A Physiologically Based Pharmacokinetic Model for Predicting Diazepam Pharmacokinetics after Intravenous, Oral, Intranasal, and Rectal Applications

Expansion of a Pharmacokinetic Model for Diazepam to Characterize Real-World IV and Oral Data in Children With and Without Obesity

Diazepam is a benzodiazepine approved for use in adults and children. The label incorporates recommended dosing for status epilepticus in children. Published population pharmacokinetic (PK) modeling recommends an intravenous bolus dose of 0.2 mg/kg capped at 8 mg to reach the suggested target exposure of 200-600 ng/mL at 10 min post dose in children up to 17 years of age. This model was developed for children generally without obesity based on IV data, and it is unclear how increased body weight may affect exposure or target attainment given capped dosing. Diazepam concentrations after IV or oral administration for 61 children aged 2.5 to 20.6 years were used to externally evaluate the model including the addition of fixed oral absorption parameters. Then, PK parameters were re-estimated with the external population alone and again in combination with the original population. Re-estimated parameters from the combined population were used to simulate recommended dosing for children with and without obesity. The external dataset included 88 plasma concentrations from 61 children (54 with obesity) receiving diazepam per standard of care. The external evaluation resulted in 34.5% of predicted values within 30% of the observed concentration. Parameter re-estimation resulted in increased central volume of distribution (26% increase from a previous model), reduced peripheral volume of distribution and intercompartmental clearance, and similar clearance estimates. Simulations demonstrated that dosing caps may prevent children with obesity from reaching the suggested target exposure that is recommended for the treatment of status epilepticus. Further study is needed to evaluate the target exposure range in this population.

Utilizing Physiologically Based Pharmacokinetic Models to Support Rational Medication in Chinese Elderly Population

Background

China is undergoing a pronounced shift towards an aging society, wherein the elderly constitute a prominent demographic relying significantly on medications. The imperative of administering rational medication to the elderly has gained considerable importance and warrants focused attention. The availability of pharmacokinetic (PK) data specific to the elderly is paramount for supporting informed medication practices. Unfortunately, studies addressing PK in the elderly are both infrequent and intricate, contributing to a lack of crucial data essential for tailoring personalized and rational medication approaches.

Methods

This study aimed to address this deficiency by employing the Physiologically Based Pharmacokinetic (PBPK) model, with the goal of supplying critical data to support rational medication strategies for the elderly. Additionally, we extended the application of PBPK models to Therapeutic Drug Monitoring (TDM) through the examination of four neuropsychiatric drugs.

Results

The PBPK models for 50 drugs in young and middle-aged Chinese adults were validated using clinical trial data. Simulated concentration-time curves closely matched the observed data, with Cmax and AUC ratios within 0.5-2.0. For Chinese elderly, PBPK models for four drugs (ticagrelor, rivaroxaban, alprazolam, midazolam) showed strong agreement with observed data. Comparing PK profiles of 50 drugs, no significant differences were found between elderly and younger adults. Dosage recommendations for four neuropsychiatric drugs in the elderly were provided based on simulation results, ensuring therapeutic effectiveness and safety.

Conclusion

In conclusion, PBPK models for 50 commonly prescribed drugs within the Chinese elderly population were developed, tackling general data gaps associated with these specific medications. Medication plans were developed specifically tailored for the elderly population, presenting an alternative methodology and perspective for the implementation of individualized and rational medication practices.

Predicting Food-Drug Interactions between Piperine and CYP3A4 Substrate Drugs Using PBPK Modeling

Piperine has been reported to inhibit the enzyme activity of cytochrome P450 (CYP) 3A4. The aim of this study was to develop and validate a physiologically based pharmacokinetic (PBPK) model for piperine and to predict potential food-drug interactions (FDIs) between piperine and CYP3A4 substrate drugs using these models. The PBPK model for piperine was successfully developed and validated. Using this model, FDIs with ten CYP3A4 substrate drugs were simulated. The predicted area under the curve (AUC) ratios (with and without piperine, following a 7-day intake of 20 mg/day) for six drugs were found to exceed 1.25, with significant increases in AUC observed for ritonavir (31%), nifedipine (34%), cyclosporine (35%), triazolam (36%), alfentanil (39%), and simvastatin (59%) in humans. These findings suggest that caution should be exercised when consuming amounts of black pepper equivalent to a daily intake of 20 mg piperine during treatment with CYP3A4 substrate drugs, as it may significantly alter their pharmacokinetics.

