A population PK model of levetiracetam for Korean neonates with seizures was developed in this study. The result of this study can be used as a basis to develop an optimal dosage regimen in Korean neonates with seizures.
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PurposeThe aims of this study were to evaluate the safety and pharmacokinetics of levetiracetam (LEV) in neonates with seizures and to establish a population pharmacokinetics (PPK) model by using the software NONMEM.MethodsA retrospective analysis of 18 neonatal patients with seizures, who were treated with LEV, including 151 serum samples, was performed. The mean loading dose was 20 mg/kg, followed by a mean maintenance dose of 29 mg/kg/day.ResultsSeventeen neonates (94%) had seizure cessation within 1 week and 16 (84%) remained seizure-free at 30 days under the LEV therapy. The mean serum concentration of LEV was 8.7 µg/mL. Eight samples (5%) were found above the therapeutic range. No serious adverse effects were detected. In the PPK analysis for Korean neonates, the half-life was 9.6 hours; clearance, 0.357 L/hr; and volume of distribution, 4.947 L, showing differences from those in adults.ConclusionLEV is a safe and effective option for the treatment of neonatal seizures with careful therapeutic drug monitoring.

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Aim: This study was conducted to develop a population pharmacokinetic (PK) model of methotrexate in Korean patients with hematologic malignancy, identify factors affecting methotrexate PK, and propose optimal dosage regimen for the Korean population. Methods: Data were retrospectively collected from 188 patients with acute leukemia or non-Hodgkin’s lymphoma who were admitted to Severance Hospital for the period from 2005 to 2015. Using demographic factors and laboratory results as potential covariates for PK parameters, model development was performed using NONMEM and optimal dosing regimens were developed using the final PK model. Results: A two-compartment model incorporating body weight via allometry best described the data, yielding typical parameter values of 25.99L for central volume of distribution (V_1), 18.76L for peripheral volume of distribution (V_2), 12.9L/h for clearance (CL) and 0.646L/h for inter-compartmental clearance. Covariate analyses showed that, at the weight of 50kg, CL decreased by 0.11 L/h for each one-year increase in age above 14 years old and decreased to 0.8-fold when serum creatinine level doubled, indicating the importance of age-specific dose individualization in methotrexate treatment. Volume of distribution at steady state derived from PK parameters (=V_1+V_2) was 0.90L/kg, which was similar to those in the Western or Chinese population. Optimal doses simulated from the final model successfully produced the PK measures close to the target chosen. Conclusion: The population PK model and optimal dosage regimens developed in this study can be used as a basis to achieve precision dosing in Korean patients with hematologic malignancy.