Improved vancomycin dosing in children using area under the curve exposure

Correlation of a Vancomycin Pharmacokinetic Model and Trough Serum Concentrations in Pediatric Patients

BACKGROUND

Vancomycin trough concentrations specific to pediatric patients have yet to be validated that achieve an area under the curve (AUC) over 24 hours to minimum inhibitory concentration (MIC) ratio ≥400. The primary objective of this study was to validate a pharmacokinetic model in a pediatric hospital and determine the correlation between a calculated AUC/MIC ratio and measured trough vancomycin concentration.

METHODS

A retrospective evaluation of patients aged 3 months to 18 years prescribed vancomycin at a pediatric hospital between January 2012 and June 2013. The correlation between patient-specific AUC/MIC and measured vancomycin trough concentration was assessed.

RESULTS

Forty pediatric patients with 40 vancomycin trough concentrations and documented Staphylococcus aureus cultures were included in the study. Median age was 8.5 (interquartile range, 2-14.3) years, median weight 28.7 (range, 14-50.2) kg, and mean baseline serum creatinine 0.51 ± 0.3 mg/dL. The mean daily dose of vancomycin prescribed was 58 ± 13.8 mg/kg/d. The mean vancomycin trough concentration was 11 ± 5.5 mcg/mL, and the mean AUC/MIC was 534 ± 373. No correlation was found between trough concentration and AUC/MIC (r = 0.082, p = 0.07).

CONCLUSIONS

This study validates the clinical applicability of a pharmacokinetic model for calculating vancomycin clearance to determine patient-specific AUC over 24 hours in pediatrics. Trough concentrations associated with proposed therapeutic AUC/MIC ratios were lower than reported in the adult population. Further research is needed to determine if AUC/MIC, trough concentration, or both is best for monitoring therapeutic efficacy of vancomycin in pediatrics.

Evaluation of Target Attainment of Vancomycin Area Under the Curve in Children With Methicillin-Resistant Staphylococcus Aureus Bacteremia

BACKGROUND

Vancomycin is often required to treat methicillin-resistant Staphylococcus aureus bacteremia in children. Treatment failure occurs in up to 50% of adults and is associated with a 24-hour area under the curve/minimum inhibitory concentration (AUC24h/MIC) <400. We sought to identify patient factors associated with vancomycin AUC and whether AUC24h/MIC <400 was predictive of treatment failure in children.

METHODS

Hospitalized children younger than 18 years with methicillin-resistant Staphylococcus aureus bacteremia receiving vancomycin were included in a retrospective cohort study. AUC24h was calculated using a validated pharmacokinetic model. Factors such as age, sex, underlying conditions, presence of foreign bodies, patient site of infection, and markers of illness severity were examined for an association with vancomycin AUC, and AUC24h/MIC was evaluated for an association with treatment failure.

RESULTS

Subjects requiring intensive care unit support were significantly more likely to have higher vancomycin AUC24h and AUCavg than those subjects not needing intensive care unit support. Although vancomycin serum trough concentrations are predictive of vancomycin AUC, suboptimal exposure of vancomycin occurred in almost 20% of subjects despite trough concentrations within the target range. A relationship between vancomycin AUC24h/MIC and treatment failure could not be established.

CONCLUSIONS

To ensure optimal AUC/MIC pharmacodynamic index, especially in critically ill patients, estimation of the AUC is critical.

Vancomycin dosing and target attainment in children

BACKGROUND/PURPOSE

The aim of this study is to determine the best dosing strategy for vancomycin by studying the associated factors and examining correlations between the area under the plasma concentration-time curve (AUC) values and trough concentrations in children.

METHODS

Children aged 3 months to 18 years were included if they received vancomycin for more than three doses between January 1, 2010 and December 31, 2012 and had one or more serum vancomycin trough concentrations. Vancomycin clearance (CL) was calculated using the following model: CL = 0.248*Wt^0.75*(0.48/serum creatinine)^0.361*[ln (age)/7.8]^0.995. The AUC (mg-h/L) was calculated by 24-hour dose (mg/kg/d)/CL(L/h). The value of AUC divided by the minimum inhibitory concentration (MIC) of vancomycin was AUC/MIC.

RESULTS

A total of 218 children were included. The mean age was 6.0 ± 5.1 years and the mean body weight was 20 ± 11.7 kg. Vancomycin trough concentrations were moderately correlated with AUC values (r² = 0.232, p < 0.01). Dosing of 15 mg/kg/dose q6h produced significantly higher AUC values (p < 0.001) and vancomycin trough concentrations (p < 0.001) compared to dosing of 10 mg/kg/dose q6h. In children receiving a 10-mg/kg/dose q6h, 5.6% (5/90) achieved the target trough concentrations of 15-20 μg/mL and 9.5% (5/90) achieved the goal AUC/MIC ≥ 400. In children receiving a 15-mg/kg/dose q6h, 13% (6/46) achieved the target trough concentrations of 15-20 μg/mL, whereas 54.3% (25/46) achieved the goal AUC/MIC ≥ 400.

CONCLUSION

A 15-mg/kg/dose q6h compared to a 10-mg/kg/dose q6h is more likely to achieve target trough concentrations of 15-20 μg/mL and the goal AUC/MIC ≥ 400.

Late-Occurring Vancomycin-Associated Acute Kidney Injury in Children Receiving Prolonged Therapy

Background: Acute kidney injury (AKI) in patients receiving vancomycin has been associated with trough concentrations ≥15 mg/L and longer therapy duration. The objective of this study was to determine the incidence and factors associated with late AKI in children receiving ≥8 days of vancomycin therapy. Methods: Children aged 30 days to 17 years who were admitted to our institution and received intravenous vancomycin for at least 8 days during January to December of 2007 and 2010 and had a suspected or proven gram-positive infection were included. Late AKI was categorized as AKI occurring after the first 7 days of therapy and within 48 hours following vancomycin discontinuation. The primary outcome was incidence of late AKI as determined by modified pRIFLE criteria. Results: One-hundred sixty-seven patients were included, with a median (interquartile range) age (years) and weight (kg) of 2 (1-7) and 12.5 (8.9-23.8). Late AKI was identified in 12.6% (21/167). A higher percentage of late AKI patients received concomitant treatment with intravenous acyclovir, amphotericin products, or piperacillin-tazobactam. Age <1 year was the only factor independently associated with late AKI development (odds ratio = 4.4; 95% confidence interval = 1.3-15.4). Conclusions: Late AKI occurred in nearly 13% of children receiving ≥8 days of vancomycin therapy. This study suggests that vancomycin trough concentrations are not associated with late AKI, but that age <1 year and concomitant administration of certain nephrotoxins may be factors associated with increased risk.

