Valproic Acid for the Prevention of Post-Amputation Pain

Inclusion Criteria: * Male and female active duty military personnel or veterans, age 18 years and older. * Patient is scheduled to undergo amputation, stump revision, or surgery for a limb injury with neurologic damage. * Patient able to provide written informed consent prior to any study procedures. Exclusion Criteria: * Severe Traumatic Brain Injury (Diagnosis of traumatic brain injury resulting in documented, permanent or prolonged cognitive deficits that would preclude participation in the study) * Significant cognitive deficits or dementia of any cause as noted in Computerized Patient Record System(CPRS). * Patient has a designated Legally Authorized Representative * Substantial hearing loss without alternative means of communication. * Patient has documented spinal cord injury with permanent or persistent deficits * Patient is under age 18 or a legal Minor * Current pregnancy or lactation * Cirrhosis with evidence of decompensation: coagulopathy International Normalized Ratio (INR) \>1.3, thrombocytopenia with platelets \<100,000, ascites or hepatic encephalopathy * Therapy with valproic acid or other valproates, coumadin, chlorpromazine and olanzapine at the time of surgery and study drug administration * Current diagnosis of seizure disorder requiring anti-epileptic medication * Current therapy with tricyclic antidepressants (eg: amitriptyline, nortriptyline, imipramine, desipramine) at doses greater than 50mg/day * Currently taking zidovudine * Current diagnosis of malaria requiring anti-malaria medication (such as mefloquine and chloroquine) * Currently taking monoamine oxide inhibitors (MAOI) * Allergy to valproates or valproic acid * Contraindication to, or refusal of, regional anesthesia catheter * BMI \> 50