Population pharmacokinetics of tipifarnib in healthy subjects and adult cancer patients

AIMS: To characterize the population pharmacokinetics of tipifarnib. METHODS: A total of 1083 subjects treated orally with a solution, capsule or tablet formulations of tipifarnib, given as a single dose or as multiple twice-daily doses (range 25-1300 mg) were combined with data from 1, 2 and 24 h intravenous infusions. A total of 3445 concentrations in the index data set were fitted by an open three-compartment linear disposition model with sequential zero-order input into the depot compartment, followed by a first-order absorption process, and lag time, using NONMEM V. The effect of patient covariates on tipifarnib pharmacokinetics was explored. The model was evaluated using goodness of fit plots and relative error measurements for 3894 concentrations in the test data set. Computer simulations were undertaken to evaluate the effect of covariates on tipifarnib pharmacokinetics. RESULTS: Tipifarnib oral bioavailability (26.7%) did not differ between the formulations. The absorption rate from the solution was faster than from the solid forms. Whereas the absorption rate and systemic clearance were more rapid in healthy subjects, the extent of absorption and the steady-state volume of distribution were comparable in cancer patients and healthy subjects. Systemic clearance in cancer patients (21.9 l h-1) exhibited a statistically significant relationship with total bilirubin. The typical volume of the central compartment in cancer patients (54.6 l 70 kg-1) was directly proportional to body weight. The clinical relevance of these covariates in cancer patients is questionable as there was a substantial overlap in simulated concentration-time profiles across a wide range of covariate values. CONCLUSIONS: A population PK approach has been used to integrate data gathered during clinical development and to characterize the pharmacokinetics of tipifarnib. Individualization of dose based on body weight or total bilirubin concentration in adult cancer patients is not warranted.     

Population pharmacokinetics of platinum after nedaplatin administration and model validation in adult patients

AIMS: The pharmacokinetics of unbound platinum after administration of an anticancer drug nedaplatin, cis-diammineglycolateplatinum were examined using population analysis. The relevant covariates and the extent of inter- and intra-individual variability were evaluated. METHODS: In order to clarify the pharmacokinetic profile of nedaplatin, unbound platinum concentrations (789 points) in plasma after intravenous infusion of nedaplatin were obtained from 183 courses for 141 patients. Plasma concentration data were analysed by nonlinear mixed effect modelling using NONMEM to evaluate the population mean parameters and variances for inter- and intra-individual random effects. The final population model was validated by parameter sensitivity analysis using objective function mapping, the bootstrap resampling and a data-splitting technique, i.e. the Jackknife method, and the predictive performance of the final model was evaluated. RESULTS: A two-compartment pharmacokinetic model with zero-order input and first order elimination described the current data well. The significant covariates were creatinine clearance (CLcr) for clearance of platinum (CL) [population mean [95% confidence interval (CI)] CL (l h(-1)) = 4.47 (3.27, 5.67) + 0.0738 (0.0581, 0.0896) x CLcr (CLcr: ml min(-1))] and body weight (BW: kg) for volume of distribution of platinum (Vc) [Vc (l) = 12.0 (7.5, 16.5) + 0.163 (0.081, 0.246) x BW]. Inter-individual variations (CV%, 95% CI) for CL and Vc were 25.5% (20.7, 29.6) and 21.4% (17.0, 24.1), respectively, and intra-individual variation (CV%, 95% CI) was 12.6% (10.5, 14.4). The effects of pretreatment with nedaplatin or other platinum agents on clearance and volume of distribution were also tested, but no significant effect was found. The relationship between the observed and predicted unbound platinum concentration by empirical Bayesian prediction showed good correlation with no bias, suggesting that the final model explains well the observed data in the patients. The mean prediction error and root mean square prediction error (95% CI) were - 0.0164 micro g ml(-1) (- 0.4379, 0.4051) and 0.2155 micro g ml(-1) (not calculable, 0.6523), respectively. The values of mean, standard error and 95% CI for objective function mapping, the bootstrap resampling, the Jackknife estimates and the final model coincided well. CONCLUSIONS: A population pharmacokinetic model was developed for unbound platinum after intravenous infusion of nedaplatin. Only creatinine clearance was found to be a significant covariate of clearance, and BW was found to be a significant covariate of volume of distribution. These population pharmacokinetic estimates are useful for setting initial dosing of nedaplatin using its population mean and can also be used for setting appropriate dosage regimens using empirical Bayesian forecasting.     

