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Opioid Analgesics Subpar for Chronic Back Pain

via Medscape Medical News

Despite the prevailing public view, opioid medicines are not powerful analgesics for low back pain, according to a meta-analysis of 20 randomized controlled trials.

The drugs are commonly prescribed for chronic low back pain, but the review finds that they give only modest short-term relief and that the effect is not likely to be clinically important within current recommended doses.

In addition, they are commonly associated with several adverse effects. The findings were published online May 23 in JAMA Internal Medicine.

Christina Abdel Shaheed, PhD, from the George Institute for Global Health in Sydney, Australia, and the School of Medicine at Western Sydney University in Penrith, and colleagues say evidence on longterm efficacy is lacking, and the efficacy of opioid analgesics in acute low back pain is unknown.

“We found some evidence of a greater effect of opioid analgesics with larger doses; however, the effects are not likely to be clinically important even at high doses,” they write.

Doctor Argues Cutoff Is Arbitrary

Pain and disability were the primary outcome measure, and the researchers converted pain and disability outcomes to a 0 to 100 scale. They considered effects greater than 20 points clinically important.

Kenneth Nguyen, DO, assistant professor of physical medicine and rehabilitation and pain medicine at The Ohio State University Wexner Medical Center in Columbus, told Medscape Medical News that the number is arbitrary and would be different for each patient. He disagrees with the authors’ conclusion that the relief is not clinically significant.

“The way I interpret this study is that opioids do have a favorable outcome for chronic low back pain, but the effect is small. Higher dosages of opioids will offer a very small increase in pain relief with more potential side effects, so dose escalation should be done with caution.”

If a patient is in severe intractable pain, doctors should still consider opioids, Dr Nguyen said, adding that even small relief may be worth the adverse effects for some patients.

“I consider opioid and nonopioid medication, physical therapy, injections, spinal cord stimulators, medical massage therapy, acupuncture, etc., as potential treatment options. Opioids are just another tool that pain physicians have to offer patients,” he said.

Partial agonists, such as buprenorphine, are proving to have some of the painkilling effects of the opioids without some of the adverse effects, he noted.

He acknowledged that he uses a numerical pain scale as part of a requirement for insurance, but the better measure is what the patient can do while receiving the medication as compared to what they are able to do without it, he said.

He added that the study does illustrate that physicians need to curb the “magic bullet” expectations of patients and emphasize it is a small part of the treatment plan.

A question that is “above my pay grade,” he said, is do we move toward a society where opioid analgesics are highly restricted, as they are in some other countries that have found benefits do not outweigh the risks.

Low back pain is the leading cause of disability worldwide. Although guidelines encourage prescribing simple analgesics, such as paracetamol or nonsteroidal antiinflammatory drugs (NSAIDs), many people with low back pain are prescribed opioids.

Researchers found that was common in Australia and the United States. In the United States, more than half the people regularly treated with prescription opioid analgesics have chronic low back pain. In Australia, the three most commonly prescribed drugs for the condition are opioid analgesics or opioid analgesic combinations: oxycodone (11.7%), tramadol (8.2%), and paracetamol and codeine combination (12.1%).

They also found that the ability of people with low back pain to tolerate opioid analgesics is not well-studied. Many trials exclude participants who do not tolerate or adequately respond to the opioid analgesic in the runin phase. Also, some trials exclude participants who do not respond to or tolerate the opioid analgesics in the randomized phase, so the estimate of treatment efficacy comes from only a proportion of participants who were enrolled to receive opioid analgesics.

Of the 20 trials (with a total of 7925 participants), 13 trials (3419 participants) evaluated shortterm effects on chronic low back pain. In half of the 13 trials, at least 50% of participants withdrew because they did not tolerate or respond to the medicine. Moderate evidence showed opioid analgesics reduce pain in the short term (mean difference [MD], −10.1; 95% confidence interv [CI], −12.8 to −7.4). Metaregression revealed a 12point greater pain relief for every 1 log unit increase in morphine equivalent dose (P = .046).

Clinically important pain relief was not observed in doses of 40 to 240 mg morphine equivalents per day.

The latest opioid prescribing guidelines caution against exceeding 200 mg of morphine equivalents per day to lessen the risk for opioidrelated complications, such as lifethreatening respiratory depression. Higher doses of opioid analgesics have also been associated with misuse and dependence, hyperalgesia, and clinically significant hormonal changes.

In 2010, there were 16,651 opioidrelated deaths reported in the United States, the authors note.

Dr Nguyen said he sees a trend in the last 10 years toward less prescribing of the opioid analgesics and more use of partial agonists.

“With the awareness of the dangers of pain medication…and with new laws and regulations, I don’t think opioids are overprescribed now,” he said.

Three coauthors are investigators on three trials evaluating medicines for low back pain. One coauthor is funded by the National Health and Medical Research Council of Australia. Another is the program director on the National Health and Medical Research Council of Australia Centre for Research Excellence on Medicines and Ageing. Dr Nguyen has disclosed no relevant financial relationships.