scholarly journals A preclinical study to model taurine pharmokinetics in the undernourished rat

2018 ◽  
Vol 119 (7) ◽  
pp. 826-835 ◽  
Author(s):  
Ana Catalán-Latorre ◽  
Amparo Nácher ◽  
Virginia Merino ◽  
Octavio Díez ◽  
Matilde Merino Sanjuán
Keyword(s):  
Preclinical Study ◽  
Population Pharmacokinetic ◽  
Process Data ◽  
Internal Organs ◽  
Linear Absorption ◽  
First Order Kinetics ◽  
Protein Energy ◽  
Non Linear ◽  
Linear Elimination ◽  
Passive Absorption

AbstractMalnutrition is a common feature of chronic and acute diseases, often associated with a poor prognosis, including worsening of clinical outcome, owing, among other factors, to dysfunction of the most internal organs and systems affecting the absorption, metabolism and elimination of drugs and nutrients. Taurine is involved in numerous biological processes and is required in increased amounts in response to pathological conditions. The aim of this study was to describe the behaviour of taurine in well-nourished (WN) rats and to analyse the influence of protein–energy undernutrition on the pharmacokinetic (PK) parameters of taurine, using a PK model. Wistar rats were randomly distributed into two groups, WN and undernourished (UN), and taurine was administered intravenously or orally at different doses: 1, 10 and 100 mg. Population pharmacokinetic modelling of plasma levels was performed using the NONMEM 7.2 program. Several distribution and absorption models were explored in combination with dose and/or time covariate effects. Covariates such as nutritional status, serum albumin, body weight and score of undernutrition were used. A two-compartment population pharmacokinetic model with zero-order endogenous formation, passive absorption, first-order kinetics distribution and non-linear elimination with parallel Michaelis–Menten excretion and reabsorption processes best described taurine pharmacokinetics. Undernutrition acted as a covariate reducing theVmaxof the active elimination process. Data analysis showed linear absorption and distribution, and non-linear elimination processes for taurine. Elimination of taurine was reduced in UN animals, suggesting that the reabsorption process via the secretion transporter was modified in that group.

scholarly journals Pregnancy-Related Effects on Nelfinavir-M8 Pharmacokinetics: a Population Study with 133 Women

2006 ◽  
Vol 50 (6) ◽  
pp. 2079-2086 ◽  
Author(s):  
Déborah Hirt ◽  
Jean-Marc Treluyer ◽  
Vincent Jullien ◽  
Ghislaine Firtion ◽  
Hélène Chappuy ◽  
...  
Keyword(s):  
Population Study ◽  
Time Course ◽  
Plasma Concentrations ◽  
Elimination Rate ◽  
Concomitant Administration ◽  
Individual Characteristics ◽  
Individual Treatment ◽  
Therapeutic Drug ◽  
Population Pharmacokinetic ◽  
Linear Absorption

ABSTRACT A relationship between nelfinavir antiretroviral efficacy and plasma concentrations has been previously established. As physiological changes associated with pregnancy have a large impact on the pharmacokinetics of many drugs, a nelfinavir population study with women was developed, and the large intersubject variability was analyzed in order to optimize individual treatment schedules for this drug during pregnancy. A population pharmacokinetic model was developed in order to describe the concentration time course of nelfinavir and its metabolite M8 in pregnant and nonpregnant women. Individual characteristics, such as age, body weight, and weeks of gestation or delivery, which may influence nelfinavir-M8 pharmacokinetics were investigated. Data from therapeutic drug monitoring in 133 women treated with nelfinavir were retrospectively analyzed with NONMEM. Nelfinavir pharmacokinetics was described by a one-compartment model with linear absorption and elimination and M8 produced from the nelfinavir central compartment. Mean pharmacokinetic estimates and the corresponding intersubject percent variabilities for a nonpregnant woman were the following: absorption rate, 0.83 h−1; absorption lag time, 0.85 h; apparent nelfinavir elimination clearance (CL10/F), 35.5 liters/h (50%); apparent volume of distribution (V/F), 596 liters (118%); apparent formation clearance to M8 (CL1M/F), 0.65 liters/h (69%); and M8 elimination rate constant (k M0), 3.3 h−1 (59%). During pregnancy, we observed significant increases in nelfinavir (44.4 liters/h) and M8 (5 h−1) elimination but unchanged nelfinavir transformation clearance to M8, suggesting an induction of CYP3A4 but no effect on CYP2C19. Apparent nelfinavir clearance and volume showed a twofold increase on the day of delivery, suggesting a decrease in bioavailability on this day. The M8 elimination rate was increased by concomitant administration of nonnucleoside reverse transcriptase inhibitors. A trough nelfinavir plasma concentration above 1 mg/liter was previously shown to improve the antiretroviral response. The Bayesian individual pharmacokinetic estimates suggested that the dosage should not be changed in pregnant women but may be doubled on the day of delivery.

