Dose Ratios between High Dose Oral Morphine or Equivalents and Oral Methadone

Conversion ratios: Why is it so challenging to construct opioid conversion tables?

Standardizing opioid management is challenging due to the absence of a ceiling dose, the unknown ideal therapeutic plasma level, and the lack of an clear relationship between dose and therapeutic response. Opioid rotation or conversion, which is switching from one opioid, route of administration, or both, to another, to improve therapeutic response and reduce toxicities, occurs in 20-40 percent of patients treated with opioids. Opioid conversion is often needed when there are adverse effects, toxicities, or inability to tolerate a certain opioid formulation. A majority of patients benefit from opioid conversion, leading to improved analgesia and less adverse effects. There are different published ways of converting opioids in the literature. This review of 20 years of literature is centered on opioid conversions and aims to discuss the complexity of converting opioids. We discuss study designs, outcomes and measures, pain phenotypes, patient characteristics, comparisons of equivalent doses between opioids, reconciling conversion ratios between opioids, routes, directional differences, half-lives and metabolites, interindividual variability, and comparison to package insert information. Palliative care specialists have not yet come to a consensus on the ideal opioid equianalgesic table; however, we discuss a recently updated table, based on retrospective evidence, that may serve as a gold standard for practical use in the palliative care population. More robust, well-designed studies are needed to validate and guide future opioid conversion data.

Ultralow-Dose Adjunctive Methadone with Slow Titration, Considering Long Half-Life, for Outpatients with Cancer-Related Pain

Background: The unique properties of methadone make it attractive for use in cancer pain. The use of very low initial doses of adjunctive methadone is a promising strategy given its simplicity and potentially reduced risk profile.

Objective: To understand if an ultralow-dose (ULD) methadone protocol (1 mg by mouth daily initial dose with gradual titration) can improve pain control in outpatients with cancer-related pain not responsive to previous opioids and/or nonopioid analgesics. We also sought to assess if the use of ULD methadone resulted in improvement in mood and sleep among other outcomes.

Design and Setting/Subjects: This study is a retrospective chart review of outpatients at the cancer pain clinic at the Tom Baker Cancer Centre in Calgary, Alberta, Canada.

Measurements: The mean ratings in maximum and average pain before methadone initiation, and at the final follow-up point are reported. Paired sample t tests evaluate for statistically significant differences in pain ratings before methadone initiation and at final follow-up. We also report the proportion of participants with a subjective improvement in pain, sleep, and mood (dichotomous “yes/no”), and the mean number of weeks to initial documented pain improvement.

Results: 68.6% of patients (24/34) reported a subjective improvement in pain. Most patients reported improved sleep and mood (78.8% and 64.7%, respectively).

Conclusions: More than two-thirds of patients reported an improvement in pain with a protocol using very low initial doses of adjunctive methadone. Our report is a preliminary retrospective chart review and larger prospective trials are warranted.

Conversion of other opioids to methadone: a retrospective comparison of two methods

CONTEXT

A rapid method of methadone conversion known as the Perth Protocol is commonly used in Australian palliative care units. There has been no follow-up or validation of this method and no comparison between different methods of conversion.

OBJECTIVES

The primary objective of this study was to test the hypothesis that the achieved doses of methadone are independent of the conversion method (rapid vs slower). The secondary objectives included examining the relationship between calculated target doses, actual achieved doses and duration of conversions.

METHODS

This is a retrospective chart audit conducted at two hospital sites in the Brisbane metropolitan area of Australia which used different methadone conversion methods.

RESULTS

Methadone conversion ratios depended on previous opioid exposure and on the method of conversion used. The method most commonly used in Australia for calculating target doses for methadone when converting from strong opioids is a poor predictor of actual dose achieved. More appropriate conversion ratios are suggested.

CONCLUSION

Further research is needed to refine the ratios used in practice when converting patients from strong opioids to methadone. Caution and clinical expertise are required. A palliative methadone registry may provide useful insights.

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.

Practical Guide for Using Methadone in Pain and Palliative Care Practice

Since the 2014 Amendment to the NDPS Act methadone has been released in India for pain management. The methadone is supplied as racemic mixture with R & S methadone with benefit in pain management and associated adverse effects. Physicians need to be aware of adverse effects so that methadone can be administered safely. Similarly, patients and families need to store and use methadone carefully and experience the benefits and not increase the risk of further morbidity. Considerable amount of literature on methadone is available and sometimes conflicting, hence the article is attempting to guide a physician to use methadone safely to acquire experience and expertise over time.

Methadone Dose Selection for Treatment of Pain Compared with Consensus Recommendations

BACKGROUND

Many factors make methadone an appealing option for treatment of pain in patients seen by palliative care; however, complex drug-related properties and variable patient response complicate appropriate conversion ratios from other opioids to methadone. Currently, there is no consensus regarding one accepted conversion method.

OBJECTIVE

Current patterns of prescribing for clinicians at a three-hospital academic health system on initial rotation to methadone for the management of pain were compared with a series of consensus recommendations for methadone dose calculation.