Population pharmacokinetics of cisplatin in Asian Indian cancer patients

The aim of this study was to describe population pharmacokinetics of cisplatin in an Indian cancer population. Dosage adjustment based on individual pharmacokinetic parameters is of considerable importance for effective and safe use of drugs. Extensive work on cisplatin and other was carried out in different cancer patient populations, but no data are available in Indian cancer patients. In the present study 154 steady state concentrations of cisplatin were analyzed from 46 patients. Pharmacostatistical work was done by using NONMEM. The covariates evaluated in this study were age, body weight, height, sex, and creatinine clearance. The model found to best describe the data following the FO and FOCE method was: Clearance (CL)?=?θ1*(CLCR/74.92) *EXP (η1) and Volume (V)?=?{θ2 *(AGE/52.3) + θ3*(BSA/1.55)}*EXP (η2). The final model estimates of CL and V estimated by FO method were 3.02?L/h and 2.72?L, respectively, and by FOCE method were 3.39?L/h and 4.48?L, respectively. These parameters are utilized for individualizing the loading and maintenance doses in pediatric patients.     

成年患者替考拉宁群体药动学研究

目的：构建中国成年患者替考拉宁（teicoplanin,TEC）群体药动学（population pharmacokinetics,PPK）模型,探讨TEC药动学参数的影响因素。方法：收集患者的用药信息、血药总浓度、性别、年龄、血清肌酐水平等信息,采用非线性混合效应模型法（nonlinear mixed effect model,NONMEM）建立替考拉宁PPK模型。用图形法、非参数自举法（bootstrap）、正态化预测分布误差法（normalized predictive distribution error,NPDE）进行模型评价。结果：共收集111例成年患者的149个替考拉宁血浆总浓度数据,建立了替考拉宁的一房室PPK模型：CL （L·h^-1）=1.26×（eGFR/82）^0.431,V（L）=83.1,协变量分析显示肌酐清除率（CKD-EPI公式）是影响替考拉宁清除率的重要因素,未发现影响替考拉宁表观分布容积的因素。经验证,最终模型具有良好的拟合优度、稳健率及预测性能。结论：临床可根据患者肌酐清除率（CKD-EPI公式）制定个体化给药方案。     

群体药物动力学及其在儿科中的临床应用

群体药物动力学(PPK)是一门新兴学科。儿科PPK研究主要聚焦于儿童治疗药物监测和个体化给药等。本文综述PPK研究的基本概念、前提条件、方法及其在儿科中的临床应用进展。     

Effect of methotrexate on the pharmacokinetics and renal excretion of cisplatin

Summary The kinetics of platinum in plasma and erythrocytes, and its renal excretion, have been examined in five patients with non-small cell carcinoma of the lung, after treatment with cisplatin 50 mg/m² (Platidiame) and, three weeks later, a combination of 50 mg/m² cisplatin and 40 mg/m² methotrexate. The patients were given 0.9% saline 11 l h prior to drug application.Plasma platinum elimination was biphasic with a short initial phase (t_1/2a 10–31 min) and a long-phase (t_1/2 65–91 h). With the exception of increased AUC values in all five patients 0–8 h after the injection, no significant change in the kinetics of platinum in plasma was found after coadministration of methotrexate.In four of the five patients renal platinum excretion was reduced in the first 6 h after administration of methotrexate. The renal clearance of platinum was 50% lower in those four patients 0–3 h after the injection.With the exception of one patient, no signs of nephrotoxicity were observed after combined drug administration. Other toxic effects were mild and showed no increase after the initial administration of methotrexate.     

