Semi-mechanistic autoinduction model of midazolam in critically ill patients: population pharmacokinetic analysis

2016 ◽  
Vol 41 (4) ◽  
pp. 392-398 ◽  
Author(s):  
T. Aoyama ◽  
K. Hirata ◽  
Y. Yamamoto ◽  
H. Yokota ◽  
H. Hayashi ◽  
...  
2009 ◽  
Vol 53 (8) ◽  
pp. 3430-3436 ◽  
Author(s):  
D. Plachouras ◽  
M. Karvanen ◽  
L. E. Friberg ◽  
E. Papadomichelakis ◽  
A. Antoniadou ◽  
...  

ABSTRACT Colistin is used to treat infections caused by multidrug-resistant gram-negative bacteria (MDR-GNB). It is administered intravenously in the form of colistin methanesulfonate (CMS), which is hydrolyzed in vivo to the active drug. However, pharmacokinetic data are limited. The aim of the present study was to characterize the pharmacokinetics of CMS and colistin in a population of critically ill patients. Patients receiving colistin for the treatment of infections caused by MDR-GNB were enrolled in the study; however, patients receiving a renal replacement therapy were excluded. CMS was administered at a dose of 3 million units (240 mg) every 8 h. Venous blood was collected immediately before and at multiple occasions after the first and the fourth infusions. Plasma CMS and colistin concentrations were determined by a novel liquid chromatography-tandem mass spectrometry method after a rapid precipitation step that avoids the significant degradation of CMS and colistin. Population pharmacokinetic analysis was performed with the NONMEM program. Eighteen patients (6 females; mean age, 63.6 years; mean creatinine clearance, 82.3 ml/min) were included in the study. For CMS, a two-compartment model best described the pharmacokinetics, and the half-lives of the two phases were estimated to be 0.046 h and 2.3 h, respectively. The clearance of CMS was 13.7 liters/h. For colistin, a one-compartment model was sufficient to describe the data, and the estimated half-life was 14.4 h. The predicted maximum concentrations of drug in plasma were 0.60 mg/liter and 2.3 mg/liter for the first dose and at steady state, respectively. Colistin displayed a half-life that was significantly long in relation to the dosing interval. The implications of these findings are that the plasma colistin concentrations are insufficient before steady state and raise the question of whether the administration of a loading dose would benefit critically ill patients.


2015 ◽  
Vol 59 (12) ◽  
pp. 7240-7248 ◽  
Author(s):  
Ilias Karaiskos ◽  
Lena E. Friberg ◽  
Konstantinos Pontikis ◽  
Konstantinos Ioannidis ◽  
Vasiliki Tsagkari ◽  
...  

ABSTRACTColistin has been revived, in the era of extensively drug-resistant (XDR) Gram-negative infections, as the last-resort treatment in critically ill patients. Recent studies focusing on the optimal dosing strategy of colistin have demonstrated the necessity of a loading dose at treatment initiation (D. Plachouras, M. Karvanen, L. E. Friberg, E. Papadomichelakis, A. Antoniadou, I. Tsangaris, I. Karaiskos, G. Poulakou, F. Kontopidou, A. Armaganidis, O. Cars, and H. Giamarellou, Antimicrob Agents Chemother 53:3430–3436, 2009,http://dx.doi.org/10.1128/AAC.01361-08; A. F. Mohamed, I. Karaiskos, D. Plachouras, M. Karvanen, K. Pontikis, B. Jansson, E. Papadomichelakis, A. Antoniadou, H. Giamarellou, A. Armaganidis, O. Cars, and L. E. Friberg, Antimicrob Agents Chemother 56:4241– 4249, 2012,http://dx.doi.org/10.1128/AAC.06426-11; S. M. Garonzik, J. Li, V. Thamlikitkul, D. L. Paterson, S. Shoham, J. Jacob, F. P. Silveira, A. Forrest, and R. L. Nation, Antimicrob Agents Chemother 55:3284–3294, 2011,http://dx.doi.org/10.1128/AAC.01733-10). In 19 critically ill patients with suspected or microbiologically documented infections caused by XDR Gram-negative strains, a loading dose of 9 MU colistin methanesulfonate (CMS) (∼270 mg colistin base activity) was administered with a maintenance dose of 4.5 MU every 12 h, commenced after 24 h. Patients on renal replacement were excluded. CMS infusion was given over 30 min or 1 h. Repeated blood sampling was performed after the loading dose and after the 5th or 6th dose. Colistin concentrations and measured CMS, determined after hydrolization to colistin and including the partially sulfomethylated derivatives, were determined with a liquid chromatography-tandem mass spectrometry assay. Population pharmacokinetic analysis was conducted in NONMEM with the new data combined with data from previous studies. Measured colistimethate concentrations were described by 4 compartments for distribution and removal of sulfomethyl groups, while colistin disposition followed a 1-compartment model. The average observed maximum colistin A plus B concentration was 2.65 mg/liter after the loading dose (maximum time was 8 h). A significantly higher availability of the measured A and B forms of colistimethate and colistin explained the higher-than-expected concentrations in the present study compared to those in previous studies. Creatinine clearance was a time-varying covariate of colistimethate clearance. The incidence of acute renal injury was 20%.


2015 ◽  
Vol 60 (1) ◽  
pp. 206-214 ◽  
Author(s):  
Mohd H. Abdul-Aziz ◽  
Azrin N. Abd Rahman ◽  
Mohd-Basri Mat-Nor ◽  
Helmi Sulaiman ◽  
Steven C. Wallis ◽  
...  

