CONCLUSION

Despite growing interest in evaluating the outcomes of LTOT, there is no harmonised terminology or gold standard definition of LTOT in observational research using routinely collected data. The most common threshold applied was 90 days of supply or use within a year. Definitions were often based on those used in prior research and less often on empirical data, with few studies reporting results according to more than one definition. The appropriateness of definitions employed should be driven by the study aims, the data available, and the strengths and limitations of each measure. Researchers should also consider improving the quality of reporting to allow research transparency, reproducibility, and comparability of findings.
ACKNOWLEDGEMENTS: This research is supported by the National Health and Medical Research Council (NHMRC) Centre of Research Excellence in Medicines and Ageing (ID: 1060407) and a Cooperative Research Centre Project (CRC-P) Grant from the Australian Government Department of Industry, Innovation and Science (ID: CRC-P-439). LD is supported by an Australian National Health and Medical Research Council Senior Principal Research Fellowship (APP1135991) and by a US National Institutes of Health grant (R01 DA144740 PI: Degenhardt). The National Drug and Alcohol Research Centre is supported by funding from the Australian Government Department of Health under the Drug and Alcohol Program.
CONFLICTS OF INTEREST: The authors report no actual, potential, or perceived conflict of interest with regards to the submission of this manuscript. The Centre for Big Data Research in Health, UNSW Sydney has received funding from AbbVie to conduct research, unrelated to the present study. Allergan did not have any knowledge of, or involvement in, the present study. LD has received untied educational grant funding from Indivior, Mundipharma, Seqirus and Reckitt Benckiser to examine new opioid medications in Australia. These companies had no knowledge of this review.