Yesterday, Dr. Busse from the Michael G. DeGroote Institute for Pain Research and Care at McMaster University published in JAMA a Systematic review and Meta-analysis on Opioids for Chronic Pain. He was the lead author of the 2017 Canadian Guideline for Opioids for Chronic Non-Cancer Pain.

The authors reviewed 96 clinical trials with 26,169 patients with chronic non-cancer pain.  It had some interesting information on the efficacy of opioids for chronic pain and function.

Bottom Line: Opioids may not offer better pain relief and function than many non-opioid analgesics. 

Opioids for Pain Relief

They converted all the of the pain studies to using the same 10 cm visual analog scale.  They said that the minimally important difference was a 1 cm reduction on this scale.  They report:

  • Opioids led to a weighted mean difference of only -0.79 cm versus placebo [95%CI, -0.90 to -0.68 cm], p<0.001
  • Only 13.6% of patients achieved the minimally important difference compared to placebo

The longer the study the worse opioids did for pain relief.  For trials that followed up patients for 3 months or longer:

  • Opioids led to a weighted mean difference of only -0.69 cm versus placebo [95%CI, -0.82 to -0.56 cm], p<0.001
  • Only 11.9% of patients achieved the minimally important difference compared to placebo

Think about that for a second, the mean difference in pain scale for people using opioids for chronic pain was < 1 cm on a 10 cm point scale.  

Opioids for Physical Functioning

High quality evidence found that opioids were associated with a small improvement in physical functioning compared with placebo, but did not meet the criterion for the minimally important difference.

The change on the 100 point SF-36 physical component  score was 2.04 points [95%CI, 1.41-2.68], p<0.01.  This was lower than the minimally important difference of 5 points.

Opioids and Other Domains

Emotional functioning – Opioids were not significantly associated with emotional functioning compared with placebo.

Social functioning – High-quality evidence from 29 RCTs (7623 patients) showed an association of opioids with improved social functioning compared with placebo but did not meet the minimally important difference.

Sleep Quality – opioids were associated with a small improvement in sleep quality but did not meet the minimally important difference.  If therapy is > 3 months, the improvement was even less.

Adverse effects – At least 20 RCTs reported each of the following adverse events: nausea, constipation, dizziness, drowsiness, headache, pruritus, and dry mouth. Except for headache, opioid use was associated with a higher incidence of these adverse events compared with placebo

Opioids Versus NSAIDs

Moderate-quality evidence showed no difference in the association of opioids vs nonsteroidal anti-inflammatory drugs for pain relief and physical functioning. 

NSAIDs offered similar pain relief and physical functioning improvement as opioids.

Opioids Versus Tricyclic Antidepressants

Low-quality evidence suggested no difference in pain relief between opioids and nortriptyline.  Low-quality evidence suggested no difference in physical functioning.

TCAs offered similar pain relief and physical functioning improvement as opioids.

Opioids Versus Anticonvulsants

Moderate-quality evidence suggested opioids were associated with greater pain relief than anticonvulsants. Low-quality evidence suggested no difference in physical functioning.

Opioids Versus Nabilone

Low-quality evidence suggested no difference between opioids and nabilone for pain relief and physical functioning. 

Cannabinoids offered similar pain relief and physical functioning improvement as opioids.

Author’s Conclusion

Opioid use was associated with statistically significant but small improvements in pain and physical functioning, and increased risk of vomiting compared with placebo. Comparisons of opioids with non-opioid alternatives suggested that the benefit for pain and functioning may be similar.

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