ABSTRACTDoripenem has been recently introduced in Malaysia and is used for severe infections in the intensive care unit. However, limited data currently exist to guide optimal dosing in this scenario. We aimed to describe the population pharmacokinetics of doripenem in Malaysian critically ill patients with sepsis and use Monte Carlo dosing simulations to develop clinically relevant dosing guidelines for these patients. In this pharmacokinetic study, 12 critically ill adult patients with sepsis receiving 500 mg of doripenem every 8 h as a 1-hour infusion were enrolled. Serial blood samples were collected on 2 different days, and population pharmacokinetic analysis was performed using a nonlinear mixed-effects modeling approach. A two-compartment linear model with between-subject and between-occasion variability on clearance was adequate in describing the data. The typical volume of distribution and clearance of doripenem in this cohort were 0.47 liters/kg and 0.14 liters/kg/h, respectively. Doripenem clearance was significantly influenced by patients' creatinine clearance (CLCR), such that a 30-ml/min increase in the estimated CLCRwould increase doripenem CL by 52%. Monte Carlo dosing simulations suggested that, for pathogens with a MIC of 8 mg/liter, a dose of 1,000 mg every 8 h as a 4-h infusion is optimal for patients with a CLCRof 30 to 100 ml/min, while a dose of 2,000 mg every 8 h as a 4-h infusion is best for patients manifesting a CLCRof >100 ml/min. Findings from this study suggest that, for doripenem usage in Malaysian critically ill patients, an alternative dosing approach may be meritorious, particularly when multidrug resistance pathogens are involved.


2020 ◽  
Vol 75 (12) ◽  
pp. 3625-3634
Author(s):  
Dagan O Lonsdale ◽  
Karin Kipper ◽  
Emma H Baker ◽  
Charlotte I S Barker ◽  
Isobel Oldfield ◽  
...  

Abstract Background The pharmacokinetics of β-lactam antibiotics in critical illness remain poorly characterized, particularly in neonates, children and the elderly. We undertook a pharmacokinetic study of commonly used β-lactam antibiotics in critically ill patients of all ages. The aims were to produce a whole-life β-lactam pharmacokinetic model and describe the extent to which standard doses achieve pharmacokinetic/pharmacodynamic targets associated with clinical cure. Patients and methods A total of 212 critically ill participants with an age range from 1 day (gestational age 24 weeks) to 90 years were recruited from a UK hospital, providing 1339 pharmacokinetic samples. Population pharmacokinetic analysis was undertaken using non-linear mixed-effects modelling (NONMEM) for each drug. Pooled data were used to estimate maturation and decline of β-lactam pharmacokinetics throughout life. Results Pharmacokinetic models for eight drugs were described, including what is thought to be the first benzylpenicillin model in critically ill adults. We estimate that 50% of adult β-lactam clearance is achieved by 43 weeks post-menstrual age (chronological plus gestational age). Fifty percent of decline from peak adult clearance occurs by 71 years. Paediatric participants were significantly less likely than adults to achieve pharmacokinetic/pharmacodynamic targets with standard antibiotic doses (P < 0.01). Conclusions We believe this to be the first prospective whole-life antibiotic pharmacokinetic study in the critically ill. The study provides further evidence that standard antibiotic doses fail to achieve pharmacokinetic/pharmacodynamic targets associated with clinical success in adults, children and neonates. Maturation and decline parameters estimated from this study could be adopted as a standard for future prospective studies.


2017 ◽  
Vol 49 (2) ◽  
pp. 204-211 ◽  
Author(s):  
Caspar J. Hodiamont ◽  
Nicole P. Juffermans ◽  
Catherine S.C. Bouman ◽  
Menno D. de Jong ◽  
Ron A.A. Mathôt ◽  
...  

2011 ◽  
Vol 55 (6) ◽  
pp. 2704-2709 ◽  
Author(s):  
Jason A. Roberts ◽  
Fabio Silvio Taccone ◽  
Andrew A. Udy ◽  
Jean-Louis Vincent ◽  
Frédérique Jacobs ◽  
...  

ABSTRACTDespite the development of novel antibiotics active against Gram-positive bacteria, vancomycin generally remains the first treatment, although rapidly achieving concentrations associated with maximal efficacy provides an unresolved challenge. The objective of this study was to conduct a population pharmacokinetic analysis of vancomycin in a large population of critically ill patients. This was a retrospective data collection of 206 adult septic critically ill patients who were administered vancomycin as a loading dose followed by continuous infusion. The concentration-versus-time data for vancomycin in serum was analyzed by a nonlinear mixed-effects modeling approach using NONMEM. Monte Carlo simulations were performed using the final covariate model. We found that the best population pharmacokinetic model consisted of a one-compartment linear model with combined proportional and additive residual unknown variability. The volume of distribution of vancomycin (1.5 liters/kg) was described by total body weight and clearance (4.6 liters/h) by 24-hour urinary creatinine clearance (CrCl), normalized to body surface area. Simulation data showed that a 35-mg/kg loading dose was necessary to rapidly achieve vancomycin concentrations of 20 mg/liter. Daily vancomycin requirements were dependent on CrCl, such that a patient with a CrCl of 100 ml/min/1.73 m2would require at least 35 mg/kg per day by continuous infusion to maintain target concentrations. In conclusion, we have found that higher-than-recommended loading and daily doses of vancomycin seem to be necessary to rapidly achieve therapeutic serum concentrations in these patients.


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