Pharmacodynamics of vancomycin for CoNS infection: experimental basis for optimal use of vancomycin in neonates

Continuous Versus Intermittent Vancomycin Infusions for Coagulase-negative Staphylococcus Bacteremia in Neonates: A Propensity-matched Cohort Study

BACKGROUND

Coagulase-negative staphylococci (CONS) are a major cause of late-onset neonatal sepsis, particularly in preterm infants, with high morbidity and mortality. While vancomycin is the first-line treatment for these infections, the optimal administration in neonates remains uncertain.

OBJECTIVE

We aim to compare the outcomes of neonates with CONS bacteremia treated with adjusted continuous infusion (CIV) versus standard intermittent infusion (IIV) of vancomycin.

METHODS

This retrospective study included 110 neonates, with 29 in the CIV group and 47 in the IIV group after propensity score matching. The primary outcome was treatment failure defined by the persistence of a positive blood culture for the same organism after at least 48 hours of vancomycin treatment.

RESULTS

After matching, the CIV group exhibited significantly lower treatment failure rates [5/29 (17%) vs. 26/47 (44%); P = 0.014] and a higher rate of achieving therapeutic vancomycin levels after 24 hours [20/29 (69%) vs. 26/47 (44%); P = 0.002] compared to the IIV group. No significant differences were observed in terms of acute kidney failure between the 2 groups.

CONCLUSION

Adjusted continuous vancomycin infusion in neonates with CONS bacteremia is associated with a lower treatment failure rate without an increase in renal toxicity compared to standard intermittent infusion. However, due to the observational design, larger prospective studies are needed to validate these results.

Association of Vancomycin AUC/MIC and Trough Concentration With Early Clinical Response in Enterococcus or Coagulase-Negative Staphylococcus Infection: A Prospective Study

This study was condcuted to examine the association of area under the curve (AUC)/minimum inhibitory concentration (MIC) and trough concentration (Ctrough) of vancomycin with treatment outcome and nephrotoxicity in infections caused by Enterococcus spp. and coagulase-negative Staphylococci (CoNS). Peak and trough concentrations were used to calculate AUC in 89 patients receiving vancomycin for infections with Enterococcus spp. (n = 65) or CoNS (n = 24). Correlations between Ctrough, AUC/MIC, early clinical response (ECR), and nephrotoxicity were assessed and cutoff values were determined. Sixty-three (70.8%) patients showed improvement in ECR and 10 (11.2%) experienced nephrotoxicity. Enterococcus spp. infections displayed correlations between AUC/MIC and ECR for AUC0-24 h/MIC (r2 = 0.27, P ≤ .05) and AUC24-48 h/MIC (r2 = 0.28, P ≤ .05), but not for Ctrough (r2 = 0.21, P > .05). There were no correlations between Ctrough (r2 = 0.26, P > .05), AUC0-24 h/MIC (r2 = -0.12, P > .05), AUC24-48 h/MIC (r2 = 0.01, P > .05) and ECR for CoNS. In the CoNS group, a moderate correlation was found between ECR and Ctrough at a cutoff value of 6.9 μg/mL. In addition, nephrotoxicity is also moderately associated with AUC0-24 h and AUC24-48 h at 505.7 and 667.1 μg•h/mL, respectively. A strong correlation between nephrotoxicity and Ctrough was observed when the cutoff value was 18.9 μg/mL. AUC/MIC during the first 48 h was a determinant of vancomycin efficacy in Enterococcus infections but not for CoNS. Ctrough was not correlated with clinical outcome. Nephrotoxicity could be predicted using Ctrough and AUC for infections with both pathogens.

Antibiotics, Analgesic Sedatives, and Antiseizure Medications Frequently Used in Critically Ill Neonates: A Narrative Review

Antibiotic, analgesic sedative, and antiseizure medications are among the most commonly used medications in preterm/sick neonates, who are at high risk of nosocomial infections, central nervous system complications, and are exposed to numerous painful/stressful procedures. These severe and potentially life-threatening complications may have serious short- and long-term consequences and should be prevented and/or promptly treated. The reported variability in the medications used in neonates indicates the lack of adequate neonatal studies regarding their effectiveness and safety. Important obstacles contributing to inadequate studies in preterm/sick infants include difficulties in obtaining parental consent, physicians' unwillingness to recruit preterm infants, the off-label use of many medications in neonates, and other scientific and ethical concerns. This review is an update on the use of antimicrobials (antifungals), analgesics (sedatives), and antiseizure medications in neonates, focusing on current evidence or knowledge gaps regarding their pharmacokinetics, indications, safety, dosage, and evidence-based guidelines for their optimal use in neonates. We also address the effects of early antibiotic use on the intestinal microbiome and its association with long-term immune-related diseases, obesity, and neurodevelopment (ND). Recommendations for empirical treatment and the emergence of pathogen resistance to antimicrobials and antifungals are also presented. Finally, future perspectives on the prevention, modification, or reversal of antibiotic resistance are discussed.

Predicting treatment response to vancomycin using bacterial DNA load as a pharmacodynamic marker in premature and very low birth weight neonates: A population PKPD study

Background: While positive blood cultures are the gold standard for late-onset sepsis (LOS) diagnosis in premature and very low birth weight (VLBW) newborns, these results can take days, and early markers of possible treatment efficacy are lacking. The objective of the present study was to investigate whether the response to vancomycin could be quantified using bacterial DNA loads (BDLs) determined by real-time quantitative polymerase chain reaction (RT-qPCR). Methods: VLBW and premature neonates with suspected LOS were included in a prospective observational study. Serial blood samples were collected to measure BDL and vancomycin concentrations. BDLs were measured with RT-qPCR, whereas vancomycin concentrations were measured by LC-MS/MS. Population pharmacokinetic-pharmacodynamic modeling was performed with NONMEM. Results: Twenty-eight patients with LOS treated with vancomycin were included. A one-compartment model with post-menstrual age (PMA) and weight as covariates was used to describe the time PK profile of vancomycin concentrations. In 16 of these patients, time profiles of BDL could be described with a pharmacodynamic turnover model. The relationship between vancomycin concentration and first-order BDL elimination was described with a linear-effect model. Slope S increased with increasing PMA. In 12 patients, no decrease in BDL over time was observed, which corresponded with clinical non-response. Discussion: BDLs determined through RT-qPCR were adequately described with the developed population PKPD model, and treatment response to vancomycin using BDL in LOS can be assessed as early as 8 h after treatment initiation.