A Comprehensive Physiologically Based Pharmacokinetic Model for Predicting Vildagliptin Pharmacokinetics: Insights into Dosing in Renal Impairment

Physiologically based pharmacokinetic (PBPK) modeling is of great importance in the field of medicine. This study aims to construct a PBPK model, which can provide reliable drug pharmacokinetic (PK) predictions in both healthy and chronic kidney disease (CKD) subjects. To do so, firstly a review of the literature was thoroughly conducted and the PK information of vildagliptin was collected. PBPK modeling software, PK-Sim®, was then used to build and assess the IV, oral, and drug-specific models. Next, the average fold error, visual predictive checks, and predicted/observed ratios were used for the assessment of the robustness of the model for all the essential PK parameters. This evaluation demonstrated that all PK parameters were within an acceptable limit of error, i.e., 2 fold. Also to display the influence of CKD on the total and unbound AUC (the area under the plasma concentration-time curve) and to make modifications in dose, the analysis results of the model on this aspect were further examined. This PBPK model has successfully depicted the variations of PK of vildagliptin in healthy subjects and patients with CKD, which can be useful for medical practitioners in dosage optimization in renal disease patients.

Characterization of Pediatric Rectal Absorption, Drug Disposition, and Sedation Level for Midazolam Gel Using Physiologically Based Pharmacokinetic/Pharmacodynamic Modeling

This study aims to explore and characterize the role of pediatric sedation via rectal route. A pediatric physiologically based pharmacokinetic-pharmacodynamic (PBPK/PD) model of midazolam gel was built and validated to support dose selection for pediatric clinical trials. Before developing the rectal PBPK model, an intravenous PBPK model was developed to determine drug disposition, specifically by describing the ontogeny model of the metabolic enzyme. Pediatric rectal absorption was developed based on the rectal PBPK model of adults. The improved Weibull function with permeability, surface area, and fluid volume parameters was used to extrapolate pediatric rectal absorption. A logistic regression model was used to characterize the relationship between the free concentrations of midazolam and the probability of sedation. All models successfully described the PK profiles with absolute average fold error (AAFE) < 2, especially our intravenous PBPK model that extended the predicted age to preterm. The simulation results of the PD model showed that when the free concentrations of midazolam ranged from 3.9 to 18.4 ng/mL, the probability of "Sedation" was greater than that of "Not-sedation" states. Combined with the rectal PBPK model, the recommended sedation doses were in the ranges of 0.44-2.08 mg/kg for children aged 2-3 years, 0.35-1.65 mg/kg for children aged 4-7 years, 0.24-1.27 mg/kg for children aged 8-12 years, and 0.20-1.10 mg/kg for adolescents aged 13-18 years. Overall, this model mechanistically quantified drug disposition and effect of midazolam gel in the pediatric population, accurately predicted the observed clinical data, and simulated the drug exposure for sedation that will inform dose selection for following pediatric clinical trials.

Advances and future perspectives of intranasal drug delivery: A scientometric review

Intranasal drug delivery is as a noninvasive and efficient approach extensively utilized for treating the local, central nervous system, and systemic diseases. Despite numerous reviews delving into the application of intranasal drug delivery across biomedical fields, a comprehensive analysis of advancements and future perspectives remains elusive. This review elucidates the research progress of intranasal drug delivery through a scientometric analysis. It scrutinizes several challenges to bolster research in this domain, encompassing a thorough exploration of entry and elimination mechanisms specific to intranasal delivery, the identification of drugs compatible with the nasal cavity, the selection of dosage forms to surmount limited drug-loading capacity and poor solubility, and the identification of diseases amenable to the intranasal delivery strategy. Overall, this review furnishes a perspective aimed at galvanizing future research and development concerning intranasal drug delivery.

