Neuropathic pain is an indication that affects 116 million people in the US alone, costing the economy $635bn a year. However, treatments for this indication are lacking, and only 30% of patients will see 30% efficacy from the drugs prescribed. This is mainly due the heterogeneity of symptoms experienced by patients and the lack of disease-modifying agents on the market.
Most of the drugs on the market target four areas of nerve injury, with the aim of either decreasing sensitization to decreasing pain perception. The classes of drugs on the market include: opioids, antidepressants, anticonvulsants and gabapentinoids.
One of the classes not commonly seen in treatment guidelines are sodium channel blockers. Indeed, only one drug from this class is published in the treatment guidelines, and that is mainly due to its safety profile rather than its efficacy. The others from this class are classified as ‘weakly recommended’, mainly due to clinical trials involving sodium channel blockers failing to meet their primary endpoints, but still displaying enough promise in secondary outcomes to show they can be effective in a subsection of patients.
At the 6th International Congress on Neuropathic Pain (NeuPSIG) in Gothenberg, Sweden, Dr Simon Haroutounian delivered a lecture on the important role sodium channel blockers will play in the future of neuropathic pain treatments. He highlighted studies that showed an injection of a sodium channel blocker proximal to the injury site or to the dorsal root ganglion (DRG) can cause a complete elimination of pain. He went on to propose the class as a potential treatment for patients with a specific sensory profile. However, a phenotype-based approach will require more data to be collected.
There are still problems that need to be addressed, including the fact that the need for re-injections every six to eight hours is not sustainable in patients that suffer from chronic pain and that the lack of specificity of sodium channel blockers needs to be investigated further. However, the benefits offered by this class seem to indicate that there is a high chance that perseverance will produce positive results.