Abstract
Previous studies have defined long-term opioid use in varying ways, decreasing comparability, reproducibility and clinical applicability of the research. Based on recent systematic reviews, we aimed to estimate long-term opioid use defined as use persisting more than three months using one of the Nordic prescription registers. We used the Norwegian Prescription Register (NorPD) to extract data on all opioid dispensations between January 1st 2004 and October 31st 2019. New users of opioids (washout 365 days) were defined as long-term users if they filled 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%) filled the criteria for long-term opioid use at least once. Compared to those who did not fill 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.