Neuropathic pain is a chronic, debilitating and widespread condition with an estimated prevalence of one per cent of the general population. Neuropathic pain arises as a consequence of damage to or dysfunction in the nervous system, either peripheral, central or both. It is usually accompanied by unpleasant burning or shooting sensations, or extreme sensitivity to touch.
Neuropathic pain may be triggered by a variety of diseases and conditions, but the mechanism that establishes and maintains neuropathic pain is specific to the characteristics of the damage and/or dysfunction of the nervous system, and is not necessarily related to the triggering disease. The list of conditions with which neuropathic pain can be associated include MS, stroke, cancer, spinal cord injury, physical trauma and peripheral neuropathy resulting from diabetes. It can also occur in patients who have previously suffered from shingles, a condition known as post-herpetic neuralgia.
Neuropathic pain is one of the most difficult types of chronic pain to treat, and relief is often unsatisfactory or short-term. Since treatment options are limited, doctors often prescribe a combination of therapies in an attempt to relieve symptoms. Existing therapies come from the drug classes of tricyclic and related antidepressants, antiepileptic agents and opioids. Currently in the UK, amitriptyline is prescribed most frequently for neuropathic pain, although it is unlicensed in this indication.
Sativex is approved in Canada for the treatment for central neuropathic pain due to MS. Sativex has also been used in a number of Phase II and III clinical trials in various models of peripheral neuropathic pain, from which a body of positive data has been generated.