Quantitative Analysis of Gentamicin Exposure in Neonates and Infants Calls into Question Its Current Dosing Recommendations.

Optimal dosing of gentamicin in neonates is still a matter of debate despite its common use. We identified gentamicin dosing regimens from eight international guidelines and seven Swiss neonatal intensive care units. The dose per administration, the dosing interval, the total daily dose, and the demographic characteristics between guidelines were compared. There was considerable variability with respect to dose (4 to 6 mg/kg), dosing interval (24 h to 48 h), total daily dose (2.5 to 6 mg/kg/day), and patient demographic characteristics that were used to calculate individualized dosing regimens. A model-based simulation study in 1071 neonates was performed to determine the achievement of efficacious peak gentamicin concentrations according to predefined MICs (Cmax/MIC ≥ 10) and safe trough concentrations (Cmin ≤ 2 mg/liter) with recommended dosing regimens. MIC targets of 0.5 and 1 mg/liter were used. Dosing optimization was performed giving priority to the first day of treatment and with the goal of simplifying dosing. Current gentamicin neonatal guidelines allow to achieve effective peak concentrations for MICs ≤ 0.5 mg/liter but not higher. Model-based simulations indicate that to attain peak gentamicin concentrations of ≥10 mg/liter, a dose of 7.5 mg/kg should be administered using an extended dosing interval regimen. Trough concentrations of ≤2 mg/liter can be maintained with a dosing interval of 36 to 48 h in neonates according to gestational and postnatal age. For treatment beyond 3 days, therapeutic drug monitoring is advised to maintain adequate serum concentrations

Alteration of postantibiotic effect during one dosing interval of tobramycin, simulated in an in vitro pharmacokinetic model

The kinetics of the postantibiotic effect (PAE) during one dosing interval of tobramycin against Staphylococcus aureus and Pseudomonas aeruginosa was investigated. We determined the PAE at different time points during this dosing interval of 12 h in an in vitro pharmacokinetic model simulating human pharmacokinetics in which the half-life of tobramycin was adjusted to 2.4 +/- 0.2 h. Using an enzymatic method to inactivate tobramycin, we determined PAEs in samples extracted from the model at 1, 5, 8, and 12 h, corresponding with tobramycin concentrations of 20, 5, 2, and 1 times the MIC for the test organism. The PAE decreased significantly from 2.5 h at 1 h to 0 h at 12 h. No change in MIC was observed for the strains during the experiments. We conclude that the PAE decreases with decreasing tobramycin concentrations during a 12-h dosing interval and completely disappears after the concentration has reached the MIC for the test organism. On the basis of these observations, the emphasis that is placed on the PAE in discussions about the optimal dosing interval in aminoglycoside therapy is questionable

Protein binding of β-lactam antibiotics in critically Ill patients: can we successfully predict unbound concentrations?

The use of therapeutic drug monitoring (TDM) to optimize beta-lactam dosing in critically ill patients is growing in popularity, although there are limited data describing the potential impact of altered protein binding on achievement of target concentrations. The aim of this study was to compare the measured unbound concentration to the unbound concentration predicted from published protein binding values for seven beta-lactams using data from blood samples obtained from critically ill patients. From 161 eligible patients, we obtained 228 and 220 plasma samples at the midpoint of the dosing interval and trough, respectively, for ceftriaxone, cefazolin, meropenem, piperacillin, ampicillin, benzylpenicillin, and flucloxacillin. The total and unbound beta-lactam concentrations were measured using validated methods. Variabilities in both unbound and total concentrations were marked for all antibiotics, with significant differences being present between measured and predicted unbound concentrations for ceftriaxone and for flucloxacillin at the mid-dosing interval (

Once-daily versus multiple-daily dosing with intravenous aminoglycosides for cystic fibrosis

Background: People with cystic fibrosis, who are chronically colonised with the organism Pseudomonas aeruginosa, often require multiple courses of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations. The properties of aminoglycosides suggest that they could be given in higher doses less often. Objectives: To assess the effectiveness and safety of once-daily versus multiple-daily dosing of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations in cystic fibrosis. Search methods: We searched the Cystic Fibrosis Specialist Register held at the Cochrane Cystic Fibrosis and Genetic Disorders Group’s editorial base, comprising references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings. Date of the most recent search: 25 November 2013. Selection criteria: All randomised controlled trials, whether published or unpublished, in which once-daily dosing of aminoglycosides has been compared with multiple-daily dosing in terms of efficacy or toxicity or both, in people with cystic fibrosis. Data collection and analysis: The two authors independently selected the studies to be included in the review and assessed the risk of bias of each study. Data were independently extracted by each author. Authors of the included studies were contacted for further information. As yet unpublished data were obtained for one of the included studies. Main results: Fifteen studies were identified for possible inclusion in the review. Four studies reporting results from a total of 328 participants were included in this review. All studies compared once-daily dosing with thrice-daily dosing. One study had a low risk of bias for all criteria assessed; the remaining three included studies had a high risk of bias from blinding, but for other criteria were judged to have either an unclear or a low risk of bias. There was no significant difference between treatment groups in: forced expiratory volume at one second, mean difference 0.33 (95% confidence interval -2.81 to 3.48); forced vital capacity, mean difference 0.29 (95% confidence interval -6.58 to 7.16); % weight for height, mean difference -0.82 (95% confidence interval -3.77 to 2.13); body mass index, mean difference 0.00 (95% confidence interval -0.42 to 0.42); or in the incidence of ototoxicity, relative risk 0.56 (95% confidence interval 0.04 to 7.96). The percentage change in creatinine significantly favoured once-daily treatment in children, mean difference -8.20 (95% confidence interval -15.32 to -1.08), but showed no difference in adults, mean difference 3.25 (95% confidence interval -1.82 to 8.33). Authors’ conclusions: Once- and three-times daily aminoglycoside antibiotics appear to be equally effective in the treatment of pulmonary exacerbations of cystic fibrosis. There is evidence of less nephrotoxicity in children

Recombinant factorVIII Fc fusion protein for the prevention and treatment of bleeding in children with severe hemophilia A

This work was supported by funding from Biogen, including funding for the editorial and writing support in the the development of this paper