Elon Eisenberg, Ewan D. McNicol and Daniel B. Carr
This systematic review assesses the efficacy of opioid agonists for the treatment of evoked neuropathic pain (NP) based upon published RCTs. Nine articles met inclusion criteria. Although the scarcity of retrieved data precluded formal meta-analysis of short-term trials, we found that the intensity of dynamic mechanical allodynia was significantly attenuated by opioids relative to placebo in all studies. In contrast, no consistent effects on the magnitude of static allodynia, the threshold for mechanical allodynia or the threshold or magnitude of heat allodynia were found. The threshold and magnitude of cold-induced allodynia generally responded positively to opioid treatments in patients with peripheral pain syndromes, but not central pain syndromes. Evoked pain was studied in only two intermediate-term trials, in both of which oxycodone was significantly superior to placebo. The authors concluded that short-term studies show that opioids can reduce the intensity of dynamic mechanical allodynia and perhaps of cold allodynia in peripheral NP. Insufficient evidence precludes drawing conclusions regarding the effect of opioids on other forms of evoked NP. A meta-analysis of intermediate-term studies demonstrates the efficacy of opioids over placebo for evoked NP. These findings are clinically relevant because dynamic mechanical allodynia and cold allodynia are the most prevalent types of evoked pain in NP.
European Journal of Pain, Volume 10, Issue 8,