Many studies have demonstrated the contribution of the central nervous system (CNS) to the development of neuropathic pain syndromes, including Complex Regional Pain Syndrome (CRPS). More specifically, modelling has demonstrated the involvement of the not-so-catchily-titled N-methyl-D-aspartate-receptors in the CNS. In turn, this has led researchers to investigate the effect of a suitable drug (antagonist) that can dampen down or block the reaction of these receptors.
One such antagonist is Memantine, a drug more usually associated with the treatment of moderate to severe confusion related to Alzheimer’s disease. Memantine is not a cure, but it may improve a person’s memory and awareness, increasing their ability to function.
As long ago as 2007, a small-scale study examined the effect of treating six people diagnosed with CRPS in one upper limb with Memantine for eight weeks.
This study showed that six months after their treatment with Memantine, all participants demonstrated a significant decrease in their pain levels, coinciding with an improvement in motor symptoms and autonomic changes. Further, brain imaging studies of the same patients provided evidence of changes in an area of the brain called the somatosensory cortex. The affected side of the brain returned to a pattern comparable with the unaffected side following the treatment.
Australian Memantine study
Now, researchers in Australia are recruiting participants for a placebo-controlled trial of Memantine in conjunction with Graded Motor Imagery (GRI) for CRPS. The trial, which has been named MEMOIR, is described as follows:
“MEMOIR is an Australian government-funded clinical trial for people living with Complex Regional Pain Syndrome (CRPS). MEMOIR is testing two new interventions for people with CRPS – a medicine and newly developed rehabilitation program.”
This trial has the potential to become the most extensive study yet involving Memantine treatment for CRPS, although results are not expected before 2023.