Inclusion Criteria:
- At least 18 years of age.
- Be in good health.
- Diagnosis of postherpetic neuralgia (PHN) made by the primary treating physician or Investigator, and at least 3 months post-vesicle crusting.
- Screening Pain Sum Score of 12 to 36.
- Intact, unbroken skin over the painful area(s) to be treated.
- If taking chronic pain medications, be on a stable (not PRN) regimen for at least 21 days prior to Treatment Visit (Day 0) and willing to maintain medications at same stable dose(s) and schedule throughout the study.
- Female subjects with child-bearing potential must have a negative serum beta hCG pregnancy test, to be performed at the Screening Visit.
- All subjects must be willing to use effective methods of birth control and/or refrain from participating in a conception process during the study and for 30 days following experimental drug exposure.
- Be willing and able to comply with protocol requirements for the duration of study participation. (Such requirements include, but are not limited to: completing a daily pain diary, attending all study visits, and refraining from elective surgery and extensive travel during study participation.)
Exclusion Criteria:
- Concomitant opioid medication, unless orally or transdermally administered and not exceeding a total daily dose of morphine 60 mg/day, or equivalent. Parenteral opioid use is excluded, regardless of dose.
- Unavailability of an effective rescue medication strategy for the subject, such as unwillingness to use opioid analgesics during treatment, or high tolerance to opioids precluding the ability to relieve treatment-associated discomfort with Roxicodone®, as judged by the Investigator.
- Active substance abuse or history of chronic substance abuse within the past year, or prior chronic substance abuse judged likely to recur during the study period by the investigator.
- Recent use (within 21 days preceding the Treatment Visit [Day 0]) of any topically applied pain medication, such as non-steroidal anti-inflammatory drugs, menthol, methyl salicylate, local anesthetics (including Lidoderm®), steroids or capsaicin products on the painful areas.
- Current use of any investigational agent, or Class 1 anti-arrhythmic drugs (such as tocainide and mexiletine).
- Significant pain of an etiology other than PHN, for example, compression-related neuropathies (e.g., spinal stenosis) or fibromyalgia or arthritis. Subjects must not have significant ongoing pain from other cause(s) that may interfere with judging PHN-related pain.
- Painful PHN areas located only on the face, above the hairline of the scalp, and/or in proximity to mucous membranes. (Investigational treatment with NGX-4010 is not allowed in these areas.)
- Any implanted medical device (spinal cord stimulator, intrathecal pump or peripheral nerve stimulator) for the treatment of neuropathic pain.
- Hypersensitivity to capsaicin (i.e., chili peppers or Over-the-Counter (OTC) capsaicin products), local anesthetics, Roxicodone® or adhesives.
- Significant ongoing or untreated abnormalities in cardiac, renal, hepatic, or pulmonary function that may interfere either with the ability to complete the study or the evaluation of adverse events.
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