Achievement of Therapeutic Vancomycin Trough Serum Concentrations with Empiric Dosing in Neonatal Intensive Care Unit Patients

BACKGROUND

The recommended goal serum trough concentration for vancomycin has increased to 10 to 20 mcg/mL, with a higher range of 15 to 20 mcg/mL for serious infections due to methicillin-resistant Staphylococcus aureus in children and adults. Although neonatal references have also recommended these higher target concentrations, dosing recommendations remained unchanged. The objective of this study was to assess the percentage of neonates and young infants achieving a serum trough concentration between 10 and 20 mcg/mL with empiric vancomycin dosing based on Neofax® in a neonatal intensive care unit (NICU) population.

METHODS

A multi-institutional retrospective chart review was conducted to identify NICU patients who received a minimum of three doses of intravenous vancomycin and had at least one appropriately drawn trough. Additional outcomes included the duration of vancomycin therapy, number of dose adjustments required to attain goal trough concentrations, time to goal trough, and incidence of nephrotoxicity and ototoxicity.

RESULTS

Of the 171 vancomycin serum trough concentrations included in the primary outcome, only 25.1% achieved a goal trough of 10 to 20 mcg/mL with empiric dosing. Only 44.6% of patients achieved the goal trough of 10 to 20 mcg/mL at any time during their vancomycin therapy. The average gestational age was 28.2 ± 4.1 weeks, average postnatal age at start of vancomycin was 34.1 ± 34.6 days, and average weight of the patients at start of vancomycin was 1602 ± 1014.5 g. The average and median total daily dose in those patients who achieved an initial vancomycin trough of 10-20 mcg/mL were 32.4 mg/kg/day and 30 mg/kg/day, respectively.

CONCLUSION

Dosing of vancomycin based on Neofax® in NICU patients is insufficient in yielding serum trough concentrations of 10 to 20 mcg/mL. Further studies are needed to evaluate the optimal dosing regimen to achieve higher trough concentrations in this patient population.

Vancomycin pharmacokinetic models: informing the clinical management of drug-resistant bacterial infections

This review aims to critically evaluate the pharmacokinetic literature describing the use of vancomycin in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. Guidelines recommend that trough concentrations be used to guide vancomycin dosing for the treatment of MRSA infections; however, numerous in vitro, animal model and clinical studies have demonstrated that the therapeutic effectiveness of vancomycin is best described by the area under the concentration versus time curve (AUC) divided by the minimum inhibitory concentration (MIC) of the infecting organism (AUC/MIC). Among patients with lower respiratory tract infections, an AUC/MIC ≥400 was associated with a superior clinical and bacteriological response. Similarly, patients with MRSA bacteremia who achieved an Etest AUC/MIC ≥320 within 48 h were 50% less likely to experience treatment failure. For other patient populations and different clinical syndromes (e.g., children, the elderly, patients with osteomyelitis, etc.), pharmacokinetic/pharmacodynamic studies and prospective clinical trials are needed to establish appropriate therapeutic targets.

Vancomycin pharmacokinetics and predicted dosage requirements in pediatric cancer patients

Purpose

To determine the pharmacokinetic parameters and compare pharmacodynamic target attainment at different dosing strategies of vancomycin in pediatric cancer patients.

Methods

Pediatric patients who received vancomycin and had at least two steady-state concentrations taken within the same dosing interval were identified. Vancomycin minimum inhibitory concentrations (MICs) for methicillin resistant staphylococcus aureus (MRSA) isolates from our institution were determined using E-test. The population-based pharmacokinetic modeling was performed using NONMEM 7.2. A one-compartment model with first-order kinetics was used to estimate clearance (CL) and volume of distribution (Vd). Monte Carlo simulations ( N = 9800) were performed to compare area-under-the-curve over 24 h (AUC24)/MIC and trough concentration at different doses.

Results

Forty-nine patients, with 120 vancomcyin serum concentrations, were included in the analysis, mean age was 6 ± 2.5 (SD) years, mean weight was 19.6 ± 6.9(SD) kg, mean baseline serum creatinine was 0.4 ± 0.11(SD) mg/dl, and mean initial vancomycin dose was 205 mg/day (range 100–460). Final model pharmacokinetic parameters were: CL (L/h) = 0.381 × weight0.75 and Vd (L) = 0.663 × weight. Mean baseline (±SD) vancomycin CL was 0.20 ± 0.07 L/h/kg and Vd 0.66 ± 0.001 L/kg. . Renal function, sex, age, stay in the intensive care unit, and co-administration of nephrotoxic medications did not have an effect on the calculated parameters. Using Monte Carlo simulation with reported MICs, a dose of 60 mg/kg/day achieved AUC24/MIC ≥400 and trough concentration ≥15 mcg/mL in only 21.5% and 11% of virtual subjects, respectively.

Conclusions

Higher than usual vancomycin doses may be required to treat serious MRSA infections in pediatric patients. The currently recommended dose of 60 mg/kg/day is unlikely to achieve the targets in most subjects. The optimal vancomycin dosing in pediatric cancer patients requires further investigations.

Pediatric Assessment of Vancomycin Empiric Dosing (PAVED): a Retrospective Review

BACKGROUND

Pediatric studies and anecdotal experience suggest that current empiric vancomycin dosing does not reach serum trough concentration targets of at least 10 mg/L for uncomplicated infections or 15-20 mg/L for serious or complicated infections.

OBJECTIVES

This study reviewed vancomycin dosing and serum concentrations to (i) determine the proportion of patients who reached initial target concentrations; (ii) describe pharmacokinetic parameters; and (iii) compare patient-specific area-under-the-curve (AUC) values to population estimates using the Rodvold equation.

METHODS

Following ethics approval, data were extracted from medical records of 200 patients aged 1 month-18 years, who received intravenous (IV) vancomycin and had at least two pharmacokinetically evaluable serum concentrations.