Assessment of flomoxef combined with amikacin in a hollow-fibre infection model for the treatment of neonatal sepsis in low- and middle-income healthcare settings

BACKGROUND

Annual mortality from neonatal sepsis is an estimated 430 000-680 000 infants globally, most of which occur in low- and middle-income countries (LMICs). The WHO currently recommends a narrow-spectrum β-lactam (e.g. ampicillin) and gentamicin as first-line empirical therapy. However, available epidemiological data demonstrate high rates of resistance to both agents. Alternative empirical regimens are needed. Flomoxef and amikacin are two off-patent antibiotics with potential for use in this setting.

OBJECTIVES

To assess the pharmacodynamics of flomoxef and amikacin in combination.

METHODS

The pharmacodynamic interaction of flomoxef and amikacin was assessed in chequerboard assays and a 16-arm dose-ranged hollow-fibre infection model (HFIM) experiment. The combination was further assessed in HFIM experiments mimicking neonatal plasma exposures of clinically relevant doses of both drugs against five Enterobacterales isolates with a range of flomoxef/amikacin MICs.

RESULTS

Flomoxef and amikacin in combination were synergistic in bacterial killing in both assays and prevention of emergence of amikacin resistance in the HFIM. In the HFIM assessing neonatal-like drug exposures, the combination killed 3/5 strains to sterility, (including 2/5 that monotherapy with either drug failed to kill) and failed to kill the 2/5 strains with flomoxef MICs of 32 mg/L.

CONCLUSIONS

We conclude that the combination of flomoxef and amikacin is synergistic and is a potentially clinically effective regimen for the empirical treatment of neonatal sepsis in LMIC settings and is therefore suitable for further assessment in a clinical trial.

Development of an innovative in vivo model of PJI treated with DAIR

Introduction

Prosthetic Joint Infection (PJI) are catastrophic complications of joint replacement. Debridement, implant retention, and antibiotic therapy (DAIR) is the usual strategy in acute infections but fails in 45% of MRSA infections. We describe the development of a model of infected arthroplasty in rabbits, treated with debridement and a course of vancomycin with clinically relevant dosage.

Materials and methods

A total of 15 rabbits were assigned to three groups: vancomycin pharmacokinetics (A), infection (B), and DAIR (C). All groups received a tibial arthroplasty using a Ti-6Al-4V implant. Groups B and C were infected per-operatively with a 5.5 log10 MRSA inoculum. After 1 week, groups C infected knees were surgically debrided. Groups A and C received 1 week of vancomycin. Pharmacokinetic profiles were obtained in group A following 1st and 5th injections. Animals were euthanized 2 weeks after the arthroplasty. Implants and tissue samples were processed for bacterial counts and histology.

Results

Average vancomycin AUC_{0–12 h} were 213.0 mg*h/L (1st injection) and 207.8 mg*h/L (5th injection), reaching clinical targets. All inoculated animals were infected. CFUs were reproducible in groups B. A sharp decrease in CFU was observed in groups C. Serum markers and leukocytes counts increased significantly in infected groups.

Conclusion

We developed a reproducible rabbit model of PJI treated with DAIR, using vancomycin at clinically relevant concentrations.

Association between Vancomycin Pharmacokinetic Parameters and Clinical and Microbiological Efficacy in a Cohort of Neonatal Patients

Vancomycin pharmacokinetic/pharmacodynamic (PK/PD) targets have not been validated in the neonatal population as no specifically designed studies are available. The main goal of this study was to analyze the therapeutic vancomycin regimen, the 24-h area under the curve (AUC₂₄), and the trough plasma concentration (C_t) obtained that achieved clinical and microbiological effectiveness in a cohort of neonates. This was an observational, prospective, single-center study covering a period of 2 years. Eligible patients were neonates and young infants who were undergoing treatment with intravenous vancomycin for ≥72 h with ≥1 C_t available. The primary outcome was the association of C_t and AUC₂₄ with clinical and microbiological efficacy at the beginning (early clinical evolution [ECE]) and the end (late clinical evolution [LCE]) of treatment with vancomycin. A total of 43 patients were included, 88.4% of whom were cured. In ECE, the cutoff points of the receiver operating characteristic (ROC) curve were 238 mg · h/L (sensitivity of 61% and specificity of 88%) for AUC₂₄ and 6.8 μg/mL (sensitivity of 61% and specificity of 92%) for C_t. In LCE, the C_t value was 11 μg/mL, with a sensitivity of 80% and a specificity of 92%. In this analysis, AUC₂₄ was not considered a good predictor. Logistic regression showed that a vancomycin C_t of ≤6.8 μg/mL was associated with an unfavorable ECE (P = 0.001), being 18 times more likely to progress poorly compared to those with higher levels. AUC₂₄ and C_t are good predictors of ECE in this population. Concentrations close to 7 μg/mL and an AUC₂₄ of around 240 mg · h/L 48 h after antibiotic initiation seem to be sufficient to achieve clinical cure in most cases.