A novel physiologically based pharmacokinetic model of rectal absorption, evaluated and verified using clinical data on 10 rectally administered drugs

We present a physiologically based pharmacokinetic (PBPK) model simulating systemic drug concentrations following administration to the human rectum. Rectum physiology is parameterized based on literature data. The model utilizes in vitro release (IVRT) profiles from which drug mass transfer through the rectal fluid and tissue and into the systemic circulation are predicted. Due to a lack of data, rectal fluid and tissue absorption parameters are predicted either from colon absorption, with modifications relevant to rectal physiology, or optimized. The PBPK model is evaluated by simulating 29 clinical studies for 10 drugs. For 8 drugs (diazepam, diclofenac, indomethacin, naproxen, paracetamol, pentobarbital, phenobarbital and theophylline) the bias (average fold error, AFE) and precision (absolute average fold error, AAFE) of Cmax, AUC0-t and AUC0-inf simulations range from 0.87 to 2.22, indicating good agreement with observed values. For prochlorperazine and promethazine, the AFEs and AAFEs of Cmax predictions are 1.30 and 2.52, respectively. TheAUC0-t and AUC0-inf are overpredicted for both compounds(AFEs and AAFEs from 2.66 to 4.90). This results from a lack of reliable elimination data for prochlorperazine and the relevance of the IVRT profiles used in the promethazine model. The model paves the way for more mechanistic rectal drug absorption studies and virtual bioequivalence methods for rectal drug products.

Physiologically Based Pharmacokinetic Model To Predict Metoprolol Disposition in Healthy and Disease Populations

The evolution in the development of drugs has increased the popularity of physiologically based pharmacokinetic (PBPK) models. This study seeks to assess the PK of metoprolol in populations with healthy, chronic kidney disease (CKD), and acute myocardial infarction (AMI) conditions by developing and evaluating PBPK models. An extensive literature review for identifying and selecting plasma concentration vs time profile data and other drug-related parameters was undergone for their integration into the PK-Sim program followed by the development of intravenous, oral, and diseased models. The developed PBPK model of metoprolol was then evaluated using the visual predictive checks, mean observed/predicted ratios (Robs/pre), and average fold error for all PK parameters, i.e., the area under the curve (AUC), maximal plasma concentration, and clearance. The model evaluation depicted that none of the PK parameters were out of the allowed range (2-fold error) in the case of the mean Robs/pre ratios. The model anticipations were executed to determine the influence of diseases on unbound and total AUC after the application of metoprolol in healthy, moderate, and severe CKD. The dosage reductions were also suggested based on differences in unbound and total AUC in different stages of CKD. The developed PBPK models have successfully elaborated the PK changes of metoprolol occurring in healthy individuals and those with renal and heart diseases (CKD & AMI), which may be fruitful for dose optimization among diseased patients.

Predicting Hydroxychloroquine Clearance in Healthy and Diseased Populations Using a Physiologically Based Pharmacokinetic Approach

Hydroxychloroquine (HCQ), a congener of chloroquine, is widely used in prophylaxis and the treatment of malaria, and also as a cure for rheumatoid arthritis, systemic lupus erythematosus, and various other diseases. Physiologically based pharmacokinetic modeling (PBPK) has attracted great interest in the past few years in predicting drug pharmacokinetics (PK). This study focuses on predicting the PK of HCQ in the healthy population and extrapolating it to the diseased populations, i.e., liver cirrhosis and chronic kidney disease (CKD), utilizing a systematically built whole-body PBPK model. The time vs. concentration profiles and drug-related parameters were obtained from the literature after a laborious search and in turn were integrated into PK-Sim software for designing healthy intravenous, oral, and diseased models. The model's evaluation was performed using observed-to-predicted ratios (Robs/Rpre) and visual predictive checks within a 2-fold error range. The healthy model was then extrapolated to liver cirrhosis and CKD populations after incorporating various disease-specific pathophysiological changes. Box-whisker plots showed an increase in AUC_0-t in liver cirrhosis, whereas a decrease in AUC_0-t was seen in the CKD population. These model predictions may assist clinicians in adjusting the administered HCQ doses in patients with different degrees of hepatic and renal impairment.