RESULTS

Trough vancomycin concentrations of 10-15 and 15-20 mg/L were achieved in 25 (29%) and 2 (2%) patients receiving vancomycin 15 mg/kg IV every 6 h (q6 h) and 22 (20%) and 9 (8%) patients receiving vancomycin 20 mg/kg IV every 8 h (q8 h), respectively. Patients were stratified into four age groups (1 month-1 year, 1-6 years, 6-13 years and 13-18 years). Median (IQR) pharmacokinetic parameters were elimination rate constant 0.25 (0.09), 0.29 (0.07), 0.24 (0.10) and 0.22 (0.07) h(-1); volume of distribution 0.56 (0.20), 0.61 (0.21), 0.47 (0.26) and 0.49 (0.22) L/kg; and half-life 2.8 (1.1), 2.4 (0.5), 2.9 (1.1) and 3.2 (1.0) h, respectively. Median (IQR) AUCs were 458 (170), 338 (132), 478 (215) and 513 (179) mg h/L and population-estimated AUCs were 67 (44), 108 (70), 299 (102) and 454 (103) mg h/L (p < 0.05 for all groups).

CONCLUSIONS

Based on these findings, we recommend vancomycin 70 and 90 mg/kg/day divided q6 h for troughs of 10-15 and 15-20 mg/L, respectively (patients 1 month-6 years) and 60 mg/kg/day divided q8 h and 70 mg/kg/day divided q6 h, respectively (patients >6 years) to undergo further testing as initial dosing regimens. Furthermore, population estimates grossly underestimate vancomycin AUC in patients 1-18 years old and thus patient-specific parameters are required.

Multidrug-Resistant Organisms: Considerations in Antibiotic Selection and Administration

Managing infections caused by multidrug-resistant organisms is a significant clinical challenge. Multidrug-resistant organisms' treatment is complicated in the pediatric population because of the lack of primary data, treatment guidelines, rapidly changing pharmacokinetic/pharmacodynamic parameters, and fewer approved antibiotic indications and dosing guidance. Treatment decisions must incorporate available pediatric data, clinical experience, and careful extrapolation from adult data while considering the unique challenges faced by children with complicated infections.

Bayesian Estimation of Vancomycin Pharmacokinetics in Obese Children: Matched Case-Control Study

PURPOSE

The study objective was to compare different body size descriptors that best estimate vancomycin Vd and clearance (CL).

METHODS

Patients between 3 months and 21 years old who received vancomycin for ≥48 hours from 2003 to 2011 were evaluated in this matched case-control study. Cases had body mass index in the ≥85th percentile; controls were nonobese individuals who were matched by age and baseline serum creatinine (SCr). Using a 1-compartment model with first-order kinetics, Bayesian post hoc individual Vd and CL were estimated.

FINDINGS

Analysis included 87 matched pairs with 389 vancomycin serum concentrations. Median ages were 10.0 (interquartile range [IQR], 4.8-15.2) years for cases (overweight and obese children) and 10.2 (IQR, 4.5-14.8) years for controls (normal-weight children). Median weights were 44.0 (IQR, 23.4-78.1) kg for cases and 31.3 (IQR, 16.8-47.1) kg for controls. Mean (SD) for the baseline SCr values were also similar between the groups: 0.51 (0.22) (IQR, 0.34-0.67) mg/dL and 0.48 (0.20) (IQR, 0.30-0.60) mg/dL for the cases and controls, respectively. Actual weight and allometric weight (ie, weight(0.75)) were used in the final model to estimate Vd and CL, respectively. The mean Vd and CL, based on weight, for cases were lower than controls by 0.012 L/kg and 0.014 L/kg/h, respectively.

IMPLICATIONS

In obese children, actual weight and allometric weight are reasonable, convenient estimations of body fat to use for estimating vancomycin Vd and CL, respectively. However, these pharmacokinetic differences between obese children and those with normal weights are small and may not likely to be clinically relevant in dose variation.

Balancing vancomycin efficacy and nephrotoxicity: should we be aiming for trough or AUC/MIC?

Sixty years later, the question that still remains is how to appropriately utilize vancomycin in the pediatric population. The Infectious Diseases Society of America published guidelines in 2011 that provide guidance for dosing and monitoring of vancomycin in adults and pediatrics. However, goal vancomycin trough concentrations of 15-20 μg/mL for invasive infections caused by methicillin-resistant Staphylococcus aureus were based primarily on adult pharmacokinetic and pharmacodynamic data that achieved an area under the curve to minimum inhibitory concentration ratio (AUC/MIC) of ≥400. Recent pediatric literature shows that vancomycin trough concentrations needed to achieve the target AUC/MIC are different than the adult goal troughs cited in the guidelines. This paper addresses several thoughts, including the role of vancomycin AUC/MIC in dosing strategies and safety monitoring, consistency in laboratory reporting, and future directions for calculating AUC/MIC in pediatrics.

Antimicrobial stewardship in the NICU

There are unique challenges to antimicrobial stewardship in neonatal intensive care units (NICUs). Diagnosis of infection is difficult as neonates can have nonspecific signs and symptoms. Between and within NICUs, significant variation exists in the treatment duration of suspected sepsis and pneumonia. Development of multidisciplinary teams and meaningful metrics are essential for sustainable antibiotic stewardship. Potential stewardship interventions include optimizing culturing techniques, guiding empiric therapy by NICU-specific antibiograms, using ancillary laboratory tests, and promptly discontinuing therapy once infection is no longer suspected. Use of large neonatal databases can be used to benchmark antibiotic use and conduct comparative effectiveness research.

Achieving therapeutic vancomycin levels in pediatric patients

BACKGROUND

Vancomycin is widely used to treat infections caused by methicillin-resistant Staphylococcus aureus. Data for dosing and monitoring of this drug in pediatric patients are lacking, and clinicians who are treating children often follow guidelines established for adults.

OBJECTIVES

To examine the total daily doses of vancomycin required to reach therapeutic trough levels (i.e., 10-20 mg/L) in infants, children, and adolescents, and to assess the number of pediatric patients in whom therapeutic trough levels are achieved with current empiric doses (40-60 mg/kg daily).

