Area under the curve achievement of once daily tobramycin in children with cystic fibrosis during clinical care.

BACKGROUND: The area under the concentration-time curve over 24 hours (AUC24 ) is frequently utilized to monitor tobramycin exposure in children with cystic fibrosis (CF). An understanding of exposure target achievement during clinical implementation of an AUC24 based approach in children is limited. METHODS: A retrospective chart review was performed in children with CF treated with once daily tobramycin and drug concentration monitoring at a pediatric CF center. During clinical care AUC24 was estimated using a traditional log-linear regression approach (LLR). AUC24 was also estimated retrospectively using a pharmacokinetic model-based Bayesian forecasting approach (BF). AUC24 achievement after both approaches were compared. RESULTS: In 77 treatment courses (mean age, 12.7 ± 5.0 years), a target AUC24 100 to 125 mg h/L was achieved after starting dose in 21 (27%) and after initial dose adjustment in 35 (45%). In the first 7 days of treatment, 24 (32%) required ≥3 dose adjustments, and the mean number of drug concentrations measured was 7.1 ± 3.2. Examination of a BF approach demonstrated adequate prediction of measured tobramycin concentrations (median bias -2.1% [95% CI -3.1 to -1.4]; median precision 7.6% [95% CI, 7.1%-8.2%]). AUC24 estimates utilizing the BF approach were higher than the LLR approach with a mean difference of 6.4 mg h/L (95% CI, 4.8 to 8.0 mg h/L). CONCLUSIONS: Achievement of a narrow AUC24 target is challenging during clinical care, and dose individualization is needed in most children with CF. Implementing a BF approach for estimating AUC24 in children with CF is supported.

Enhancement of diuresis with metolazone in infant paediatric cardiac intensive care patients.

BACKGROUND: Few data are available regarding the use of metolazone in infants in cardiac intensive care. Researchers need to carry out further evaluation to characterise the effects of this treatment in this population. METHODS: This is a descriptive, retrospective study carried out in patients less than a year old. These infants had received metolazone over a 2-year period in the paediatric cardiac intensive care unit at our institution. The primary goal was to measure the change in urine output from 24 hours before the start of metolazone therapy to 24 hours after. Patient demographic variables, laboratory data, and fluid-balance data were analysed. RESULTS: The study identified 97 infants with a mean age of 0.32±0.25 years. Their mean weight was 4.9±1.5 kg, and 58% of the participants were male. An overall 63% of them had undergone cardiovascular surgery. The baseline estimated creatinine clearance was 93±37 ml/minute/1.73 m2. Initially, the participants had received a metolazone dose of 0.27±0.10 mg/kg/day, the maximum dose being 0.43 mg/kg/day. They had also received other diuretics during metolazone initiation, such as furosemide (87.6%), spironolactone (58.8%), acetazolamide (11.3%), bumetanide (7.2%), and ethacrynic acid (1%). The median change in urine output after metolazone was 0.9 ml/kg/hour (interquartile range 0.15-1.9). The study categorised a total of 66 patients (68.0%) as responders. Multivariable analysis identified acetazolamide use (p=0.002) and increased fluid input in the 24 hours after metolazone initiation (p0.05). CONCLUSIONS: Metolazone increased urine output in a select group of patients. Efficacy can be maximised by strategic selection of patients.