Opioid use among Danish patients with severe knee osteoarthritis: a drug utilization study

Knee osteoarthritis (OA) is one of the most common musculoskeletal diseases. Opioids have been increasingly used in the treatment of severe knee OA-related pain, particularly in the USA. Less is known about the patterns of use of opioids among Danish patients with severe knee OA. We investigated opioid use among Danish patients with severe knee OA in the 5 years preceding knee replacement surgery (KR).

We identified adults who had undergone KR from January 1st, 2005, to December 31st, 2018, using the Danish National Patient Register. These patients were considered to have severe knee OA in the 5-year period leading up to KR. Individual-level data on prescribed opioids were retrieved from the Danish National Prescription Registry.

We identified 77,168 severe knee OA patients (mean age 66 years). The prevalence of opioid users increased from 21% 5 years before KR to 40% 1 year before. Total use of opioids increased each year and doubled from 3254 mg oral morphine equivalents (OMEQ)/1000 individuals/day 5 years before to 6396 mg OMEQ/1000 individuals/day the year before KR corresponding to an increase of 3141 mg OMEQ (95% confidence interval 3010 to 3273). Tramadol was the most frequently used opioid. About 10% of the population accounted for 90% of the total opioid use.

Among patients with severe knee OA, the prevalence and total use of opioids doubled during the 5 years before KR. In addition, 10% of the study population was responsible for 90% of the opioids used.