C hronic non-cancer-related pain (CNCP) includes chronic pain of a nociceptive or neuropathic nature with variable influence by psychological and socioenvironmental factors. Opioids are the most potent analgesics available and are well established for the treatment of severe acute, 1 surgical 2 and cancer pain.3 However, their use to ameliorate CNCP is still controversial because of the side effects of opioids, the physical tolerance they build up (with the related withdrawal reactions and possibility of addiction) and anxiety over disapproval by regulatory bodies. 4The prevalence of CNCP varies according to the type of pain and the population studied. A study conducted in the United Kingdom in a community in the greater London area to quantify the prevalence of chronic pain found that 46.5% of the general population reported chronic pain; low-back problems and arthritis were the leading causes.5 A recent epidemiological study in Denmark 6 found that nearly 130 000 adults, corresponding to 3% of the Danish population, regularly used opioids. CNCP had a prevalence of 19%, and 12% of those who had CNCP used opioid medications.The objectives of this review were 4-fold: to determine the efficacy of opioids for CNCP compared with placebo; to compare the effectiveness of opioids for CNCP with that of other drugs; to identify categories of CNCP with better response to opioids; and to determine the most common side effects and complications of opioid therapy for CNCP, including incidences of opioid addiction and sexual dysfunction. MethodsWe followed the QUOROM guidelines for reporting metaanalyses of randomized controlled trials.7 We searched the literature up to May 2005 through the OVID interface: MEDLINE (from 1960), EMBASE (from 1988), the Cochrane Database of Systematic Reviews, the Cochrane Controlled Trials Register (CENTRAL), the ACP Journal Club and DARE. We also reviewed the reference lists in the articles, reviews and textbooks retrieved. Our search strategies for MEDLINE and EMBASE are available online as Appendix 1 and Appendix 2, respectively (all appendices for this article are available at www.cmaj.ca /cgi/content/full/174/11/1589/DC1). A single reviewer (J.A.S.) ran the electronic searches and entered the data into Reference Manager 10, removing all duplicates.Each of 2 independent reviewers (A.D.F., J.A.S.) screened Methods: This meta-analysis was carried out with these objectives: to compare the efficacy of opioids for CNCP with other drugs and placebo; to identify types of CNCP that respond better to opioids; and to determine the most common side effects of opioids. We searched MEDLINE, EMBASE, CENTRAL (up to May 2005) and reference lists for randomized controlled trials of any opioid administered by oral or transdermal routes or rectal suppositories for CNCP (defined as pain for longer than 6 mo). Extracted outcomes included pain, function or side effects. Methodological quality was assessed with the Jadad instrument; analyses were conducted with Revman 4.2.7.Results: Included were 41 randomized tr...

Diminished perception of innocuous and noxious stimuli is associated with altered activity in many parts of the somatosensory pathway or other supraspinal areas. The cortical findings indicate a neurobiological component for at least part of the symptoms in patients presenting with nondermatomal somatosensory deficits.

Limited research suggests that there may be Warm complex regional pain syndrome (CRPS) and Cold CRPS subtypes, with inflammatory mechanisms contributing most strongly to the former. This study for the first time used an unbiased statistical pattern recognition technique to evaluate whether distinct Warm vs Cold CRPS subtypes can be discerned in the clinical population. An international, multisite study was conducted using standardized procedures to evaluate signs and symptoms in 152 patients with clinical CRPS at baseline, with 3-month follow-up evaluations in 112 of these patients. Two-step cluster analysis using automated cluster selection identified a 2-cluster solution as optimal. Results revealed a Warm CRPS patient cluster characterized by a warm, red, edematous, and sweaty extremity and a Cold CRPS patient cluster characterized by a cold, blue, and less edematous extremity. Median pain duration was significantly (P < 0.001) shorter in the Warm CRPS (4.7 months) than in the Cold CRPS subtype (20 months), with pain intensity comparable. A derived total inflammatory score was significantly (P < 0.001) elevated in the Warm CRPS group (compared with Cold CRPS) at baseline but diminished significantly (P < 0.001) over the follow-up period, whereas this score did not diminish in the Cold CRPS group (time × subtype interaction: P < 0.001). Results support the existence of a Warm CRPS subtype common in patients with acute (<6 months) CRPS and a relatively distinct Cold CRPS subtype most common in chronic CRPS. The pattern of clinical features suggests that inflammatory mechanisms contribute most prominently to the Warm CRPS subtype but that these mechanisms diminish substantially during the first year postinjury.

EERW trial designs appear not to bias the results of efficacy, but they underestimate the adverse effects. The present updated meta- analysis shows that weak and strong opioids are effective for CNCP of both nociceptive and neuropathic origin.