Opioid analgesia for acute low back pain and neck pain (the OPAL trial): a randomised placebo-controlled trial

PainSci » bibliography » Jones et al 2023
updated Jul 22, 2024

Tags: medications, back pain, neck, self-treatment, treatment, pain problems, spine, head/neck

One page on PainSci cites Jones 2023: Opioids for Chronic Aches & Pains

PainSci notes on Jones 2023:

The OPAL study was a 2023 Australian trial of a short course of slow-release opioids for subacute low back and neck pain of moderate severity. Three hundred people got either a placebo or an oxycodone/naloxone combo, plus standard care, for up to six weeks. There was no major difference in pain relief at the end of the test. The opioid group got more side effects, like constipation. The paper concludes:

Opioids should not be recommended for acute non-specific low back pain or neck pain.

Or as put by one of the authors on social media:

The OPAL trial findings provide strong evidence that opioids should not be prescribed to people with acute back and/or neck pain.

Is it really “strong” evidence for that, though? Many experts disagree. OPAL wasn’t all bad, of course, but there are two categories of legitimate concern about it:

The science itself. There are legitimate concerns about OPAL’s design, especially whether they studied the right drug for the right patients. These were ignored by The Lancet for a year before they finally published three response letters.
How the science was interpreted and presented. Namely, as if the results were much more broadly applicable than the evidence could actually support (even if they could be trusted, which they can’t, see concern 1.)

Read a detailed blog post about the debate.

Common issues and characteristics relevant to this paper: ?Scientific papers have many common characteristics, flaws, and limitations, and many of these are rarely or never acknowledged in the paper itself, or even by other reviewers. I have reviewed thousands of papers, and described many of these issues literally hundreds of times. Eventually I got sick of repeating myself, and so now I just refer to a list common characteristics, especially flaws. Not every single one of them applies perfectly to every paper, but if something is listed here, it is relevant in some way. Note that in the case of reviews, the issue may apply to the science being reviewed, and not the review itself.

Conflation of statistical “significance” with “importance” — or the reverse, ignoring/minimizing statistical insignificance.
Major flaws in experimental design or execution.
Damned with faint praise — technically positive results (at least partially) that don’t actually impress.
Reaching beyond the data with the interpretation, conclusions, and/or public representation of trial results.

original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

BACKGROUND: Opioid analgesics are commonly used for acute low back pain and neck pain, but supporting efficacy data are scarce. We aimed to investigate the efficacy and safety of a judicious short course of an opioid analgesic for acute low back pain and neck pain.

METHODS: OPAL was a triple-blinded, placebo-controlled randomised trial that recruited adults (aged ≥18 years) presenting to one of 157 primary care or emergency department sites in Sydney, NSW, Australia, with 12 weeks or less of low back or neck pain (or both) of at least moderate pain severity. Participants were randomly assigned (1:1) using statistician-generated randomly permuted blocks to guideline-recommended care plus an opioid (oxycodone-naloxone, up to 20 mg oxycodone per day orally) or guideline-recommended care and an identical placebo, for up to 6 weeks. The primary outcome was pain severity at 6 weeks measured with the pain severity subscale of the Brief Pain Inventory (10-point scale), analysed in all eligible participants who provided at least one post-randomisation pain score, by use of a repeated measures linear mixed model. Safety was analysed in all randomly assigned eligible participants. The trial was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12615000775516).

FINDINGS: Between Feb 29, 2016, and March 10, 2022, 347 participants were recruited (174 to the opioid group and 173 to the placebo group). 170 (49%) of 346 participants were female and 176 (51%) were male. 33 (19%) of 174 participants in the opioid group and 25 (15%) of 172 in the placebo group had discontinued from the trial by week 6, due to loss to follow-up and participant withdrawals. 151 participants in the opioid group and 159 in the placebo group were included in the primary analysis. Mean pain score at 6 weeks was 2·78 (SE 0·20) in the opioid group versus 2·25 (0·19) in the placebo group (adjusted mean difference 0·53, 95% CI -0·00 to 1·07, p=0·051). 61 (35%) of 174 participants in the opioid group reported at least one adverse event versus 51 (30%) of 172 in the placebo group (p=0·30), but more people in the opioid group reported opioid-related adverse events (eg, 13 [7·5%] of 174 participants in the opioid group reported constipation vs six [3·5%] of 173 in the placebo group).

INTERPRETATION: Opioids should not be recommended for acute non-specific low back pain or neck pain given that we found no significant difference in pain severity compared with placebo. This finding calls for a change in the frequent use of opioids for these conditions.

FUNDING: National Health and Medical Research Council, University of Sydney Faculty of Medicine and Health, and SafeWork SA.

original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

related content