Trends in Occurrence and Phenotypic Resistance of Coagulase-Negative Staphylococci (CoNS) Found in Human Blood in the Northern Netherlands between 2013 and 2019

Background: For years, coagulase-negative staphylococci (CoNS) were not considered a cause of bloodstream infections (BSIs) and were often regarded as contamination. However, the association of CoNS with nosocomial infections is increasingly recognized. The identification of more than 40 different CoNS species has been driven by the introduction of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Yet, treatment guidelines consider CoNS as a whole group, despite increasing antibiotic resistance (ABR) in CoNS. This retrospective study provides an in-depth data analysis of CoNS isolates found in human blood culture isolates between 2013 and 2019 in the entire region of the Northern Netherlands. Methods: In total, 10,796 patients were included that were hospitalized in one of the 15 hospitals in the region, leading to 14,992 CoNS isolates for (ABR) data analysis. CoNS accounted for 27.6% of all available 71,632 blood culture isolates. EUCAST Expert rules were applied to correct for errors in antibiotic test results. Results: A total of 27 different CoNS species were found. Major differences were observed in occurrence and ABR profiles. The top five species covered 97.1% of all included isolates: S. epidermidis, S. hominis, S. capitis, S. haemolyticus, and S. warneri. Regarding ABR, methicillin resistance was most frequently detected in S. haemolyticus (72%), S. cohnii (65%), and S. epidermidis (62%). S. epidermidis and S. haemolyticus showed 50–80% resistance to teicoplanin and macrolides while resistance to these agents remained lower than 10% in most other CoNS species. Conclusion: These differences are often neglected in national guideline development, prompting a focus on ‘ABR-safe’ agents such as glycopeptides. In conclusion, this multi-year, full-region approach to extensively assess the trends in both the occurrence and phenotypic resistance of CoNS species could be used for evaluating treatment policies and understanding more about these important but still too often neglected pathogens.

Role of fluid status markers as risk factors for suboptimal vancomycin concentration during continuous infusion in neonates: an observational study

Vancomycin is widely used in neonatal sepsis but proportion of newborn reaching recommended concentration is variable. Fluid status impact on vancomycin level remains understudied. We aimed to study fluid factors impacting vancomycin concentration at 24 h of treatment. We performed a prospective and retrospective observational monocentric study of NICU patients requiring a vancomycin treatment. We used a continuous infusion protocol, with age-appropriate loading and maintenance doses. Vancomycin target serum concentration after 24 h (C_24h) was above 20 mg/L. Demographic, infections, and organ failure variables were analyzed as potential predictors of C_24h. Over the study period, 70 infective episodes in 52 patients were included. At treatment initiation, the median post-natal age was 12.5 days (IQR 7-23), post menstrual age 30 weeks (IQR 28-35), and median weight 1140 g (IQR 835-1722). Germs isolated were mainly gram-positive with 73.5% being coagulase-negative Staphylococci. Median C_24h was 18.7 mg/L (IQR 15.4-22.4). Overall, 41 (58.6%) treatments had a C_24h < 20 mg/L. After multivariate analysis, higher creatinine level (OR 1.03 (95% CI 1.002-1.06)) was associated with C_24h ≥ 20 mg/L; weight gain the day before infection (OR 0.21 (95% CI 0.05-0.79)) and positive biomarkers of inflammation (OR 0.22 (0.05-0.94)) were associated with C_24h < 20 mg/L.

CONCLUSION

Vancomycin C_24h was underdosed in 60% of patients and factors linked to changes in vancomycin pharmacokinetic such as volume of distribution and clearance, linked to creatinine level, inflammation, or weight gain, were identified.

WHAT IS KNOWN

• Adjustment of vancomycin regimen remains difficult due to inter- and intra-individual variability of vancomycin pharmacokinetics. • Impact of fluid status on vancomycin concentration in critically ill neonates is incompletely studied.

WHAT IS NEW

• Proportion of patients with adequate vancomycin concentration using a target adapted to nosocomial gram-positive bacteria MIC is low. • We confirmed the role of creatinine level and report two new factors associated with low vancomycin concentration: presence of systemic inflammation and weight gain.

Optimal exposure targets for vancomycin in the treatment of neonatal coagulase-negative Staphylococcus infection: A retrospective study based on electronic medical records

BACKGROUND

The currently advocated ratio of area under the curve (AUC) over 24 h to minimum inhibitory concentration (AUC/MIC) > 400 and AUC < 600 mg h/L as the therapeutic drug monitoring (TDM) target of vancomycin is based on data from multiple observational studies in adult patients with methicillin-resistant Staphylococcus aureus (MRSA) infection. It may not be applicable to newborns with coagulase-negative Staphylococcus (CoNS) infection. We conducted a retrospective study to identify the optimal exposure targets for vancomycin in the treatment of neonatal CoNS infection.

METHODS

Based on the inclusion and exclusion criteria, serum vancomycin concentration, demographics, clinical data, and related laboratory data of newborns who received vancomycin intravenous infusion from June 1, 2016 to February 1, 2021 were collected retrospectively. The AUC was calculated using the maximum a posteriori Bayesian (MAPB) method. The vancomycin exposure threshold of AUC/MIC for efficacy and AUC for toxicity (acute kidney injury, AKI) were determined based on receiver operating characteristic (ROC) curve analysis. The correlation between vancomycin exposure and both clinical effect and nephrotoxicity was analyzed using logistic multivariate regression.

RESULTS

In total, 153 patients and 245 vancomycin concentrations (160 trough and 85 peak concentrations) were included. The ROC curve analysis showed that the exposure thresholds of AUC/MIC for clinical efficacy and AUC for nephrotoxicity were 281 and 602 mg h/L, respectively. The multivariate regression analysis showed that AUC/MIC > 280 was a predictor of efficacy (OR: 13.960, 95% CI: 1.891-103.078, P < 0.05) and AUC > 600 mg h/L was associated with AKI (OR: 9.008, 95% CI: 2.706-29.983, P < 0.05). The vancomycin AUC/MIC threshold for treating neonatal CoNS infection with vancomycin is lower than the currently advocated AUC/MIC >400.

CONCLUSION

The optimal exposure targets for vancomycin in neonatal CoNS infection were AUC/MIC > 280 and AUC < 600 mg h/L.

Flomoxef and fosfomycin in combination for the treatment of neonatal sepsis in the setting of highly prevalent antimicrobial resistance

BACKGROUND

Neonatal sepsis is a serious bacterial infection of neonates, globally killing up to 680 000 babies annually. It is frequently complicated by antimicrobial resistance, particularly in low- and middle-income country (LMIC) settings with widespread resistance to the WHO's recommended empirical regimen of ampicillin and gentamicin.

OBJECTIVES

We assessed the utility of flomoxef and fosfomycin as a potential alternative empirical regimen for neonatal sepsis in these settings.

