Clinical Question

Is controlled-release (CR) oxycodone (Oxycontin) a safe and effective treatment for chronic neuropathic pain and fibromyalgia?

Evidence-Based Answer

Oxycodone CR has limited effectiveness for the treatment of diabetic neuropathy or postherpetic neuralgia. Evidence is lacking regarding treatment benefit for other neuropathic pain syndromes or fibromyalgia. Adverse effects of oxycodone CR therapy are common. (Strength of Recommendation: B, based on inconsistent or limited-quality patient-oriented evidence.)

Practice Pointers

Chronic neuropathic pain and fibromyalgia are estimated to affect 10% of adults older than 30 years.¹ Neuropathic pain is classically difficult to treat, requiring a multidisciplinary approach with pharmacologic, physical, and mental health interventions. Even with a multifaceted approach, few patients achieve appreciable pain relief (i.e., at least a 50% reduction in pain intensity), typically achieving 10% to 25% more relief than with placebo.² Although opioid agonists are commonly used for the management of postoperative, posttraumatic, and cancer-related pain, their effectiveness in neuropathic pain syndromes is unclear.

This Cochrane review is one of a series exploring medications to treat neuropathic pain and fibromyalgia, and specifically looks at the effectiveness of oxycodone CR for these pain syndromes. Study arms included treatment groups using oxycodone in any dose and by any route compared with placebo or an active comparator. Participants were adults 18 years or older with one or more of a range of chronic neuropathic pain conditions. Primary outcome measures were patient-reported percentage in pain intensity reduction, and secondary outcomes included adverse effects and withdrawals from studies because of adverse effects or lack of effectiveness.

Of 2,583 reports identified, three studies involving 254 participants met inclusion criteria. These studies tested oxycodone CR in diabetic neuropathy or postherpetic neuralgia. No studies were found that used oxycodone CR to treat fibromyalgia. Oral oxycodone CR was used in all three studies, all used a placebo group, and one used an active placebo group arm (benztropine). All studies had one or more sources of major bias.

None of the studies reported that participants had a 50% reduction in pain or felt “much improved” while taking oxycodone CR. One study reported a 30% reduction in pain in the oxycodone CR group. Outcomes regarding significant pain relief and high patient satisfaction with oxycodone CR were derived from third-tier data, meaning they had a small number of participants, bias present, and/or limited clinical usefulness of outcomes.

Adverse effects were more common in the treatment arms than in the placebo groups. At least one adverse effect was reported by 86% of persons in the oxycodone CR groups compared with 63% in the placebo groups. Somnolence, dizziness, and constipation were the most commonly reported adverse effects. Of those taking oxycodone CR, 11% withdrew from the study because of adverse effects compared with 6.4% in the placebo groups. However, 1.1% of those in the oxycodone CR groups withdrew from the study because of a lack of treatment effectiveness vs. 11% of those in the placebo group. The number needed to harm for participants taking oxycodone CR compared with placebo is 4.3 (95% confidence interval, 3.1 to 7.0).

Current guidelines for the treatment of neuropathic pain recommend opioid agonists as second-line agents only after first-line agents such as antidepressants, gabapentin (Neurontin), pregabalin (Lyrica), or topical lidocaine have failed.³ Although all treatment for chronic pain should be individualized to the patient, there is no compelling evidence that oxycodone CR improves neuropathic pain from diabetic neuropathy or postherpetic neuralgia, and it should not be considered first-line treatment for these conditions.