Some antidepressant and antiepileptic drugs are used in chronic pain management and act primarily within the pain pathways of the central nervous system, though peripheral mechanisms have been attributed as well. They are generally used to treat nerve brain that results form injury to the nervous system. Neuropathy can be due to chronic high glood sugar levels (diabetic neuropathy); and viruses, such as shingles; phantom limb pain; or post-stroke pain. These mechanisms vary and in general are more effective in neuropathic pain disorders as well as complex regional pain syndrome. A common anti-epileptic drug is gabapentin, and an example of an antidepressant would be amitriptyline.