METHODS

We studied the combination in a 16-arm dose-ranged hollow-fibre infection model (HFIM) experiment and chequerboard assays. We further assessed the combination using clinically relevant regimens in the HFIM with six Enterobacterales strains with a range of flomoxef/fosfomycin MICs.

RESULTS

Pharmacokinetic/pharmacodynamic modelling of the HFIM experimental output, along with data from chequerboard assays, indicated synergy of this regimen in terms of bacterial killing and prevention of emergence of fosfomycin resistance. Flomoxef monotherapy was sufficient to kill 3/3 strains with flomoxef MICs ≤0.5 mg/L to sterility. Three of three strains with flomoxef MICs ≥8 mg/L were not killed by fosfomycin or flomoxef monotherapy; 2/3 of these were killed with the combination of the two agents.

CONCLUSIONS

These data suggest that flomoxef/fosfomycin could be an efficacious and synergistic regimen for the empirical treatment of neonatal sepsis in LMIC settings with prevalent antimicrobial resistance. Our HFIM results warrant further assessment of the flomoxef/fosfomycin combination in clinical trials.

Pharmacodynamics of Meropenem and Tobramycin for Neonatal Meningoencephalitis: Novel Approaches to Facilitate the Development of New Agents to Address the Challenge of Antimicrobial Resistance

Neonatal sepsis is an underrecognized burden on health care systems throughout the world. Antimicrobial drug resistance (AMR) is increasingly prevalent and compromises the use of currently recommended first-line agents. The development of new antimicrobial agents for neonates and children is mandated by regulatory agencies. However, there remains uncertainty about suitable development pathways, especially because of the propensity of premature babies to develop meningoencephalitis as a complication of neonatal sepsis and difficulties studying this disease in clinical settings. We developed a new platform and approach to accelerate the development of antimicrobial agents for neonatal bacterial meningoencephalitis using Pseudomonas aeruginosa as the challenge organism. We defined the pharmacodynamics of meropenem and tobramycin in these models. The percentage of partitioning of meropenem and tobramycin into the cerebrospinal fluid was comparable at 14.3 and 13.7%, respectively. Despite this similarity, there were striking differences in their pharmacodynamics. Meropenem resulted in bactericidal activity in both the cerebrospinal fluid and cerebrum, whereas tobramycin had minimal antibacterial activity. A hollow fiber infection model (HFIM) using neonatal CSF concentration time profiles yielded pharmacodynamics comparable to those observed in the rabbit model. These new experimental models can be used to estimate the pharmacodynamics of currently licensed agents and those in development and their potential efficacy for neonatal bacterial meningoencephalitis.

Identifying a therapeutic target for vancomycin against staphylococci in young infants

OBJECTIVES

To determine the therapeutic target of vancomycin in young infants with staphylococcal infections.

METHODS

Retrospective data were collected for infants aged 0 to 90 days with CoNS or MRSA bacteraemia over a 4 year period at the Royal Children's Hospital Melbourne, Australia. Vancomycin broth microdilution MICs were determined. A published pharmacokinetic model was externally validated using the study dataset and a time-to-event (TTE) pharmacodynamic model developed to link the AUC of vancomycin with the event being the first negative blood culture. Simulations were performed to determine the trough vancomycin concentration that correlates with a 90% PTA of the target AUC24.

RESULTS

Thirty infants, 28 with CoNS and 2 with MRSA bacteraemia, who had 165 vancomycin concentrations determined were included. The vancomycin broth microdilution MIC was determined for 24 CoNS and 1 MRSA isolate, both with a median MIC of 1 mg/L (CoNS range = 0.5-4.0). An AUC0-24 target of ≥300 mg/L·h or AUC24-48 of ≥424 mg/L·h. increased the chance of bacteriological cure by 7.8- and 7.3-fold, respectively. However, AUC0-24 performed best in the pharmacokinetic-pharmacodynamic model. This correlates with 24 to 48 h trough concentrations of >15-18 mg/L and >10-15 mg/L for 6- and 12-hourly dosing, respectively, and can be used to guide vancomycin therapy in this population.

CONCLUSIONS

An AUC0-24 ≥300 mg/L·h or AUC24-48 ≥424 mg/L·h was associated with an increase in bacteriological cure in young infants with staphylococcal bloodstream infections.

Optimised versus standard dosing of vancomycin in infants with Gram-positive sepsis (NeoVanc): a multicentre, randomised, open-label, phase 2b, non-inferiority trial

BACKGROUND

Vancomycin is the most widely used antibiotic for neonatal Gram-positive sepsis, but clinical outcome data of dosing strategies are scarce. The NeoVanc programme comprised extensive preclinical studies to inform a randomised controlled trial to assess optimised vancomycin dosing. We compared the efficacy of an optimised regimen to a standard regimen in infants with late onset sepsis that was known or suspected to be caused by Gram-positive microorganisms.

METHODS

NeoVanc was an open-label, multicentre, phase 2b, parallel-group, randomised, non-inferiority trial comparing the efficacy and toxicity of an optimised regimen of vancomycin to a standard regimen in infants aged 90 days or younger. Infants with at least three clinical or laboratory sepsis criteria or confirmed Gram-positive sepsis with at least one clinical or laboratory criterion were enrolled from 22 neonatal intensive care units in Greece, Italy, Estonia, Spain, and the UK. Infants were randomly assigned (1:1) to either the optimised regimen (25 mg/kg loading dose, followed by 15 mg/kg every 12 h or 8 h dependent on postmenstrual age, for 5 ± 1 days) or the standard regimen (no loading dose; 15 mg/kg every 24 h, 12 h, or 8 h dependent on postmenstrual age for 10 ± 2 days). Vancomycin was administered intravenously via 60 min infusion. Group allocation was not masked to local investigators or parents. The primary endpoint was success at the test of cure visit (10 ± 1 days after the end of actual vancomycin therapy) in the per-protocol population, where success was defined as the participant being alive at the test of cure visit, having a successful outcome at the end of actual vancomycin therapy, and not having a clinically or microbiologically significant relapse or new infection requiring antistaphylococcal antibiotics for more than 24 h within 10 days of the end of actual vancomycin therapy. The non-inferiority margin was -10%. Safety was assessed in the intention-to-treat population. This trial is registered at ClinicalTrials.gov (NCT02790996).

