The purpose of this study was to determine the analgesic effect of GW493838 in patients with post-herpetic neuralgia or peripheral nerve injury caused by trauma or surgery.

Inclusion criteria (subjects must meet all of the following criteria in order to be eligible for this study):

• Females of non-child-bearing potential
• diagnosis of peripheral neuropathic pain as a result of: postherpetic neuralgia (PHN) from shingles for at least 3 months duration OR focal neuropathic pain related to nerve injury caused by trauma or surgery
• defined area of pain

Exclusion criteria

• discontinue agents for the treatment of neuropathic pain
• unable to refrain from alcohol and sedative use during the study
• confounding chronic pain which could not be differentiated from the peripheral neuropathic pain under study
• intractable pain of unknown origin or active infection in the area of nerve injury.
• clinically significant medical history or abnormality found on physical examination, laboratory assessment or ECG at Screening or Baseline
• severe asthma that has required oral corticosteroid use in the last 12 months or the subject had severe asthma that required, at anytime, hospitalization or mechanical ventilation support.
• clinical evidence of major depression (by medical history) except those subjects controlled by SSRIs.
• a known allergy or hypersensitivity to any of the investigational products (including rescue analgesia- acetaminophen), or pharmacological class of the investigational product (i.e. adenosine) and/or investigational product excipients.
• a clinically significant abuse of substances, defined as: Patterns of substance intake consistent with disruption of normal function in society; Past or current impairment of organ function reasonably related to substance intake; Any indication of difficulty in abstaining from substances for the duration of the study.
• had previously participated in a clinical study during the past 30 days in which the subject was exposed to an investigational or non-investigational drug or device
• currently participating in another clinical study in which the subject was exposed to an investigational or non-investigational drug or device
• prior blood reduction (450 mL or more) during the previous 30 days
• at risk of non-compliance
• a woman of childbearing potential or a woman who was lactating.