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.
- MeSH
- asfyxie novorozenců * komplikace farmakoterapie MeSH
- asfyxie komplikace farmakoterapie MeSH
- dospělí MeSH
- fenobarbital farmakokinetika terapeutické užití MeSH
- lidé MeSH
- mozková hypoxie a ischemie * terapie MeSH
- novorozenec MeSH
- terapeutická hypotermie * metody MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- novorozenec MeSH
- Publikační typ
- časopisecké články MeSH
WHAT IS KNOWN AND OBJECTIVE: Phenobarbital is the first-line treatment of seizures in asphyxiated neonates; however, due to the high pharmacokinetic variability in this population, there is no consensus on the optimal dosage regimen. This study was conducted to identify variables that affect phenobarbital fate during routine clinical care and then to evaluate the dosage schedule that could be applied in term asphyxiated neonates with respect to achieving the target therapeutic range. METHODS: Phenobarbital pharmacokinetics was calculated based on serum concentrations measurements using one-compartmental model. Body weight, body surface area, gestational age, creatinine clearance, total bilirubin, alanine aminotransferase, aspartate aminotransferase, international normalized ratio, Apgar scores, umbilical cord arterial pH and base excess were explored as covariates in linear regression models. Based on this analysis, phenobarbital loading and maintenance dose regimen were projected. RESULTS AND DISCUSSION: In the whole study population (N = 36), phenobarbital volume of distribution, clearance and half-life median (interquartile range) values were 0.49 (0.38-0.59) L/kg, 0.0045 (0.0034-0.0055) L/h/kg and 75.1 (60.2-103.3) hours, respectively. The drug volume of distribution was associated with body weight, length and body surface area, whereas clearance was not in relationship with any explored features. Weight-normalized loading dose of 15 mg/kg and weight-normalized daily maintenance dose of 3 mg/kg proved to be optimal in our study population to reach phenobarbital therapeutic range. WHAT IS NEW AND CONCLUSIONS: This study presents basis for phenobarbital initial dosing in term asphyxiated neonates during first week of life. Phenobarbital weight-normalized loading dose of 15 mg/kg lead to simulated target peak concentrations in 72% of neonates, weight-normalized maintenance dose of 3 mg/kg lead to steady state within therapeutic window in the same proportion of patients.
- MeSH
- asfyxie farmakoterapie metabolismus MeSH
- fenobarbital aplikace a dávkování farmakokinetika MeSH
- gestační stáří MeSH
- lidé MeSH
- mozková hypoxie a ischemie farmakoterapie metabolismus MeSH
- novorozenec MeSH
- poločas MeSH
- retrospektivní studie MeSH
- tkáňová distribuce MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- novorozenec MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- pozorovací studie MeSH
