Study highlights limited evidence for antidepressants in treating pain in older adults

University of Sydney research has found people over 65 are being prescribed antidepressants as pain treatment based on international guidelines that use limited evidence.

The study found that in the last 40 years there have been only 15 trials globally focusing on the benefit of antidepressants for pain in older people. This study fills a much-needed gap in research by bringing together the information from these trials to look at the efficacy and harms of antidepressants for acute and chronic non-cancer pain in those over 65-years old.

It finds a lack of evidence to inform the use of antidepressants for most pain conditions in older adults, and urges prescribing and treatment practices that consider the unique needs and risks of older adults.

Lead author Dr Sujita Narayan, a Research Fellow at the University's Institute for Musculoskeletal Health said international guidelines recommending antidepressants for chronic pain are heavily based on studies that either exclude older adults or include only a small number of them.

Health professionals use these as a reference point when treating older patients with conditions causing chronic pain, such as osteoarthritis.

"If I am a busy clinician and want to look at the guidelines for quick reference, I will probably have time to look at only the key points regarding management of chronic pain, some of which advise the use of antidepressants," said Dr Narayan, from the Faculty of Medicine and Health.

Senior author Associate Professor Christina Abdel Shaheed from the University's School of Public Health and the Institute for Musculoskeletal Health emphasized no trials examined the growing use of antidepressants for acute pain such as that experienced by those with shingles or muscular pain.

These medicines are being prescribed to remedy patients' pain, despite the lack of evidence to adequately inform their use. However, harms of antidepressant use in older people are well documented."

Associate Professor Abdel Shaheed

In relation to harm, the study found people taking antidepressants experienced more negative effects, like falling, feeling dizzy, and getting injured, judged against suitable comparison groups.

These adverse effects saw more people in the antidepressant group stop taking their medication than those in placebo groups or groups taking other drugs for pain management.

"Withdrawal from antidepressants can be as bad as withdrawal from opioids. I would recommend that anyone considering discontinuing their medication to not stop taking their antidepressants immediately, but to consult with their clinician and devise a tapering plan, as necessary," Dr Narayan.

The study found one exception. Researchers found the SNRI duloxetine was able to relieve knee osteoarthritis pain in older adults during the intermediate term, but not short-term or longer term.

"There was higher quality evidence on its efficacy for chronic pain related to knee osteoarthritis. This was based on using it for a period of roughly two to four months. It wasn't significant in the immediate term, if used for up to two weeks, and no data was available for use beyond a 12-month period.

"For clinicians and patients who might be using or considering duloxetine for knee osteoarthritis, the message is clear: benefits may be seen with a little persistence, but the effects may be small and need to be weighed up against the risk," said Dr Narayan.

Current evidence on antidepressant efficacy and safety in older people comes mostly from small trials. Disclosed industry-funded trials with fewer than 100 participants highlight the need to update guidelines and rethink the clinical practice of prescribing antidepressants for pain in older adults, the research found.

The study supports guidelines on the management of chronic non-cancer pain in older people recommending a multidimensional approach using non-pharmacological strategies, such as physical exercise and cognitive behavior therapy based on trials done specifically in older people.

"The key point is that we shouldn't rely on findings from studies with younger people and apply them to older adults because they are different, older people's bodies undergo changes that alter how they respond to medications. This can lead to different effects in older people compared to younger people," said Dr Narayan.