Describing long-term opioid use utilizing Nordic prescription registers-A Norwegian example.

Previous studies have defined long-term opioid use in varying ways, decreasing comparability, reproducibility and clinical applicability of the research. Based on recommendations from recent systematic reviews, we aimed to develop a methodology to estimate the prevalence of use persisting more than three months utilizing one of the Nordic prescription registers. We used the Norwegian Prescription Register (NorPD) to extract data on all opioid dispensations between 1 January 2004 and 31 October 2019. New users of opioids (washout 365 days) were defined as long-term users if they fulfilled two criteria: (1) they had ≥2 dispensations of opioids, 91-180 days apart; (2) days 0-90 included ≥90 dispensed administration units (e.g., tablets) of opioids. Overall, there were 2,543,224 new users of opioids during the study period. Of these, 354,666 (13.9%) fulfilled the criteria for long-term opioid use at least once. Compared with those who did not fulfil the criteria (short-term users), long-term users were older, more likely women and used tramadol, oxycodone and buprenorphine more frequently as their first opioid. In conclusion, we found that 1/7 of opioid users continued use longer than 3 months. Future outcome research should identify the clinically most important dose requirements for long-term opioid use criteria.