Specialist chronic pain solicitor, Andrew Atkinson, considers a new study that casts considerable doubt on the efficacy of most antidepressants in treating chronic pain.
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Some medications commonly prescribed for chronic pain were originally developed to treat other conditions. Examples of such “off-label prescribing” for chronic pain include anticonvulsants such as Gabapentin and Pregabalin, used in treating seizures, and antidepressants.
Indeed, antidepressants are a mainstay in managing many chronic pain conditions, even where depression is not a recognised factor. The most common type of antidepressants prescribed for chronic pain are tricyclic antidepressants such as:
Initially developed in the 1950s, tricyclic antidepressants increase the level of two body chemicals, serotonin and norepinephrine. These chemicals are found in the brain and spinal cord and help regulate mood. However, it’s also believed that both are involved in pain pathways, transmitting pain signals from the brain to other parts of the body.
But many people prescribed tricyclic antidepressants report various side effects, which can be severe. For that reason, it’s becoming more common to prescribe one of two newer types of antidepressants with fewer reported side effects:
- serotonin and norepinephrine reuptake inhibitors (SNRIs) such as Venlafaxine and Duloxetine; and
- selective serotonin reuptake inhibitors (SSRIs) such as Fluoxetine and Paroxetine.
Are antidepressants helpful for chronic pain?
Over the years, there have been many studies examining the effectiveness of antidepressants in the management of chronic pain. And periodically, systemic reviews of those studies appear. A systemic review is one that extracts and analyses data from other studies, rather than engaging in primary research.
Now, an international group of researchers has gone one step further, producing an overview of past systemic reviews. Their stated aim in doing so was “To provide a comprehensive overview of the efficacy, safety, and tolerability of antidepressants for pain according to condition.” Their conclusions appear in the British Medical Journal.
An advantage of a systemic review is the ability to analyse and include data gathered from large numbers of participants. And of course, a review of systemic reviews means even more data to analyse. In this recent review, researchers accessed data from 26 reviews covering 156 unique trials involving over 25,000 participants.
In summary, the results were:
- Evidence for the effectiveness of antidepressants in treating chronic pain was found in only 26% of cases.
- There was “moderate certainty” that SNRIs were efficacious for fibromyalgia, chronic back pain, postoperative pain, and neuropathic pain.
- The SNRIs Duloxetine and Venlafaxine had a higher efficacy for treating pain.
- Although SSRIs are helpful with comorbid depression in cases of chronic pain, they are not otherwise beneficial for pain.
- There was little evidence for the efficacy of tricyclic antidepressants. Despite comprising around 75% of antidepressants prescribed for chronic pain, the review found evidence for their efficacy in only 3 out of 14 pain conditions.
- While SNRIs were helpful in cases of fibromyalgia, there was no evidence of benefit from SSRIs for the same condition, compared to placebo. In addition, SSRIs were ineffective for back pain, functional dyspepsia, and non-cardiac chest pain.
In many respects, these results are startling, particularly given the number of people suffering chronic pain whose medication regime includes tricyclic antidepressants.
Although published only in the last few days, expert reaction was swift. A major criticism of the study raised by several commentators concerns the fact that almost half of the trials reviewed were sponsored or connected in some way to industry, raising questions of bias.
We can but hope that the inevitable (and likely heated) debate triggered by this review ultimately results in more effective prescribing for chronic pain.