Population Pharmacokinetics Research Articles

Population Pharmacokinetic and Toxicity Analysis of High-Dose Methotrexate in Patients with Central Nervous System Lymphoma.

High-dose methotrexate (HD-MTX)-based polychemotherapy is widely used for patients with central nervous system (CNS) lymphoma. The pharmacokinetic (PK) variability and unpredictable occurrence of toxicity remain major concerns in HD-MTX treatment. This study aimed to characterize the population PK of HD-MTX in patients with CNS lymphoma and to identify baseline predictors and exposure thresholds that predict a high risk of nephro- and hepatotoxicity. Routinely monitored serum MTX concentrations after intravenous infusion of HD-MTX and MTX dosing information were collected retrospectively. Acute event of toxicity (≥ grade 1) was defined according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 on the basis of serum creatinine and alanine aminotransferase. A population PK model was developed in NONMEM. Toxicity data were analyzed using a logistic regression model, and potential baseline and exposure-related predictors were investigated. In total, 1584 MTX concentrations from 110 patients were available for analysis. A two-compartment population PK model adequately described the data. Estimated glomerular filtration rate (eGFR), treatment regimen, albumin, alkaline phosphatase, and body weight were identified as significant covariates that explain the PK variability of HD-MTX. Baseline eGFR and sex were identified as significant predictors for renal toxicity, and MTX dose (mg/m2) was the strongest predictor for hepatotoxicity. The MTX area under the concentration-time curve (AUC24-∞) and concentration at 24 h (C24h) were shown to correlate with renal toxicity only, and 49,800 μg/L × h (109.6 μmol/L × h) and C24h > 3930 μg/L (8.65 μmol/L) were potential exposure thresholds predicting high risk (proportion > 60%). A population PK model was developed for HD-MTX in patients with CNS lymphoma. The toxicity analysis showed that lower baseline eGFR and male sex, and higher MTX dose are associated with increased risk of acute nephro- and hepatotoxicity, respectively. The proposed exposure thresholds that predict high risk of renal toxicity and the developed models hold the potential to guide HD-MTX dosage individualization and better prevent acute toxicity.

Description and Modeling of Relevant Demographic and Laboratory Variables in a Large Oncology Cohort to Generate Virtual Populations

Background/Objectives: Pathophysiological variability in patients with cancer is associated with differences in responses to pharmacotherapy. In this work, we aimed to describe the demographic characteristics and hematological, biochemical, and coagulation variables in a large oncology cohort and to develop, optimize, and provide open access to modeling equations for the estimation of variables potentially relevant in pharmacokinetic modeling. Methods: Using data from 1793 patients with cancer, divided into training (n = 1259) and validation (n = 534) datasets, a modeling network was developed and used to simulate virtual oncology populations. All analyses were conducted in RStudio 4.3.2 Build 494. Results: The simulation network based on sex, age, biogeographic origin/ethnicity, and tumor type (fixed or primary factors) was successfully validated, able to predict age, height, weight, alpha-1-acid glycoprotein, albumin, hemoglobin, C-reactive protein and lactate dehydrogenase serum levels, platelet–lymphocyte and neutrophil–lymphocyte ratios, and hematocrit. This network was then successfully extrapolated to simulate the laboratory variables of eight oncology populations (n = 1200); only East Asians, Sub-Saharan Africans, Europeans, only males, females, patients with an ECOG performance status equal to 2, and only patients with pancreas cancer or ovarian cancer. Conclusions: this network constitutes a valuable tool to predict relevant characteristics/variables of patients with cancer, which may be useful in the evaluation and prediction of pharmacokinetics in virtual oncology populations, as well as for model-based optimization of oncology treatments.

Population pharmacokinetic analysis of quizartinib in patients with newly diagnosed FLT3-internal-tandem-duplication-positive acute myeloid leukemia.

