongation was defined as ≥460 milliseconds (ms) for prepubertal children, ≥470 ms for pubertal males, and ≥480 ms for pubertal females.

RESULTS

Baseline ECGs were completed in 42 patients. Follow-up ECGs were completed in 38 of 42 (91%) and 31 of 42 (74%) patients at 1-2 weeks and 4-6 weeks, respectively. No patients had prolongation of the QTc at baseline, and 1 of 38 (3%) patients had a prolonged QTc at weeks 1-2. This patient had a history of prolonged QTc that the family did not initially report. No patients had prolongation of the QTc at weeks 4-6. No patients had torsades de pointes or ventricular fibrillation, and none died suddenly. Median (interquartile range [IQR]) baseline QTc was 391 (377-400) ms; median (IQR) 1-2 week follow-up QTc was 399 (374-411) ms (P = .05), and median (IQR) 4-6 week follow-up QTc was 393 (379-423) ms (P = .01).

CONCLUSION

Clinically significant prolongation of the QTc interval occurred only in one patient who had a history of prolonged QTc. Prolonged QTc is rare in this population.

Attitudes, Beliefs, and Practices of Pediatric Palliative Care Physicians Regarding the Use of Methadone in Children With Advanced Cancer

CONTEXT

Methadone is a long-acting opioid known for its unique pharmacokinetic and pharmacodynamic properties. Most research on methadone in children is limited to its effect on the prolongation of the corrected QT (QTc) interval.

OBJECTIVES

To better understand the attitudes, beliefs, and practices of pediatric palliative care physicians regarding the use of methadone in children with advanced cancer.

METHODS

A survey was sent to the American Academy of Pediatrics Section of Hospice and Palliative Medicine LISTSERV. Information on demographics, dosing of methadone, and the use of electrocardiograms (ECGs) was collected.

RESULTS

One-hundred and five respondents (91%) provide palliative care to children ≥ 50% of the time, and a majority (81, 77%) prescribe methadone. Most (62, 77%) physicians were board certified in Hospice and Palliative Medicine, and most (39, 63%) certified via the direct pathway ("grandfathering"). Most physicians (57, 70%) do not use loading doses of methadone. Board-certified physicians trended toward decreasing methadone dose more (40% ± 19%) than non-board-certified physicians (28%, ±20%) when changing from the oral to intravenous route (P = 0.07). Respondents defined a QTc interval as "prolonged" (mean ± SD) at 444 milliseconds (±68 milliseconds). The percentage of patients receiving a baseline ECG was 65% (±33%). The most common reason for not performing a baseline ECG was that the patient was on hospice (13, 36%).

CONCLUSIONS

There are consistent practices, attitudes, and beliefs of pediatric palliative care providers with regard to methadone. More education is needed on the accurate value of a prolonged QTc interval.