Analgesic utilization in people with knee osteoarthritis: A population-based study using primary care data

Osteoarthritis (OA) is a chronic painful condition that often affects large joints such as the knee. Treatment guidelines recommend paracetamol, nonsteroidal anti-inflammatory drugs (NSAIDs), and opioids. Antidepressants and anti-epileptic drugs (AEDs) are commonly prescribed for chronic noncancer pain conditions including OA, as an off-label use. This study describes analgesic utilization in patients with knee OA at population level using standard pharmaco-epidemiological methods.

This was a cross-sectional study between 2000 and 2014 using data from the U.K. Clinical Practice Research Datalink (CPRD). The use of antidepressants, AEDs, opioids, NSAIDs, and paracetamol was studied in adults with knee OA using the following measures: annual number of prescriptions, defined daily doses (DDD), oral morphine equivalent dose (OMEQ), and days' supply.

In total, there were 8,944,381 prescriptions prescribed for 117,637 patients with knee OA during the 15-year period. There was a steady increase in the prescribing of all drug classes, except for NSAIDs, over the study period. Opioids were the most prevalent class prescribed in every study year. Tramadol was the most commonly prescribed opioid, with the number of DDD increasing from 0.11 to 0.71 DDDs per 1000 registrants in 2000 and 2014, respectively. The largest increase in prescribing was for AEDs, where the number of prescriptions increased from 2 to 11 per 1000 CPRD registrants.

There was an overall increase in the prescribing of analgesics apart from NSAIDs. Opioids were the most frequently prescribed class; however, the greatest increase in prescribing between 2000 and 2014 was observed in AEDs.