Clinical Pharmacokinetics最新文献

Background and objective: Apixaban is increasingly being used for stroke prevention in patients with end-stage kidney disease with atrial fibrillation undergoing haemodialysis, but no pharmacostatistical model is available for dosage adjustment. This study aimed to develop a population pharmacokinetic model of apixaban in these patients to characterise its dialytic clearance and determine optimal dosing regimens and discontinuation timing before surgery.

Methods: Patients received 2.5 mg of apixaban twice daily for 9 days, followed by 5 mg twice daily for 8 days after a 5-day washout period (NCT02672709). Apixaban concentrations were measured on and off dialysis. A population pharmacokinetic model was developed using parametric and non-parametric methods. Simulations were performed to assess plasmatic exposure and the time to reach clinically relevant apixaban concentrations after treatment discontinuation for seven dosing regimens and 13 dialysis schedules.

Results: A total of 289 apixaban concentrations were measured, including 85 during haemodialysis. The best model was a two-compartment model with first-order elimination. Dialytic clearance was estimated at 1.20 L/h with high inter-individual variability. Apixaban daily exposure was proportional to the total daily dose, independent of dosing frequency and dialysis timing. The standard discontinuation period of 48-72 h before surgery was insufficient to achieve clinically negligible concentrations in patients undergoing haemodialysis.

Conclusions: We propose the first pharmacokinetic model to characterise apixaban clearance in patients with end-stage kidney disease with atrial fibrillation undergoing haemodialysis. Simulations suggest that dialysis timing is not critical for monitoring apixaban, and the discontinuation period before surgery should be extended beyond current recommendations.

Background and objective: Vancomycin is a glycopeptide antibiotic used for the treatment of severe gram-positive infections. Despite decades of clinical experience, optimized dosing for vancomycin in pediatric populations still warrants further investigation. Patients admitted to the pediatric intensive care unit (PICU) after cardiac surgery are often treated with vancomycin in case of (suspected) infection. However, vancomycin dosing in this population is often challenging due to fluctuations in volume status, (temporarily) compromised renal function or the use of diuretics or extracorporeal membrane oxygenation (ECMO). The main objective of this study was to describe vancomycin pharmacokinetics (PK) in pediatric cardiac surgery patients. Secondary objectives were to potentially optimize vancomycin dosing and to assess the suitability of the model to be used for model informed precision dosing (MIPD).

Methods: A retrospective cohort study was performed with patients admitted to the PICU of the Leiden University Medical Center. Clinical data from post-cardiac surgery PICU patients receiving intravenous vancomycin between January 2020 and December 2023 were included in the analysis. Patients received vancomycin 10 mg/kg 4 times daily (qid), after which a trough concentration was generally sampled just before the fourth dose. Pharmacokinetic data were used to develop a population PK model by using a non-linear mixed effects modeling approach (NONMEM). In addition, potential covariates such as renal function, body weight (BW) and post-menstrual age were tested. The final model was used for vancomycin dose optimization using Monte Carlo simulations.

Results: In total, 193 pediatric post-cardiac surgery patients, contributing a total of 706 vancomycin blood samples were included. The 2-compartmental population PK model best described the data. Renal function and BW were identified as significant and clinically relevant covariates on vancomycin PK. Model parameters were: elimination clearance: 4.01 L/min at 70 kg; intercompartmental clearance: 0.425 L/min at 70 kg; central volume of distribution: 56.1 L/70 kg; and peripheral volume of distribution: 21.7 L/70 kg (fixed). Dose simulations suggested a non-linear dosing algorithm, with relatively lower per kg dose for increasing BW to be optimal for our population. Furthermore, the model was considered to be suitable for the (a posteriori) prediction of future vancomycin serum concentrations.

Conclusion: We successfully developed a population PK model for vancomycin in post-cardiac surgery children. Vancomycin PK were shown to be significantly influenced by serum creatinine and BW. Furthermore, we suggest a new vancomycin dosing regimen based on allometric scaling. The developed PK model can be used for model informed precision dosing of vancomycin in pediatric post-cardiac surgery patients.