METHODS

This chart review evaluated patients 1 month to 18 years of age for whom vancomycin was prescribed at a single institution between November 2011 and October 2012. Patients' demographic characteristics, vancomycin dosing parameters, and subsequent steady-state trough concentrations were analyzed.

RESULTS

Overall, the proportion of patients who reached therapeutic trough levels with current empiric doses was 39% (74 of 188). The mean total daily dose (± standard deviation) required to achieve therapeutic trough levels was 57.8 ± 11.5 mg/kg for patients 1 to 5 months of age, 68.9 ± 15.4 mg/kg for those 6 to 23 months of age, 65.8 ± 13.0 mg/kg for those 2 to 12 years of age, and 55.7 ± 11.8 mg/kg for those 13 to 18 years of age.

CONCLUSIONS

Common empiric vancomycin dosing regimens (40-60 mg/kg daily) are not high enough to achieve trough levels of 10-20 mg/L in the majority of pediatric patients. Given these data, the authors suggest a starting dose of 60 mg/kg daily for patients 1 to 5 months of age and those 13 to 18 years of age and a starting dose of 70 mg/kg daily for patients 6 months to 12 years of age.

Evaluation of vancomycin dosing and corresponding drug concentrations in pediatric patients

OBJECTIVE

To describe the relationships between dosing strategy, age, and vancomycin trough concentrations in pediatric patients.

METHODS

This is a retrospective review of hospitalized pediatric patients between 2 months and 17 years of age treated with intravenous vancomycin from 2008 to 2011. The primary outcome was the number of patients achieving a target trough concentration of 10 to 20 μg/mL in each age group and dosing group. The secondary outcomes were the number of patients in each group to achieve a trough concentration of 15 to 20 μg/mL and the incidence of vancomycin-induced nephrotoxicity.

RESULTS

A total of 102 patients were included in the analysis. Forty-six of 159 evaluated troughs (28.9%) were within the target range of 10 to 20 μg/mL. Dose was found to have a statistically significant effect on the ability to achieve a trough within the target range (P = .01). Of the 159 trough concentrations evaluated, only 11 (6.9%) were within the range of 15 to 20 μg/mL. Nephrotoxicity occurred in 7 patients and was not associated with supratherapeutic trough concentration or dose.

CONCLUSIONS

The number of trough concentrations within the target range of 10 to 20 μg/mL was low, and younger patients often needed doses >60 mg/kg per day to achieve a trough concentration in this range. The dose of vancomycin was found to have a statistically significant effect on the ability to achieve a trough concentration within the target range.

Assessment of initial vancomycin dosing in neonates

BACKGROUND

Vancomycin is recommended for optimal treatment of late-onset sepsis caused by coagulase-negative Staphylococcus in neonates.

OBJECTIVES

To assess the performance of an empirical vancomycin dosing regimen in achieving target trough levels, and to revise this regimen if needed.

METHODS

Data regarding doses and levels were collected and pharmacokinetic parameters were calculated, where possible, for neonates receiving vancomcyin in a neonatal intensive care unit. The primary measure was the percentage of neonates with initial prevancomycin levels of <10 mg/L, 10 mg/L to 20 mg/L and >20 mg/L. Secondary measures included the percentage of neonates with extrapolated trough levels in these ranges, total daily doses that achieved target levels (10 mg/L to 20 mg/L) and total daily doses/dosing intervals that were pharmacokinetically predicted to achieve trough levels of 15 mg/L.

RESULTS

Of 153 infants started on the empirical regimen (15 mg/kg/day to 45 mg/kg/day, depending on postnatal age and weight), 34.2% initially achieved target trough levels (mean 8.7 mg/L). Analysis of actual doses and pharmacokinetically predicted doses required to reach target levels suggested increasing the empirical dosing for all neonatal age groups. The revised regimen used in the present study (20 mg/kg/day to 40 mg/kg/day, depending on postmenstrual age and postnatal age) was predicted to result in 72% of infants achieving initial target trough levels (mean 15.4 mg/L).

CONCLUSIONS

A revised empirical vancomycin dosage regimen for neonates was required based on poor achievement of target trough levels (10 mg/L to 20 mg/L) using the previous regimen. The modified regimen is predicted to reach target trough levels more often and increase the mean initial trough levels achieved. This regimen requires clinical validation in an independent cohort in the future.

Vancomycin dosing in healthy-weight, overweight, and obese pediatric patients

OBJECTIVES

With an increase in vancomycin resistance and the prevalence of obesity in children, alterations of vancomycin dosing regimens may be necessary to achieve target serum concentrations. The primary objective of this study was to describe initial vancomycin dosing with resulting serum concentrations in healthy-weight and overweight/obese children. Secondary objectives include comparing vancomycin dosing regimens of healthy-weight and overweight/obese patients that produced target trough serum concentrations and evaluating the likelihood of attaining target concentrations by patient characteristics.

METHODS

This retrospective review evaluated healthy-weight and overweight/obese patients, aged 2 to 18 years, who had vancomycin trough serum concentrations obtained between 2005 and 2010. Vancomycin dosing, initial trough serum concentrations, pharmacokinetic parameters, and patient demographics were collected for analysis. Target trough serum concentrations were defined as 10 to 20 mg/L.

RESULTS

The study included 98 patients (48 healthy weight, 50 overweight/obese) of which only 14 patients (14.2%, 6 healthy weight, 8 obese) reached a target trough serum concentration with empiric dosing. No difference was found between the mean daily dosing of vancomycin that produced target trough serum concentrations in healthy-weight or overweight/obese patients (53.63 mg/kg/day vs 51.6 mg/kg/day, respectively). Demographic or clinical characteristics were not found to be associated with the likelihood of target trough serum concentration attainment.

CONCLUSIONS

Vancomycin dosing in healthy-weight and overweight/obese pediatric patients did not reach target trough serum concentrations most of the time. In obtaining initial target serum concentrations, no dosing difference was identified for overweight/obese patients compared with healthy-weight patients. Alternate dosing strategies, therapeutic monitoring, and clinical outcomes should continue to be evaluated in this population.

