Comparing opioids: A guide to estimating oral morphine equivalents (OME) in research

July 2014
Nielsen, S., Degenhardt, L., Hoban, B., & Gisev, N.(2014). Comparing opioids: A guide to estimating oral morphine equivalents (OME) in research. Technical Report No. 329 Sydney: National Drug and Alcohol Research Centre, University of NSW.

Global use of opioids has risen dramatically since the early 2000s. The highest levels of opioid consumption accounted for by use in high income countries such as the United States, Canada and Australia. In many countries there have been well-documented increases in morbidity and mortality associated with the increased use of opioids, which has led to a need to gain a deeper understanding of the manner in which opioids are used and changing patterns of use.

The growing research area examining pharmaceutical opioid use has led to a need to develop clear ways to represent and compare opioid use. The two most common methods are Defined Daily Doses (DDD) and oral morphine equivalents (OMEs).

DDDs may not optimally represent clinical dosing of opioids, partly because opioids require highly individualised dosing and need to be titrated to pain response, rather than having standard therapeutic dose ranges.

Oral morphine equivalents are based on the idea that different doses of different opioids may give a similar analgesic effect. Where the doses of two different opioids are considered to give a comparable analgesic effect, they are deemed to be equianalgesic doses. 

Currently, available tables do not cover the full range of opioids used in Australia, and international references appear to report only a limited number of opioids used in Australia. For this reason the authors have developed a comprehensive dose conversion table, accompanied by a transparent methodology to support the conversion used. As most of the published literature and guidelines report doses in OMEs, the table represents a broad range of opioids with simple conversion factors to facilitate representing doses of a wide range of opioids in OMEs.