Scaling approaches are used to describe or predict clearance for paediatric or obese populations from normal-weight adult values. Theoretical allometry assumes the existence of a universal bodyweight-based scaling relationship. Although theoretical allometry is highly disputed, it is commonly applied in pharmacological data analyses and clinical practice. The aim of the current review is to (1) increase pharmacologists' understanding of theoretical allometry to better understand the (implicit) assumptions and (dis)advantages and (2) highlight important methodological considerations with the application of this methodology. Theoretical allometry originated in an empirical, and later debated, observation by Kleiber of a scaling exponent of 0.75 between basal metabolic rate and body mass of mammals. The mathematical framework of West, Brown, and Enquist provides one possible explanation for this value. To date, multiple key assumptions of this framework have been disputed or disproven, and an increasing body of evidence is emerging against the existence of one universal allometric exponent. The promise of ease and universality of use that comes with theoretical approaches may be the reason they are so strongly sought after and defended. However, ecologists have suggested that the theory should move from a 'Newtonian approach', in which physical explanations are sought for a universal law and variability is of minor importance, to a 'Darwinian approach', in which variability is considered of primary importance for which evolutionary explanations can be found. No scientific support was found for the application of allometry for within-species scaling, so the application of basal metabolic rate-based scaling principles to clearance scaling remains unsubstantiated. Recent insights from physiologically based modelling approaches emphasise the interplay between drugs with different properties and physiological variables that underlie drug clearance, which drives the variability in the allometric scaling exponent in the field of pharmacology. To deal with this variability, drug-specific or patient-specific adaptations to theoretical allometric scaling are proposed, that introduce empiric elements and reduce the universality of the theory. The use of allometric scaling with an exponent of 0.75 may hold empirical merit for paediatric populations, except for the youngest individuals (aged ≤ 5 years). Nevertheless, biological interpretations and extrapolation potential attributed to models based on 0.75 allometric scaling are theoretically unfounded, and merits of the empirical application of this function should, as for all models, always be supported by appropriate model validation procedures. In this respect, it is not the value of the allometric exponent but the description and prediction of individual clearance values and drug concentrations that are of primary interest.

Background and objective: Fexofenadine is commonly used as a probe substrate to assess P-glycoprotein (Pgp) activity. While its use in healthy volunteers is well documented, data in older adult and polymorbid patients are lacking. Age- and disease-related physiological changes are expected to affect the pharmacokinetics of fexofenadine. This study aims to investigate the pharmacokinetics of fexofenadine in hospitalized older adult patients as a potential marker of Pgp activity, using data from the OptimAT study (ClinicalTrials.gov identifier: NCT03477331).

Methods: Population pharmacokinetic (popPK) modeling was conducted using data from 449 hospitalized patients with a median age of 71 years (range: 25-97) and 10 healthy volunteers (median age: 23 years, range: 20-36). Fexofenadine plasma concentrations were analyzed using a refined two-compartment model with sequential zero/first-order absorption, while investigating the impact of covariates such as age, renal function, and Pgp inhibitors on fexofenadine pharmacokinetics.

Results: Age, renal insufficiency, and Pgp inhibitors significantly influenced fexofenadine exposure. Renal function was a key factor, with AUC_0-6 increasing by 79% in mild-to-moderate and by 154% in moderate-to-severe renal impairment compared with normal renal function. Co-administration of Pgp inhibitors led to a 35% increase in AUC_0-6. Across chronic kidney disease (CKD) stages, age, and Pgp inhibitor status, fexofenadine AUC_0-6 ratio ranged from 1.15 (stage 1, 20-30 years) to 4.59 (stage 5, 91-100 years, with Pgp inhibitors), relative to a reference subject of 20 years, normal renal function, and no Pgp inhibitors.

Conclusion: Clinicians should consider the risk of Pgp substrate accumulation in older adults, particularly those with advanced renal impairment. We propose typical values stratified by age and renal function to assist in interpreting Pgp phenotyping using fexofenadine exposure, thereby supporting drug optimization in this population. Further studies are needed to explore underlying mechanisms, such as reduced Pgp activity or expression.

