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).