Perioperative Rectal Methadone in Spine Surgery

Patients undergoing spinal surgery require pain control medication after their surgery. Investigators have successfully used intravenous Methadone to manage pain after surgery. However, doctors in Canada do not have the intravenous form of Methadone to prescribe to their patients. The investigators in Canada propose a pilot trial to investigate whether Methadone administered rectally could be used to manage pain after spinal surgery. The main questions are: 1. Are investigators able to recruit participants for this trial and learn from this study to plan a larger trial? 2. Does Methadone administered rectally during surgery, reduce participants' pain intensity, use less pain medication, and have a better recovery after surgery? Investigators will compare Methadone to a placebo (a look-alike substance that contains no drug) to see if Methadone works to manage pain after surgery better than the usual pain management. Participants will: * receive either Methadone or placebo during surgery. * be asked some questions about their pain during days 1 to 3 after surgery * be contacted by phone to ask about their recovery At this time, the study aims to recruit 40 participants from St. Michael's Hospital, to learn whether it will be feasible to plan a larger study.