The population pharmacokinetics (PK) of quizartinib and its pharmacologically active metabolite AC886 have been previously described in healthy volunteers (HV) and relapsed/refractory (R/R) FLT3-internal-tandem-duplication-positive (FLT3-IDT-positive) acute myeloid leukemia (AML) patients receiving quizartinib monotherapy. In this analysis, we characterized the population PK of quizartinib and AC886 in newly diagnosed FLT3-ITD-positive AML patients receiving standard induction and consolidation chemotherapy as background treatment, using data from the Phase 3 QuANTUM-First trial and 12 earlier studies. Quizartinib PK were best described by a three-compartment model with sequential zero- and first-order absorption and first-order elimination. A two-compartment model with first-order metabolite formation and first-order elimination best fitted AC886 data. The PK of both moieties showed large interindividual variability (approximately 70% coefficient of variation for systemic clearances). The use of strong cytochrome P450 3A (CYP3A) inhibitors had the largest impact on exposure, increasing the steady-state area under the curve during the dosing interval (AUCss) by 1.8-fold. This is consistent with observations in HV and R/R AML patients and confirms the need for dose adjustments during coadministration. A novel finding in newly diagnosed AML patients was the phase-dependent change in steady-state quizartinib exposure: dose-normalized AUCss values were 0.6-fold during induction, similar during consolidation, and 1.4-fold during continuation compared to R/R AML patients receiving quizartinib monotherapy. The present analysis highlighted the comparison of quizartinib and AC886 PK between newly diagnosed AML patients and previously studied populations, informed dose modifications needed with strong CYP3A inhibitors, and supported the use of derived individual exposure metrics in separate exposure-response analyses.

Population Pharmacokinetics and Dosing Regimen Analysis of Nirmatrelvir in Chinese Patients with COVID-19 Infection

Population Pharmacokinetics and Dosing Regimen Analysis of Nirmatrelvir in Chinese Patients with COVID-19 Infection

First Clinical Application of Aztreonam–Avibactam in Treating Carbapenem-Resistant Enterobacterales: Insights from Therapeutic Drug Monitoring and Pharmacokinetic Simulations

Background: A novel fixed combination of aztreonam (ATM) and avibactam (AVI) offers promising potential to treat infections with carbapenem-resistant Enterobacterales (CRE) producing metallo-β-lactamases (MBL). This study aimed to assess the accuracy of population pharmacokinetic (PK) models for ATM-AVI in predicting in vivo concentrations in a critically ill patient with CRE infection during its first clinical use. Methods: A 70-year-old male with septic shock due to hospital-acquired pneumonia (HAP) caused by MBL-producing Klebsiella pneumoniae was treated with ATM-AVI. Trough and peak serum concentrations (32 samples over 7 days) were measured using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Population PK models were used to simulate complete concentration–time profiles. Bland–Altman analysis assessed model performance by comparing predicted and measured concentrations. Results: Median ATM trough concentrations (18.4 mg/L) remained above the minimum inhibitory concentration (MIC) of 1 mg/L for the pathogen. The Bland–Altman analysis demonstrated reasonable agreement between predicted and observed concentrations, with a relative bias (rBias) of −50.5% for ATM and −14.4% for AVI. ATM-AVI ratios remained stable. Clinical improvement and sterile blood cultures within 12 days led to intensive care unit (ICU) discharge. Conclusions: Population PK models for ATM-AVI accurately predicted in vivo concentrations in a severely ill patient with HAP. Therapeutic drug monitoring (TDM) with PK modeling ensured optimal antimicrobial exposure and contributed to clinical recovery.

The use of population pharmacokinetics to extrapolate food effects from human adults and beagle dogs to the pediatric population illustrated with ibuprofen as a case

Oral drug administration is the most convenient route of administration in the pediatric population. However, children are often not fasted when drugs are orally administered, hence potential food-drug interactions might occur. Most of these interactions are extrapolated from studies performed in human adults where a recommended high-fat, high-calorie meal is administered prior to drug dosing. As the recommended protocols are based on studies in support of adult drug development, these studies do not mimic the meal composition administered to the pediatric population, especially the very young ones, which renders food-drug interactions in this population understudied. Therefore, it was evaluated to what extent population pharmacokinetics could reliably extrapolate food effects from human adults and beagle dogs to mimic the real-life situation in the pediatric population. Eight human adults and six beagle dogs received ibuprofen under different dosing conditions (fasted, reference meal fed condition, infant formula fed condition). Population pharmacokinetic analysis was performed to derive the pharmacokinetic parameters to be scaled to pediatric ages. For both species, a one-compartment model best described the data, where in human adults a dual-input function to capture the double absorption peak significantly improved the model fit. Simulations for a virtual pediatric population demonstrated that the predictive ability of human adults and beagle dogs to inform absorption effects under different dosing conditions using population pharmacokinetic modeling appeared to be reasonable. However, to be able to fully validate the predictability of both species for ibuprofen, additional studies in the pediatric population are required to generate more informative data.