Population pharmacokinetics of sirolimus in de novo Chinese adult renal transplant patients

AIMS

This study was aimed at determining the population pharmacokinetics of sirolimus and identifying factors that explain pharmacokinetic variability in de novo Chinese adult renal transplant patients.

METHODS

Data were retrospectively extracted from a formal multicentre clinical trial, which was originally designed to evaluate the safety and efficacy of ciclosporin dose reduction and ciclosporin elimination in patients receiving sirolimus. All patients received 12-month treatment, i.e. induction therapy with ciclosporin, sirolimus and corticosteroids during the first 3 months followed by either ciclosporin dose reduction or ciclosporin discontinuation thereafter. Eight-hundred and four sirolimus trough blood concentrations (C₀) from 112 patients were used to develop a population pharmacokinetic model using the nonmem program. A one-compartment model with first-order absorption and elimination was selected as the base model. The influence of demographic characteristics, biochemical and haematological indices, ciclosporin daily dose, ciclosporin C₀ as well as other commonly used co-medications were explored.

RESULTS

The typical values with interindividual variability for apparent clearance (CL/F) and apparent volume of distribution (V/F) were 10.1 l h⁻¹ (23.8%) and 3670 l (56.7%), respectively. The residual variability was 29.9%. CL/F decreased significantly with silymarin or glycyrrhizin co-therapy in hepatically impaired patients, and with increasing total cholesterol levels or ciclosporin C₀. Moreover, CL/F increased nonlinearly with increasing sirolimus daily dose. The median parameter estimates from a nonparametric bootstrap procedure were comparable and within 5% of the estimates from nonmem.

CONCLUSIONS

These results provide important information for clinicians to optimize sirolimus regimens in Chinese renal transplant patients.     

Population pharmacokinetics of ceftazidime in burn patients

AIM: The aim of this study was to characterize, via a population pharmacokinetic approach, the pharmacokinetics of ceftazidime in burn patients who were not in the acute post-injury phase. METHODS: The development of the pharmacokinetic model was based on data from therapeutic drug monitoring (41 patients, 94 samples). The estimation of population pharmacokinetic parameters and the selection of covariates (age, gender, body weight, size of burn and creatinine plasma concentration) that could affect the pharmacokinetics were performed with a nonlinear mixed effect modelling method. RESULTS: No relationship between covariates and the pharmacokinetic parameters was established with the exception of an inverse-linear relationship between creatinine plasma concentration and ceftazidime total clearance. The total clearance of ceftazidime was 2.72 l h-1[coefficient variation (CV) = 56.3%] and the distribution volume of the central compartment was 0.28 l kg-1 (CV = 13.2%) The transfer rate constants (k12, k 21) between the central and peripheral compartments were 0.06718 h-1 (CV = 87.2%) and 0.001823 h-1 (CV = 82.7%), respectively. From these parameters, the total ceftazidime volume of distribution (10.64 l kg-1) was calculated. CONCLUSION: The population parameters were different from those obtained in a previous study performed in fewer patients and in the early period after burn injury. In our study, the lower ceftazidime clearance could be explained by the relative decrease in ceftazidime elimination in relation to the burn area, and the higher ceftazidime volume of distribution in the presence of interstitial oedema, which could act as a reservoir from which ceftazidime returns slowly to the circulation.     

