Chronic pain is a debilitating disorder that affects millions of people world-wide and has a considerable detrimental impact on quality of life. There are multiple events which can lead to chronic pain including trauma, diabetes, surgical procedures, cancer and HIV. Effective analgesic therapies are inadequate in the majority of chronic pain patients and are often associated with unpleasant side-effects. Consequently at present there is a substantial, unmet, clinical need for more effective analgesics for chronic pain patients.