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Population Pharmacokinetic Modelling (population + pharmacokinetic_modelling)
Selected AbstractsCYCLOSPORIN DOSING IN CHILDREN FOLLOWING RENAL TRANSPLANTATION: POPULATION PHARMACOKINETIC MODELLINGNEPHROLOGY, Issue 3 2000McTaggart Sj [source] Population pharmacokinetic modelling of carbamazepine in epileptic elderly patients: implications for dosageJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 3 2006I. B. Bondareva PhD Summary Background:, Proper use of antiepileptic drugs in the elderly involves knowledge of their pharmacokinetics to ensure a patient-specific balance between efficacy and toxicity. However, populations of epileptic patients on chronic carbamazepine (CBZ) therapy which have been studied have included data of relatively few elderly patients. Aims:, The aim of the present study was to evaluate the population pharmacokinetics of CBZ in elderly patients on chronic monotherapy. Methods:, We have used the non-parametric expectation maximization (NPEM) program in the USC*PACK collection of PC programs to estimate individual and population post-induction pharmacokinetics of CBZ in epileptic elderly patients who received chronic CBZ monotherapy. Age-related changes of CBZ population pharmacokinetics were evaluated from routine therapeutic drug monitoring (TDM) data of 37 elderly and 35 younger patients with epilepsy. As a ,historical control' we used previously published population modelling results from 99 young epileptic patients on chronic CBZ monotherapy. In that control group, TDM was performed in the same pharmacokinetic (PK) laboratory, using the same sampling strategy as in the present study, and the same PK population modelling software was used for data analysis. Results and conclusions:, A poor correlation was found between daily CBZ dose and serum concentrations in the elderly patients (r = 0·2, P = 0·25). Probably statistically significant difference in the median values of the CBZ metabolic rate constant (P < 0·001) between elderly and relatively young epileptic patients was found. Our results showed that age-related influences in CBZ pharmacokinetics in elderly patients should be considered in the optimal planning of CBZ dosage regimens. Most elderly patients with epilepsy will usually need CBZ dosages lower than those based on the median population PK parameter values obtained from younger patients. The present population model is also uniquely well suited for the new ,multiple model' design of dosage regimens to hit target therapeutic goals with maximum precision. [source] Population pharmacokinetic modelling of aripiprazole and its active metabolite, dehydroaripiprazole, in psychiatric patientsBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 6 2008Jung-Ryul Kim WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , Almost all reported studies have investigated the pharmacokinetics of aripiprazole in healthy volunteers. , The pharmacokinetics of dehydroaripiprazole have not been identified in a combined model with aripiprazole. WHAT THIS STUDY ADDS , The data on aripiprazole and dehydroaripiprazole in psychiatric patients were modelled jointly using a population approach. , The apparent clearance of aripiprazole in cytochrome P450 (CYP) 2D6 intermediate metabolizers (IM) was approximately 60% of that in CYP2D6 extensive metabolizers (EM) having two functional alleles, but the exposure to dehydroaripiprazole in CYP2D6 IM was similar to that in EM. AIMS The aims of this study were to develop a combined population pharmacokinetic model for both aripiprazole and its active metabolite, dehydroaripiprazole, in psychiatric patients and to identify to what extent the genetic polymorphisms of cytochrome P450 (CYP) enzymes contribute to the variability in pharmacokinetics (PK). METHODS A population pharmacokinetic analysis was performed using NONMEM software based on 141 plasma concentrations at steady state from 80 patients receiving multiple oral doses of aripiprazole (10,30 mg day,1). RESULTS A one-compartment model with first-order kinetics for aripiprazole and dehydroaripiprazole each was developed to describe simultaneously the concentration data. The absorption rate constant was fixed to 1.06 h,1. The typical value of apparent distribution volume of aripiprazole was estimated to be 192 l. Covariate analysis showed that CYP2D6 genetic polymorphisms significantly influenced the apparent clearance of aripiprazole (CL/F), reducing the interindividual variability on CL/F from 37.8% CV (coefficient of variation) to 30.5%. The CL/F in the CYP2D6 IMs was approximately 60% of that in CYP2D6 EMs having two functional alleles. Based on the CYP2D6 genotype, the metabolic ratios were calculated at 0.20,0.34. However, the plasma concentration : dose ratios of dehydroaripiprazole