Debate continues on efficacy of opioids for non-malignant neuropathic pain

Clinical trials provide equivocal evidence for the efficacy of opioids in short term control of neuropathic pain (less than 24 hours) but demonstrate benefits over placebo during longer treatment.A meta-analysis identified 14 studies of acute pain control with opioids including morphine, fentanyl, meperidine and codeine, administered intravenously in 12 of the trials. Only six trials demonstrated superiority over placebo, with five showing equivalence, two showing 'partial efficacy' (meaning some patients responded and others did not), and one indicating a reduction in affective but not sensory components of pain.Results in intermediate-term studies, with a median treatment duration of 28 days, were more consistent. On average there was a 14-point greater improvement in a 100-point visual analogue score compared to placebo, representing a 20-30% benefit that was likely to be clinically significant.Side effects of opioids were predictable and not life threatening - most commonly nausea (occurring in about one-third of patients) followed by constipation, drowsiness, vomiting and dizziness.Analysis of quality of life issues such as sleep, mood, work and social function was not possible because of the variety of measures used in the studies."Further randomised controlled trials assessing longer-term efficacy, safety (including addiction potential) and improved quality of life should be undertaken before the value of opioids for management of neuropathic pain is finally established," the analysis concluded.Treatment of neuropathic pain was currently based on antidepressants or anticonvulsants, but effective analgesia was achieved in less than half of patients. Common causes of the condition included diabetic neuropathy, postherpetic neuralgia, trigeminal neuralgia, central post-stroke pain, pain associated with multiple sclerosis, and pain following spinal cord injury.Reference...