Abstract: We included 15 trials (5540 participants). Tramadol was examined in five trials (1378 participants); it was found to be better than placebo for pain (SMD -0.55, 95% CI -0.66 to -0.44; low quality evidence) and function (SMD -0.18, 95% CI -0.29 to -0.07; moderate quality evidence). Transdermal buprenorphine (two trials, 653 participants) may make little difference for pain (SMD -2.47, 95%CI -2.69 to -2.25; very low quality evidence), but no difference compared to placebo for function (SMD -0.14, 95%CI -0.53 to 0.25; very low quality evidence). Strong opioids (morphine, hydromorphone, oxycodone, oxymorphone, and tapentadol), examined in six trials (1887 participants), were better than placebo for pain (SMD -0.43, 95%CI -0.52 to -0.33; moderate quality evidence) and function (SMD -0.26, 95% CI -0.37 to -0.15; moderate quality evidence). One trial (1583 participants) demonstrated that tramadol may make little difference compared to celecoxib (RR 0.82, 95% CI 0.76 to 0.90; very low quality evidence) for pain relief. Two trials (272 participants) found no difference between opioids and antidepressants for either pain (SMD 0.21, 95% CI -0.03 to 0.45; very low quality evidence), or function (SMD -0.11, 95% -0.63 to 0.42; very low quality evidence). The included trials in this review had high drop-out rates, were of short duration, and had limited interpretability of functional improvement. They did not report any serious adverse effects, risks (addiction or overdose), or complications (sleep apnea, opioid-induced hyperalgesia, hypogonadism). In general, the effect sizes were medium for pain and small for function. There is some evidence (very low to moderate quality) for short-term efficacy (for both pain and function) of opioids to treat CLBP compared to placebo. The very few trials that compared opioids to non-steroidal anti-inflammatory drugs (NSAIDs) or antidepressants did not show any differences regarding pain and function. The initiation of a trial of opioids for long-term management should be done with extreme caution, especially after a comprehensive assessment of potential risks. There are no placebo-RCTs supporting the effectiveness and safety of long-term opioid therapy for treatment of CLBP.

Plain-language summary: We searched for trials, both published and unpublished, up to October 2012. We included fifteen trials which included 5540 participants and compared opioids against a placebo (fake medication) or other drugs that have been used for LBP. Most people included in the trials were aged 40 to 50 years and all reported at least moderate pain across the low-back area. The trials included a slightly higher proportion of women. Most of the trials followed the patients during three months and were supported by the pharmaceutical industry. In general, people that received opioids reported more pain relief and had less difficulty performing their daily activities in the short-term than those who received a placebo. However, there is little data about the benefits of opioids based on objective measures of physical functioning. We have no information from randomized controlled trials supporting the efficacy and safety of opioids used for more than four months. Furthermore, the current literature does not support that opioids are more effective than other groups of analgesics for LBP such as anti-inflammatories or antidepressants. This review partially supports the effectiveness of several opioids for CLBP relief and function in the short-term. However, the effectiveness of prescribing of these medications for long-term use is unknown and should take into consideration the potential for serious adverse effects, complications, and increased risk of misuse, abuse, addiction, overdose, and deaths. As expected, side effects are more common with opioids but non-life-threatening with short-term use. Insufficient data prevented making conclusions about the side-effect profile of opioids versus other type of analgesics (for example, antidepressants or anti-inflammatories). The quality of evidence in this review ranged between "very low" and "moderate". The review results should be interpreted with caution and may not be appropriate in all clinical settings. High quality randomized trials are needed to address the long-term (months to years) risks and benefits of opioid use in CLBP, their relative effectiveness compared with other treatments, and to better understand which people may benefit most from this type of intervention.