"Gabapentin (Neurontin) is now widely used for neuropathic pain. Controlled clinical trials in diabetic neuropathy and postherpetic neuralgia show that gabapentin at 2400-3600 mg/day has an efficacy similar to the tricyclic antidepressants. Consistent, though less compelling clinical evidence supports its use for a variety of other neuropathic pain syndromes, including cancer pain syndromes, pain associated with HIV infection, chronic back pain and others. The exact mechanism and site of action of gabapentin is unknown. Its use for neuropathic pain has become widespread because it is generally well-tolerated, easily titrated, has few drug interactions, and does not require laboratory monitoring. However, cost may be a limiting factor for some patients.
Patients suitable for Neurontin should ideally have a clear neuropathic pain syndrome, characterized by sharp, shooting, lancinating and/or burning pain, in a nerve root (radicular) or stocking/glove distribution."
This as a good reference for Gabapentin and Neuropathic Pain.