The proposed research is an important extension of an ongoing perioperative personalized analgesia and intravenous opioid pharmacogenetic research. This research focuses on two of the most commonly used oral opioid analgesics, oxycodone, and methadone, in adults following lumbar spinal fusion and decompression surgery. Genetic signature and combinatorial pharmacogenetic approaches perform better than single-gene associations. This innovative translational research will for the first time evaluate simultaneously the effects of multiple genes and interactions on oxycodone and methadone's pharmacokinetics and optimal clinical dosing and on its safety and efficacy in the highly vulnerable pediatric population. This research's multigenetic signature findings can be easily extrapolated to adults undergoing surgery or using oxycodone and/or methadone for chronic and cancer pain and in identifying opioid abusers at risk of severe respiratory depression and death. When methadone is given in addition to oxycodone for inpatient pectus excavatum repair and idiopathic scoliosis spinal fusions according to new departmental protocols, methadone pharmacokinetics and pharmacodynamics will also be evaluated.