A Study to Determine if an Investigational Pain Medicine Provides Relief of Chronic Pain After a Shingles Outbreak

Inclusion Criteria: * Has a clinical diagnosis of Postherpetic Neuralgia (PHN) * Experiencing pain for at least 3 months after the healing of shingles rash * Has at least a weekly average pain intensity of equal to or greater than 4 out of 10 * Females must not be pregnant or breastfeeding and practicing an acceptable method of birth control, or be surgically sterile or post-menopausal * Will not consume grapefruit or grapefruit juice during the study Exclusion Criteria: * Has a current acute or unstable chronic disease other than Postherpetic Neuralgia (PHN) * Has clinically important medical disorder * Uses certain types of medications for heart conditions * Unwilling/unable to discontinue use of medications for treatment of neuropathic pain * Has a history of hypersensitivity to any medication or soy product * Has liver or kidney disease * Has asthma that required treatment within the last year * Has HIV or hepatitis (other than hepatitis A) * Has a history of alcohol abuse within the past 2 years * Has a history of (within last 2 years) or currently abuses prescription or illegal drugs