By Roger Chriss, PNN Columnist

An overarching question in pain management and the opioid crisis is whether or not prescription opioids have any value in treating chronic non-cancer pain. 

Some say that the answer is a resounding “No.” Studies to date on the effectiveness of opioids are often too small, methodologically weak or too short-term to be convincing. But these same studies are often used to claim lack of efficacy, and for the same reasons they cannot do that.

At present, we don’t know if or how well opioids work for chronic pain. To establish efficacy, we’d need major studies or clinical trials that run for years, using many hundreds or even thousands of patients. Opioids would need to be compared to placebo or other treatments for various forms of chronic non-cancer pain, from inflammatory and autoimmune conditions to neuropathies and genetic disorders.

Such studies have not been done. A U.S. government website that tracks clinical studies lists 685 trials for “opioids and chronic pain,” with several terminated or withdrawn, others just now recruiting, and only a handful completed. Many of these studies look at substance use disorders, tapering or de-prescribing, or are small-scale efforts at comparing two opioids.

There are no large-scale studies of opioids for chronic non-cancer pain getting started or underway at present.

There are over 14,500 studies on “opioids and chronic pain” listed in PubMed, a database maintained by the National Institutes of Health. One of the few that looked at long-term use of opioids is the 2018 SPACE study, which found that opioids were not superior to non-opioid medications over 12 months.

But the SPACE study has important limitations: It only looked at patients with chronic back pain or osteoarthritis of the hip and knee. Researchers also put the opioid tramadol in the non-opioid group and let some patients switch from the non-opioid to the opioid arm in order to achieve good analgesia.

Another study found that only one in five patients benefited from long-term opioid therapy, with young and middle-aged women showing the least improvement in pain and function. But this was a telephone survey that relied on a pain scale to assess outcomes, with no mention of diagnoses and no randomization or placebo control.

Similar studies with more positive outcomes can be found. According to a Cochrane review, the opioid tapentadol (Nucynta) worked better than oxycodone and a placebo in treating chronic musculoskeletal pain. But the clinical significance of this finding is uncertain.

In other words, we don’t have the kinds of studies we need to figure out if opioids work for chronic pain. This means that when people claim there is no good evidence for opioids in long-term pain management, they have a point. But for the same reason, there is no good evidence against opioid efficacy, either.

Of course, there is good evidence about opioid risks. As PNN reported, an Australian study found that people on long-term opioids do sometimes engage in risky behavior such as filling a prescription early. But this study didn’t find major risks of dose escalation, diversion or overdose that are often claimed to be common.

The solution would be to do major trials. But there seems to be little incentive to do this. The opioid crisis and associated ideological debate about drug legalization have combined with lawsuits and public health policy to remove any motivation to find out more about efficacy. The results of such a study could sway outcomes in the ongoing opioid litigation or ignite new lawsuits, or could even cripple advocacy groups on either side of the opioid divide.

There are, arguably, subtle incentives not to pursue high-quality clinical trials on opioids for long-term pain management. Instead, we’re seeing lots of meta-analyses, reviews, and retrospective studies, none of which is particularly convincing because summarizing old studies with known weaknesses generally cannot answer big questions.

For the foreseeable future, we may be stuck with ideology instead of science guiding clinical pain care.

Roger Chriss lives with Ehlers Danlos syndrome and is a proud member of the Ehlers-Danlos Society. Roger is a technical consultant in Washington state, where he specializes in mathematics and research.