The rise in global obesity prevalence has increased the need to understand the pharmacokinetics of drugs in overweight and obese individuals. Tuberculosis remains a significant health challenge, and its treatment outcomes can be influenced by the pharmacokinetic profiles of antitubercular agents. This literature review aims to point out the clinical pharmacokinetics of antitubercular drugs in the overweight and obese patient population, highlighting considerations for potential dosage adjustments. We conducted a comprehensive search of the PubMed US National Library of Medicine from inception to January 2024. Articles focusing on the pharmacokinetics of antitubercular agents used for both drug-susceptible and multidrug-resistant tuberculosis in overweight and obese adults were included. In total, 349 scientific articles were identified and examined for human pharmacokinetic parameters. Of these, 19 were included in this article. To highlight potential differences, pharmacokinetic data for normal-weight tuberculosis patients are also presented, albeit selectively. In general, pharmacokinetic studies of antitubercular agents in overweight and obese individuals are lacking. Fixed-dose combinations often used in the treatment of drug-susceptible tuberculosis are not recommended when treating these population groups. Rather, individual dosing based on therapeutic drug monitoring and the known solubility of the substance should be considered. To improve the management of tuberculosis in overweight and obese patients, there is an urgent need for pharmacokinetic studies and, ultimately, adequate dosing in this patient population, especially given the increasing prevalence of obesity.

Background: Cefotaxime is a widely prescribed cephalosporin antibiotic used to treat various infections. It is mainly eliminated unchanged by the kidney through tubular secretion and glomerular filtration. Therefore, a reduction of kidney function may increase exposure to the drug and induce toxic side effects.

Objectives: The objectives of this study were to develop a physiologically based pharmacokinetic (PBPK) model of cefotaxime in healthy European adults, to mechanistically describe the impact of chronic kidney disease (CKD) on cefotaxime pharmacokinetics, and to assess the applicability of the model to patients requiring intensive care.

Methods: Using PK-Sim^® software, we developed a PBPK model for cefotaxime, including basolateral and apical renal transporters and renal esterases, in healthy subjects and then extrapolated to patients with CKD by incorporating pathophysiological changes and reductions in activity of drug-metabolizing enzymes and transporters into the model. We then evaluated the predictive performance of the model in patients requiring intensive care using clinical routine data.

Results: Model predictions were considered adequate in healthy subjects and patients with CKD, with predicted-to-observed area under the curve ratios within the two-fold acceptance criterion. Mean prediction error and mean absolute prediction error did not exceed ± 30 and 30%, respectively, except in patients with stage 4 CKD, where they were 70.5 and 75.6%, respectively. The model showed good predictive performance when applied to patients requiring intensive care, but its clinical applicability in this population needs to be further evaluated.

Conclusion: We successfully developed whole-body PBPK models to predict cefotaxime pharmacokinetics in different populations. These models represent an additional step toward improving personalized cefotaxime dosing regimens in vulnerable populations.

Background and objective: Telmisartan exhibits significant pharmacokinetic (PK) variability, but it remains unclear whether its PK profile is altered in hypertensive patients. This study aimed to characterize telmisartan PKs by conducting a meta-analysis and developing a pooled population PK model based on data from healthy subjects and hypertensive patients.

Methods: Relevant literature was identified by a systematic approach. Eighteen studies were selected for analysis, which included 394 healthy subjects receiving single doses of telmisartan, 190 healthy subjects receiving repeated doses, along with 295 hypertensive patients receiving repeated doses. Pooled population PK analysis incorporated 20 mean concentration-time profiles from 14 studies. Meta-analyses were performed using OpenMeta-Analyst, and population PK modeling was performed using NONMEM^®.

Results: Repeated telmisartan doses increased peak plasma concentrations. However, other noncompartmental PK parameters remained consistent across healthy and hypertensive populations. Telmisartan PKs were best described using a two-compartment model with first-order absorption and elimination in pooled analysis. Typical PK parameter values for apparent clearance (CL/F), apparent central and peripheral volumes of distribution (V₁/F and V₂/F), absorption rate constant (k_a), and absorption lag time were 18.3 L/h, 20.7 L, 360 L, 0.183 h^-1 and 0.228 h, respectively. Interindividual variabilities in CL/F, V₁/F, and k_a were 84%, 122%, and 106%, respectively. Covariate analysis revealed significantly lower CL/F (63.7%) and V₁/F (90.3%) values in hypertensive patients than healthy subjects.

Conclusion: These findings quantified the variability of telmisartan PK profile and highlighted the differences between healthy individuals and hypertensive patients, suggesting the need for optimized dosage strategies to improve therapeutic outcomes.

Background and objective: We conducted an opportunistic pharmacokinetic study to evaluate the population pharmacokinetics of meropenem, an antimicrobial commonly used to treat Gram-negative infections in adults of different ages, including older adults, and determined optimal dosing regimens.