Population Pharmacokinetics and Dose Optimization of Piperacillin in Infants and Children with Pneumonia.

We aimed to determine the piperacillin disposition and optimize the dosing regimens for infants and children with pneumonia. An opportunistic sampling strategy was used in this pharmacokinetic study. High-performance liquid chromatography was used to measure the concentrations of piperacillin in plasma samples. A population pharmacokinetic model was conducted using NONMEM. The pharmacokinetic data of 90 samples from 64 infants and children with pneumonia (age range: 0.09-1.72 years for infants and 2.12-11.10 years for children) were available. A two-compartment model with first-order elimination was the most suitable model to describe the population pharmacokinetics of piperacillin. A covariate analysis indicated that body weight and age were significant factors affecting clearance. Monte Carlo simulations showed that a 50-mg/kg every 8 h or every 12 h dosing regimen results in underdosing. Results both in infants and children showed that an extended infusion (3 h) of various dosing regimens (80, 100, or 130 mg/kg) three times daily or a 300-mg/kg continuous infusion can reach a therapeutic level based on the chosen target for the probability of target attainment threshold of 70%, 80%, and 90% at minimum inhibitory concentration breakpoints of 8 mg/L and 16 mg/L. A population pharmacokinetic model was obtained to evaluate the disposition of piperacillin, and the optimal dosing regimens were provided for use in infants and children with pneumonia.

Population pharmacokinetics and dose optimization of ceftazidime in critically ill children

ObjectiveThe aim of this study was to develop a population pharmacokinetic model for ceftazidime in critically ill children in the pediatric intensive care unit (PICU) and optimize an appropriate dosing regimen for this population.MethodsWe performed a prospective pharmacokinetic study on critically ill children aged 0.03–15 years. A population pharmacokinetic model was developed using the NLME program. Statistical and graphical methods were used to assess the stability and predictive performance of the model. Monte Carlo simulations were conducted to determine the optimal ceftazidime dosing regimen to achieve 70% fT > minimum inhibitory concentration (MIC).ResultsThis study included 88 critically ill children and 100 ceftazidime serum concentrations. The pharmacokinetic characteristics of ceftazidime were best described by a one-compartment linear elimination model. The weight and estimated glomerular filtration rate (eGFR) were determinant covariates for the clearance (CL) of ceftazidime. The recommended ceftazidime dosage regimens achieved a probability of target attainment (PTA) >90% for critically ill children at MIC values of 2, 4, and 8 mg/L. For bacterial infection at an MIC of 16 mg/L, it is difficult to achieve effective pharmacodynamic (PD) targets in vivo with the commonly used dose of ceftazidime.ConclusionThe population pharmacokinetic model of ceftazidime was established in critically ill children. Based on this model, we recommend evidence-based, individualized dosing regimens for subgroups with different weights and renal functions. The current daily dosage for children adequately meets the treatment requirements for MICs of 2, 4, and 8 mg/L, while for bacterial infection at an MIC of 16 mg/L, an elevated dosage regimen may be required.Clinical Trial Registrationhttps://www.medicalresearch.org.cn/login, Identifier MR-42-22-000220.

Vancomycin population pharmacokinetic models: Uncovering pharmacodynamic divergence amid clinicobiological resemblance.

Vancomycin is an antibiotic used for severe infections. To ensure microbiological efficacy, a ratio of AUC/MIC ≥400 is recommended. However, there is significant interindividual variability in its pharmacokinetic parameters, necessitating therapeutic drug monitoring to adjust dosing regimens and ensure efficacy while avoiding toxicity. Population pharmacokinetic (PopPK) models enable dose personalization, but the challenge lies in the choice of the model to use among the multitude of models in the literature. We compared 18 PopPK models created from populations with the same sociodemographic and clinicobiological characteristics. Simulations were performed for a 47 years old man, weighing 70 kg, with an albumin level of 35.5 g/L, a creatinine clearance of 100 mL/min, an eGFR of 106 mL/min/1.73 m2, and receiving an intravenous infusion of 1 g × 2/day of VCM over 1 h for 48 h. Simulations of time-concentration profiles revealed differences, leading us to determine the probability of achieving microbiological efficacy (AUC/MIC ≥ 400) with each model. Depending on some models, a dose of 1 g × 2/day is required to ensure microbiological efficacy in over 90% of the population, while with the same dose other models do not exceed 10% of the population. To ensure that 90% of the patients are correctly exposed, a dose of vancomycin ranging from 0.9 g × 2/day to 2.2 g × 2/day is necessary a priori depending on the chosen model. These differences raise an issue in choosing a model for performing therapeutic drug monitoring using a PopPK model with or without Bayesian approach. Thus, it is fundamental to evaluate the impact of these differences on both efficacy/toxicity.