Selection and self-locking of modes in He-Ne lasers with non-linear absorption

1968 ◽  
Vol 4 (5) ◽  
pp. 339-339 ◽  
Author(s):  
V. Chebotayev ◽  
I. Beterov ◽  
V. Lisitsyn
Keyword(s):  
Linear Absorption ◽  
Non Linear

scholarly journals Characterizing the non-linear pharmacokinetics of miltefosine in paediatric visceral leishmaniasis patients from Eastern Africa

2020 ◽  
Vol 75 (11) ◽  
pp. 3260-3268
Author(s):  
Semra Palić ◽  
Anke E Kip ◽  
Jos H Beijnen ◽  
Jane Mbui ◽  
Ahmed Musa ◽  
...  
Keyword(s):  
Visceral Leishmaniasis ◽  
Cumulative Dose ◽  
Drug Exposure ◽  
Compartment Model ◽  
Eastern Africa ◽  
Model Following ◽  
Two Compartment Model ◽  
Non Linear ◽  
Linear Elimination ◽  
Dosing Regimens

Abstract Background Conventional miltefosine dosing (2.5 mg/kg/day) for treatment of visceral leishmaniasis (VL) is less effective in children than in adults. A higher allometric dose (median 3.2 mg/kg/day) was therefore investigated in paediatric VL patients in Eastern Africa. Results of this trial showed an unforeseen, lower than dose-proportional increase in exposure. Therefore, we performed a pooled model-based analysis of the paediatric data available from both dosing regimens to characterize observed non-linearities in miltefosine pharmacokinetics (PK). Methods Fifty-one children with VL were included in this analysis, treated with either a conventional (n = 21) or allometric (n = 30) miltefosine dosing regimen. PK data were analysed using non-linear mixed-effects modelling. Results A two-compartment model following first-order absorption and linear elimination, with two separate effects on relative oral bioavailability, was found to fit these data best. A 69% lower bioavailability at treatment start was estimated, presumably due to initial malnourishment and malabsorption. Stagnation in miltefosine accumulation in plasma, hampering increased drug exposure, was related to the increase in cumulative dose (mg/kg/day). However, the allometric regimen increased exposure 1.7-fold in the first treatment week and reduced the time to reach the PK target by 17.4%. Conclusions Miltefosine PK in children suffering from VL are characterized by dose-dependent non-linearities that obstruct the initially expected exposure levels. Bioavailability appeared to be affected by the cumulative dose, possibly as a consequence of impaired absorption. Despite this, allometric dosing led to a faster target achievement and increased exposure compared with conventional dosing.

scholarly journals Population Pharmacokinetics of Piperacillin following Continuous Infusion in Critically Ill Patients and Impact of Renal Function on Target Attainment

2020 ◽  
Vol 64 (7) ◽  
Author(s):  
Vibeke Klastrup ◽  
Anders Thorsted ◽  
Merete Storgaard ◽  
Steffen Christensen ◽  
Lena E. Friberg ◽  
...  
Keyword(s):  
Continuous Infusion ◽  
Critically Ill ◽  
Critically Ill Patients ◽  
Bacterial Infections ◽  
Population Pharmacokinetic ◽  
Target Attainment ◽  
Content Type ◽  
Daily Dose ◽  
Linear Elimination ◽  
Severe Infections