Methods: A total of 99 patients were included. The population pharmacokinetic models used had two compartments: zero-order input and linear elimination. Covariates evaluated included renal function, body size, age, sex, vasopressor use, and frailty, using the Canadian Study of Health and Aging Clinical Frailty score (in patients aged ≥ 65 years). We simulated optimal dosing regimens by renal function and by age group to achieve therapeutic target attainment.

Results: Participants' ages ranged from 20 to 95 years, with an average age of 57.4 years, and 22% (23/103) were aged ≥ 75 years. Creatinine clearance had the greatest impact on the clearance of meropenem. After accounting for renal function and body size, no other covariates resulted in a significant impact on the pharmacokinetics of meropenem. Simulations indicated that patients with normal renal function achieved ≥ 90% target attainment only for organisms with minimum inhibitory concentrations (MICs) ≤ 4 mg/L using the least strict surrogate target of unbound concentration > MIC (fT_>MIC) for 40% of the dosing interval. For the conservative target fT_>4xMIC for 100% of the dosing interval, extended infusion may be required even for organisms with MICs up to 0.25 mg/L. Patients with renal impairment could achieve ≥ 90% target attainment for more resistant organisms, but extended infusion did not increase the MICs up to which target attainment could be achieved.

Conclusions: Meropenem dosing should be based on renal function rather than age. For patients without renal impairment, extended infusion may increase the probability of target attainment.

Background and objective: Limited information is available on the pharmacokinetics of rifampicin (RIF) along with that of its active metabolite, 25-deacetylrifampicin (25-dRIF). This study aimed to analyse the pharmacokinetic data of RIF and 25-dRIF collected in adult patients treated for tuberculosis.

Methods: In adult patients receiving 10 mg/kg of RIF as part of a standard regimen for drug-susceptible pulmonary tuberculosis enrolled in the Opti-4TB study, plasma RIF and 25-dRIF concentrations were measured at various occasions. The RIF and 25-dRIF concentrations were modelled simultaneously by using a population approach. The area under the concentration-time curves of RIF and 25-dRIF were estimated on each occasion of therapeutic drug monitoring. Optimal RIF exposure, defined as an area under the concentration-time curve over 24 hours/minimum inhibitory concentration > 435, was assessed.

Results: Concentration data (247 and 243 concentrations of RIF and 25-dRIF, respectively) were obtained in 35 patients with tuberculosis (10 women, 25 men). Mycobacterium tuberculosis minimum inhibitory concentration ranged from 0.06 to 0.5 mg/L (median = 0.25 mg/L). The final model was a two-compartment model including RIF metabolism into 25-dRIF and auto-induction. Exposure to 25-dRIF was low, with a mean area under the concentration-time curve over 24 h ratio of 25-dRIF/RIF of 14 ± 6%. The area under the concentration-time curve over 24 h of RIF and 25-dRIF rapidly decreased during therapy, with an auto-induction half-life of 1.6 days. Optimal RIF exposure was achieved in only six (19.3%) out of 31 patients upon first therapeutic drug monitoring.

Conclusions: Exposure to both RIF and 25-dRIF rapidly decreased during tuberculosis therapy. The contribution of 25-dRIF to overall drug exposure was low. Attainment of the target area under the concentration-time curve over 24 hours/minimum inhibitory concentration for RIF was poor, supporting an increased RIF dosage as an option to compensate for auto-induction.

As people age, the efficiency of various regulatory processes that ensure proper communication between cells and organs tends to decline. This deterioration can lead to difficulties in maintaining homeostasis during physiological stress. This includes but is not limited to cognitive impairments, functional difficulties, and issues related to caregivers which contribute significantly to medication errors and non-adherence. These factors can lead to higher morbidity, extended hospital stays, reduced quality of life, and even mortality. The decrease in homeostatic capacity varies among individuals, contributing to the greater variability observed in geriatric populations. Significant pharmacokinetic and pharmacodynamic alterations accompany ageing. Pharmacokinetic changes include decreased renal and hepatic clearance and an increased volume of distribution for lipid-soluble drugs, which prolong their elimination half-life. Pharmacodynamic changes typically involve increased sensitivity to various drug classes, such as anticoagulants, antidiabetic and psychotropic medications. This review examines the primary age-related physiological changes in geriatrics and their impact on the pharmacokinetics and pharmacodynamics of medications.