Use of Real-World Data and Physiologically-Based Pharmacokinetic Modeling to Characterize Enoxaparin Disposition in Children With Obesity

Enoxaparin treatment dosing for venous thromboembolism in pediatric patients with obesity

BACKGROUND

The optimal enoxaparin dosing for treatment of venous thromboembolism (VTE) in pediatric patients with obesity remains uncertain. We described the mean enoxaparin dose required to attain anti-factor Xa (anti-Xa) levels of 0.5-1 unit/mL in pediatric patients with obesity.

METHODS

Pediatric patients with obesity (body mass index [BMI] ≥95th percentile) who received treatment dose of enoxaparin from 2013 to 2022 and had at least one appropriately timed anti-Xa level were retrospectively evaluated. Daily enoxaparin dose required to achieve an anti-Xa level of 0.5-1 unit/mL was reviewed and compared by the severity of obesity. The correlation coefficients between enoxaparin dose requirement and BMI, BMI percentile, and weight were measured by Spearman's rank correlation coefficient.

RESULTS

Pediatric patients with obesity (n = 89) required a mean enoxaparin dose of 0.8 ± 0.18 mg/kg twice daily to attain a therapeutic anti-Xa level. Children with BMI 95th-99th percentile and weight ≤100 kg achieved the target level on a significantly higher weight-based enoxaparin dose compared to BMI greater than 99th percentile (0.95 ± 0.15 vs. 0.75 ± 0.15 mg/kg twice daily; p < .001) and weight greater than 100 kg (0.95 ± 0.14 vs. 0.7 ± 0.12 mg/kg twice daily; p < .001). BMI, BMI percentile, and weight showed a moderate to strong negative correlation with enoxaparin dose requirement.

CONCLUSIONS

Pediatric patients with obesity required a lower weight-based dose of enoxaparin to achieve a therapeutic anti-Xa than the recommended starting dose of 1 mg/kg twice daily for treatment of VTE. Among obesity indices, weight showed the strongest negative correlation with total daily enoxaparin requirement.

Enoxaparin thromboprophylaxis in hospitalized obese pediatric patients

BACKGROUND

Enoxaparin is an anticoagulant used for pharmacologic thromboprophylaxis in pediatrics. Enoxaparin pharmacokinetics can be altered in the setting of obesity. Optimal enoxaparin dosing for thromboprophylaxis in children with obesity remains unclear.

PROCEDURE

A retrospective review was conducted of pediatric patients who weighed ≥60 kg with BMI ≥ 95th percentile, received enoxaparin for thromboprophylaxis, and had at least one appropriately drawn anti-factor Xa (anti-Xa) from 2013 to 2022. Anti-Xa levels were reviewed for patients initially treated with enoxaparin 30 mg every 12 h. The average daily enoxaparin dose required to achieve an anti-Xa of 0.2-0.4 unit/mL, which was stratified by BMI percentile and weight, was calculated.

RESULTS

Of 116 patients (median age 15.8 years) included for analysis, 106 patients were initially treated with enoxaparin 30 mg every 12 h. Anti-Xa levels were <0.2 unit/mL in 53% of patients with BMI > 99th percentile and 54% of patients >100 kg. Ninety-one patients had at least one anti-Xa 0.2-0.4 unit/mL with an average daily enoxaparin dosing of 66 mg. When stratified by severity of obesity, higher doses were required to attain an anti-Xa 0.2-0.4 unit/mL in patients with BMI > 99th percentile compared with those with 95th-99th percentile (67.8 ± 15.7 vs. 62 ± 5.6 mg/day, p = .01). Patients > 100 kg required significantly higher dose than those ≤100 kg (69.1 ± 15.5 vs 61.2 ± 7.3 mg/day, p = .002).

CONCLUSIONS

Increased initial dosing and/or anti-Xa level monitoring should be considered in adolescents with severe obesity receiving enoxaparin thromboprophylaxis.

Physiologically based pharmacokinetic modeling in obesity: applications and challenges

INTRODUCTION

Rising global obesity rates pose a threat to people's health. Obesity causes a series of pathophysiologic changes, making the response of patients with obesity to drugs different from that of nonobese, thus affecting the treatment efficacy and even leading to adverse events. Therefore, understanding obesity's effects on pharmacokinetics is essential for the rational use of drugs in patients with obesity.