were not different across the CYP2D6 genotype. CONCLUSIONS This population pharmacokinetic model provided an adequate fit to the data for both aripiprazole and dehydroaripiprazole in psychiatric patients. The usefulness of CYP genotyping as an aid to select the starting dose should be further investigated. [source] Population pharmacokinetics of oral diclofenac for acute pain in childrenBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 6 2008Joseph F. Standing WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , Diclofenac is an effective oral analgesic for acute postoperative pain. In adults 25 mg is half as effective as 50 mg, but 50 mg and 100 mg are similarly effective (ceiling effect). Diclofenac has linear pharmacokinetics in this range. , Diclofenac is frequently used ,off-label' in children for acute pain but optimum dosing is unclear (dosing of diclofenac in clinical paediatric studies ranges from 0.5,2.5 mg kg,1). There is currently no licensed oral paediatric formulation of diclofenac. WHAT THIS STUDY ADDS , Using a new diclofenac oral suspension, a dose of 1 mg kg,1 in children aged 1 to 12 years gives a similar exposure to 50 mg in adults; paediatric patients are unlikely to benefit from higher doses. AIMS To develop a population pharmacokinetic model for a new diclofenac suspension (50 mg 5 ml,1) in adult volunteers and paediatric patients, and recommend a dose for acute pain in children. METHODS Blood samples were drawn at the start and end of surgery, and on removal of the venous cannula from 70 children (aged 1 to 12 years, weight 9 to 37 kg) who received a preoperative oral 1 mg kg,1 dose; these were pooled with rich (14 post-dose samples) data from 30 adult volunteers. Population pharmacokinetic modelling was undertaken with NONMEM. The optimum adult dose of diclofenac for acute pain is 50 mg. Simulation from the final model was performed to predict a paediatric dose to achieve a similar AUC to 50 mg in adults. RESULTS A total of 558 serum diclofenac concentrations from 100 subjects was used in the pooled analysis. A single disposition compartment model with first order elimination and dual absorption compartments was used. The estimates of CL/F and VD/F were 53.98 l h,1 70 kg,1 and 4.84 l 70 kg,1 respectively. Allometric size models appeared to predict adequately changes in CL and VD with age. Of the simulated doses investigated, 1 mg kg,1 gave paediatric AUC(0,12 h) to adult 50 mg AUC(0,12 h) ratios of 1.00, 1.08 and 1.18 for ages 1,3, 4,6 and 7,12 years respectively. CONCLUSIONS This study has shown 1 mg kg,1 diclofenac to produce similar exposure in children aged 1 to 12 years as 50 mg in adults, and is acceptable for clinical practice; patients are unlikely to obtain further benefit from higher doses. [source] Population pharmacokinetic modelling of gentamicin and vancomycin in patients with unstable renal function following cardiothoracic surgeryBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 2 2006Christine E. Staatz Aims To describe the population pharmacokinetics of gentamicin and vancomycin in cardiothoracic surgery patients with unstable renal function. Methods Data collected during routine care were analyzed using NONMEM. Linear relationships between creatinine clearance (CLCr) and drug clearance (CL) were identified, and two approaches to modelling changing CLCr were examined. The first included baseline (BCOV) and difference from baseline (DCOV) effects and the second allowed the influence of CLCr to vary between individuals. Final model predictive performance was evaluated using independent data. The data sets were then combined and parameters re-estimated. Results Model building was performed using data from 96 (gentamicin) and 102 (vancomycin) patients, aged 17,87 years. CLCr ranged from 9 to 172 ml min,1 and changes varied from ,76 to 58 ml min,1 (gentamicin) and ,86 to 93 ml min,1 (vancomycin). Inclusion of BCOV and DCOV improved the fit of the gentamicin data but had little effect on that for vancomycin. Inclusion of interindividual variability (IIV) in the influence of CLcr resulted in a poorly characterized model for gentamicin and had no effect on vancomycin modelling. No bias was seen in population compared with individual CL estimates in independent data from 39 (gentamicin) and 37 (vancomycin) patients. Mean (95% CI) differences were 4% (,3, 11%) and 2% (,2, 6%), respectively. Final estimates were: CLGent (l h,1) = 2.81 × (1 + 0.015 × (BCOVCLCr -BCOVCLCr,Median) + 0.0174 × DCOVCLCr); CLVanc (l h,1) = 2.97 × (1 + 0.0205 ×, (CLCr -CLCr,Median)). IIV in CL was 27% for both drugs. Conclusions A parameter describing individual changes in CLcr with time improves population pharmacokinetic modelling of gentamicin but not vancomycin in clinically unstable patients. [source] | ||||||||||