Tolerability of Three Local Anesthetic Formulations in Conjunction With NGX-4010 for the Treatment of Neuropathic Pain

Key Eligibility Criteria: * Must have had for at least 3 months painful diabetic neuropathy, or postherpetic neuralgia, or painful HIV-associated neuropathy, with moderate to severe pain on average. * Must not have significant pain due to other causes (for example, arthritis). * Must have intact skin at the treatment area. * Must be prepared to remain on the same pain medications at the same doses as before the study for the entire duration of the study (12 weeks). * Must not use topical pain medications on painful areas. * Must be able to comply with study requirements such as completing daily pain diary and attending study visits and refrain from extensive travel during study participation. * Must be at least 18 years old, not pregnant, and able to take care of self independently, with only occasional assistance if needed. * No significant medical problems of the heart, kidneys, liver or lungs, or cancer. * No history or current problem with substance abuse.