@article {7743, title = {Pharmacokinetic/pharmacodynamic evaluation of linezolid in hospitalized paediatric patients: a step toward dose optimization by means of therapeutic drug monitoring and Monte Carlo simulation.}, journal = {J Antimicrob Chemother}, volume = {70}, year = {2015}, month = {2015 Jan}, pages = {198-206}, abstract = {

OBJECTIVES: To report on linezolid exposure in a paediatric population who routinely underwent therapeutic drug monitoring (TDM) for dosage optimization and to assess the factors affecting interpatient variability.

METHODS: We performed a retrospective study of patients whose plasma C(min) and Cmax levels were measured during linezolid treatment. Adequate exposure was defined as a C(min) of 2-7 mg/L and/or an estimated AUC24 of 160-300 mg {\textperiodcentered} h/L. Patients were divided into two subgroups (Group 1, 2-11 years; Group 2, 12-18 years). Monte Carlo simulation was performed to investigate whether or not the currently recommended dosages might enable a high probability of target attainment (PTA) of two thresholds for linezolid efficacy (AUC24/MIC >= 80 or >= 100). Data on demographic characteristics, disease, microbiology and haematochemical parameters and outcomes were collected.

RESULTS: A total of 23 patients were included. Standard dosages were suboptimal in 50.0\% and 44.4\% of patients in Group 1 and Group 2, respectively. Among those who underwent multiple instances of TDM, the dosages were increased in 33.3\% of cases in both groups, and decreased in 6.6\% and 9.5\% of cases in Group 1 and Group 2, respectively. Co-treatment with phenobarbital, proton pump inhibitors and amiodarone accounted for most of the variability in C(min) (adjusted R(2) of 0.692). Simulations showed a PTA of >= 90\% with the current dosing regimens in both groups only for pathogens with an MIC <= 1 mg/L.

CONCLUSIONS: Higher dosages of linezolid may be needed, especially in Group 1 when in the presence of pathogens with an MIC >1 mg/L. The role of TDM should be encouraged for optimization of linezolid exposure in the paediatric setting in the presence of infections caused by pathogens with borderline susceptibility and/or for patients co-treated with drugs that may alter linezolid exposure.

}, keywords = {Acetamides, Anti-Bacterial Agents, Area Under Curve, Child, Child, Preschool, Drug Monitoring, Female, Gram-Positive Bacterial Infections, Hospitalization, Humans, Infant, Inpatients, Linezolid, Male, Monte Carlo Method, Oxazolidinones, Plasma, Retrospective Studies, Tertiary Care Centers}, issn = {1460-2091}, doi = {10.1093/jac/dku337}, author = {Cojutti, Piergiorgio and Maximova, Natalia and Crichiutti, Giovanni and Isola, Miriam and Pea, Federico} } @article {7707, title = {Pharmacokinetics and pharmacodynamics of continuous-infusion meropenem in pediatric hematopoietic stem cell transplant patients.}, journal = {Antimicrob Agents Chemother}, volume = {59}, year = {2015}, month = {2015 Sep}, pages = {5535-41}, abstract = {

This study explored the pharmacokinetics and the pharmacodynamics of continuous-infusion meropenem in a population of pediatric hematopoietic stem cell transplant (HSCT) patients who underwent therapeutic drug monitoring. The relationship between meropenem clearance (CLM) and estimated creatinine clearance (CLCR) was assessed by nonlinear regression. A Monte Carlo simulation was performed to investigate the predictive performance of five dosing regimens (15 to 90 mg/kg of body weight/day) for the empirical treatment of severe Gram-negative-related infections in relation to four different categories of renal function. The optimal target was defined as a probability of target attainment (PTA) of >=90\% at steady-state concentration-to-MIC ratios (C SS/MIC) of >=1 and >=4 for MICs of up to 8 mg/liter. A total of 21 patients with 44 meropenem C SS were included. A good relationship between CLM and estimated CLCR was observed (r (2) = 0.733). Simulations showed that at an MIC of 2 mg/liter, the administration of continuous-infusion meropenem at doses of 15, 30, 45, and 60 mg/kg/day may achieve a PTA of >=90\% at a C SS/MIC ratio of >=4 in the CLCR categories of 40 to <80, 80 to <120, 120 to <200, and 200 to <300 ml/min/1.73 m(2), respectively. At an MIC of 8 mg/liter, doses of up to 90 mg/kg/day by continuous infusion may achieve optimal PTA only in the CLCR categories of 40 to <80 and 80 to <120 ml/min/1.73 m(2). Continuous-infusion meropenem at dosages up to 90 mg/kg/day might be effective for optimal treatment of severe Gram-negative-related infections in pediatric HSCT patients, even when caused by carbapenem-resistant pathogens with an MIC of up to 8 mg/liter.

}, issn = {1098-6596}, doi = {10.1128/AAC.00787-15}, author = {Cojutti, Piergiorgio and Maximova, Natalia and Pea, Federico} }