Although common treatments for osteoarthritis (OA) pain, such as nonsteroidal antiinflammatory drugs (NSAIDs), simple analgesics, and weak opioids, provide relief in some cases, they fail to control pain or are poorly tolerated in many cases. Strong opioids have been used to successfully treat several types of noncancer pain but have rarely been tested in controlled studies. Therefore, we tested the effects of transdermal fentanyl (TDF) in patients with moderate-to-severe OA pain, in a placebo-controlled study.
The cohort comprised patients with radiologically confirmed OA of the hip or knee (meeting the American College of Rheumatology criteria) requiring joint replacement and with moderate-to-severe pain that had been inadequately controlled by weak opioids. The patients were randomized to receive TDF or placebo for 6 weeks after a 1-week pretreatment run-in phase. During study treatment, previously prescribed NSAIDs and simple analgesics were continued, but weak opioids were discontinued. All patients had access to paracetamol and metoclopramide. Pain was recorded on a visual analog scale (VAS), and function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
Data were available for 399 patients (202 receiving TDF, 197 receiving placebo), of whom 199 (50%) completed the study. TDF provided significantly better pain relief than placebo, as demonstrated by the primary outcome measure (area under the curve for VAS scores -20 in the TDF group versus -14.6 in the placebo group; P = 0.007). TDF was also associated with significantly better overall WOMAC scores and pain scores. The most common adverse events were nausea, vomiting, and somnolence, and these occurred more often in the TDF group.
TDF can reduce pain and improve function in patients with knee or hip OA.