RUMPOH-1: Descriptive study of conversion ratios between conventional opioids and methadone in pediatric pain, a...

To present the conversion ratios used for transitioning from conventional short-acting opioid (CSO) to methadone in a diverse pediatric population at methadone initiation and steady state. Oral-to-intravenous methadone conversion ratios were measured as an exploratory objective.

This study is a retrospective descriptive review that spans a 13-year period from January 1, 2010, to March 31, 2023.

The study was conducted in a quaternary pediatric university healthcare center and included patients from general and specialized pediatric wards.

All patients who were initially treated with CSO and subsequently switched to methadone for pain, 3 months to 18 years old, were included. Neonates, patients treated with methadone for less than 48 hours, and patients treated with methadone for opioid use disorder were excluded.

Switch from CSO to methadone for treatment of pain.

Conversion ratios from CSO to methadone were calculated at initiation, on day 3, and on day 5 after the conversion.

Sixty-five patients, aged 10.6 years, were identified, the majority of whom were treated for neuropathic or mixed-type pain. Treatment duration was 184 days on average (median 79 days). Methadone doses ranged from 0.1 to 300 mg/day (0.01-10.72 mg/kg/day). Initial conversion ratios from oral morphine equivalent doses to methadone ranged from 0.64 to 162:1.

Similar to the adult studies, we describe dose-dependent conversion ratios. Progressive titration of methadone was observed with high CSO doses, while low initial CSO doses had stable conversion ratios from the beginning. We have also highlighted the importance of a full 5-day switching period for patients with high CSO doses.