Opioids Don't Stretch Out Relief of Chronic Back Pain

NEW HAVEN, Conn., Jan. 18 -- Although opioids may give patients with chronic back pain temporary relief, the drugs' long-term efficacy is uncertain, and they carry a high potential for abuse, found a systematic review of clinical studies.

So reported Bridget A. Martell, M.D., of Yale, and colleagues, in the Jan. 16 issue of the Annals of Internal Medicine. They found that the drugs were generally no better than placebo or non-opioid controls, and that a fourth of patients on opioids displayed behaviors consistent with substance abuse.

"The findings in this review suggest that clinicians should reconsider treating chronic back pain with opioids medications, and consider other treatments with similar benefit yet fewer long-term adverse effects," they wrote.

To better grasp the prevalence, efficacy, and risk for addiction with these agents, the authors scanned the medical literature to identify studies with an adult, non-obstetric population who were taking opioids in either oral, topical, or transdermal forms for treatment of chronic back pain. The final analysis included 38 studies that met the criteria.

Eleven of the studies included data on opioid prescribing rates, and these studies revealed a wide variation, from only 3% of patients with chronic back pain to 66%.

Patients were more likely to receive opioids if they reported "greater disability, poorer function, greater distress and suffering, and higher functional disability scores than if they had higher pain severity scores," the authors wrote.

In a meta-analysis of four studies that compared efficacy of opioids with placebo or a non-opioid control, such as an NSAID, the authors found that opioids did not appear to be superior at reducing pain, as determined by a Hedges g estimate of the effect of size for continuous measures (g, -0.199 composite standardized mean difference, 95% confidence interval, -0.49 to 0.11, P=0.136).

In addition, when they conducted a meta-analysis of studies pitting one opioid against another (e.g., oxycodone versus codeine), they found that differences in the reduction of pain from baseline were non-significant (g. -0.93 composite standardized mean difference, 95% CI, -1.89 to -0.03]; P=0.055).

And when the authors evaluated the question of substance abuse disorder prevalence, they found that studies reported a range of 3% to 43% prevalence of current abuse, and 36% to 54% lifetime prevalence. The prevalence of "aberrant medication-taking behaviors" (essentially behaviors that don't meet criteria for full-blown addiction) were reported to occur in anywhere from 5% to 24% of patients.

"Our findings are not consistent with previous reviews on the efficacy of opioids for chronic back pain," the authors acknowledged. "Opioids, in some instances, have been found to be efficacious for treatment for painful conditions. Our review, however, found that the evidence in favor of opioids is not always consistent, and when supportive, only supports this treatment for short periods (for example, less than four months). Long-term trials of opioid efficacy for chronic back pain are lacking, and there is other evidence that indicates that the long-term efficacy of opioids for chronic pain may be limited."

They cautioned that the studies they included in their analyses varied widely in quality, and that many were lacking information on trial design or follow-up. They also noted that in many of the studies analyzed, there was no association between pain relief and improvement in functional status, and that most of the trials were funded by pharmaceutical companies, and could therefore be subject to various biases,.