ORIGINAL ARTICLE   

Minerva Pediatrics 2022 April;74(2):107-15

DOI: 10.23736/S2724-5276.20.05740-0

Copyright © 2020 EDIZIONI MINERVA MEDICA

lingua: Inglese

Severity parameters for asphyxia or hypoxic-ischemic encephalopathy do not explain inter-individual variability in the pharmacokinetics of phenobarbital in newborns treated with therapeutic hypothermia

Pavla POKORNÁ ^{1, 2, 3, 4}, Danica MICHALIČKOVÁ ² ✉, Swantje VÖLLER ⁴, Karolina HRONOVÁ ², Dick TIBBOEL ^{1, 3}, Ondřej SLANAŘ ², Elke H. KREKELS ⁴

¹ Department of Pediatrics and Inherited Metabolic Disorders, General University Hospital, 1st Faculty of Medicine, Charles University, Prague, Czech Republic; ² Institute of Pharmacology, General University Hospital, 1st Faculty of Medicine, Charles University, Prague, Czech Republic; ³ Intensive Care and Department of Pediatric Surgery, Erasmus MC - Sophia Children’s Hospital, Rotterdam, the Netherlands; ⁴ Department of Physiology and Pharmacology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden; ⁵ Division of Systems Biomedicine and Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, the Netherlands

BACKGROUND: The current study uses a population modeling approach to evaluate and quantify the impact of severity of asphyxia and hypoxic-ischemic encephalopathy (HIE) on the pharmacokinetics of phenobarbital in asphyxiated newborns treated with therapeutic hypothermia.
METHODS: Included newborns received phenobarbital (the TOBY trial protocol). 120 plasma samples were available from 50 newborns, median (IQR) weight 3.3 (2.8-3.5) kg and gestational age 39 (39-40) weeks. NONMEM^® version 7.2 was used for the data analysis. Age, body weight, sex, concomitant medications, kidney and liver function markers, as well as severity parameters of asphyxia and HIE were tested as potential covariates of pharmacokinetics of phenobarbital. Severe asphyxia was defined as pH of arterial umbilical cord blood ≤7.1 and Apgar 5 ≤5, and severe HIE was defined as time to normalization of amplitude-integrated electroencephalography (aEEG) >24 h.
RESULTS: Weight was found to be the only statistically significant covariate for the volume of distribution. At weight of 1 kg volume of distribution was 0.91 L and for every additional kg it increased in 0.91 L. Clearance was 0.00563 L/h. No covariates were statistically significant for the clearance of phenobarbital.
CONCLUSIONS: Phenobarbital dose adjustments are not indicated in the studied population, irrespective of the severity of asphyxia or HIE.

KEY WORDS: Newborn infant; Induced hypothermia; Asphyxia neonatorum; Phenobarbital