 Postoperative pain is severe after major spine surgery. Opioids such as morphine and hydromorphone are routinely used for postoperative pain control. These drugs have significant side effects, most importantly respiratory depression, nausea, constipation and tolerance. Moreover, many spine surgery patients have used opioid pain medication for back pain long term, leading to pre-surgical opioid tolerance and increased postoperative pain. This has led to a search for adjuvant medications to reduce the use of opioids and reduce opioid mediated side effects and tolerance. 