INTRODUCTION
The increasing availability of opioid analgesics has been accompanied by
an alarming rise in opioid misuse and related harm. Worldwide, opioid
utilisation increased 2.5-fold between 2001-03 and 2011-13,[1] with the United States and Canada having the
largest per capita opioid consumption. Opioid-related deaths rose more
than 20% in developed countries in the same period. In 2018, 46,800
people died due to opioid overdoses in the United States with 32%
involving prescription opioids. [2, 3]
Opioid analgesics were initially introduced to manage acute and
cancer-related pain and subsequently registered to treat chronic
noncancer pain (CNCP). [4] Short-term opioid use
for CNCP has limited to moderate clinical benefit [5,
6] and there is limited evidence of long-term effectiveness.[5, 7, 8] Prolonged opioid use has been associated
with adverse events, hospitalisations, dependence and overdose.[9-12] Therefore, guidelines for CNCP encourage
initiating therapy with low-doses and limiting treatment to no more than
eight to 12 weeks. [9, 13]
Routinely collected data and drug monitoring programs, using dispensing
claims and prescribing data, represent a rich source of information
supporting large-scale population-based research to quantify, monitor
and develop evidence-informed strategies to reduce long-term opioid
therapy (LTOT). However, translating guideline recommendations to
measurement in routinely collected data can be challenging. Despite the
growing literature of opioid use and harms, there is no gold standard
definition of LTOT for use in routinely collected data.
Recent systematic reviews have identified between 29 and 41 variants of
definitions. [14, 15] These studies did not focus
exclusively on definition applied to routinely collected dispensing and
prescribing data. Rather they included studies ascertaining opioid use
across a broad spectrum of methods including surveys. They also focused
mostly on the use of opioids in surgical settings and did not shed light
on the rationale for the various definitions operationalised in the
studies.
Understanding the terminologies and definitions currently in place in
observational research is crucial for planning research, evaluating
findings, and informing evidence-based recommendations. Given the
increasing role of routinely collected data to evaluate opioid use and
outcomes, especially for CNCP management, we aimed to catalogue the
definitions and terminology relating to LTOT, the rationale for
definitions, and LTOT rates in observational research using routinely
collected data in non-surgical settings.