AREAS COVERED

Articles related to physiologically based pharmacokinetic (PBPK) modeling in patients with obesity from inception to October 2023 were searched in PubMed, Embase, Web of Science and the Cochrane Library. This review outlines PBPK modeling applications in exploring factors influencing obesity's effects on pharmacokinetics, guiding clinical drug development and evaluating and optimizing clinical use of drugs in patients with obesity.

EXPERT OPINION

Obesity-induced pathophysiologic alterations impact drug pharmacokinetics and drug-drug interactions (DDIs), altering drug exposure. However, there is a lack of universal body size indices or quantitative pharmacology models to predict the optimal for the patients with obesity. Therefore, dosage regimens for patients with obesity must consider individual physiological and biochemical information, and clinically individualize therapeutic drug monitoring for highly variable drugs to ensure effective drug dosing and avoid adverse effects.

Pharmacokinetics of Dexamethasone in Children and Adolescents with Obesity

Dexamethasone is a synthetic glucocorticoid approved for treating disorders of various organ systems in both adult and pediatric populations. Currently, approved pediatric dosing recommendations are weight-based, but it is unknown whether differences in dexamethasone drug disposition and exposure exist for children with obesity. This study aimed to develop a population pharmacokinetic (PopPK) model for dexamethasone with data collected from children with obesity. Dexamethasone was given as either IV or oral/enteral administration, and a salt factor correction was used for dexamethasone sodium phosphate injection. A PopPK analysis using dexamethasone plasma concentration versus time was performed using the software NONMEM. A virtual population of 1000 children with obesity across three age groups was generated for dosing simulations. Data from 59 study participants with 82 PK plasma samples were used in the PopPK analysis. A one-compartment model with first-order absorption and the inclusion of total body weight as a covariate characterized the data. No other covariates were included in the PopPK model. Single and multiple IV dose(s) of 0.5 and 1 mg/kg every 8 h resulted in 68% or more of virtual children with obesity attaining simulated exposures that were within exposure ranges previously reported in adult studies. In conclusion, this was the first study to characterize dexamethasone's PopPK in children with obesity. Simulation results suggest that virtual children with obesity receiving oral doses of 0.5 and 1 mg/kg had generally comparable dexamethasone exposures as adult estimates. Additional studies are needed to characterize the dexamethasone's target exposure in children.

Physiologically-based pharmacokinetic modeling of pantoprazole to evaluate the role of CYP2C19 genetic variation and obesity in the pediatric population

Pantoprazole is a proton pump inhibitor indicated for the treatment of gastroesophageal reflux disease, a condition that disproportionately affects children with obesity. Appropriately dosing pantoprazole in children with obesity requires understanding the body size metric that best guides dosing, but pharmacokinetic (PK) trials using traditional techniques are limited by the need for larger sample sizes and frequent blood sampling. Physiologically-based PK (PBPK) models are an attractive alternative that can account for physiologic-, genetic-, and drug-specific changes without the need for extensive clinical trial data. In this study, we explored the effect of obesity on pantoprazole PK and evaluated label-suggested dosing in this population. An adult PBPK model for pantoprazole was developed using data from the literature and accounting for genetic variation in CYP2C19. The adult PBPK model was scaled to children without obesity using age-associated changes in anatomical and physiological parameters. Lastly, the pediatric PBPK model was expanded to children with obesity. Three pantoprazole dosing strategies were evaluated: 1 mg/kg total body weight, 1.2 mg/kg lean body weight, and US Food and Drug Administration-recommended weight-tiered dosing. Simulated concentration-time profiles from our model were compared with data from a prospective cohort study (PAN01; NCT02186652). Weight-tiered dosing resulted in the most (>90%) children with pantoprazole exposures in the reference range, regardless of obesity status or CYP2C19 phenotype, confirming results from previously published population PK models. PBPK models may allow for the efficient study of physiologic and developmental effects of obesity on PK in special populations where clinical trial data may be limited.