Factors Associated With Acute Kidney Injury in Children Receiving Vancomycin

Background: As higher vancomycin doses have been used in children, concern for acute kidney injury (AKI) has increased. Data describing factors associated with AKI, particularly dose-related factors, are limited. Objective: To determine the incidence of AKI in children receiving intravenous vancomycin and to identify factors associated with increased odds of AKI. Methods: A retrospective review of patients admitted to a tertiary academic pediatric hospital from February 2009 to September 2010 was performed. Patients 3 months to <19 years old with normal kidney function, receiving vancomycin for at least 48 hours were included. Incidence of AKI was assessed as defined by the Pediatric-Modified RIFLE criteria. Patients with and without AKI were compared to determine factors associated with increased odds of AKI, focusing on vancomycin dose. Results: Of 175 patients included, 24 (13.7%) met AKI criteria. In a multivariate regression, likelihood of AKI increased with each 5 mg/kg increase in vancomycin dose (odds ratio [OR] = 1.16; 95% CI = 1.01-1.33). Odds of AKI increased with each additional day of therapy (OR = 1.11; 95% CI = 1.01-1.22) and use of concomitant nephrotoxic medications (OR = 5.02; 95% CI = 1.09-23.19). The study was limited by small sample size and retrospective design. Conclusions: AKI was common in children receiving vancomycin. Higher doses of vancomycin were associated with increased odds of AKI. The risks and benefits of higher vancomycin dosing should be considered for each patient. Patients should be monitored closely for AKI, especially with higher doses, extended durations of therapy, or concomitant use of nephrotoxic medications.

Association between vancomycin trough concentration and area under the concentration-time curve in neonates

National treatment guidelines for invasive methicillin-resistant Staphylococcus aureus (MRSA) infections recommend targeting a vancomycin 24-h area under the concentration-time curve (AUC0-24)-to-MIC ratio of >400. The range of vancomycin trough concentrations that best predicts an AUC0-24 of >400 in neonates is not known. This understanding would help clarify target trough concentrations in neonates when treating MRSA. A retrospective chart review from a level III neonatal intensive care unit was performed to identify neonates treated with vancomycin over a 5-year period. Vancomycin concentrations and clinical covariates were utilized to develop a one-compartment population pharmacokinetic model and examine the relationships between trough and AUC0-24 in the study neonates. Monte Carlo simulations were performed to examine the effect of dose, postmenstrual age (PMA), and serum creatinine level on trough and AUC0-24 achievement. A total of 1,702 vancomycin concentrations from 249 neonates were available for analysis. The median (interquartile range) PMA was 39 weeks (32 to 42 weeks) and weight was 2.9 kg (1.6 to 3.7 kg). Vancomycin clearance was predicted by weight, PMA, and serum creatinine level. At a trough of 10 mg/liter, 89% of the study neonates had an AUC0-24 of >400. Monte Carlo simulations demonstrated that troughs ranging from 7 to 11 mg/liter were highly predictive of an AUC0-24 of >400 across a range of PMA, serum creatinine levels, and vancomycin doses. However, a trough of ≥10 mg/liter was not readily achieved in most simulated subgroups using routine starting doses. Higher starting doses frequently resulted in troughs of >20 mg/liter. A vancomycin trough of ∼10 mg/liter is likely adequate for most neonates with invasive MRSA infections based on considerations of the AUC0-24. Due to pharmacokinetic and clinical heterogeneity in neonates, consistently achieving this target vancomycin exposure with routine starting doses is difficult. More robust clinical dosing support tools are needed to help clinicians with dose individualization.

Vancomycin monitoring in children using bayesian estimation

BACKGROUND

Optimal monitoring of vancomycin in children needs evaluation using the exposure target with area under the curve (AUC) of the serum concentrations versus time over 24 hours. Our study objectives were to: (1) compare the accuracy and precision of vancomycin AUC estimations using 2 sampling strategies-1 serum concentration sample (1S, near trough) versus 2 samples (2S, near peak and trough) against the rich sample (RS) method; and (2) determine the performance of these strategies in predicting future AUC against an internal validation sample (VS).

METHODS

This was a retrospective cohort study using population-based pharmacokinetic modeling with Bayesian post hoc individual estimations in nonlinear mixed effects modeling (version 7.2). Pediatric subjects 3 months-21 years of age who received vancomycin ≥48 hours and had more than 3 drug samples within the first ≤96 hours of therapy were enrolled. Outcome measures were the accuracy, precision, and internal predictive performance of AUC estimations using 2 monitoring strategies (ie, 1S versus 2S) against the RS (which was derived from modeling all serum vancomycin concentrations obtained anytime during therapy) and VS (from serum concentrations obtained after 96 hours of therapy).

RESULTS

Analysis included 138 subjects with 712 vancomycin serum concentrations. Median age was 6.1 (interquartile range, 2.2-12.2) years, weight 22 (13-38) kg, and baseline serum creatinine 0.37 (0.30-0.50) mg/dL. Both accuracy and precision were improved with the 2S, compared with 1S, for AUC estimations (-2.0% versus -7.6% and 10.3% versus 12.8%, respectively) against the RS. Improved accuracy and precision were also observed for 2S when evaluated against VS in predicting future AUC.

CONCLUSIONS

Compared with 1S, the 2S sampling strategy for vancomycin monitoring improved accuracy and precision in estimating and predicting future AUC. Evaluating 2 drug concentrations in children may be prudent to ensure adequate drug exposure.

Inadequate vancomycin therapy in term and preterm neonates: a retrospective analysis of trough serum concentrations in relation to minimal inhibitory concentrations

Background

Vancomycin is effective against gram-positive bacteria and the first-line antibiotic for treatment of proven coagulase-negative staphylococcal infections. The aim of this study is bipartite: first, to assess the percentage of therapeutic initial trough serum concentrations and second, to evaluate the adequacy of the therapeutic range in interrelationship with the observed MIC-values in neonates.

Methods

In this study, preterm and term neonates admitted at a tertiary NICU in the Netherlands from January 2009 to December 2012 and treated with vancomycin for a proven gram-positive infection were included. Trough serum concentrations were measured prior to administration of the 5th dose. Trough concentrations in the range of 10 to 15 mg/L were considered therapeutic. Staphylococcal species minimal inhibitory concentrations (MIC’s) were determined using the E-test method. Species identification was performed by matrix-assisted laser desorption/ionisation mass spectrometry.