Application of a physiologically based pharmacokinetic model in predicting captopril disposition in children with chronic kidney disease

Over the last several decades, angiotensin-converting enzyme inhibitors (ACEIs) have been a staple in the treatment of hypertension and renovascular disorders in children. One of the ACEIs, captopril, is projected to have all the benefits of traditional vasodilators. However, conducting clinical trials for determining the pharmacokinetics (PK) of a drug is challenging, particularly in pediatrics. As a result, modeling and simulation methods have been developed to identify the safe and effective dosages of drugs. The physiologically based pharmacokinetic (PBPK) modeling is a well-established method that permits extrapolation from adult to juvenile populations. By using SIMCYP simulator, as a modeling platform, a previously developed PBPK drug-disease model of captopril was scaled to renally impaired pediatrics population for predicting captopril PK. The visual predictive checks, predicted/observed ratios (ratio_pred/obs), and the average fold error of PK parameters were used for model evaluation. The model predictions were comparable with the reported PK data of captopril in mild and severe chronic kidney disease (CKD) patients, as the mean ratio_pred/obs C_max and AUC_0-t were 1.44 (95% CI 1.07 - 1.80) and 1.26 (95% CI 0.93 - 1.59), respectively. The successfully developed captopril-CKD pediatric model can be used in suggesting drug dosing in children diagnosed with different stages of CKD.

Physiologically-Based Pharmacokinetic and Pharmacodynamic Modeling of Diazepam: Unbound Interstitial Brain Concentrations Correspond to Clinical Endpoints

Benzodiazepines induce a series of clinical effects by modulating subtypes of GABA_A receptors in the central nervous system. The brain concentration-time profiles of diazepam that correspond to these effects are unknown, but can be estimated with physiologically-based pharmacokinetic (PBPK) modeling. In this study, a PBPK model for the 1,4-benzodiazepines diazepam and nordiazepam was developed from plasma concentration time-courses with PK-Sim^® software to predict brain concentrations. The PBPK model simulations accurately parallel plasma concentrations from both an internal model training data set and an external data set for both intravenous and peroral diazepam administrations. It was determined that the unbound interstitial brain concentration-time profiles correlated with diazepam pharmacodynamic endpoints. With a 30 mg intravenous diazepam dose, the peak unbound interstitial brain concentration from this model is 160 nM at 2 minutes and 28.9 nM at 120 minutes. Peak potentiation of recombinant GABA_A receptors composed of α1β2γ2s, α2β2γ2s, and α5β2γ2s subunit combinations that are involved in diazepam clinical endpoints is 108%, 139% and 186%, respectively, with this intravenous dose. With 10 mg peroral administrations of diazepam delivered every 24 hours, steady-state peak and trough unbound interstitial brain diazepam concentrations are 22.3 ± 7.5 nM and 9.3 ± 3.5 nM. Nordiazepam unbound interstitial brain concentration is 36.1 nM at equilibrium with this diazepam dosing schedule. Pharmacodynamic models coupled to the diazepam unbound interstitial brain concentrations from the PBPK analysis account for electroencephalographic drug effect, change in 13-30 Hz electroencephalographic activity, amnesia incidence, and sedation score time-courses from human subjects. This article is protected by copyright. All rights reserved.

In Vitro and In Vivo Bioequivalence Study of 3D-Printed Instant-Dissolving Levetiracetam Tablets and Subsequent Personalized Dosing for Chinese Children Based on Physiological Pharmacokinetic Modeling

Recently, the development of Binder Jet 3D printing technology has promoted the research and application of personalized formulations, which are especially useful for children’s medications. Additionally, physiological pharmacokinetic (PBPK) modeling can be used to guide drug development and drug dose selection. Multiple technologies can be used in combination to increase the safety and effectiveness of drug administration. In this study, we performed in vivo pharmacokinetic experiments in dogs with preprepared 3D-printed levetiracetam instant-dissolving tablets (LEV-IDTs). Bioequivalence analysis showed that the tablets were bioequivalent to commercially available preparations (Spritam^®) for dogs. Additionally, we evaluated the bioequivalence of 3D-printed LEV-IDTs with Spritam^® by a population-based simulation based on the established PBPK model of levetiracetam for Chinese adults. Finally, we established a PBPK model of oral levetiracetam in Chinese children by combining the physiological parameters of children, and we simulated the PK (pharmacokinetics) curves of Chinese children aged 4 and 6 years that were administered the drug to provide precise guidance on adjusting the dose according to the effective dose range of the drug. Briefly, utilizing both Binder jet 3D printing technology and PBPK models is a promising route for personalized drug delivery with various age groups.