Pharmacokinetic Modelling of 5-FU Production from Capecitabine—A Population Study in 40 Adult Patients with Metastatic Cancer

Aims: To model the biotransformation steps of 5-FU production from capecitabine and identify patient characteristics that may influence the drug disposition. Methods: Blood samples and demographic data were collected from two phase I studies in which adult patients received oral capecitabine for various malignancies. Capecitabine, 5′-deoxy-5-fluorocytidine (5′-DFCR), 5′-deoxy-5-fluorouridine (5′-DFUR) and 5-fluorouracile (5-FU) concentration-time data were analysed via a population approach using NONMEM. Results: Forty patients and 75 pharmacokinetic time-courses were available for analysis. Capecitabine pharmacokinetics was ascribed to a one compartment model from which 5′-DFCR, 5′-DFUR and 5-FU were sequentially produced. Capecitabine oral absorption was characterized by a rapid first order input (K_a=2.1 ± 0.3 hr⁻¹) with a lag time (0.28 ± 0.11 hr), but related inter-occasion (IOV) and inter-subject (ISV) variabilities for these parameters, 167% and 110%, indicated that this oral absorption was highly variable. The capecitabine CL (CL₁₀ = 218± 18 L/hr, ISV = 18%) and 5′-DFUR elimination rate constant (K₃₄ = 5.3 ± 2.0 hr⁻¹, ISV = 25%) were influenced by total bilirubin (BILT). The elimination rate constant of plasma 5-FU (K₄₀) was 66 ± 24 hr⁻¹ (ISV = 34%).The final pharmacokinetic model was validated using 2000 bootstrap runs and provided non-parametric statistics of the parameters (median, 2.5th and 97.5th percentiles). Conclusions: This study supported the possibility of modelling a complex sequential metabolic pathway which produces pharmacologicaly active compounds from a prodrug. Only BILT significantly influenced the pharmacokinetics but this effect was not considered as relevant for dosing adjustment.     

HPLC法检测大鼠血浆中吡非尼酮的浓度及其药动学研究

目的:建立大鼠血浆吡非尼酮检测的高效液相色谱方法,研究吡非尼酮的药代动力学。方法:血浆经乙酸乙酯,采用ZORBAX SB-C18色谱柱;流动相为乙腈-水-0.1%TFA(三氟乙酸),流速为1.0 mL·min-1;检测波长为318(0～8 min)、246nm(8～10 min)。6只雄性大鼠单剂量灌胃给予15 mg.kg-1吡非尼酮,分别在给药后多点尾静脉采血;用该方法检测血浆中吡非尼酮的浓度。用DAS(数据采集系统)计算药代动力学参数。结果:吡非尼酮浓度在0.025～4.00 mg·L-1范围内线性关系良好(r=0.999 9);定量下限为0.025 mg·L-1;低、中、高3个浓度的相对回收率分别为(100.40±4.66)%、(102.17±4.02)%和(101.12±2.89)%;日内RSD分别为4.6%,3.9%,2.9%,日间RSD分别为5.5%,4.8%,3.7%。大鼠吡非尼酮灌胃后,血浆吡非尼酮在0.39 h达到1.69 mg·L-1的峰值浓度,血浆半衰期为2.21 h。吡非尼酮在大鼠体内符合一级吸收的二室模型。结论:本方法准确可靠、简便快速,适用于大鼠血浆吡非尼酮浓度的测定及其药代动力学研究。     

Population pharmacokinetics of teicoplanin in patients with endocarditis

Teicoplanin is a new glycopeptide antibiotic, active against aerobic and anaerobic gram-positive bacteria. The drug is intended for the treatment of systemic infections including endocarditis. In two U.S. clinical safety and efficacy trials, loading doses of 6 to 30 mg/kg doses of teicoplanin were administered initially to 197 patients, followed by once-a-day treatment of approximately the same doses over several weeks. Blood samples were collected sporadically during the study to monitor serum teicoplanin concentrations either by FPIA or microbiological assay. Nonlinear mixed-effects modeling was performed on these data to characterize the population pharmacokinetics of teicoplanin that were best described by a two-compartment model. Patient body weight, concomitant gram-positive drug treatment, and serum creatinine had significant influences on systemic clearance(CL) of the glycopeptide. In addition, body weight affected the volume of distribution of the central compartment(Vc). Other demographic factors such as age, gender, etc., had no effects. The FPIA assay method was more precise than the microbiological assay.     