Pharmacokinetic Modeling and Model-Based Hypothesis Generation for Dose Optimization of Clonidine in Neonates With Neonatal Opioid Withdrawal Syndrome.

The No-POPPY study (NCT03396588), a double-blind, randomized trial compared morphine with clonidine therapy for neonatal opioid withdrawal syndrome (NOWS) and found that the duration of treatment was similar across groups. This is significant because perinatal use of morphine has the potential for neurodevelopmental consequences. Still, the clonidine group reached symptom stabilization (Finnegan score (FS) < 8) later than the morphine group and had a more significant number of patients who required adjunct therapy. However, the mean FS was consistently lower in the clonidine group after day 6. This prompted us to use pharmacokinetic (PK) and parametric time-to-event (TTE) modeling to simulate dosage schedules that may decrease the time to stabilization and reduce the need for adjunct therapy. Population PK (popPK) analysis was conducted, and the final model was a one-compartment model with first-order absorption and elimination, incorporating allometric scaling and age effect on apparent clearance (CL/F) and apparent volume (V/F). The population estimates for CL/F and V/F were 13.6 L/h/70 kg and 416 L/70 kg, respectively, similar to the reported values. A Weibull model described the TTE data best, followed by incorporating predicted average concentrations to yield the final Weibull accelerated failure time model. Simulations of dosing strategies showed that increasing both the starting and maximum doses could potentially shorten the time to stabilization, and thus, length of treatment and hospital stay. Given the hypothesis-generating nature of this analysis, the recommended dosing regimens should be tested prospectively to evaluate their benefits.

Clinical study design strategies to mitigate confounding effects of time-dependent clearance on dose optimization of therapeutic antibodies.

Time-dependent pharmacokinetics (TDPK) is a frequent confounding factor that misleads exposure-response (ER) analysis of therapeutic antibodies, where a decline in clearance results in increased drug exposure over time in patients who respond to therapy, causing a false-positive ER finding. The object of our simulation study was to explore the influence of clinical trial designs on the frequency of false-positive ER findings. Two previously published population PK models representative of slow- (pembrolizumab) and fast-onset (rituximab) TDPK were used to simulate virtual patient cohorts with time-dependent clearance and the frequency of false-positive ER findings. The impact of varying the number of dose groups, dose range, and sample size was evaluated over time. Study designs with a single tested dose level showed a high probability of showing a false-positive ER finding. When TDPK has a slow onset, use of exposure measures from early timepoints in ER analysis significantly reduces the risk of a false-positive, while with fast onset it did not. Randomization of patients to two dose levels greatly reduced the risk, with a threefold or greater dose range offering the greatest benefit. The likelihood of false-positive increases with a larger sample size, where greater care should be taken to identify confounding factors. Clinical trial simulation supports that appropriate clinical study design and analysis with adequate dose exploration can reduce but cannot entirely eliminate the risk of misleading ER findings.

Population Pharmacokinetics of Intravenous Paracetamol and Its Metabolites in Extreme Preterm Neonates in the Context of Patent Ductus Arteriosus Treatment.