FINDINGS

Between March 3, 2017, and July 29, 2019, 242 infants were randomly assigned to the standard regimen group (n=122) or the optimised regimen group (n=120). Primary outcome data in the per-protocol population were available for 90 infants in the optimised group and 92 in the standard group. 64 (71%) of 90 infants in the optimised group and 73 (79%) of 92 in the standard group had success at test of cure visit; non-inferiority was not confirmed (adjusted risk difference -7% [95% CI -15 to 2]). Incomplete resolution of clinical or laboratory signs after 5 ± 1 days of vancomycin therapy was the main factor contributing to clinical failure in the optimised group. Abnormal hearing test results were recorded in 25 (30%) of 84 infants in the optimised group and 12 (15%) of 79 in the standard group (adjusted risk ratio 1·96 [95% CI 1·07 to 3·59], p=0·030). There were six vancomycin-related adverse events in the optimised group (one serious adverse event) and four in the standard group (two serious adverse events). 11 infants in the intention-to-treat population died (six [6%] of 102 infants in the optimised group and five [5%] of 98 in the standard group).

INTERPRETATION

In the largest neonatal vancomycin efficacy trial yet conducted, no clear clinical impact of a shorter duration of treatment with a loading dose was demonstrated. The use of the optimised regimen cannot be recommended because a potential hearing safety signal was identified; long-term follow-up is being done. These results emphasise the importance of robust clinical safety assessments of novel antibiotic dosing regimens in infants.

FUNDING

EU Seventh Framework Programme for research, technological development and demonstration.

Children may need higher vancomycin doses to achieve therapeutic levels

AIM

Vancomycin is frequently used in paediatric hospitals. Data suggest trough levels of 10-20 mg/L are needed to achieve bacterial killing. This study aimed to evaluate if commonly used dosing regimens are efficient in reaching these levels and if therapeutic drug monitoring (TDM) was appropriately used.

METHODS

All children receiving intravenous vancomycin at the Children´s Hospital Iceland between 2012 and 2016 were included. Vancomycin trough levels were registered. Student t test, Wilcoxon test and regression models were used for statistical analysis.

RESULTS

A total of 105 children received 163 vancomycin treatments (55/105 neonates). Average daily dose in neonates was 23.4 mg/kg/day and 38.4 mg/kg/day for older children. No TDM was done in 58 treatments (35.6%). First trough levels were <10mg/L in 52.4% and <15mg/L in 92% of cases. Therapeutic levels were less likely achieved in children with malignancy (11.8%) compared with others (36.8%, p = 0.09).

CONCLUSIONS

In more than half of the cases, trough drug levels were <10 mg/L and malignancy was associated with the lowest probability of reaching therapeutic levels. This study suggests that starting doses of vancomycin in children should be higher, especially in relation to malignant diseases and supports the importance of antibiotic stewardship to ensure optimal antibiotic use.

Application of the hollow fibre infection model (HFIM) in antimicrobial development: a systematic review and recommendations of reporting

OBJECTIVES

This systematic review focuses on the use of the in vitro hollow fibre infection model (HFIM) for microbial culture. We summarize the direction of the field to date and propose best-practice principles for reporting of the applications.

METHODS

Searches in six databases (MEDLINE®, EMBASE®, PubMed®, BIOSIS®, SCOPUS® and Cochrane®) up to January 2020 identified 129 studies meeting our inclusion criteria. Two reviewers independently assessed and extracted data from each publication. The quality of reporting of microbiological and technical parameters was analysed.

RESULTS

Forty-seven out of 129 (36.4%) studies did not report the minimum pharmacokinetic parameters required in order to replicate the pharmacokinetic profile of HFIM experiments. Fifty-three out of 129 (41.1%) publications did not report the medium used in the HFIM. The overwhelming majority of publications did not perform any technical repeats [107/129 (82.9%)] or biological repeats [97/129 (75.2%)].

CONCLUSIONS

This review demonstrates that most publications provide insufficient data to allow for results to be evaluated, thus impairing the reproducibility of HFIM experiments. Therefore, there is a clear need for the development of laboratory standardization and improved reporting of HFIM experiments.

Vancomycin-induced ototoxicity in very-low-birthweight infants

BACKGROUND

Vancomycin is an extensively used anti-infective drug in neonatal ICUs. However, exposure-toxicity relationships have not been clearly defined.

OBJECTIVES

To evaluate the risk profile for hearing deficits in vancomycin-exposed very-low-birthweight infants (VLBWI).

METHODS

In a large cohort study of the German Neonatal Network (GNN; n = 16 967 VLBWI) we assessed the association of vancomycin treatment and pathological hearing tests at discharge and at 5 year follow-up. We performed audits on vancomycin exposure, drug levels, dose adjustments and exposure to other ototoxic drugs in a subgroup of 1042 vancomycin-treated VLBWI.

RESULTS

In the GNN cohort, 28% (n = 4739) were exposed to IV vancomycin therapy. In multivariable logistic regression analysis, vancomycin exposure proved to be independently associated with pathological hearing test at discharge (OR 1.18, 95% CI 1.03-1.34, P = 0.016). Among vancomycin-treated infants, a cumulative vancomycin dose above the upper quartile (>314 mg/kg bodyweight) was associated with pathological hearing test at discharge (OR 2.1, 95% CI 1.21-3.64, P = 0.009), whereas a vancomycin cumulative dose below the upper quartile was associated with a reduced risk of pathological tone audiometry results at 5 years of age (OR 0.29, 95% CI 0.1-0.8, P = 0.02, n = 147).

CONCLUSIONS

Vancomycin exposure in VLBWI is associated with an increased, dose-dependent risk of pathological hearing test results at discharge and at 5 years of age. Prospective studies on long-term hearing impairment are needed.