DESIGN

Retrospective chart review of 98 hospital patients. Settings/Participants: Adult subjects hospitalized in an academic medical center between January 1, 2013, and January 1, 2015, who were initiated on oral methadone for pain during the same admission.

MEASUREMENTS

Final target daily dose of methadone was calculated using End of Life/Palliative Education Resource Center (EPERC) and Friedman conversion methods based on opioids provided in the prior 24 hours. This was then compared with actual dosing as ordered by clinicians and received by the patient.

RESULTS

Average range of final daily methadone dose for new starts was 18.1 ± 16.7 mg. Final methadone dose as received by two-thirds of patients was below the dosing target calculated by EPERC and Friedman guidelines by an average of 35 mg. In addition, more than 80% of patients' final methadone doses fell below the range recommended by these two methods. No patients received opioid reversal agents during their index hospitalization.

CONCLUSIONS

These findings may question the best approach to clinical application of EPERC and Friedman methods and call for more research to determine the safest, lowest, and most effective methadone target dosing selection. Final methadone dosing as received by patients compared favorably with a conservative methadone dosing method that recommends starting doses no higher than 30-40 mg per day.

Efficacy and Safety of Methadone as a Second-Line Opioid for Cancer Pain in an Outpatient Clinic: A Prospective Open-Label Study

INTRODUCTION

Most clinical reports on methadone rotation describe outcomes in hospitalized patients. The few studies that have included outpatients are retrospective. The aim of this study was to assess the efficacy and safety of methadone as a second-line opioid in adult patients with advanced cancer after rotation in routine clinical practice at a palliative care outpatient clinic.

PATIENTS AND METHODS

This was a prospective, open-label study of 145 patients whose treatment was rotated from other opioids to methadone. Informed consent was obtained in all cases. The main outcome measure was change in the variable "worst pain" at day 28. Pain and pain interference were assessed with the Brief Pain Inventory, with side effects evaluated according to the Common Terminology Criteria for Adverse Events version 3.0. Pain levels were evaluated at study entry and at days 3, 7, 9, 14, 21, and 28.

RESULTS

Rotation to methadone was performed for the following reasons: poor pain control (77.9%), opioid side effects (2.1%), or both (20%). The mean daily oral morphine equivalent dose before rotation was 193.7 mg. The median worst and average pain scores decreased significantly (p < .0001) from baseline to day 28: The median worst pain score decreased from 9 (interquartile range [IQR]: 8-10) to 6 (IQR: 3-8), and the median average pain score decreased from 6 (IQR: 5-7) to 4 (IQR: 2-5). The proportions of patients with moderate to severe worst and average pain decreased by 30.3% and 47.5%, respectively, by day 28. No increase in opioid toxicity was observed during the study.

CONCLUSION

In outpatients with advanced cancer, rotation to methadone as a second-line opioid was efficacious and safe when using a tiered scheme with close follow-up by experienced health professionals.

IMPLICATIONS FOR PRACTICE

The results of this study, conducted prospectively under real clinical conditions, support the efficacy and safety of oral methadone as a second-line opioid in ambulatory patients with cancer. Moreover, these findings corroborate previously reported outcomes in retrospective outpatient studies and prospective studies that evaluated inpatient populations. Although more research into methadone rotation strategies is still needed, this study describes a successful tiered scheme of oral methadone rotation that was proven safe and effective during follow-up.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Methadone safety: a clinical practice guideline from the American Pain Society and College on Problems of Drug Dependence, in collaboration with the Heart Rhythm Society

Methadone is used for the treatment of opioid addiction and for treatment of chronic pain. The safety of methadone has been called into question by data indicating a large increase in the number of methadone-associated overdose deaths in recent years that has occurred in parallel with a dramatic rise in the use of methadone for chronic pain. The American Pain Society and the College on Problems of Drug Dependence, in collaboration with the Heart Rhythm Society, commissioned an interdisciplinary expert panel to develop a clinical practice guideline on safer prescribing of methadone for treatment of opioid addiction and chronic pain. As part of the guideline development process, the American Pain Society commissioned a systematic review of various aspects related to safety of methadone. After a review of the available evidence, the expert panel concluded that measures can be taken to promote safer use of methadone. Specific recommendations include the need to educate and counsel patients on methadone safety, use of electrocardiography to identify persons at greater risk for methadone-associated arrhythmia, use of alternative opioids in patients at high risk of complications related to corrected electrocardiographic QTc interval prolongation, careful dose initiation and titration of methadone, and diligent monitoring and follow-up. Although these guidelines are based on a systematic review, the panel identified numerous research gaps, most recommendations were based on low-quality evidence, and no recommendations were based on high-quality evidence.

PERSPECTIVE

This guideline, based on a systematic review of the evidence on methadone safety, provides recommendations developed by a multidisciplinary expert panel. Safe use of methadone requires clinical skills and knowledge in use of methadone to mitigate potential risks, including serious risks related to risk of overdose and cardiac arrhythmias.