Results

Of the 112 neonates, 53 neonates (47%) had sub-therapeutic initial trough serum concentrations of vancomycin, whereas 22% had supra-therapeutic initial trough serum concentrations. In all patients doses were adjusted on basis of the initial trough concentration. In 40% (23/57) of the neonates the second trough concentration remained sub-therapeutic. MIC’s were determined for 30 coagulase-negative Staphylococcus isolates obtained from 19 patients. Only 4 out of 19 subjects had a trough concentration greater than tenfold the MIC.

Conclusions

Forty-seven percent of the neonates had sub-therapeutic initial trough serum concentrations of vancomycin. The MIC-data indicate that the percentages of underdosed patients may be greater. It may be advisable to increase the lower limit of the therapeutic range for European neonates.

Prospective validation of neonatal vancomycin dosing regimens is urgently needed

BACKGROUND

Although vancomycin is frequently used to treat neonatal late-onset sepsis, there is no consensus on the optimal dosing regimen. Because many neonates needed dosing adaptation due to suboptimal trough values, the vancomycin dosing regimen in our neonatal department was changed during 2012.

OBJECTIVE

We aimed to document the need for validation of neonatal vancomycin dosing by exploring serum trough levels achieved using 2 published dosing regimens (previous regimen: based on postmenstrual age and serum creatinine and new regimen: based on postmenstrual age and postnatal age) and to identify covariates associated with suboptimal vancomycin trough levels (<10 mg/L).

METHODS

Routine therapeutic drug monitoring serum trough levels quantified after initiation of intravenous vancomycin therapy and clinical covariates were retrospectively collected. Median vancomycin trough levels of both dosing regimens were compared using the Mann-Whitney U test. The influence of continuous and dichotomous covariates on achieving a suboptimal trough level was explored using the Van Elteren test (stratified Mann-Whitney U test) and Mantel-Haenszel test (stratified χ(2) test), respectively. Covariates significant in monovariate analysis were subsequently included in a logistic regression analysis.

RESULTS

In total, 294 observations (median current weight 1870 g [range = 420-4863 g] and median postmenstrual age 35.07 weeks [range = 25.14-56.00 weeks]) were included. Using the previous and new dosing regimens, 66.3% and 76.2% of trough levels, respectively, were below 10 mg/L. Overall, suboptimal vancomycin trough values were significantly associated with lower weight (birth weight and current weight) and age (gestational age and postmenstrual age).

CONCLUSIONS

The majority of vancomycin trough levels in neonates achieved using 2 published dosing regimens did not reach the target of 10 mg/L. This illustrates the urgent need for prospective validation of neonatal vancomycin dosing regimens. We anticipate that dosing regimens integrating covariates reflecting general physiological maturation and renal maturation, as well as disease characteristics, could improve vancomycin exposure in neonates.

Clinical evaluation of vancomycin dosage in pediatric oncology patients

Vancomycin trough serum concentrations were below therapeutic range (8-15 mg/L) in 58% of 124 pediatric oncology patients receiving 60 mg/kg/d divided qid. Patients <6 and between 6 and 12 years had significantly lower trough concentrations than patients >12 years. A vancomycin dosage of 60 mg/kg/d is inadequate for pediatric oncology patients >12 years.

Neonatal vancomycin continuous infusion: still a confusion?

BACKGROUND

Continuous infusions of vancomycin over 24 hours have been shown in adults to reduce drug toxicity, lower treatment costs and require fewer blood samples for therapeutic drug monitoring. They may also improve clinical outcome through earlier attainment of target drug concentrations. In neonates, there is no consensus on vancomycin dosing. We reviewed the literature to assess the evidence for vancomycin dosing regimens for continuous infusion in neonates.

METHODS

Medline and Embase were searched for studies about continuous vancomycin dosing regimens in neonates that reported serum drug concentrations. The search identified 469 articles, of which 5 were relevant.

RESULTS

Five prospective studies were included; 2 studies used non-linear mixed effects modeling. Vancomycin was administered with parenteral nutrition or 5% dextrose. Target serum concentrations varied (range: 10-30 mg/L). Four studies used loading doses before continuous infusion; only 1 documented achievement of therapeutic concentrations after the load. The time to a therapeutic concentration was not reported for the other studies. Attainment of target concentrations ranged from 56% to 89% of measurements. Only 1 study compared intermittent to continuous infusions, reporting higher attainment of target concentrations with continuous dosing (82% vs. 46%). No adverse effects were reported, although 3 neonates developed a reversible raised serum creatinine in the setting of septicemia.

CONCLUSION

Continuous infusions of vancomycin in neonates are well tolerated, require less blood sampling and may result in improved attainment of target concentrations. Further prospective studies are needed in this population.

Are Elevated Vancomycin Serum Trough Concentrations Achieved Within the First 7 Days of Therapy Associated With Acute Kidney Injury in Children?

BACKGROUND

In 2008, the empiric vancomycin dosing recommendation in children at our institution was changed from 40 to 60 mg/kg per day. Subsequently, an increased incidence of acute kidney injury (AKI) in patients receiving vancomycin was suspected. The objective of this study was to evaluate AKI in children receiving vancomycin and to determine risk factors for AKI development.

METHODS

Medical records of patients aged 30 days through 17 years who received vancomycin for at least 72 hours between January and December 2007 (40 mg/kg per day) and January and December 2010 (60 mg/kg per day) were reviewed. Patients with cystic fibrosis, an elevated baseline serum creatinine, or without a serum creatinine concentration obtained after receipt of vancomycin were excluded. Acute kidney injury was defined using adapted pediatric RIFLE criteria as an increase in serum creatinine from baseline of 50% or more.

RESULTS

Acute kidney injury occurred in 19.4% of the 859 children included, with no difference between the 2007 and 2010 periods (18.8% vs 20%, respectively; P = .636). Intensive care unit admission (odds ratio [OR], 1.86; 95% confidence interval [CI], 1.20-2.94) and an initial vancomycin trough concentration ≥15 mg/L (OR, 2.18; 95% CI, 1.21-3.92) were determined to be significantly associated with AKI.

CONCLUSIONS

These results suggest an initial vancomycin serum trough concentration of ≥15 mg/L and intensive care unit admission are predictors of AKI in this pediatric population.

