Population pharmacokinetics of phenytoin in critically ill children

Area of Science:

• Pharmacology
• Pediatric Critical Care Medicine
• Pharmacokinetics

Background:

• Phenytoin is an anticonvulsant commonly used in critically ill children.
• Understanding phenytoin pharmacokinetics, including protein binding, is crucial for effective therapeutic drug monitoring.
• Variability in protein binding can affect phenytoin efficacy and toxicity in pediatric patients.

Purpose of the Study:

• To characterize the population pharmacokinetics of bound and unbound phenytoin in critically ill children.
• To investigate factors influencing phenytoin's protein binding profile in this population.
• To develop a model for predicting unbound phenytoin concentrations.

Main Methods:

• Population pharmacokinetic analysis of paired unbound and total phenytoin plasma concentrations.
• Utilized a 1-compartment model with first-order absorption and a linear partition coefficient.
• Employed visual predictive checks and bootstrapping for model evaluation.

Main Results:

• A partition coefficient of 8.22 was estimated for phenytoin binding to albumin.
• Weight (allometrically scaled) and albumin concentration significantly influenced the protein binding partition coefficient.
• Nonlinear elimination of unbound phenytoin was not supported in this pediatric cohort.

Conclusions:

• A population pharmacokinetic model effectively describes unbound phenytoin pharmacokinetics in critically ill children.
• The model incorporates weight and albumin concentration to predict the fraction of unbound phenytoin.
• This model can aid in optimizing phenytoin dosing and improving therapeutic outcomes in pediatric intensive care settings.