Opioids for neuropathic pain

Eisenberg E, McNicol ED, Carr DB

Published Online:

January 21, 2009

Opioids, pain killers such as morphine, are effective for the treatment of long-term pain due to nerve damage. Neuropathic pain, pain caused by nerve damage, is often difficult to diagnose and treat. The use of opioids (strong pain killers such as morphine) to treat neuropathic pain is controversial owing to concerns about addiction and beliefs that this type of pain does not always respond well to opioids. The review authors looked at both short- and intermediate-term trials. They found mixed results regarding the effectiveness of short-term use of opioids. Intermediate-term trials demonstrated that opioids are effective for the subtypes of neuropathic pain tested and for the relatively short duration of published studies. Side effects such as nausea, dizziness, and drowsiness were common, but not life threatening.

Abstract (click to read)

Background:

The use of opioids for neuropathic pain remains controversial. Studies have been small, have yielded equivocal results, and have not established the long-term risk-benefit ratio of this treatment.

Objectives:

To assess the efficacy and safety of opioid agonists for the treatment of neuropathic pain.

Search strategy:

We searched the Cochrane Central Register of Controlled Trials (2nd Quarter 2005), MEDLINE (1966 to June 2005), and EMBASE (1980 to 2005 Week 27) for articles in any language, and reference lists of reviews and retrieved articles.

Selection criteria:

Trials were included in which opioid agonists were given to treat central or peripheral neuropathic pain of any etiology, pain was assessed using validated instruments, and adverse events were reported. Studies in which drugs other than opioid agonists were combined with opioids or opioids were administered epidurally or intrathecally were excluded.

Data collection and analysis:

Data were extracted by two independent investigators and included demographic variables, diagnoses, interventions, efficacy, and adverse effects.

Main results:

Twenty-three trials met the inclusion criteria and were classified as short-term (less than 24 hours; n = 14) or intermediate-term (median = 28 days; range = eight to 70 days; n = 9). The short-term trials had contradictory results. In contrast all nine intermediate-term trials demonstrated opioid efficacy for spontaneous neuropathic pain. Meta-analysis of seven intermediate-term studies showed mean post-treatment visual analog scale scores of pain intensity after opioids to be 13 points lower on a scale from zero to 100 than after placebo (95% confidence interval -16 to -9; P < 0.00001). The most common adverse events were nausea (33% opioid versus 9% control: number needed to treat to harm (NNH) 4.2) and constipation (33% opioid versus 10% control: NNH 4.2), followed by drowsiness (29% opioid versus 12% control: NNH 6.2), dizziness (21% opioid versus 6% control: NNH 7.1), and vomiting (15% opioid versus 3% control: NNH 8.3). Where reported, 23 (11%) of 212 participants withdrew because of adverse events during opioid therapy versus nine (4%) of 202 receiving placebo.

Authors' conclusions:

Short-term studies provide only equivocal evidence regarding the efficacy of opioids in reducing the intensity of neuropathic pain, whereas intermediate-term studies demonstrate significant efficacy of opioids over placebo, which is likely to be clinically important. Reported adverse events of opioids are common but not life threatening. Further randomized controlled trials are needed to establish long-term efficacy, safety (including addiction potential), and effects on quality of life.

This record should be cited as:

Eisenberg E, McNicol ED, Carr DB. Opioids for neuropathic pain. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD006146. DOI: 10.1002/14651858.CD006146

Assessed as up to date:

April 7, 2006

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Primary Review Group:

Pain, Palliative and Supportive Care Group

Health topics:

Anaesthesia & pain control > Chronic non-cancer pain management > Pharmacological therapies

Cochrane group topics:

Pain, Palliative and Supportive Care > Chronic non-cancer pain > Management > Pharmacological therapies

Cochrane Summaries^beta

Independent high-quality evidence for health care decision making

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