Our aim was to describe the pharmacokinetics of paracetamol and its metabolites in extreme preterm neonates in the context of patent ductus arteriosus treatment. Factors associated with inter-individual variability and metabolic pathways were studied. The association between drug exposure and clinical outcomes were investigated. Preterm neonates of 23-26 weeks' gestational age received paracetamol within 12 h after birth. Plasma concentrations of paracetamol and its metabolites were measured throughout 5 days of treatment. Clinical success was defined as ductus closure on two consecutive days or at day 7. Aspartate aminotransferase and alanine aminotransferase levels were used as surrogates for liver damage. Data from 30 preterm neonates were available for pharmacokinetic analysis. Paracetamol pharmacokinetics were described using a two-compartment model with significant positive effects of weight on clearance and of birth length on peripheral compartment volume. Paracetamol was mainly metabolised into sulphate (89%) then glucuronide (6%), and the oxidative metabolic pathway was reduced (4%). The glucuronidation pathway increased with gestational age, whereas the sulfation pathway decreased. No difference was observed in drug exposure between successful and unsuccessful patients. No increase in aspartate aminotransferase and alanine aminotransferase levels were observed during treatment, and no association was found with either paracetamol or oxidative metabolite exposures. The relative proportions of the metabolic pathways were characterised with gestational age. In the range of observed drug exposures, no association was found with clinical response or liver biomarkers. These findings may suggest that paracetamol concentrations were within the range that already guarantee a maximum effect on ductus closure.

Population pharmacokinetic analyses for sulbactam-durlobactam using Phase 1, 2, and 3 data.

Sulbactam-durlobactam is a β-lactam/β-lactamase inhibitor combination approved in the United States for the treatment of hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus in adults. A population pharmacokinetic (PK) model of sulbactam-durlobactam in plasma was developed using data from eight Phase 1-3 studies. A total of 432 subjects and 8,100 plasma concentrations were available for the population PK data set. The combined model was a four-compartment (two compartments per drug) model with linear kinetics. Both renal clearance and nonrenal clearance were estimated, and total clearance was calculated as the sum of renal and nonrenal clearance. Individual renal clearances were scaled by baseline creatinine clearance. The sampling-importance-resampling analysis indicated that the parameters were estimated reliably with adequate precision. Hemodialysis (HD) and epithelial lining fluid (ELF) sub-models were developed for each analyte separately. Intermittent HD resulted in an approximately 30% decrease in the daily area under the concentration-time curve (AUC0-24) when HD was started 1 hour after the end of the infusion. Assuming protein binding estimates of 10% and 38% for durlobactam and sulbactam, respectively, ELF penetration ratios were found to be 41.3% for durlobactam and 86.0% for sulbactam. Of the statistically significant covariates of PK identified, which included body weight, body mass index, infection type, and region of origin, renal function was the only clinically relevant covariate. Overall, a robust description of the plasma PK of sulbactam and durlobactam was achieved. The resultant population PK model was expected to be appropriate for model-based simulations and assessment of pharmacokinetic-pharmacodynamic relationships.

Population pharmacokinetics of selexipag for dose selection and confirmation in pediatric patients with pulmonary arterial hypertension.

Selexipag is an oral selective prostacyclin receptor agonist approved for the treatment of pulmonary arterial hypertension (PAH) in adults. To date, no treatment targeting the prostacyclin pathway is approved for pediatric patients. Our goal is to identify a pediatric dose regimen that results in comparable exposures to selexipag and its active metabolite JNJ-68006861 as those shown to be efficacious in adult PAH patients. Extrapolation from the population pharmacokinetic (PK) model developed in adults (GRIPHON study; NCT01106014) resulted in the definition of three different pediatric body weight groups (≥9 to <25 kg, ≥25 to <50 kg, and ≥50 kg) with corresponding starting doses (100, 150, and 200 μg twice daily) and maximum allowed doses (800, 1200, and 1600 μg twice daily). The proposed pediatric dose regimen was subsequently tested in a clinical study (NCT03492177), including 63 pediatric PAH patients ≥2 to <18 years of age and a body weight range of 9.9-93.5 kg. The body weight-adjusted dose regimen for selexipag resulted in comparable systemic exposures to selexipag and its active metabolite in pediatric patients as previously observed in adult PAH patients. Updating the adult selexipag population PK model provided overall consistent parameters and confirmed that the PK characteristics of selexipag and its active metabolite were comparable between pediatric and adult patients. The presented selexipag dose regimen for pediatric PAH patients is considered appropriate for continuing the clinical evaluation of the safety and efficacy of selexipag in pediatric patients ≥2 years of age.

Population Pharmacokinetics of Ensitrelvir in Healthy Participants and Participants with SARS-CoV-2 Infection in the SCORPIO-SR Study.

