Pain associated with osteoarthritis is a significant cause of disability and has a negative impact on motor function, sleep and mood. By 75 years of age, up to 80 percent of the population is affected by osteoarthritis. The need to manage moderate to severe pain associated with osteoarthritis has led to the reappraisal of the use of opioids. The long-term effectiveness of opioids in relieving non-cancer pain has been a subject of debate. Roth and associates evaluated the effects of oral controlled-release (CR) oxycodone treatment compared with placebo on pain and function in patients with moderate to severe osteoarthritis pain.

A total of 133 patients who had persistent osteoarthritis-related pain for at least one month and moderate to severe pain at baseline were enrolled in the study. Patients were randomized to one of three double-blind treatment groups: placebo, 10 mg or 20 mg of CR oxycodone every 12 hours. Each day, patients rated pain intensity and sleep quality. Patients taking nonsteroidal anti-inflammatory drugs could continue their use if the dosage had been stable for one month and would not be changed during the study. A total of 106 patients who participated in the placebo-controlled phase were enrolled in the long-term, open-label extension trial.

Fifty-eight patients completed six months of treatment, 41 patients completed 12 months and 15 patients completed 18 months. Thirty-nine patients discontinued treatment because it was deemed ineffective, and 28 discontinued treatment because of adverse effects, predominately nausea, vomiting and somnolence. The number of patients discontinuing for ineffective treatment was significantly lower in the active drug groups. The number of patients discontinuing for adverse events was significantly higher in the active drug group than in the placebo group.

In many trials of analgesics, a 20 percent average reduction in baseline pain intensity is considered clinically meaningful. The use of 20 mg of CR oxycodone twice daily attained this goal within one day, and the use of 10 mg of CR oxycodone twice daily attained this goal by day 2. The placebo-treated group never achieved a 20 percent reduction in pain intensity. The 20-mg CR oxycodone group showed significant mean improvement from baseline in mitigating the effect of pain on mood, sleep and enjoyment of life. Other parameters, such as walking ability, normal work and relationships with others, showed improvement but it was not significant. Treatment with 10 or 20 mg of CR oxycodone twice daily did not result in increased impairment of performance of daily functions.

Eighty-seven of 133 patients reported at least one treatment-related adverse event, most of which were common opioid-related side effects. The common gastrointestinal events appeared to be dosage related, while no dosage relationship was apparent for central nervous system events. Somnolence was significantly more common in elderly patients.

During the long-term phase of the study, the dosage of CR oxycodone became constant at approximately 40 mg per day by week 16, while analgesia was maintained. A higher percentage of patients required downward titration as the trial progressed. Pain was controlled below a “moderate” level throughout the long-term trial with no significant trends from week 2 to the end of the trial. Withdrawal syndrome was not reported as an adverse event during scheduled respites, indicating that CR oxycodone at dosages less than 60 mg per day can be discontinued without tapering the dosage, if necessary. The use of CR oxycodone did not lead to a deterioration or an improvement in daily activities over the long course of therapy.

The authors conclude that patients with moderate to severe pain from osteoarthritis can achieve effective pain relief without deterioration in function when opioids are included as part of a comprehensive pain management program.

editor's note: One of the significant results from this study was the finding that patients treated with sustained dosages of opioids were not impaired during their daily activities. In addition to the reduction in daily pain intensity, the patients were able to obtain better sleep with fewer night awakenings. Even adverse events such as nausea, pruritus, somnolence and constipation decreased as the study progressed. During the long-term phase, there were no clinically significant safety concerns, even among the patients who experienced somnolence. Safe relief of pain that affects enjoyment of life events should be a high priority for our patients.—b.a.