By Pat Anson, PNN Editor

Prescription opioids relieve pain, improve physical functioning and help people with chronic pain sleep. But the improvements are small and come with side effects such as vomiting.

Those are the findings from a new meta-analysis (a study of studies) published in the Journal of the American Medical Association (JAMA). Researchers at McMaster University in Canada reviewed 96 clinical trials involving over 26,000 participants who received either prescription opioids or a placebo.

The findings do little to resolve the debate over the safety and effectiveness of opioids.

"Despite widespread use, there is not enough known about the benefits and harms of opioids for chronic non-cancer pain," said lead author Jason Busse, DC, a researcher with the DeGroote Institute for Pain Research and Care at McMaster University.

"We found that, compared to a placebo, 12 per cent more patients treated with opioids will experience pain relief, 8 per cent more will notice an improvement in their physical functioning, and about 6 per cent more will find improvement in their sleep quality.”

One expert questioned the designs of the studies used in Busse’s analysis. Because most participants received a relatively low dose of opioids, it’s not surprising such a small number experienced pain relief, according to Stephen Nadeau, MD, a research advisor for the Alliance for the Treatment of Intractable Pain (ATIP).      

“With few exceptions, doses of opioids achieved were low (median dose 45 MME), trials were short, and opioids were rapidly titrated,” said Nadeau, a neurologist at the VA Medical Center in Gainesville, Florida.

“Because the study designs in all but a handful of studies did not remotely emulate clinical practice, it cannot be inferred that the results of this analysis are applicable to management of the general population of patients requiring opioid management of moderate to severe chronic nonmalignant pain.”

None of the opioid studies reviewed by Busse and his colleagues lasted longer than six months and many were considered low-to-moderate quality evidence. But the same thing could be said about virtually every pain reliever on the market. There is no good quality evidence proving that acetaminophen, pregabalin, ibuprofen, gabapentin or any other non-opioid pain medication is safe or effective long-term.

But opioid critics were quick to focus on the Busse study as proof that opioids should rarely be prescribed for pain.

“The findings reported by Busse et al illustrate that most patients who are prescribed opioids for the treatment of chronic noncancer pain will not benefit from those drugs,” wrote Michael Ashburn, MD, and Lee Fleisher, MD, in a JAMA editorial. “Given the clear risk of serious harm, opioids should not be continued without clear evidence of a clinically important benefit.”

But the only significant side effect the Busse study found was a 6% risk of vomiting. The study drew no conclusions about opioids increasing the risk of addiction, overdose and death – although Busse says those risks should not be overlooked.

“Given their risks, modest benefits, and the comparable effectiveness of alternatives, our results support that opioids should not be first line therapy for chronic non-cancer pain," said Busse, a chiropractor who was the lead author of Canada’s opioid prescribing guideline.

The study was funded by the Canadian Institutes of Health Research and Health Canada.