Implications of serum creatinine measurements on GFR estimation and vancomycin dosing in children

BACKGROUND

Different serum creatinine (sCr) assays may obtain different values in the same patient, causing discrepancies in estimated glomerular filtration rate (eGFR) and sCr-based vancomycin dosing calculations.

OBJECTIVE

To identify potential discrepancies in sCr concentrations obtained by different assays, the compensated Jaffe (sCr-Jaffe) and the enzymatic (sCr-enz), and to compare between the eGFR and vancomycin daily dose, based on these sCr values.

METHOD

sCr-Jaffe and, sCr-enz concentrations of 890 healthy children, aged 1-18 years, were available from the Canadian Laboratory Initiative in Pediatric Reference Intervals study in Ontario. For each subject, eGFR (eGFR-Jaffe, eGFR-enz) was calculated using the revised Schwartz equation, and vancomycin daily dose (Vdose-Jaffe, Vdose-enz) was calculated using a sCr-based pharmacokinetic model.

RESULT

Significant, age-related differences were found in sCr concentrations, and in subsequent eGFR and Vdose, between the two assays. In children aged 1-5 years, mean sCr-Jaffe was higher than sCr-enz (44.0 ± 5.0 vs. 27.7 ± 7.3 μmol/L, P < 0.001), leading to lower eGFR-Jaffe (83.2 ± 9.0 vs. 137.9 ± 27.1 mL/min/1.73m2, P < 0.001) and lower Vdose-Jaffe (44.7 ± 2.5 vs. 53.5 ± 5.1 mg/kg/24 h, P < 0.001).

CONCLUSION

Based on these findings, young children may be at risk for vancomycin under-treatment. Further research is needed to define the more accurate sCr assay in young children treated with renally excreted drugs.

Population-Based Pharmacokinetic Modeling of Vancomycin in Children with Renal Insufficiency

BACKGROUND

Vancomycin dosing to achieve the area-under-the-curve to minimum inhibitory concentration (AUC/MIC) target of ≥ 400 in children with renal insufficiency is unknown. Our objectives were to compare vancomycin clearance (CL) and initial dosing in children with normal and impaired renal function.

METHODS

Using a matched case-control study in subjects ≥ 3 months old who received vancomycin ≥ 48 hr, we performed population-based modeling with empiric Bayesian post-hoc individual parameter estimations and Monte Carlo simulations. Cases, defined by baseline serum creatinine (SCr) ≥ 0.9 mg/dL, were matched 1:1 to controls by age and weight.

RESULTS

Analysis included 63 matched pairs with 319 serum concentrations. Mean age (± SD) was 13 ± 6 yr and weight, 51 ± 25 kg. Mean baseline SCr was 0.6 ± 0.2 mg/dL for controls, and 1.3 ± 0.5 for cases. Age, SCr, and weight were independent covariates for CL. Final model parameters and inter-subject variability (ISV) were: CL(L/hr) = 0.235*Weight^0.75*(0.64/SCr)^0.497*(ln(DOL)/8.6)^1.19 ISV=39%, where DOL is day of life. Target AUC/MIC ≥ 400 was achieved in 80% of cases at vancomycin 45 mg/kg/day, but required 60 mg/kg/day for controls. Drug CL improved in 87% of cases due to recovery of renal function.

CONCLUSION

Due to reduced CL, a less frequent dosing at 15 mg/kg every 8 hr (i.e., 45 mg/kg/day) may be appropriate for some children with renal impairment. Close monitoring of renal function and drug concentrations is prudent to ensure adequate drug exposure, especially in those with renal impairment since recovery of renal function may occur during therapy.

Dose optimisation of antibiotics in children: application of pharmacokinetics/pharmacodynamics in paediatrics

The judicious use of antibiotics to combat infections in children relies upon appropriate selection of an agent, dose and duration to maximise efficacy and to minimise toxicity. Critical to dose optimisation is an understanding of the pharmacokinetics and pharmacodynamics of available drugs. Optimal dosing strategies may take advantage of pharmacokinetic/pharmacodynamic (PK/PD) principles so that antibiotic dosing can be individualised to assure effective bacterial killing in patients who have altered pharmacokinetics or who have infections with less susceptible or resistant organisms. This review will outline the fundamentals of antimicrobial pharmacokinetics/pharmacodynamics through discussion of antibacterial agents most often used in children. We aim to highlight the importance of dose optimisation in paediatrics and describe non-conventional dosing strategies that can take advantage of PK/PD principles at the bedside.

Vancomycin dosing in children: what is the question?

Vancomycin has been in clinical use for over 60 years, but it is still not clear what dose should be given to children. Effective treatment with vancomycin requires a serum concentration well above the minimum inhibitory concentration (MIC) of the bacteria being treated. This is predicted by the area under the concentration curve (AUC) divided by the MIC being >400 (AUC/MIC). Recent concerns about increasing MIC in staphylococci have lead to recommendations to aim for higher trough vancomycin levels (15-20 mg/L). In current practice, most children do not achieve these trough levels. Modelling and pharmacokinetic studies in children suggest these trough levels may not be necessary if the MIC of the organisms is 1 mg/L or less. Further, large-scale studies are needed to determine the most appropriate dosing of vancomycin in children. While awaiting these, it is time to consider moving to 15 mg/kg 6 h as a standard starting regime for vancomycin. It is also vital to determine the MIC of the organism being treated, as this may give some guidance about suitable trough levels to be aimed for. There is currently little evidence to guide the use of loading doses or continuous vancomycin infusions in children.

Treating paediatric community-acquired pneumonia in the era of antimicrobial resistance

Increasing levels of paediatric community-acquired pneumonia (CAP), caused by drug-resistant bacteria and antimicrobial resistance, vary with age and countries and, in some cases, serotypes. When empirical first-line treatment administration fails, paediatricians should consider second-line treatments based on the prevalence of local resistance. A more judicious use of antimicrobial agents is also required.

CONCLUSION

Knowledge of local epidemiology and an appropriate use of antimicrobial drugs are necessary to treat CAP in this era of antimicrobial resistance.

A randomized controlled trial of a vancomycin loading dose in children

BACKGROUND

Despite its frequent use, the optimal dosing regimen of intravenous vancomycin remains controversial. Achievement of therapeutic trough early in the course of illness may be beneficial. Our objective was to assess whether a loading dose of vancomycin would increase the proportion of children reaching target trough concentrations 8 hours after initiation of therapy.

