The findings from preclinical animal models confirm the peripheral anti-inflammatory/analgesic activity of GW406381 and also suggest contribution of a central site of action to the anti-hyperalgesic efficacy that may not be shared by other COX-2 inhibitors. A central action is consistent with distribution of GW406381 into the CNS in animals. Furthermore, preliminary data from a positron emission tomography study in which 6 healthy male volunteers received a tracer dose of 11C labelled GW406381 indicate that GW406381 is rapidly absorbed into the central nervous system in man.

Inclusion criteria:

• Baseline average daily Pain Score of greater than or equal to 4 (averaged over the 7 days prior to Treatment Visit 1), as reported on the 11 point pain intensity numerical rating scale.
• Subjects on medications for neuropathic pain or received nerve blocks for neuropathic pain.

Exclusion criteria:

• Known history of hypersensitivity or intolerance to acetaminophen, paracetamol, aspirin, COX-2 inhibitors or NSAIDs.
• Subject is unable to discontinue NSAIDs or COX-2 inhibitors (except aspirin as a cardioprotective; certain doses apply), topical lidocaine and topical capsaicin for the treatment of pain for the period prior to randomization and for the duration of the study.
• Subject is unable to refrain from sedative use during the study (benzodiazepines prescribed as hypnotic sleep agents allowed).
• Subject is unable to refrain from nerve blocks for 4 weeks prior to randomisation and during the study.