Ensitrelvir, a novel oral inhibitor of the 3C-like protease of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has shown efficacy and safety in participants with mild to moderate coronavirus disease 2019 (COVID-19) with once-daily multiple doses of 375mg on day 1 followed by 125mg on days 2-5. The aims of this study were to characterize the pharmacokinetics of ensitrelvir and to explore its exposure-response relationships on the dose regimen. Pharmacokinetic data, including 8034 plasma concentration datasets from 2060 participants, from two phase I and one phase II/III study in healthy participants and participants infected with SARS-CoV-2 were used to develop a population pharmacokinetic model. The correlation between exposure and drug response was evaluated using observed plasma concentrations and estimated pharmacokinetic parameters as pharmacokinetic indexes and viral RNA as drug response. A two-compartment model with a first-order absorption model effectively described plasma ensitrelvir concentrations. The effects of body weight on clearance and volume of distribution and of food conditions and formulation on the absorption rate constant were selected as significant covariates. The efficacy indexes changed in the active group, but the responses were similar across the exposure range in the phase II/III study (SCORPIO-SR) regardless of the effects of the pharmacokinetic covariates. Population pharmacokinetics revealed that body weight is the most important covariate in the pharmacokinetics of ensitrelvir. The antiviral effect, independent of ensitrelvir exposure, was demonstrated on the current dose regimen for treatment of SARS-CoV-2 infection.

Population pharmacokinetics of unfractionated heparin and multivariable analysis of activated clotting time in patients undergoing radiofrequency ablation of atrial fibrillation

IntroductionAtrial fibrillation (AF) increases cardiovascular morbidity and mortality. To reduce thrombosis and bleeding risks, and due to high variability of unfractionated heparin (UFH) effect, activated clotting time (ACT) is used during radiofrequency catheter ablation (RFCA) of AF to guide UFH dose. This study aimed to develop a population PK-PD model and perform multivariable analysis in order to identify the most significant covariates associated with interindividual variability of UFH. MethodsElectronic medical records from 668 patients undergoing RFCA were analyzed, including relevant covariates. The relationship between UFH dose and ACT and the impact of the main covariates were characterized using a mixed-effect PK-PD model. Multivariable analysis was then used to identify predictors of ACT 15 minutes after UFH administration (ACT15). ResultsA two-compartment PK model with linear elimination and a direct Emax PD model with a baseline and sigmoidicity best described the observed ACT values. Pretreatment with dabigatran, warfarin, or fluindione significantly influenced baseline ACT. Pretreatment with vitamin K antagonists or low molecular weight heparin explained Emax variability. The multivariable model identified baseline ACT, initial UFH dose, and previous anticoagulant as the main predictors of ACT15. Model evaluation through resampling and external validation showed accurate ACT15 predictions. ConclusionThis study presents the first population PK-PD model characterizing the relationship between UFH doses and ACT during RFCA, along with multivariable analysis. Additionally, predictive calculators for ACT15 and UFH dose based on patient and procedural characteristics were developed, enhancing personalized anticoagulation management during RFCA.

Population pharmacokinetic study of the effect of polymorphisms in the ABCB1 and CES1 genes on the pharmacokinetics of dabigatran.

The impact of genetic polymorphisms in the ABCB1 and CES1 genes on dabigatran plasma concentrations remains a subject of debate, and the purpose of this study was to quantitatively assess the effects of genetic polymorphisms on dabigatran esters in healthy Chinese subjects employed a population pharmacokinetic (PopPK) approach. In total, 1,926 pharmacokinetic (PK) samples from 123 healthy individuals who were given 150mg of dabigatran orally during a fasting state or postprandially were analyzed using the PopPK model. A two-compartment model with first-order absorption was found to adequately describe the PK data. The results showed that covariates food intake and ABCB1 SNP rs4148738 were shown to have statistically significant impacts. Specifically, in postprandial administration increased lag time (ALAG) and clearance (CL) by 2.65% and 0.51%, respectively, and decreased absorption rate constant (KA) by 0.24%. Additionally, in subjects with CT genotype ABCB1 (rs4148738), the central ventricular volume of distribution (V2) was increased by 0.38%. In summary, the PopPK model developed in this study was robust and effectively characterized the pharmacokinetics of dabigatran in healthy Chinese adults, demonstrating that both food and ABCB1 genetic variation significantly influence the absorption and plasma concentration levels of dabigatran.

