Switching from Methadone to a Different Opioid: What Is the Equianalgesic Dose Ratio?

Abstract

Introduction: Methadone (ME) is a highly effective opioid agonist used for difficult pain syndromes. However, in the management of cancer pain with strong opioids, rotation to a different opioid (opioid rotation) may be required because of side effects or poor pain control. Rotation from methadone to another opioid has received limited study and therefore may be difficult because of the absence of a uniformly accepted dose conversion ratio. Methods: Retrospectively reviewed consecutive medical records of patients undergoing an opioid rotation from methadone to an alternative opioid were evaluated. For inclusion, patients were required to have received methadone for at least 3 days and have reached stable dose of the alternative opioid(s) during the 7 days following. Stable dose was defined as a 30% or less change in opioid dose from one day to the next. Results: Records of 39 patients met inclusion criteria. Excluded from analysis were 5 patients who were restarted on methadone within 7 days, 2 with irregular opioid use resulting in negligible regular opioid doses postswitch, and 3 due to concerns about reliability of multiple routes used for fentanyl. Data from 29 patients, 10 female, mean age 48 Ϯ 14.4 years, were evaluable. The mean dose ratio for oral methadone to oral morphine equivalent daily dose (MEDD) was 1:4.7 (95% confidence interval [CI], 3.0-6.5; n ϭ 16), and for intravenous (IV) methadone to MEDD was 1:13.5 (95% CI, 6.6-20.5; n ϭ 13), p ϭ 0.06. Methadone dose was significantly correlated to stable MEDD after switching opioids for both methadone IV and oral (Spearman ϭ 0.86, p ϭ 0.0001 and Spearman ϭ 0.72, p ϭ 0.0024), respectively. Mean day of achieving stable dose was day 2.5 Ϯ 0.2 for IV methadone and day 2.6 Ϯ 0.3 for oral methadone. Conclusion: These dose ratios are new findings that may assist in switching patients more safely to alternative opioids when side effects or pain problems occur when patients are receiving methadone. An important difference in analgesic potency appears to exist between IV and oral ME. Future research with prospective studies is required.

Methadone for Patients with Malignant Psoas Syndrome: Case Series of Three Patients

“…From the aspect of morphine equivalent daily dose (MEDD), the MEDD of all three patients was decreased by switching to oral methadone (Case I, 175.0 mg to 47.0 mg MEDD/day; Case II, 90.0 mg to 70.5 mg MEDD/day; Case III, 120.0 mg to 47.0 mg MEDD/day). 9 Although there are no standard criteria for the switch from other opioids to methadone, all three patients in the present series had tried up to two different opioids before switching to methadone-Case I: morphine rescue and fentanyl; Case II: tramadol and oxycodone; Case III: oxycodone and fentanylwhich had resulted in a poor response and unacceptable toxicity. For these reasons we decided to use methadone.…”

Response to Pain Management among Patients with Active Cancer, No Evidence of Disease, or Chronic Nonmalignant Pain in an Outpatient Palliative Care Clinic

“…Standard conversion ratios 7 were used for all opioids and a conversion factor of 5 was used for methadone. 8 Pain response. The pain scores from the Numerical Rating Scale (NRS) were collected at both visits.…”

Implementation of an Opioid Management Initiative by a State Medicaid Program

“…These ratios are not universally agreed upon, and there are differing ratios found in the literature. [33][34][35][36] Another limitation could be the time frame between the implementation of changes and evaluation of outcomes when it comes to cost benefit. The overall cost of LAOAs decreased during the study period of 2002 to 2005, which correlated with an overall plan PMPM cost decrease of 6.3%.…”