Methadone dosage for prevention of opioid withdrawal in children

Background: Opioids are frequently used for sedation in the Paediatric Intensive Care Unit (PICU). With time the dosing often increases because of tolerance. On cessation of the sedation there is a risk of the opioid withdrawal syndrome. The aim of our study was to evaluate methadone dosing as a risk factor for opioid withdrawal and to determine optimal dose and efficacy of methadone to prevent withdrawal. Method: We undertook a clinical, retrospective, chart review study. Data were analysed from the quality improvement initiative database of a tertiary-care 18 bed PICU. Results: Data from 30 children who received an opioid infusion for greater than or equal to7 days and subsequently received methadone for opioid withdrawal (between January 2000 and July 2001) were analysed. Nurses documented the presence or absence of withdrawal signs daily. Our unit protocol has recommended converting the patient's opioid dose into fentanyl equivalents and a dose of methadone equal to the total daily dose of fentanyl to be given three times a day. Twenty patients had no or minimal withdrawal symptoms and 10 experienced significant withdrawal. Age, weight, PRISM score, lorazepam dose, muscle relaxant use and fentanyl dose were not statistically significantly between these groups. Receiver Operator Characteristics analysis showed that 80% of the suggested methadone dose was effective in minimizing withdrawal symptoms. The odds ratio for withdrawal with <80% of the predicted methadone dose was 21. Conclusions: Inadequate methadone is a risk factor for opioid withdrawal. A daily starting methadone dose equivalent to 2.5 times the daily fentanyl dose is effective in minimizing withdrawal symptoms.