Neuropathic pain can be difficult to treat, and a 2014 Cochrane systematic review brings the efficacy of one treatment option into question. The March 1 issue of AFP includes a "Cochrane for Clinicians" about this review that showed minimal benefit to patients with neuropathic pain from controlled-release oxycodone (Oxycontin or "oxycodone CR").
The Cochrane authors sought to include randomized controlled trials (RCTs) of oxycodone CR for any type of neuropathic pain and/or fibromyalgia. They found only three studies that met these criteria; the studies included patients with diabetic neuropathy and postherpetic neuralgia, but none investigated fibromyalgia. Each study compared oxycodone CR with a placebo (1 used benztropine as its placebo). The Cochrane authors concluded that:
No convincing, unbiased evidence suggests that oxycodone (as oxycodone CR) is of value in treating people with painful diabetic neuropathy or postherpetic neuralgia.A meta-analysis published in The Lancet Neurology earlier this year studied this question more broadly; they sought to include all treatments for all types of neuropathic pain. The authors categorized "strong opiates" as "a weak recommendation for use and [proposed them] as third-line" treatment behind first-line options of tricyclic antidepressants (TCAs), serotonin-noradrenaline reuptake inhibitors (SNRIs), pregabalin, and gabapentin and second-line options of tramadol and topical capsaicin patches.
Although both of these reviews come to different conclusions, it is possible that both are accurate within their self-defined parameters. Perhaps other opiates are more effective for neuropathic pain than oxycodone CR, or perhaps opiates, in general, are more effective for other types of neuropathic pain besides diabetic neuropathy and postherpetic neuralgia. Both systematic reviews agree in placing the utility of opiates for neuropathic pain below that of other medication classes. Both reviews noted the high incidence of unpleasant side effects with opiate use.
I suspect that many family physicians, though, could relate stories of patients who have benefited from oxycodone CR or other opiates for intractable neuropathic pain. These two new pieces of evidence still allow for individual physician judgment and specific patient needs; "EBM [evidence-based medicine] integrates clinical experience and patient values with the best available research information." Most patients with neuropathic pain should start with one of the first- or second-line options above, but for some patients those options may not suffice. Oxycodone and other opiates for neuropathic pain remain an option for treating patients whose symptoms have inadequately responded to other modalities, but family physicians should remain cautious with their use given the risk of adverse events.
You can read more about treating neuropathy in the AFP By Topics on Pain: Chronic and Diabetes: Type 2.
How do you care for patients with neuropathic pain? Will these systematic reviews change your management?