A common treatment for osteoporosis may offer pain relief for complex regional pain syndrome (CRPS) — a rare, debilitating chronic pain disorder.

CRPS usually develops in a limb after injury or surgery and has extremely limited effective treatment options. Bisphosphonates are medicines commonly used to treat osteoporosis, but have also been proposed as a first-line treatment for CRPS. 

Researchers from NeuRA (Neuroscience Research Australia), UNSW Sydney, Brunel University London, University of Liverpool, and colleagues undertook a systematic review and meta-analysis of bisphosphonates analysing 11 randomised controlled trials involving 754 adults with CRPS. 

NeuRA postdoctoral researcher, Dr Michael Ferraro, said this was the largest analysis ever undertaken of a treatment from CRPS, bringing together all available randomised trials.

“We undertook this review because bisphosphonates have been considered the most promising treatment for CRPS more than a decade,” he said.

“While the review found that bisphosphonates may reduce pain intensity in the short-term – that is up to 3 months after treatment — the effects in the immediate‑, and longer-term were unclear, and treatment is accompanied by side effects such as joint and muscle pain.”

The researchers noted variability in results across studies that couldn’t be fully explained, with some studies showing benefits and others no benefit at all.

“One theory is that the benefits of bisphosphonates are limited to a particular patient group – those with very early CRPS symptoms and disrupted bone metabolism,” Dr Ferraro said. 

“Clinicians should weigh the potential benefits of short-term pain relief for CRPS patients against adverse effects and the lack of long-term efficacy data.

“More research is needed to identify who is most likely to benefit and to determine optimal dosing and treatment duration.” 

The study was published in Annals of Internal Medicine and is available here.