This is a pilot study to determine the pharmacokinetics of (R,S) methadone in adolescents. A total of approximately 15 patients will be required. The purpose is to determine the levels of R, S methadone at various time intervals after drug administration. Patients will receive methadone 0.25 mg/kg IV at induction and a standardized anesthetic of remifentanil and propofol. At the conclusion of surgery (45 minutes prior to the completion), the patients will receive a loading dose of morphine based on respiratory rate. A morphine PCA will be utilized for postoperative analgesia. Pharmacokinetic data will be collected in addition to VAS scores, patient and parental satisfaction with analgesia, and a functional pain assessment.

Study Procedures Following Surgery:

• VAS scores will be recorded at intervals of 1,2,3,4,5,6,8,12,16,20,24, 36, 48 , 72 hrs (after extubation).
• Blood samples for PK will require 5ml per sample and may be obtained from an existing IV or direct phlebotomy and will be obtained at 0min, 5min, 10 min, 15min, 20 min, 40 min, 1hr, 2hrs, 3hrs, 4hrs, 5hrs, 6hrs, 8hrs, 10 hrs, 12hrs, 24hrs, 48 hrs, 72hrs, and 96hrs after study drug administration.

Inclusion Criteria:

• Pediatric scoliosis surgery secondary idiopathic scoliosis, congenital scoliosis,
• Age 12 - 19 inclusive
• ASA class I-II.

Exclusion Criteria:

• Preoperative opioid therapy in previous 2 weeks
• Known hepatic or renal impairment
• Inability to assess pain score due to neurological impairment, hearing impairment
• Allergy to methadone, morphine, fentanyl, propofol or remifentanil
• Pregnant or nursing
• Taking SSRI's, MAOI,anticonvulsants, gabapentin or lyrica
• ASA III or greater patients are excluded
• pre-existing chronic pain