Fosphenytoin dosing regimen including optimal timing for the measurement of serum phenytoin concentration in pediatric patients.

INTRODUCTION: We aimed to evaluate the pediatric fosphenytoin dosing regimen, including optimal timing for the measurement of total serum phenytoin concentration (CPHT). METHODS: We retrospectively investigated pediatric patients with status epilepticus or seizure clusters treated with fosphenytoin between April 2013 and March 2018. Two CPHT measurements were analyzed, one 2-4 h after the loading dose and another before the second dose. Individual pharmacokinetic parameters were estimated using the Bayesian method and were used to simulate CPHT. RESULTS: The present study involved 12 pediatric patients; the loading dose of fosphenytoin was 22.1 (17.2-27.2) mg/kg. The CPHT was 13.4 (8.6-18.9) µg/mL 2-4 h after the loading dose. The CPHT estimated from individual pharmacokinetic parameters 12 and 24 h after the loading dose was 9.5 (6.7-14.2) and 5.8 (3.7-10.0) µg/mL, respectively. If fosphenytoin was administered at a loading dose of 22.5 mg/kg and a maintenance dose of 5 or 7.5 mg/kg (administered every 12 h, starting 12 h after the loading dose), then the CPHT on day 8 was estimated to be 5.74 (2.6-15.4) µg/mL at 5 mg/kg and 13.9 (5.7-31.0) µg/mL at 7.5 mg/kg. CONCLUSIONS: In pediatric patients, a maintenance dose of fosphenytoin should be started 12 h after the loading dose, and a maintenance dose of 5-7.5 mg/kg/dose every 12 h may be better than every 24 h. We recommend measuring CPHT at 2 and 12 h after the loading dose to simplify and safely adjust the dosage in clinical practice.

Pharmacokinetic variability of vancomycin in patients with nosocomial meningitis.

WHAT IS KNOWN AND OBJECTIVE: High doses of vancomycin are required early in the treatment of nosocomial meningitis. However, the dosage is often reduced later during treatment, irrespective of renal function. This study was designed to investigate the pharmacokinetic variability of vancomycin and the associated factors throughout the treatment course for patients with nosocomial bacterial meningitis. METHODS: This study included 17 patients who received vancomycin for nosocomial bacterial meningitis at the Tokyo Women's Medical University Yachiyo Medical Center from April 2013 to May 2020. All patients had their serum vancomycin concentrations and cerebrospinal fluid (CSF) parameters measured within 7 days of initiating treatment (early period) and after 8 days (later period) of treatment. RESULTS AND DISCUSSION: The relative error between the predicted serum vancomycin concentration and the measured value was significantly higher in the later period than in the early period. In 13 patients who did not have their dosing interval shortened, the vancomycin dosage/serum vancomycin concentration/estimated glomerular filtration rate (D/C/eGFR) ratio significantly decreased in the later period. Moreover, the rate of change in the D/C/eGFR ratio significantly correlated with that in the CSF protein and C-reactive protein levels. WHAT IS NEW AND CONCLUSION: This study suggests that the clinical condition and inflammatory response of a patient with meningitis influence the pharmacokinetics of vancomycin. Therefore, the vancomycin dosage for the treatment of nosocomial bacterial meningitis must be adjusted according to changes in the clinical condition and renal function of the patient, necessitating careful therapeutic drug monitoring.

Nucleosomes of polyploid trophoblast giant cells mostly consist of histone variants and form a loose chromatin structure.

Trophoblast giant cells (TGCs) are one of the cell types that form the placenta and play multiple essential roles in maintaining pregnancy in rodents. TGCs have large, polyploid nuclei resulting from endoreduplication. While previous studies have shown distinct gene expression profiles of TGCs, their chromatin structure remains largely unknown. An appropriate combination of canonical and non-canonical histones, also known as histone variants, allows each cell to exert its cell type-specific functions. Here, we aimed to reveal the dynamics of histone usage and chromatin structure during the differentiation of trophoblast stem cells (TSCs) into TGCs. Although the expression of most genes encoding canonical histones was downregulated, the expression of a few genes encoding histone variants such as H2AX, H2AZ, and H3.3 was maintained at a relatively high level in TGCs. Both the micrococcal nuclease digestion assay and nucleosome stability assay using a microfluidic device indicated that chromatin became increasingly loose as TSCs differentiated. Combinatorial experiments involving H3.3-knockdown and -overexpression demonstrated that variant H3.3 resulted in the formation of loose nucleosomes in TGCs. In conclusion, our study revealed that TGCs possessed loose nucleosomes owing to alterations in their histone composition during differentiation.