老年心衰患者口服地高辛群体药动学模型的建立

目的:应用非线性混合效应模型计算国人老年心衰患者口服地高辛(digxion)群体药动学参数,以促进个体化给药。方法:采用荧光偏振免疫法(FPIA)测定84例老年患者120例次地高辛的血清浓度并收集相关临床指标,运用NONMEM软件建立群体药动学模型。结果:地高辛的药动学符合一室线性开放模型,固定效应参数中,体质量、剂量、血肌酐及尿素氮对参数有影响。最终回归模型中地高辛血药浓度估算值与实测浓度间线性关系良好。结论:用群体药动学模型分析常规监测数据可为老年患者个体化给药提供依据。     

Population pharmacokinetics of raltitrexed in patients with advanced solid tumours

AIMS: To investigate the population pharmacokinetics of raltitrexed in patients with advanced solid tumours and to identify patient covariates contributing to the interpatient variability in the pharmacokinetics of raltitrexed. METHODS: Patient covariate and concentration-time data were collected from patients receiving 0.1-4.5 mg m(-2) raltitrexed during the early clinical trials of raltitrexed. Data were fitted using nonlinear mixed effects modelling to generate population mean estimates for clearance (CL) and central volume of distribution (V). The relationship between individual estimates of the pharmacokinetic parameters and patient covariates was examined and the influence of significant covariates on the population parameter estimates and their variance was investigated using stepwise multiple linear regression. The performance of the developed model was tested using an independent validation dataset. All patient data were pooled in the total cohort to refine the population pharmacokinetic model for raltitrexed. RESULTS: three-compartment pharmacokinetic model was used to fit the concentration-time data of raltitrexed. Estimated creatinine clearance (CL(CR)) was found to influence significantly the CL of raltitrexed and explained 35% of variability in this parameter, whilst body weight (WT) and serum albumin concentrations (ALB) accounted for 56% of the variability in V. Satisfactory prediction (mean prediction error 0.17 micro g l(-1) and root mean square prediction error 4.99 micro g l(-1)) of the observed raltitrexed concentrations was obtained in the model validation step. The final population mean estimates were 2.17 l h(-1)[95% confidence interval (CI) 2.06, 2.28] and 6.36 l (95% CI 6.02, 6.70) for CL and V, respectively. Interpatient variability in the pharmacokinetic parameters was reduced (CL 28%, V 25%) when influential covariates were included in the final model. The following covariate relationships with raltitrexed parameters were described by the final population model: CL (l h(-1)) = 0.54 + 0.02 CL(CR) (ml min(-1)) and V (l) = 6.64 + 0.08 WT (kg) - 0.16 ALB (g l(-1)). CONCLUSIONS: A population pharmacokinetic model has been developed for raltitrexed in patients with advanced cancer. Pharmacokinetic parameters of raltitrexed are markedly influenced by the patient's renal function, body weight and serum albumin levels, which may be taken into account in dose individualization. The use of influential covariates to guide anticancer dosage selection may result in less variability in drug exposure and potentially a better clinical outcome.     

伏立康唑在肾移植患者中的群体药动学研究

目的：建立肾移植患者服用伏立康唑的群体药动学（PopPK）特征,探究影响伏立康唑药动学参数的因素,为临床个体化给药提供依据。方法：回顾性收集84例肾移植患者进行治疗药物监测的谷浓度和生理病理资料,利用Phoenix NLME软件建模,并用VPC法和Bootstrap法进行内部验证。结果：肾移植患者的伏立康唑的药动学特征符合一级消除一室模型,最终PopPK模型为：表观分布容积V（L）=183.69×[1+（HGB-98）×0.016]×exp（η_V）,清除率CL（L·h^-1）=7.24×[1+（ALB-36）×0.037]×exp（η_CL）。结论：血红蛋白（HGB）对V有显著影响,白蛋白（ALB）对CL有显著影响,所建PopPK模型较稳定,可以较好地描述肾移植患者伏立康唑的药动学特征。     

Population pharmacokinetics of dolutegravir in HIV-infected treatment-naive patients

Aim

Dolutegravir is the newest integrase inhibitor approved for HIV treatment and has demonstrated potent antiviral activity in patient populations with a broad range of treatment experience. This analysis aimed to characterize the population pharmacokinetics of dolutegravir in treatment-naive patients and to evaluate the influence of patient covariates.