ABSTRACT Pharmacokinetic changes are often seen in patients with severe infections. Administration by continuous infusion has been suggested to optimize antibiotic exposure and pharmacokinetic/pharmacodynamic (PK/PD) target attainment for β-lactams. In an observational study, unbound piperacillin concentrations (n = 196) were assessed in 78 critically ill patients following continuous infusion of piperacillin-tazobactam (ratio 8:1). The initial dose of 8, 12, or 16 g (piperacillin component) was determined by individual creatinine clearance (CRCL). Piperacillin concentrations were compared to the EUCAST clinical breakpoint MIC for Pseudomonas aeruginosa (16 mg/liter), and the following PK/PD targets were evaluated: 100% free time (fT) > 1× MIC and 100% fT > 4× MIC. A population pharmacokinetic model was developed using NONMEM 7.4.3 consisting of a one-compartment disposition model with linear elimination separated into nonrenal and renal (linearly increasing with patient CRCL) clearances. Target attainment was predicted and visualized for all individuals based on the utilized CRCL dosing algorithm. The target of 100% fT > 1× MIC was achieved for all patients based on the administered dose, but few patients achieved the target of 100% fT > 4× MIC. Probability of target attainment for a simulated cohort of patients showed that increasing the daily dose by 4-g increments (piperacillin component) did not result in substantially improved target attainment for the 100% fT > 4× MIC target. To conclude, in patients with high CRCL combined with high-MIC bacterial infections, even a continuous infusion (CI) regimen with a daily dose of 24 g may be insufficient to achieve therapeutic concentrations.

Non-linear elimination processes of theophylline

1983 ◽  
Vol 24 (1) ◽  
pp. 71-78 ◽  
Author(s):  
U. Gundert-Remy ◽  
R. Hildebrandt ◽  
N. Hengen ◽  
E. Weber
Keyword(s):  
Non Linear ◽  
Linear Elimination

Population Pharmacokinetics of Siplizumab (MEDI-507), a Humanized Anti-CD2 Monoclonal Antibody, in Cancer Patients.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2670-2670
Author(s):  
Chunlin Chen ◽  
John E Janik ◽  
Karen Kaucic ◽  
Lorin Roskos ◽  
Bahija Jallal ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Body Weight ◽  
Serum Concentration ◽  
Dose Escalation ◽  
Pharmacokinetic Parameters ◽  
Population Pharmacokinetic ◽  
Serum Concentrations ◽  
Concentration Data ◽  
Non Linear ◽  
Volumes Of Distribution

Abstract Abstract 2670 Poster Board II-646 Introduction: Siplizumab, a humanized IgG1k class monoclonal antibody that targets CD2 expressing T-and NK-cells, was evaluated in phase I dose-escalation trials in patients with CD2-positive lymphoproliferative disorder. The objective of this study was to develop a population pharmacokinetic (PK) model for siplizumab and identify covariates that could explain the variability in siplizumab pharmacokinetic parameters. Methods: A Phase 1, open label, dose-escalation study was conducted in 29 patients (14 males/15 females, age range 34–79 years) who received 0.2–4.8 mg/kg of siplizumab as 1-3 consecutive daily doses every 14 days for a total of 1-8 cycles. Siplizumab serum concentration data was analyzed using a nonlinear mixed effects modeling approach with software (NONMEM). Based on exploratory analysis, 1-and 2-compartment non-linear models were evaluated. Demographic covariates including body weight, age, sex and race (Caucasian/Black/Asian) were screened using Generalized Additive Model (GAM) analysis. Covariates selected during the GAM analysis were further tested for significance in NONMEM using the forward inclusion and backward elimination approach. Results: Siplizumab concentrations were obtained from all 29 patients in the study yielding a total of 619 serum concentration observations. Pronounced non-linearity in siplizumab serum concentrations was observed after the initial and later dosing cycles, with serum concentrations declining faster at lower dose levels. The data was best described by a two-compartment pharmacokinetic model with zero-order input with parallel linear and non-linear elimination pathways. Goodness of fit plots and model diagnostics indicated good agreement between observed and model predicted serum concentration values. The population estimates for linear clearance was 0.168 L/day with inter-subject variability (ISV) of 50%, and inter-compartmental clearance was 2.83 L/day. Nonlinear elimination parameters, Vmax and Km were 10.32 mcg/day (56% ISV) and 51.8 mcg/L, respectively. Sex of the patients was identified as a significant covariate impacting volumes of distribution. Male patients had higher central and peripheral volumes of distribution of 2.8 L and 3.0 L, respectively, compared to1.38 L and 2.4 L in females [32% vs 50% ISV]. Conclusion: The serum concentration-time profile of siplizumab was adequately described by a two-compartment non-linear PK model. Population parameters were precisely estimated and correspond well to reported PK behaviour of monocolonal antibodies with significant target mediated elimination. The lower volume distribution in females is most likely due to lower body weight compared to males in this study. The population PK model combined with pharmacodynamic data could serve as a tool to guide selection of optimal dose regimens for siplizumab. Disclosures: No relevant conflicts of interest to declare.

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