Characterizing Enoxaparin's Population Pharmacokinetics to Guide Dose Individualization in the Pediatric Population

BACKGROUND AND OBJECTIVE

Pediatric dosing of enoxaparin was derived based on extrapolation of the adult therapeutic range to children. However, a large fraction of children do not achieve therapeutic anticoagulation with initial dosing. We aim to use real-world anti-Xa data obtained from children receiving enoxaparin per standard of care to characterize the population pharmacokinetics (PopPK).Author names: Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Also, kindly confirm the details in the metadata are correct.The author names are accurately presented and the metadata are correct.  METHODS: A PopPK analysis was performed using NONMEM, and a stepwise covariate modeling approach was applied for the covariate selection. The final PopPK model, developed with data from 1293 patients ranging in age from 1 day to 18 years, was used to simulate enoxaparin subcutaneous dosing for prophylaxis and treatment based on total body weight (0-18 years, TBW) or fat-free mass (2-18 years, FFM). Simulated exposures in children with obesity (body mass index percentile ≥95th percentile) were compared with those without obesity.

RESULTS

A linear, one-compartment PopPK model that included allometric scaling using TBW (<2 years) or FFM (≥2 years) characterized the enoxaparin pharmacokinetic data. In addition, serum creatinine was identified as a significant covariate influencing clearance. Simulations indicated that in patients aged <2 years, the recommended 1.5 mg/kg TBW-based dosing achieves therapeutic simulated concentrations. In pediatric patients aged ≥2 years, the recommended 1.0 mg/kg dose resulted in exposures more comparable in children with and without obesity when FFM weight-based dosing was applied.

CONCLUSION

Using real-world data and PopPK modeling, enoxaparin's pharmacokinetics were characterized in pediatric patients. Using FFM and twice-daily dosing might reduce the risk of overdosing, especially in children with obesity.

Virtual twins for model-informed precision dosing of clozapine in patients with treatment-resistant schizophrenia

Model-informed precision dosing using virtual twins (MIPD-VTs) is an emerging strategy to predict target drug concentrations in clinical practice. Using a high virtualization MIPD-VT approach (Simcyp version 21), we predicted the steady-state clozapine concentration and clozapine dosage range to achieve a target concentration of 350 to 600 ng/mL in hospitalized patients with treatment-resistant schizophrenia (N = 11). We confirmed that high virtualization MIPD-VT can reasonably predict clozapine concentrations in individual patients with a coefficient of determination (R2 ) ranging between 0.29 and 0.60. Importantly, our approach predicted the final dosage range to achieve the desired target clozapine concentrations in 73% of patients. In two thirds of patients treated with fluvoxamine augmentation, steady-state clozapine concentrations were overpredicted two to four-fold. This work supports the application of a high virtualization MIPD-VT approach to inform the titration of clozapine doses in clinical practice. However, refinement is required to improve the prediction of pharmacokinetic drug-drug interactions, particularly with fluvoxamine augmentation.

Anti-Obesity and Anti-Inflammatory Synergistic Effects of Green Tea Catechins and Citrus β-Cryptoxanthin Ingestion in Obese Mice

Chronic obesity causes various diseases, leading to an urgent need for its treatment and prevention. Using monosodium-glutamate-induced obesity mice, the present study investigated the synergistic obesity-reducing effects of tea catechins and the antioxidant β-cryptoxanthin present in mandarin oranges. The results show that the obese mice that ingested both tea catechin and β-cryptoxanthin for 4 weeks had a significantly decreased body weight, with no difference in body weight compared with control mice. Moreover, the blood biochemical test results were normal, and the body fat percentage was significantly decreased according to the histopathological analysis. Additionally, the abundance of M1 macrophages, which release pro-inflammatories, was significantly reduced in adipose tissue. Indeed, a significant decrease was detected in M1-macrophage-secreted tumor necrosis factor-alpha levels. Meanwhile, M2 macrophage levels were recovered, and adiponectin, which is released from adipocytes and involved in suppressing metabolic syndrome, was increased. Collectively, these results suggest that the combination of tea catechins and antioxidant foods can alleviate chronic obesity, indicating that a combination of various ingredients in foods might contribute to reducing chronic obesity.

