Efficacy, Tolerability, and Safety of NXN-462 in Patients With Post-Herpetic Neuralgia

Inclusion Criteria: * Male, or a non-pregnant, non-lactating female 18 years or older * Have voluntarily provided written informed consent * able to speak, read, write, and understand English * clinical diagnosis of PHN for a minimum of 6 months * pain intensity score of ≥3 on a 0-10 Numerical Rating Scale (NRS) at the Screening Visit * generally in good health (other than PHN) at Screening Exclusion Criteria: * Are pregnant and/or lactating * Diagnosis of any chronic pain syndrome that would interfere with the assessment of PHN * evidence of multiple causes of neuropathic pain,e.g.lumbar radiculopathy in the lumbosacral area * Have had neuroablation or neurosurgical intervention for PHN * Have been taking opioid analgesics for \>5 days/week * Have received nerve block or intrathecal analgesia within 6 weeks of the study * History of significant gastrointestinal disease, liver disease, renal disease, endocrine disease, or cardiovascular disease * clinically significant abnormal clinical laboratory test results or vital signs * Are immunocompromised or immunosuppressed for any reason * History of alcohol or other substance abuse (not including nicotine or tobacco) within 5 years * Significant psychiatric disorder which requires drug treatment (except depression or anxiety treated with Selective Serotonin Re-uptake Inhibitors) * Have received an investigational drug or have used an investigational device within 30 days of Screening. * Have previously been randomized to this study