Most antidepressants used for chronic pain lack evidence: Study

Matt Woodley

10/05/2023 4:24:14 PM

The effectiveness and safety of many drugs commonly prescribed for chronic pain is not known, a Cochrane Review has found.

Holding medication
The authors of a new study looking at antidepressant use for chronic pain say their findings represent a global public health concern.

The largest ever investigation into antidepressant treatment for chronic pain suggests there is insufficient evidence to support their use.
The review of 176 trials consisting of nearly 30,000 patients looked into medications commonly prescribed for chronic pain, including amitriptyline, fluoxetine, citalopram, paroxetine, sertraline and duloxetine – with only the latter showing reliable evidence for pain relief.
Lead author Professor Tamar Pincus from the University of Southampton said the findings represent a global public health concern.
‘Chronic pain is a problem for millions who are prescribed antidepressants without sufficient scientific proof they help, nor an understanding of the long-term impact on health,’ she said.
‘Our review found no reliable evidence for the long-term efficacy of any antidepressant, and no reliable evidence for their safety for chronic pain at any point.
‘Though we did find that duloxetine provided short-term pain relief for patients we studied, we remain concerned about its possible long-term harm due to the gaps in current evidence.’
The Cochrane Review produced similar findings to University of Sydney research published earlier this year, which found no high certainty evidence on the efficacy of antidepressant use for pain for any condition.
Statistician Gavin Stewart, a co-author of the review, said the researchers are now calling on governing health bodies such as the UK’s National Institute for Health and Care Excellence (NICE) and the US Food and Drug Administration (FDA) to update their guidelines, as well as for funders to stop supporting ‘small and flawed trials’.
‘Evidence synthesis is often complex and nuanced,’ he said. ‘But the evidence underpinning the use of these treatments is not equivalent, so current treatment modalities are hard to justify.’
According to the review, duloxetine was consistently found to be the highest-rated medication, being equally as effective for fibromyalgia, musculoskeletal, and neuropathic pain conditions.
Other results showed:

  • standard doses of duloxetine are as successful for reducing pain as higher quantities
  • milnacipran was also effective at reducing pain, but scientists are not as confident as duloxetine due to fewer studies with fewer people.
‘We simply cannot tell about other antidepressants because sufficiently good studies are not available,’ Professor Pincus said.
‘But it does not mean that people should stop taking prescribed medication without consulting their GP.’
The team assessed the trials using a statistical method that enables researchers to combine data from relevant studies to estimate the effects of different drugs, which have not been compared directly in individual trials.
And although some previous investigations have shown that certain antidepressants ‘might relieve pain’ co-author Dr Hollie Birkinshaw said the new research is the first comprehensive study examining all medications across all chronic conditions.
‘The only reliable evidence is for duloxetine,’ she said.
‘Adopting a person-centred approach is critical to treatment and, when patients and clinicians decide together to try antidepressants, they should start from the drug for which there is good evidence.’
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