Pre-operative Pregabalin and Ketamine to Prevent Phantom Pain

Patients undergoing unilateral lower extremity amputation (n=30) will be randomized in this double blind parallel placebo control clinical trial to evaluate the efficacy of pre-operative pregabalin (lyrica) and ketamine in eliminating phantom limb pain. Patient will receive either pregabalin and ketamine treatment (Group 1) or placebo (Group 2) during pre-operative period approximately 4 days (2-4 days). Patients will be identified during their anesthesia preoperative clinic or orthopedic inpatient unit (Parkland Hospital or UT Southwestern University Hospital) for the eligibility. Data base (EPIC) will also be used for prescreening of potential subject by reviewing clinic visit daily schedule or operating room schedule. Then patients chart will be reviewed for initial data collection to determine the eligibility of potential subjects with the use of a HIPAA waiver form. Eligible subject will be approached by the study PI, investigators, or research coordinator and written consent obtained prior to any study procedures. A pregnancy test will be performed before the preoperative treatment start for women in child-bearing age: exceptions include surgically sterile women or women with medically confirmed menopause. Women with a positive pregnancy test or who report unprotected heterosexual sex since their previous menses or not currently using and/or willing to use a medically approved form of contraception (e.g., birth control pill) will not enrolled to the study. Pain will be documented using the visual analog pain score (0=no pain, 10=worst imaginary pain) during preoperative period before the treatment and daily on pain diary and on the day of surgery and during postoperative period at PACU, 24 and 48 hrs. and long-term follow-up 1, 3, and 6 months after the surgery. Total opioid dose over the 48-h study period will be documented as PCA pump morphine consumption for postoperative first 24 hrs. and postoperative oral opioid usage for 48 hrs. after surgery. Patients will receive a standard general anesthetic for their surgery and postoperative standard of care pain treatment similar to all patients. Study does not limit standard post-operative pain medication. Long-term analgesic success will be evaluated at 1, 3, and 6 months after surgery. At follow-up period, a pain diary will be used for the patients' self-assessment on pain occurrence, intensity, duration for phantom and stump pain, and documentation of oral analgesic usage. Analgesic medication use and daily pain scores will be documented on pain diary for 1 month period following surgery. At first follow-up visit, patient will be seen in Pain Clinic 1 month after the surgery. Patient will be called from home 3 and 6 months after the surgery for long-term follow-up. At all-time points, the Self-Rating Depression Scale will be used to assess depression and the patients will complete the Pain-Related Self-Statement Scale (PRSS). The duration of the involvement in the study will be 6 months. Randomization: This is randomized double-blinded placebo controlled clinical trial. Investigational Drug Pharmacy (IDS) will randomize subjects either treatment group or placebo. IDS will dispense the drugs/placebo.