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 lessof low back or neck pain (or both) of at least moderate pain severity. Participants were randomly assigned (1:1) usingstatistician-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 to6 weeks. The primary outcome was pain severity at 6 weeks measured with the pain severity subscale of the Brief PainInventory (10-point scale), analysed in all eligible participants who provided at least one post-randomisation painscore, by use of a repeated measures linear mixed model. Safety was analysed in all randomly assigned eligibleparticipants. The trial was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12615000775516).

The OPAL study was a triple-blinded, placebo-controlled randomized trial that involved adults aged 18 years and above. These participants were suffering from low back or neck pain (or both) of at least moderate severity for 12 weeks or less. They were recruited from 157 primary care or emergency department sites in Sydney, NSW, Australia.

The participants were randomly assigned in a 1:1 ratio to two groups. The assignment was done using randomly permuted blocks generated by a statistician. One group received guideline-recommended care plus an opioid (oxycodone–naloxone, up to 20 mg oxycodone per day orally), while the other group received guideline-recommended care and an identical placebo. This treatment was given for up to 6 weeks.

The primary outcome of the study was the pain severity at 6 weeks. This was measured using the pain severity subscale of the Brief Pain Inventory (10-point scale). The analysis was done on all eligible participants who provided at least one post-randomisation pain score. This was done using 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).