In this paper we describe the results of a systematic search of the literature on conversion ratios during opioid switching. This is part of a project of the European Palliative Care Research Collaboration to update the European Association for Palliative Care recommendations for the use of opioid analgesics in the treatment of cancer pain. Studies were eligible for inclusion if they involved adult patients with chronic cancer pain, contained data on opioid conversion ratios, were prospective and were written in English. Thirty-one studies were identified and included. The majority of the studies had methodological flaws and were not designed to explore or demonstrate equianalgesic dose data. However, the data allow some recommendations to be made that could be helpful to clinicians for whom there are few reliable experimental data on which to base dosing guidelines. Switching to transdermal fentanyl (TDfe) or buprenorphine (TDbu) is an option for patients with stable, controlled pain. Reliable and consistent studies show a ratio of 100 : 1 between oral morphine (ORmo) and TDfe. A ratio of 75 : 1 between ORmo and TDbu may be appropriate, but the supporting evidence here is much less robust. Data are relatively consistent to support a conversion ratio between ORmo and oral hydromorphone (ORhy) of 5 : 1. Despite some limitations, there is evidence to support the use of an approximate conversion ratio of ORmo:oral oxycodone (ORox) of 1.5 : 1. The conversion between ORox and ORhy is estimated to be 1 : 4. When switching from different opioids to methadone the conversion ratio is highly variable, ranging from 5 : 1 to 10 : 1 and much higher in some studies. The derived ratios are influenced by several factors, including the reasons for switching and previous opioid doses. An individual treatment decision and strict monitoring is recommended for patients considered at risk. (PsycINFO Database Record (c) 2016 APA, all rights reserved)
OBJECTIVE: Review and analyze the evidence base comprising methadone conversion methods and associated dosing ratios for the treatment of pain.
DESIGN: Systematic review.
METHODS: Clinical trials and retrospective analyses, case series, and case reports of human subjects published in the English language between January 1966 and June 2006 were included; review articles and reports with incomplete opioid data were excluded. Scatterplots displayed the relationship between previous morphine dose and final methadone dose and dose ratio. Correlation analyses were conducted using Pearson's and Spearman's correlation coefficient with a one-tailed test of significance.
RESULTS: Twenty-two clinical studies and 19 case reports or series were reviewed (N = 730 patients). Methadone rotations were most common in cancer patients (N = 625, 88.9%) and those prescribed morphine (N = 259 patients, 41.7% of rotations where prerotation opioid was identified [N = 621]) or hydromorphone (N = 234 patients, 37.7% of rotations). In clinical studies, the most common reason for switching to methadone was a combination of inadequate analgesia and adverse effects (N = 254, 38.6%). Despite various approaches, 46-89% of rotations were successful. Overall, there was a relatively strong, positive correlation between the previous morphine dose and the final methadone dose and dose ratio, but ratios varied widely.
CONCLUSIONS: There was no evidence to support the superiority of one method of rotation to methadone over another. Patients may be successfully rotated to methadone despite discrepancies between rotation ratios initially used and those associated with stabilization. Further research is needed to identify patient-level factors that may explain the wide variance in successful methadone rotations.
OBJECTIVE: To discuss the historical basis and limitations of opioid conversion tables, review the relevant literature, and establish an evidence-based equianalgesic dose ratio (EDR) table for performing conversions in the acute care setting.
DATA SOURCES: Articles were identified through searches of MEDLINE (1966-January 2007) using the key words opioid, tolerance, conversion, dose, equianalgesic, equipotent, acute care, morphine, hydromorphone, fentanyl, methadone, and oxycodone. Additional references were located through a review of the bibliographies of articles cited and references cited in conversion tables.
STUDY SELECTION AND DATA EXTRACTION: All data sources identified were evaluated, and all information deemed relevant was included, with the exception of case series and case reports when higher level evidence was available.
DATA SYNTHESIS: Opioid conversion tables are published in major textbooks, medical references, national guidelines, and review articles. Some conversion tables do not accurately reflect the dose ratios for which evidence is available. There is marginal evidence-based clinical data to support the dose ratios cited in these tables, particularly in the acute care setting where the clinical status of patients often changes rapidly. The barriers when performing route and opioid-to-opioid conversions in the acute care setting are formidable, but EDRs are provided, based on the best available evidence.
CONCLUSIONS: In the acute care setting, calculation of dose ratios for opioids, based solely on opioid conversion tables, is an oversimplification of pain management, with a potential for adverse consequences. The calculation of EDRs is one step in an interdisciplinary process that must take into account patient- and institution-specific factors.
Clinicians involved in the opioid pharmacotherapy of cancer-related pain should be acquainted with a variety of opioids and be skilled in the selection of doses when the type of opioid or route of administration needs changing. The optimal dose should avoid under-dosing or overdosing, both associated with negative outcomes for the patient. Although equianalgesic dose tables are generally used to determine the new doses in these circumstances, the evidence to support the ratios indicated in these tables largely refers to the context of single dose administration. The applicability of these ratios to the setting of chronic opioid administration has been questioned. A systematic search of published literature from 1966 to September 1999 was conducted to critically appraise the emerging evidence on equianalgesic dose ratios derived from studies of chronic opioid administration. There were six major findings: 1) there exists a general paucity of data related to long-term dosing and studies are heterogeneous in nature; 2) the ratios exhibit extremely wide ranges; 3) methadone is more potent than previously appreciated; 4) the ratios related to methadone are highly correlated with the dose of the previous opioid; 5) the ratio may change according to the direction the opioid switch; and 6) discrepancies exist with respect to both oxycodone and fentanyl. Overall, these findings have important clinical implications for clinicians and warrant consideration in the potential revision of current tables. The complexity of the clinical context in which many switches occur must be recognized and also appreciated in the design of future studies.
In this paper we describe the results of a systematic search of the literature on conversion ratios during opioid switching. This is part of a project of the European Palliative Care Research Collaboration to update the European Association for Palliative Care recommendations for the use of opioid analgesics in the treatment of cancer pain. Studies were eligible for inclusion if they involved adult patients with chronic cancer pain, contained data on opioid conversion ratios, were prospective and were written in English. Thirty-one studies were identified and included. The majority of the studies had methodological flaws and were not designed to explore or demonstrate equianalgesic dose data. However, the data allow some recommendations to be made that could be helpful to clinicians for whom there are few reliable experimental data on which to base dosing guidelines. Switching to transdermal fentanyl (TDfe) or buprenorphine (TDbu) is an option for patients with stable, controlled pain. Reliable and consistent studies show a ratio of 100 : 1 between oral morphine (ORmo) and TDfe. A ratio of 75 : 1 between ORmo and TDbu may be appropriate, but the supporting evidence here is much less robust. Data are relatively consistent to support a conversion ratio between ORmo and oral hydromorphone (ORhy) of 5 : 1. Despite some limitations, there is evidence to support the use of an approximate conversion ratio of ORmo:oral oxycodone (ORox) of 1.5 : 1. The conversion between ORox and ORhy is estimated to be 1 : 4. When switching from different opioids to methadone the conversion ratio is highly variable, ranging from 5 : 1 to 10 : 1 and much higher in some studies. The derived ratios are influenced by several factors, including the reasons for switching and previous opioid doses. An individual treatment decision and strict monitoring is recommended for patients considered at risk. (PsycINFO Database Record (c) 2016 APA, all rights reserved)