Establishment of a population pharmacokinetic model for linezolid in neonates with sepsis

To establish the pharmacokinetic model of linezolid in neonates, and to optimize the administration regimen. A prospective study was conducted among 64 neonates with sepsis who received linezolid as anti-infective therapy, and liquid chromatography-tandem mass spectrometry was used to measure the plasma concentration of the drug. Clinical data were collected, and nonlinear mixed effects modeling was used to establish a population pharmacokinetic (PPK) model. Monte Carlo simulation and evaluation was performed for the optimal administration regimen of children with different features. The pharmacokinetic properties of linezolid in neonates could be described by a single-compartment model with primary elimination, and the population typical values for apparent volume of distribution and clearance rate were 0.79 L and 0.34 L/h, respectively. The results of goodness of fit, visualization verification, and the Bootstrap method showed that the model was robust with reliable results of parameter estimation and prediction. Monte Carlo simulation results showed that the optimal administration regimen for linezolid in neonates was as follows: 6 mg/kg, q8h, at 28 weeks of gestational age (GA); 8 mg/kg, q8h, at 32 weeks of GA; 9 mg/kg, q8h, at 34-37 weeks of GA; 11 mg/kg, q8h, at 40 weeks of GA. The PPK model established in this study can provide a reference for individual administration of linezolid in neonates. GA and body weight at the time of administration are significant influencing factors for the clearance rate of linezolid in neonates.

Population Pharmacokinetics of Tamibarotene in Pediatric and Young Adult Patients with Recurrent or Refractory Solid Tumors.

Tamibarotene is a synthetic retinoid that inhibits tumor cell proliferation and promotes differentiation. We previously reported on the safety and tolerability of tamibarotene in patients with recurrent or refractory solid tumors. Therefore, in this study, we aimed to evaluate the pharmacokinetic properties of tamibarotene and construct a precise pharmacokinetic model. We also conducted a non-compartmental analysis and population pharmacokinetic (popPK) analysis based on the results of a phase I study. Targeted pediatric and young adult patients with recurrent or refractory solid tumors were administered tamibarotene at doses of 4, 6, 8, 10, and 12 g/m2/day. Serum tamibarotene concentrations were evaluated after administration, and a popPK model was constructed for tamibarotene using Phoenix NLME. During model construction, we considered the influence of various parameters (weight, height, body surface area, and age) as covariates. Notably, 22 participants were included in this study, and 109 samples were analyzed. A two-compartment model incorporating lag time was selected as the base model. In the final model, the body surface area was included as a covariate for apparent total body clearance, the central compartment volume of distribution, and the peripheral compartment volume of distribution. Visual prediction checks and bootstrap analysis confirmed the validity and predictive accuracy of the final model as satisfactory.

Population Pharmacokinetics of Vancomycin in Intensive Care Patients with the Time-Varying Status of Temporary Mechanical Circulatory Support or Continuous Renal Replacement Therapy.

This study characterized the population pharmacokinetics (PK) of vancomycin in patients treated with and without continuous renal replacement therapy (CRRT) or temporary mechanical circulatory support (tMCS), including extracorporeal membrane oxygenation or extracorporeal ventricular assist device. Critically ill adults with and without tMCS or CRRT prescribed vancomycin were enrolled for population PK modeling. MonteCarlo simulation provided dosing recommendations based on the probability of target attainment (PTA), achieving a 24-h area under curve (AUC24h) of 400-600mg*h/L. Twenty-five patients with 184 plasma samples were analyzed. The median age was 61.0years. The final model was a two-compartment PK model. CRRT, serum creatinine, and body weight were significant predictors of clearance. CRRT was a covariate on the central volume of distribution. tMCS significantly decreased the intercompartmental clearance. The simulated mean trough levels at the 48th hour were lower in the tMCS group (13.4 versus 14.2mg/dL in non-tMCS, p < 0.001) in a 70-kg subject with a creatinine of 1mg/dL and a daily dose of 20mg/kg, but the PTA was similar (61.8% versus 62.2%). A reduction of maintenance dose from 30 to 10mg/kg/day with loading dose from 25 to 15mg/kg is recommended while serum creatinine progresses from 0.5 to 4.0mg/dL. For CRRT, the optimal regimen consists of 20-25mg/kg loading and maintenance of 15mg/kg/day. The dosing strategy of vancomycin can be based on body weight or renal function, regardless of tMCS. Intercompartmental clearance decreases under tMCS, which can mislead a dosing adjustment based on trough level.