Efficacy and Safety Study of SLC022 in Treating Pain Associated With Post Herpetic Neuralgia

Inclusion Criteria: 1. Male or female age 18 years or older. 2. A history of cutaneous herpes zoster infection and sustained pain associated with the site of the herpes zoster skin rash for \>6 months, after onset of the herpes zoster skin rash. 3. Well established consistent pain during baseline phase. 4. Completed a washout period of 7 days for existing pain medications. 5. Evidence of a personally signed and dated informed consent document indicating that the subject has been informed of all pertinent aspects of the study. 6. A willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures. Exclusion Criteria: 1. Pregnant or breast feeding. 2. Female subjects who are not surgically sterile (hysterectomy or bilateral tubal ligation), postmenopausal for at least one year, or are not willing to practice adequate methods of contraception if of childbearing potential. 3. Previous neurolytic or neurosurgical therapy for PHN. 4. Treatment with local anesthetic nerve blocks within the last 30 days. 5. Failure of an adequate dose of 3 or more first line drug treatments for PHN-related pain due to efficacy. 6. Any other type of pain which may impair the self assessment of the pain due to PHN. 7. Skin conditions in the affected dermatome that could alter sensation. 8. Participation in other studies within 30 days before the current study begins and/or during study participation. 9. Taking CYP1A2 inhibitors such as fluvoxamine, certain fluoroquinolones (e.g., ciprofloxacin, enoxacin, pefloxacin, etc), mexiletine, and zileuton. 10. History of drug or alcohol abuse during the last 5 years. 11. Creatinine clearance \<50 mL/min. 12. History of malignancy other than basal cell carcinoma and carcinoma in situ. 13. History of chronic hepatitis B or C, or human immunodeficiency virus (HIV) infection. 14. Clinically significant hepatic, respiratory, hematological, cardiovascular or neurological disease. 15. Immunocompromised state. 16. Other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the subject inappropriate for entry into this study.