Methods

A population pharmacokinetic model was developed using a non-linear mixed effect modelling approach based on data from 563 HIV-infected, treatment-naive adult patients in three phase 2/3 trials who received dolutegravir (ranging from 10–50 mg once daily) alone or in combination with abacavir/lamivudine or tenofovir/emtricitabine.

Results

The pharmacokinetics of dolutegravir were adequately described by a linear one compartment model with first order absorption, absorption lag time and first order elimination. Population estimates for apparent clearance, apparent volume of distribution, absorption rate constant and absorption lag time were 0.901 l h^–1, 17.4 l, 2.24 h⁻¹, and 0.263 h, respectively. Weight, smoking status, age and total bilirubin were predictors of clearance, weight was a predictor of volume of distribution and gender was a predictor of bioavailability. However, the magnitude of the effects of these covariates on steady-state dolutegravir plasma exposure was relatively small (<32%) and was not considered clinically significant. Race/ethnicity, HBV/HCV co-infection, CDC classification, albumin, creatinine clearance, alanine aminotransferase or aspartate aminotransferase did not influence the pharmacokinetics of dolutegravir in this analysis.

Conclusions

A population model that adequately characterizes dolutegravir pharmacokinetics has been developed. No dolutegravir dose adjustment by patient covariates is necessary in HIV-infected treatment-naive patients.     

Population pharmacokinetics and bioavailability of tacrolimus in kidney transplant patients

What is already known about this subject

• In spite of its success in ensuring graft survival, therapeutic use of tacrolimus is complicated by its narrow therapeutic index and wide intra- and interpatient variability.
• Some studies of population pharmacokinetics have already been conducted in liver transplant recipients and in paediatric patients.

What this study adds

• Our work determined population pharmacokinetic parameters, in particular bioavailability, in kidney transplant recipients and the relative importance of factors influencing the disposition of tacrolimus.
• Clearance was modelled and days postoperation and corticosteroids dose were significant covariates.

Aims

The use of tacrolimus is complicated by its narrow therapeutic index and wide intra- and interpatient variability. Tacrolimus population pharmacokinetics, including bioavailability, were investigated in an adult kidney transplant cohort to identify patient characteristics that influence pharmacokinetics.

Methods

The database (drug monitoring data) included 83 adult kidney transplant recipients and analysis was performed by a population approach with NONMEM. Data were collected during the first months after transplantation. Patients were administered oral or intravenous tacrolimus as part of a triple immunosuppressive regimen that also included mycophenolate mofetil and corticosteroids. Subsequent doses were adjusted on the basis of clinical evidence of efficacy and toxicity as in routine therapeutic drug monitoring.

Results

A one compartment open model with linear absorption and elimination adequately described the data. The typical value of minimal clearance was 1.8 ± 0.2 l h⁻¹. Clearance increased with time post transplantation to reach 50% of maximal value after 3.8 ± 0.5 days, with a maximal value of 5.6 l h⁻¹. Moreover clearance increased by approximately 1.6 fold (range 0.5–1.6) if the dose of prednisone was >25 mg. The typical value for volume of distribution, V, (98 ± 13 l kg⁻¹) was similar to reported values in kidney transplant patients. The oral bioavailability of tacrolimus was poor and ranged from 11.2 to 19.1%. No covariates significantly influenced V or F.

Conclusions

The number of days postoperation and corticosteroid dose were significant covariates influencing tacrolimus clearance.     

Population pharmacokinetics of clindamycin orally and intravenously administered in patients with osteomyelitis

AIMS

This study was performed to describe clindamycin, administered either orally or intravenously, concentration−time courses to patients with osteomyelitis, to study the effects of different covariates on clindamycin pharmacokinetics and to simulate an optimized administration scheme.

