The purpose of the study is determine if an investigational drug, NGX-4010 (high-concentration capsaicin dermal patches) is effective in treating pain associated with post-herpetic neuralgia (PHN).

Participants will be randomly assigned to receive initial treatment according to one of three doses (application durations), and will receive either NGX-4010 patch (high-concentration capsaicin) or matching control (low-concentration capsaicin).

Participants who complete the study evaluations for 12 weeks will have the option of receiving up to 3 additional open-label re-treatments over 1 year.

Key Eligibility Criteria:

• Must be diagnosed with PHN and be at least 6 months after crusting of the skin vesicles, with moderate to severe pain.
• Must not have significant pain due to causes other than PHN (for example, arthritis).
• Painful areas should not be located on the face, above the hairline of the scalp, and/or in proximity to mucous membranes.
• Must have intact and unbroken 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 (1-year).
• Must not have any implanted medical device (spinal cord stimulator, intrathecal pump or peripheral nerve stimulator) for the treatment of pain.
• Must not use topical pain medications for PHN.
• Must be able to comply with study requirements such as completing a daily pain diary, attending study visits and refraining from extensive travel during study participation.
• No significant medical problems of the heart, kidneys, liver or lungs, or cancer.
• No history or current problem with substance abuse.