Amikacin Combined with Fosfomycin for Treatment of Neonatal Sepsis in the Setting of Highly Prevalent Antimicrobial Resistance

Antimicrobial resistance (particularly through extended-spectrum β-lactamase and aminoglycoside-modifying enzyme production) in neonatal sepsis is a global problem, particularly in low- and middle-income countries, with significant mortality rates. High rates of resistance are reported for the current WHO-recommended first-line antibiotic regimen for neonatal sepsis, i.e., ampicillin and gentamicin. We assessed the utility of fosfomycin and amikacin as a potential alternative regimen to be used in settings of increasingly prevalent antimicrobial resistance. The combination was studied in a 16-arm dose-ranged hollow-fiber infection model (HFIM) experiment. The combination of amikacin and fosfomycin enhanced bactericidal activity and prevented the emergence of resistance, compared to monotherapy with either antibiotic. Modeling of the experimental quantitative outputs and data from checkerboard assays indicated synergy. We further assessed the combination regimen at clinically relevant doses in the HFIM with nine Enterobacterales strains with high fosfomycin and amikacin MICs and demonstrated successful kill to sterilization for 6/9 strains. From these data, we propose a novel combination breakpoint threshold for microbiological success for this antimicrobial combination against Enterobacterales strains, i.e., MIC_F × MIC_A < 256 (where MIC_F and MIC_A are the fosfomycin and amikacin MICs, respectively). Monte Carlo simulations predict that a standard fosfomycin-amikacin neonatal regimen would achieve >99% probability of pharmacodynamic success for strains with MICs below this threshold. We conclude that the combination of fosfomycin with amikacin is a viable regimen for the empirical treatment of neonatal sepsis and is suitable for further clinical assessment in a randomized controlled trial.

Pediatric Pharmacokinetics and Dose Predictions: A Report of a Satellite Meeting to the 10th Juvenile Toxicity Symposium

On April 24, 2019, a symposium on Pediatric Pharmacokinetics and Dose Predictions was held as a satellite meeting to the 10th Juvenile Toxicity Symposium. This symposium brought together scientists from academia, industry, and clinical research organizations with the aim to update each other on the current knowledge on pediatric drug development. Through more knowledge on specific ontogeny profiles of drug metabolism and transporter proteins, integrated into physiologically-based pharmacokinetic (PBPK) models, we have gained a more integrated understanding of age-related differences in pharmacokinetics (PKs), Relevant examples were presented during the meeting. PBPK may be considered the gold standard for pediatric PK prediction, but still it is important to know that simpler methods, such as allometry, allometry combined with maturation function, functions based on the elimination pathway, or linear models, also perform well, depending on the age range or the mechanisms involved. Knowledge from different methods and information sources should be combined (e.g., microdosing can reveal early read-out of age-related differences in exposure), and such results can be a value to verify models. To further establish best practices for dose setting in pediatrics, more in vitro and in vivo research is needed on aspects such as age-related changes in the exposure-response relationship and the impact of disease on PK. New information coupled with the refining of model-based drug development approaches will allow faster targeting of intended age groups and allow more efficient design of pediatric clinical trials.

An Algorithm for Nonparametric Estimation of a Multivariate Mixing Distribution with Applications to Population Pharmacokinetics

Population pharmacokinetic (PK) modeling has become a cornerstone of drug development and optimal patient dosing. This approach offers great benefits for datasets with sparse sampling, such as in pediatric patients, and can describe between-patient variability. While most current algorithms assume normal or log-normal distributions for PK parameters, we present a mathematically consistent nonparametric maximum likelihood (NPML) method for estimating multivariate mixing distributions without any assumption about the shape of the distribution. This approach can handle distributions with any shape for all PK parameters. It is shown in convexity theory that the NPML estimator is discrete, meaning that it has finite number of points with nonzero probability. In fact, there are at most N points where N is the number of observed subjects. The original infinite NPML problem then becomes the finite dimensional problem of finding the location and probability of the support points. In the simplest case, each point essentially represents the set of PK parameters for one patient. The probability of the points is found by a primal-dual interior-point method; the location of the support points is found by an adaptive grid method. Our method is able to handle high-dimensional and complex multivariate mixture models. An important application is discussed for the problem of population pharmacokinetics and a nontrivial example is treated. Our algorithm has been successfully applied in hundreds of published pharmacometric studies. In addition to population pharmacokinetics, this research also applies to empirical Bayes estimation and many other areas of applied mathematics. Thereby, this approach presents an important addition to the pharmacometric toolbox for drug development and optimal patient dosing.

Development and external evaluation of a population pharmacokinetic model for continuous and intermittent administration of vancomycin in neonates and infants using prospectively collected data

BACKGROUND

Vancomycin is commonly used for nosocomial bacterial pathogens causing late-onset septicaemia in preterm infants. We prospectively collected pharmacokinetic data aiming to describe pharmacokinetics and determine covariates contributing to the variability in neonatal vancomycin pharmacokinetics. Further, we aimed to use the model to compare the ratio of AUC24 at steady-state to the MIC (AUC24,ss/MIC) of several intermittent and continuous dosing regimens.

METHODS

Newborns receiving vancomycin for suspected or confirmed late-onset sepsis were included. Peak and trough concentrations for intermittent vancomycin dosing and steady-state concentrations for continuous vancomycin dosing were measured. NONMEM 7.3 was used for population pharmacokinetic analysis. Monte Carlo simulations were performed to compare dosing schemes.

RESULTS

Data from 54 infants were used for model development and from 34 infants for the model evaluation {corrected gestational age [median (range)] = 29 (23.7-41.9) weeks and 28 (23.4-41.7) weeks, respectively}. The final model was a one-compartment model. Weight and postmenstrual age were included a priori, and then no additional covariate significantly improved the model fit. Final model parameter estimates [mean (SEM)]: CL = 5.7 (0.3) L/h/70 kg and V = 39.3 (3.7) L/70 kg. Visual predictive check of the evaluation dataset confirmed the model can predict external data. Simulations using MIC of 1 mg/L showed that for neonates with gestational age ≤25 weeks and postnatal age ≤2 weeks AUC24,ss/MIC was lower with the intermittent regimen (median 482 versus 663).

