Poster Presentation Sydney Spinal Symposium 2025

Why did a short course of opioid analgesia cause worse pain in the long term in patients with acute neck/back pain (#35)

Zhiwei Yang 1 , Aidan Cashin 2 , Caitlin Jones 1 , Laurent Billot 3 , Sana Shan 3 , Richard Day 4 , Melanie Hamilton 1 , Bart Koes 5 , Latimer Jane 1 , Christopher Maher 1 , Andrew McLachlan 6 , Hanan McLachlan 1 , Melissa Webb 1 , Christine Lin 1
  1. Institute for Musculoskeletal Health, Camperdown, NSW, Australia
  2. NeuRA, Neuroscience Research Australia, Randwick, NSW, Australia
  3. The George Institute for Global Health, Sydney, NSW, Australia
  4. St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales, Australia
  5. Department of General Practice, Erasmus MC, Rotterdam, Netherlands
  6. Sydney Pharmacy School, The University of Sydney, Sydney, New South Wales, Australia

Introduction

The OPAL trial (n = 347) revealed that an opioid (oxycodone/naloxone) was not superior to placebo in reducing pain among an acute neck/back pain population. But at 1-year follow-up, the opioids group reported slightly worse pain compared to the placebo. Mediation analysis is a quantitative approach to investigate how an intervention causes an effect on an outcome. The analyses aim to explore the underlying mechanisms of why a short course of opioids led to worse pain in the long term.

 

Methods

Proposed mediators were short term pain severity, poorer mental health, poorer physical function, and the presence of opioid-related adverse events. We controlled for confounders (age, sex, BMI, pain duration, pain location, previous episodes, work status, income, baseline pain, function, and mental health). We used the R package CMAverse to fit two regression models - the mediator model and the outcome model - to estimate the intervention-mediator and mediator-outcome effects considering each mediator individually.

Results

A total of 346 participants provided their characteristic at baseline, 289 participants (84%) provided data on mediators at the end of the 6-week prescription period, and 256 participants (74%) had the data at 52 weeks. Mean age was 45 (16) years and 51% were female. Proposed mediators (mental health, pain severity, opioid related adverse events and physical function) at week 6 did not mediate the worse pain severity at 52 weeks.

Conclusion

It remains uncertain why a short course of opioids would cause worse pain in the long term.