METHODS

Clindamycin concentrations were measured in 50 patients. A total of 122 plasma concentrations were available (58 from oral administration and 64 from i.v. infusion). A population pharmacokinetic model was developed with MONOLIX 4 software.

RESULTS

A one compartment model adequately described the data. Clindamycin clearance increased significantly with body weight (BW). The typical population estimates (interindividual variability) for clearance, volume of distribution and absorption rate constant were 16.2 l h⁻¹ (0.39), 70.2 l and 0.92 h⁻¹, respectively. The bioavailability of the oral form was estimated to be 87.6%. According to BW, theoretical doses needed to reach a C_min of 2 mg l⁻¹ were then calculated.

CONCLUSIONS

The current recommendation of 600 mg three times daily seems to be effective up to 75 kg but the dose should be raised to 900 mg three times daily thereafter. These assumptions should be prospectively confirmed.     

氯氮平在中国精神分裂症人群的群体药物动力学研究

本研究旨在考察口服氯氮平 (clozapine) 在中国精神分裂症患者中的群体药物动力学特征, 探讨各项动力学参数与人口统计学因素及CYP1A2酶基因多态性的关系, 通过建立群体药物动力学模型指导临床个体化给药。研究中采集了临床服用氯氮平的183例精神分裂症患者的626份稳态血样本资料, 随机分组为建模组 (168例) 和外部验证组 (15例)。用非线性混合效应模型 (NONMEM) 程序中的一级评估法 (first-order estimation, FO) 对建模组的数据进行分析, 估算清除率 (CL/F)、表观分布容积 (V/F) 和吸收速率常数 (K_a) 的群体值, 并且定量评价人口统计学指标和CYP1A2酶基因型因素对药物动力学参数的影响。建模中单室一级吸收和消除模型能够较好地拟合数据。最终模型包含了经体表面积归一化的单日剂量 (DBSA) 和吸烟 (SMOK) 因素对CL/F的影响。CL/F (非吸烟组)、V/F和K_a的群体典型值分别为28.5 L·h⁻¹ (5.05%)、1 290 L (16.7%) 和2.26 h⁻¹ (fixed), 相应的个体间变异分别为42.2%和10.0%。研究发现吸烟组的清除率有所上升。观测值与预测值之间的残留误差SD为45.8 μg·L⁻¹。     

Population pharmacokinetics and exploratory pharmacodynamics of ifosfamide according to continuous or short infusion schedules: an n = 1 randomized study

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT
• The optimal infusion duration for ifosfamide remains to be determined.
• No differences according to time of infusion have been identified in traditional pharmacokinetic endpoints, such as area under the curve.
• The impact on pharmacodynamics has never been modelled or correlated with pharmacokinetics.
WHAT THIS STUDY ADDS
• The pharmacokinetics and pharmacodynamics of ifosfamide and its main metabolites can both be modelled with no influence of infusion duration.
• Pharmacodynamic modelling (renal and haematological toxicity) allows further simulations of new schedules with favourable toxicity profiles.  

AIMS

To model the pharmacokinetics and pharmacodynamics of ifosfamide and its key metabolites. The pharmacodynamic parameters included were renal toxicity and myelosuppression measured using urinary β₂-microglobulin (BMG) and absolute neutrophil count (ANC), respectively.  

METHODS

Seventeen patients were enrolled into an n  = 1 randomized trial during two consecutive cycles of ifosfamide 9 g m⁻² during each cycle given by a 3 h or 72 h infusion. Data were analyzed using NONMEM.  

RESULTS

Ifosfamide and metabolite concentration–time profiles were described by a one-compartment open-model with auto-induction of clearance. BMG and ANC time-courses were related to ifosfamide concentration via indirect response models.  

CONCLUSIONS

This modelling allowed the simulation of weekly schedules of flat doses with favourable myelotoxic profiles.