Methadone is an opioid with the potential to provide prolonged and constant analgesia. It has a half-life that is significantly longer than other clinically-used opioids (25-52 hours). This unique property of methadone suggests that a single dose administered in the operating room can result in extended pain relief following surgery. When given intravenously to surgical patients, a half-life of 35 hours was observed, resulting in a median duration of analgesia of 26 hours. In patients undergoing abdominal, orthopedic, or gynecologic surgery, the use of a single dose of methadone (20 mg or 0.2-0.3 mg/kg) at induction of anesthesia resulted in reduced analgesic requirements and improved pain scores for the first 24-48 postoperative hours (when compared to patients given traditional intraoperative opioids). Only one retrospective study has examined the use of intraoperative methadone in adult patients undergoing spinal instrumentation. In this investigation, methadone use was associated with a 50% reduction in postoperative opioid requirements, compared to patients receiving shorter-acting opioids. Despite the use of methadone and postoperative PCA opioids, however, average pain scores were greater than 3 (on a 0 to 10 scale) in the methadone group. These findings suggest that methadone alone is insufficient in alleviating pain after major spine surgery.