CONCLUSIONS

A population pharmacokinetic model for continuous and intermittent vancomycin administration in infants was developed. Continuous administration might be favourable for treating infections caused by resistant microorganisms in very young and immature infants.

An optimised dosing regimen versus a standard dosing regimen of vancomycin for the treatment of late onset sepsis due to Gram-positive microorganisms in neonates and infants aged less than 90 days (NeoVanc): study protocol for a randomised controlled trial

BACKGROUND

Vancomycin has been used in clinical practice for over 50 years; however, validated, pharmacokinetic (PK) data relating clinical outcomes to different dosing regimens in neonates are lacking. Coagulase negative staphylococci (CoNS) are the most commonly isolated organisms in neonatal, late-onset sepsis (LOS). Optimised use to maximise efficacy while minimising toxicity and resistance selection is imperative to ensure vancomycin's continued efficacy.

METHODS

NeoVanc is a European, open-label, Phase IIb, randomised, controlled, non-inferiority trial comparing an optimised vancomycin regimen to a standard vancomycin regimen when treating LOS known/suspected to be caused by Gram-positive organisms (excluding Staphylococcus aureus) in infants aged ≤ 90 days. Three hundred infants will be recruited and randomised in a 1:1 ratio. Infants can be recruited if they have culture confirmed (a positive culture from a normally sterile site and at least one clinical/laboratory criterion) or clinical sepsis (presence of any ≥ 3 clinical/laboratory criteria) in the 24 h before randomisation. The optimised regimen consists of a vancomycin loading dose (25 mg/kg) followed by 5 ± 1 days of 15 mg/kg q12h or q8h, dependent on postmenstrual age (PMA). The standard regimen is a 10 ± 2 day vancomycin course at 15 mg/kg q24h, q12h or q8h, dependent on PMA. The primary endpoint is a successful outcome at the test of cure visit (10 ± 1 days after the end of vancomycin therapy). A successful outcome consists of the patient being alive, having successfully completed study vancomycin therapy and having not had a clinical/microbiological relapse/new infection requiring treatment with vancomycin or other anti-staphylococcal antibiotic for > 24 h. Secondary endpoints include clinical/microbiological relapse/new infection at the short-term follow-up visit (30 ± 5 days after the initiation of vancomycin), evaluation of safety (renal/hearing), vancomycin PK and assessment of a host biomarker panel over the course of vancomycin therapy.

DISCUSSION

Based on previous pre-clinical data and a large meta-analysis of neonatal, PK/pharmacodynamic data, NeoVanc was set up to provide evidence on whether a loading dose followed by a short vancomycin course is non-inferior, regarding efficacy, when compared to a standard, longer course. If non-inferiority is demonstrated, this would support adoption of the optimised regimen as a way of safely reducing vancomycin exposure when treating neonatal, Gram-positive LOS.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02790996. Registered on 7 April 2016. EudraCT, 2015-000203-89. Entered on 18 July 2016.

Pharmacokinetic-Pharmacodynamic Modeling in Pediatric Drug Development, and the Importance of Standardized Scaling of Clearance

Pharmacokinetic/pharmacodynamic (PKPD) modeling is important in the design and conduct of clinical pharmacology research in children. During drug development, PKPD modeling and simulation should underpin rational trial design and facilitate extrapolation to investigate efficacy and safety. The application of PKPD modeling to optimize dosing recommendations and therapeutic drug monitoring is also increasing, and PKPD model-based dose individualization will become a core feature of personalized medicine. Following extensive progress on pediatric PK modeling, a greater emphasis now needs to be placed on PD modeling to understand age-related changes in drug effects. This paper discusses the principles of PKPD modeling in the context of pediatric drug development, summarizing how important PK parameters, such as clearance (CL), are scaled with size and age, and highlights a standardized method for CL scaling in children. One standard scaling method would facilitate comparison of PK parameters across multiple studies, thus increasing the utility of existing PK models and facilitating optimal design of new studies.

Desired vancomycin trough concentration to achieve an AUC0-24 /MIC ≥400 in Chinese children with complicated infectious diseases

A vancomycin steady-state trough concentration (C_min ) of 15-20 mg/L is recommended for achieving a ratio of the 24-hour area under the curve to the minimum inhibitory concentration (AUC_0-24 /MIC) of ≥400 in adults. Since few paediatric data are available, our objectives were to (a) measure the pharmacokinetic indices of vancomycin and (b) determine the correlation between C_min and AUC_0-24 /MIC in paediatric patients. Population-based pharmacokinetic modelling was performed for paediatric patients to estimate the individual parameters. The relationship between C_min and the calculated AUC_0-24 /MIC was explored using linear regression and a probabilistic framework. A sensitivity analysis was also conducted using Monte Carlo simulations. Body-weight significantly influenced the pharmacokinetics of vancomycin. Based on real data and simulations, C_min ranges of 5.0-5.9 and 9.0-12.9 mg/L were associated with AUC_0-24 /MIC ≥400 for MIC values of ≤0.5 and ≤1 mg/L, respectively. Vancomycin regimens of 10 and 15 mg/kg every 6 hours achieved a C_min of 5.0-5.9 mg/L and AUC_0-24 /MIC ≥400 in >90% of the children when MIC was ≤0.5 mg/L. At a MIC of ≤1 mg/L, vancomycin at 15 mg/kg every 6 hours achieved C_min of 9.0-12.9 mg/L and AUC_0-24 /MIC ≥400 in 2.0- and 1.6-fold as many children compared to a dose of 10 mg/kg every 6 hours, respectively. Vancomycin C_min values of 5.0-12.9 mg/L were strongly predictive of achieving AUC_0-24 /MIC ≥400, and rational dosing regimens of 10-15 mg/kg q6h were required in paediatric patients, depending on the pathogen.

