A Multi-Centre, Randomized, Double-Blind, Placebo Controlled Pilot Trial to Assess the Efficacy, Safety, and Tolerability of SPM 927 in Subjects With Postherpetic Neuralgia (PHN).

Inclusion Criteria: * Subject has clinically diagnosed painful postherpetic neuralgia present at least six months after healing of a herpes zoster skin rash and has at least one form of allodynia * Subject must have at least moderate pain (mean pain intensity ≥ 4 out of 10 during the baseline week on Likert scale). Exclusion Criteria: * Subject has other conditions that cause pain at least as severe as the postherpetic neuralgia. * Subject has had any surgical treatment or any neurolytic injections for PHN * Subject has clinically significant ECG and laboratory abnormalities. * Subject is receiving treatment with anti-epileptic drugs (AEDs), muscle relaxants, mexiletine, topical analgesics, antidepressants, opioids, non-steroidal anti-inflammatory drugs (NSAIDs), paracetamol, benzodiazepines, and antiviral agents. * Subject has liver function tests (AST, ALT, alkaline phosphatase, total bilirubin and GGT out of the reference range) \> 1,5 x ULN (upper limit of normal) at visit 1 * Subject has serum creatinine ≥ 2 times the upper limit of reference range at Visit 1.