Methadone conversion in infants and children: Retrospective cohort study of 199 pediatric inpatients.

OBJECTIVE: Methadone administration has increased in pediatric clinical settings. This review is an attempt to ascertain an equianalgesic dose ratio for methadone in the pediatric population using standard adult dose conversion guidelines.

SETTING: US tertiary children's hospital.

PATIENTS: Hospitalized pediatric patients, 0-18 years of age.

MAIN OUTCOME MEASURES: A retrospective chart review was conducted for patients who were converted from their initial opioid therapy regimen (morphine, hydromorphone, and/or fentanyl) to methadone. The primary endpoint was whether or not a dose correction was needed for methadone in the 6 days following conversion using standard dose conversion charts for adults. Documented clinical signs of withdrawal, unrelieved pain, or oversedation were examined.

RESULTS: The majority (53.7 percent) of the 199 children were converted to methadone on intensive care units prior extubation or postextubation. The mean conversion ratio was 23.7 mg of oral morphine to 1 mg of oral methadone (median, 18.8 mg:1 mg, SD=25.7). Most patients experienced an adequate conversion (n=115, 57.8 percent), while 83 (41.7 percent) appeared undermedicated, and one child was oversedated. There were no associations found with conversion ratios for initial morphine dose, days to conversion, or effect of withdrawal of concomitant agents with potential for withdrawal.

CONCLUSIONS: Opioid conversion to methadone is commonly practiced at our institution; however, dosing was significantly lower compared to adult conversion ratios, and more than 40 percent of children were undermedicated. The majority of children in this study received opioids for sedation while intubated and ventilated; therefore, safe and efficacious pediatric methadone conversion rates remain unclear. Prospective studies are needed.