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.