Perioperative Acetaminophen Dosing in Obese Children

Acetaminophen is a commonly used perioperative analgesic drug in children. The use of a preoperative loading dose achieves a target concentration of 10 mg/L associated with a target analgesic effect that is 2.6 pain units (visual analogue scale 1–10). Postoperative maintenance dosing is used to keep this effect at a steady-state concentration. The loading dose in children is commonly prescribed per kilogram. That dose is consistent with the linear relationship between the volume of distribution and total body weight. Total body weight is made up of both fat and fat-free mass. The fat mass has little influence on the volume of distribution of acetaminophen but fat mass should be considered for maintenance dosing that is determined by clearance. The relationship between the pharmacokinetic parameter, clearance, and size is not linear. A number of size metrics (e.g., fat-free and normal fat mass, ideal body weight and lean body weight) have been proposed to scale clearance and all consequent dosing schedules recognize curvilinear relationships between clearance and size. This relationship can be described using allometric theory. Fat mass also has an indirect influence on clearance that is independent of its effects due to increased body mass. Normal fat mass, used in conjunction with allometry, has proven a useful size metric for acetaminophen; it is calculated using fat-free mass and a fraction (Ffat) of the additional mass contributing to total body weight. However, the Ffat for acetaminophen is large (Ffat = 0.82), pharmacokinetic and pharmacodynamic parameter variability high, and the concentration–response slope gentle at the target concentration. Consequently, total body weight with allometry is acceptable for the calculation of maintenance dose. The dose of acetaminophen is tempered by concerns about adverse effects, notably hepatotoxicity associated with use after 2–3 days at doses greater than 90 mg/kg/day.

Clinical Decision Support for Precision Dosing: Opportunities for Enhanced Equity and Inclusion in Health Care

Precision dosing aims to tailor doses to individual patients with the goal of improving treatment efficacy and avoiding toxicity. Clinical decision support software (CDSS) plays a crucial role in mediating this process, translating knowledge derived from clinical trials and real-world data (RWD) into actionable insights for clinicians to use at the point of care. However, not all patient populations are proportionally represented in clinical trials and other data sources that inform CDSS tools, limiting the applicability of these tools for underrepresented populations. Here, we review some of the limitations of existing CDSS tools and discuss methods for overcoming these gaps. We discuss considerations for study design and modeling to create more inclusive CDSS, particularly with an eye toward better incorporation of biological indicators in place of race, ethnicity, or sex. We also review inclusive practices for collection of these demographic data, during both study design and in software user interface design. Because of the role CDSS plays in both recording routine clinical care data and disseminating knowledge derived from data, CDSS presents a promising opportunity to continuously improve precision dosing algorithms using RWD to better reflect the diversity of patient populations.

Predicting the correct dose in children: Role of computational Pediatric Physiological-based pharmacokinetics modeling tools

The pharmacokinetics (PKs) and safety of medications in particular groups can be predicted using the physiologically-based pharmacokinetic (PBPK) model. Using the PBPK model may enable safe pediatric clinical trials and speed up the process of new drug research and development, especially for children, a population in which it is relatively difficult to conduct clinical trials. This review summarizes the role of pediatric PBPK (P-PBPK) modeling software in dose prediction over the past 6 years and briefly introduces the process of general P-PBPK modeling. We summarized the theories and applications of this software and discussed the application trends and future perspectives in the area. The modeling software's extensive use will undoubtedly make it easier to predict dose prediction for young patients.

Integrating real-world data to accelerate and guide drug development: A clinical pharmacology perspective

Pharmaceutical products in the current accelerated drug development landscape can benefit from tools beyond data generated from randomized control trials. We have seen an abundance of real-world data (RWD) and real-world evidence, driven by the digitalization of healthcare systems and an increased awareness that has inspired a heightened interest in their potential use. Literature review suggest leveraging RWD as a promising tool to answer key questions in the areas of clinical pharmacology and translational science. RWD may increase our understanding regarding the impact of intrinsic (e.g., liver, renal impairment, or genetic polymorphisms) and extrinsic (e.g., food consumption or concomitant medications) factors on the clearance of administered drugs. Changes in clearance may lead to clinically relevant changes in drug exposure that may require clinical management strategies, such as change in dose or dosing regimen. RWD can be leveraged to potentially bridge the gaps among research, development, and clinical care. This paper highlights promising areas of how RWD have been used to complement clinical pharmacology throughout various phases of drug development; case examples will include dose/regimen extrapolation, dose adjustments for special populations (organ impairment, pediatrics, etc.), and pharmacokinetic/pharmacodynamic models to assess impact of prognostic factors on outcomes. In addition, this paper will also juxtapose limitations and promises of utilizing RWD to answer key scientific questions in drug development and articulate challenges posed by quality issues, data availability, and integration from various sources as well as the increased need for multidimensional-omics data that can better guide the development of personalized and predictive medicine.