NCT01094522.

Methods	Unclear
Participants	Neonates, infants and children after cardiac surgery
Interventions	Fentanyl will be administered for intraoperative analgesia by the treating anesthesiologist in a dose range of 25‐50 mcg/kg. No other intraoperative opioids will be given. Subjects will receive intravenous methadone or morphine ("study drug") delivered by an initial IV "bolus" injection followed by a nurse‐administered patient controlled analgesia (PCA) device for postoperative pain for a period of 24 hours. The initial dose of study drug will be 0.2 mg/kg IV administered following admission to the ICU after surgery. The study drug will then be given at a dose of 0.035 mg/kg IV as needed q30 min via PCA. The study drug may be increased or decreased in increments of 20‐25% according to the discretion of the investigator as needed to maintain a FLACC pain assessment tool < 4. Subjects will also receive lorazepam 0.025 mg/kg IV q2 hr as needed for agitation as indicated by specific criteria. The study drug will be discontinued after 24 hours to facilitate "washout" sampling and determination of elimination half‐life. Beginning at 24 hours, fentanyl will be used for analgesia at an equianalgesic dose to be determined by the investigator based upon the current PCA "study drug" dose.
Outcomes	Primary endpoints: Pharmacokinetics of methadone and morphine, including its metabolites (morphine‐3‐glucuronide and morphine‐6‐glucuronide). Secondary endpoints: Pain scores (FLACC) during the 24 hours study period; amount of study drug administered during the 24‐hour dosing period; changes in heart rate, systemic arterial blood pressure and laboratory test values
Notes

FLACC: Face, Legs, Activity, Cry, Consolability
ICU: intensive care unit|
IV: intravenously
NICU: neonate intensive care unit
NIPS: Neonatal Infant Pain Scale
PCA: patient controlled analgesia