Inclusion Criteria:

• male or female outpatient greater than or equal to 18 years of age.
• suffering presently from neuralgia, which has been present for at least 3 months since healing of acute herpes zoster skin rash.
• PHN pain at entry into the study must meet the following criteria: a VAS of at least 40 mm at visit 2 (to assess pain intensity during the past week) and with an average daily score of at least 4 on the PIS during the baseline period as evaluated on a minimum of 4 days.
• an estimated creatinine clearance of at least 50 ml/min.

Exclusion Criteria:

• receiving professional psychological support (such as cognitive behavioral therapy) currently or within 2 weeks prior to visit 1 specifically for coping with PHN.
• previous neurolytic or neurosurgical therapy for PHN, at any time in the subject's history or treatment with TENS (transelectroneuro stimulation) currently or within the past 2 weeks.
• known co-existent source of pain or painful peripheral neuropathy.
• known significant neurological disorder other than the study disease or a condition which can mimic stroke with distal neurological deficit (amyotrophy, radiculopathy, history of TIAs, multiple sclerosis, or any amputations).
• conditions known to be associated with immunosuppressive states.
• clinically significant major depression defined as a Beck Depression Inventory Score > 21 at selection including those with a history of Bipolar Disorder.