Day 2 (first post-op day) Subjects will receive oral ketamine (1.0 mg/kg) 3 times/day. The first dose will be administered at 6 AM .If a subject experiences any adverse events after the first dose, but one that resolves within 8 hours after that dose, the second dose will be reduced by 33% (1.0 mg/mg to 0.67 mg/kg). If a subject experiences any adverse events after the second dose, but one that resolves within 8 hours, the dose will be reduced again by 33% (0.67 mg/kg to 0.45 mg/kg). If this dose reduction protocol does not eliminate adverse events, then oral ketamine will be discontinued. In addition, subsequent subjects will receive a 33% reduction in the Day 2 oral ketamine doses