METHODS

We enrolled hospitalized children aged 2-18 years prescribed vancomycin at Boston Children's Hospital between February 2011 and January 2012. Participants were randomized to receive a loading dose (30 mg/kg) or a conventional initial dose (20 mg/kg). These were followed by a 20 mg/kg/dose every 8 hours in both groups. Serum vancomycin concentrations were measured before the second and third doses. Pharmacokinetic parameters were calculated using individual and population pharmacokinetic models.

RESULTS

Two of nineteen (11%) loading dose recipients had a trough 15-20 mg/L before the second dose, compared with 0 of 27 in the conventional dose group (P=0.17). However, the median area under the curve/minimum inhibitory concentration estimates (for a hypothetical minimum inhibitory concentration=1 mg/L) were above 400 in both groups. Red man syndrome incidence was higher in loading dose recipients (48% vs. 24%, P=0.06).

CONCLUSIONS

A vancomycin loading dose did not result in earlier achievement of therapeutic trough concentrations in this study. However, the systemic exposure to vancomycin in children administered 60 mg/kg/day was adequate, despite lower than recommended measured trough levels. Therefore, the need for higher target trough concentrations should be questioned.

Are vancomycin trough concentrations adequate for optimal dosing?

The current vancomycin therapeutic guidelines recommend the use of only trough concentrations to manage the dosing of adults with Staphylococcus aureus infections. Both vancomycin efficacy and toxicity are likely to be related to the area under the plasma concentration-time curve (AUC). We assembled richly sampled vancomycin pharmacokinetic data from three studies comprising 47 adults with various levels of renal function. With Pmetrics, the nonparametric population modeling package for R, we compared AUCs estimated from models derived from trough-only and peak-trough depleted versions of the full data set and characterized the relationship between the vancomycin trough concentration and AUC. The trough-only and peak-trough depleted data sets underestimated the true AUCs compared to the full model by a mean (95% confidence interval) of 23% (11 to 33%; P = 0.0001) and 14% (7 to 19%; P < 0.0001), respectively. In contrast, using the full model as a Bayesian prior with trough-only data allowed 97% (93 to 102%; P = 0.23) accurate AUC estimation. On the basis of 5,000 profiles simulated from the full model, among adults with normal renal function and a therapeutic AUC of ≥400 mg · h/liter for an organism for which the vancomycin MIC is 1 mg/liter, approximately 60% are expected to have a trough concentration below the suggested minimum target of 15 mg/liter for serious infections, which could result in needlessly increased doses and a risk of toxicity. Our data indicate that adjustment of vancomycin doses on the basis of trough concentrations without a Bayesian tool results in poor achievement of maximally safe and effective drug exposures in plasma and that many adults can have an adequate vancomycin AUC with a trough concentration of <15 mg/liter.

The effect of age and weight on vancomycin serum trough concentrations in pediatric patients

BACKGROUND

Vancomycin treatment failure has been associated with low serum vancomycin trough concentrations, prompting recommendations to increase the daily doses in adults and children. Despite more aggressive vancomycin dosing, there continues to be significant variability in vancomycin trough concentrations in pediatric patients.

METHODS

To determine if vancomycin trough concentrations in pediatric patients differ by age and weight, we reviewed records of hospitalized patients who received vancomycin between 2008 and 2012. Patients were divided into groups that received vancomycin 40 mg/kg/day (2008-2009) or 60 mg/kg/day (2010-2012). Vancomycin trough concentrations were compared between groups and within the 60 mg/kg/day group, stratified by patient age and weight.

RESULTS

After increasing the vancomycin dose from 40 to 60 mg/kg/day, initial trough concentrations increased significantly in patients younger than 2 and greater than 6 years of age, but not in patients between the ages of 2 and 5 years. In the 60 mg/kg/day group, only 16.7% of patients between 2 and 5 years of age had initial trough concentrations in the therapeutic range (10-20 μg/ml). Initial trough concentrations were therapeutic in a greater proportion of patients ages 6-12 years (38.7%) and 13-18 years (63.0%). Patients between the ages of 13 and 18 had the highest proportion of supratherapeutic initial vancomycin trough concentrations (14.8%). Patients weighing over 50 kg had significantly higher trough concentrations than patients  50 kg or less (17.1 μg/ml vs 9.3 μg/ml, p<0.001).

CONCLUSION

Although increasing the vancomycin dose from 40 to 60 mg/kg/day led to a significant increase in vancomycin trough concentrations, a large proportion of patients receiving 60 mg/kg/day of vancomycin had trough concentrations outside of the therapeutic range. Specifically, patients younger than 6 years tended to have low trough concentrations, whereas adolescents and children over 50 kg were more likely to have elevated trough concentrations. Vancomycin dosing strategies in pediatric patients should consider age and weight as well as renal function and indication.

Vancomycin trough concentrations in overweight or obese pediatric patients

STUDY OBJECTIVES

To compare vancomycin trough concentrations in overweight or obese pediatric patients to those with normal body habitus, after initial dosing based on total body weight (TBW).

DESIGN

Retrospective observational case-control study.

SETTING

Free-standing academic pediatric hospital.

PATIENTS

Forty-two overweight or obese pediatric patients were matched to 84 children of normal body habitus (NBH).

MEASUREMENTS AND MAIN RESULTS

Empiric vancomycin dosing was based on TBW and guided by an age-stratified dosing algorithm previously developed at our center. Initial steady-state vancomycin trough concentrations were retrieved from the electronic medical record. Overweight and obese children had significantly higher initial vancomycin trough concentrations compared with children who had an NBH (median 14.4 μg/ml vs 10.5 μg/ml, p<0.001). Initial vancomycin trough concentrations above 20 μg/ml occurred more often in overweight and obese children (p=0.016). Our dosing algorithm suggested that initial vancomycin trough concentrations below 10 μg/ml occurred significantly more often in children with NBH (p<0.001).

CONCLUSIONS

Overweight and obese pediatric patients may have elevated initial vancomycin trough concentrations when empiric dosing is based on TBW. Special attention to therapeutic drug monitoring is warranted in all children.