Pharmacokinetic modelling and Bayesian estimation-assisted decision tools to optimize vancomycin dosage in neonates: only one piece of the puzzle

Introduction: Vancomycin is commonly administered to neonates, while observational data on therapeutic drug monitoring (TDM, trough levels) suggest that vancomycin exposure and dosage remain substandard. Area covered: Data on vancomycin pharmacokinetics (PK) and its covariates are abundant. Consequently, modeling is an obvious tool to improve targeted exposure, with a shift from TDM trough levels to area under the curve (AUC_24h) targets, as in adults. Continuous administration appeared as a practice to facilitate AUC_24h target attainment, while Bayesian model-supported targeting emerged as a novel tool. However, the AUC_24h/MIC (minimal inhibitory concentration) target itself should consider neonate-specific aspects (bloodstream infections, coagulase-negative staphylococci, protein binding, underexplored causes of variability, like assays, preparation and administration inaccuracies, or missing covariates). Expert opinion: To improve targeted exposure in neonates, initial vancomycin prescription should be based on 'a priori model-based individual dosing' using validated dosing regimens, followed by further tailoring by dosing optimization applying Bayesian estimation-assisted TDM. Future research should focus on the feasibility to integrate these tools (individualized dosing, Bayesian models) in clinical practice, and to perform PK/PD studies in the relevant animal models and human neonatal setting (coagulase-negative staphylococci, bloodstream infections).

Optimizing Vancomycin Use Through 2-Point AUC-Based Therapeutic Drug Monitoring in Pediatric Patients

The 24-hour vancomycin area under the serum concentration-time curve (AUC₂₄ ) divided by the minimum inhibitory concentration (MIC) (AUC₂₄ /MIC) is more closely related to patient outcomes than serum trough concentrations (C_trough ). Two-point simplified equations for calculating AUC based on serum peak concentrations (C_peak ) and C_trough , named equation A (EqA) and equation B (EqB), have recently been adopted into clinical use for adult pediatric patients. We aimed to find the agreement between predicted AUC₂₄ using the reference method (ref) relative to EqA and EqB and the correlation between C_trough and AUC₂₄ . From June to December 2018, 43 pediatric patients with normal renal function, receiving 15 mg/kg of vancomycin intravenously every 6 hours, were enrolled. The pediatric patients' median age was 2.2 years (range 0.1-15.3). At steady state, vancomycin C_peak and C_trough were measured at 2 hours after infusion completion and within 30 minutes before the next dosing, respectively. AUC₂₄ was estimated using ref, EqA, and EqB. From Bland-Altman analysis, the 2 AUC₂₄ s estimated by ref and EqA showed less bias than those estimated by ref and EqB (bias 1.3 and -72.1 mg⋅h/L, respectively). C_trough and AUC₂₄ using either ref or EqA were correlated more closely (r² = 0.94) than with EqB (r² = 0.86). Assuming a vancomycin MIC of 1 mg/L, an AUC₂₄ ≥400 mg⋅h/L was targeted. Regardless of the method used, AUC₂₄ ≥400 mg⋅h/L was never seen with C_trough <8 mg/L but was always seen with C_trough >10 mg/L. In conclusion, EqA based on the 2 measured serum concentrations was sufficiently accurate for AUC₂₄ estimation. C_trough >10 mg/L correlated highly to AUC₂₄ ≥400 mg⋅h/L.

Continuous-Infusion Vancomycin in Neonates: Assessment of a Dosing Regimen and Therapeutic Proposal

Introduction: Vancomycin remains the reference antibiotic in neonates for care-related infections caused by ß-lactam-resistant Gram-positive bacteria. Achieving the optimal serum vancomycin level is challenging because of high inter-individual variability and the drug's narrow therapeutic window. Continuous infusion might offer pharmacokinetic and practical advantages, but we lack consensus on the dosing regimen. The aim was to determine the proportion of neonates achieving an optimal therapeutic vancomycin level at the first vancomycin concentration assay and which dosing regimen is the most suitable for neonates. Methods: All neonates receiving continuous-infusion vancomycin (loading dose 15 mg/kg and maintenance dose 30 mg/kg/d) in a neonatal intensive care unit were retrospectively analyzed. The proportion of neonates reaching the target serum vancomycin level was calculated. After reviewing the literature to identify all published articles proposing a dosing regimen for continuous-infusion vancomycin for neonates, regimens were theoretically applied to our population by using maintenance doses according to covariate(s) proposed in the original publication. Results: Between January 2013 and December 2014, 75 neonates received 91 vancomycin courses by continuous infusion. Median gestational age, birth weight, and postnatal age were 27 weeks (interquartile range 26-30.5), 815 g (685-1,240), and 15 days (9-33). At the first assay, only 28/91 (30.8%) courses resulted in vancomycin levels between 20 and 30 mg/L (target level), 23/91 (25.3%) >30 mg/L and 40/91 (43.9%) <20 mg/L. We applied six published dosing regimens to our patients. One of these dosing regimens based on corrected gestational age (CGA) and serum creatinine level (SCR) would have allowed us to prescribe lower doses to neonates with high vancomycin levels and higher doses to neonates with low levels. Conclusions: A simplified dosing regimen of continuous-infusion vancomycin did not achieve therapeutic ranges in neonates; a patient-tailored dosing regimen taking into account CGA and SCR level or an individualized pharmacokinetic model can help to anticipate the inter-individual variability in neonates and would have been more suitable.

Evolution of empiric vancomycin dosing in a neonatal population

BACKGROUND

In 2014, we assessed the effectiveness of our neonatal vancomycin empirical dosing regimen (15-45 mg/kg/day) which led to development of a revised regimen (20-60 mg/kg/day).

OBJECTIVE

To validate the revised empirical vancomycin dosage regimen in achieving target troughs.

METHODS

The primary outcome of this multicenter retrospective before-and-after cohort study was the proportion of neonates in the present cohort achieving trough levels below, at or above target (<10, 10-20 and >20 mg/L). Secondary outcomes included difference between cohorts (historical and present) in mean troughs and proportion of patients achieving target levels.

RESULTS

Out of 118 participants, 63 (53.39%) achieved target troughs, 44 (37.29%) had below target troughs and 11 (9.32%) reached above target levels. Mean trough levels and proportion of patients achieving target levels were higher in the present versus historical cohort (p < 0.01 for all comparisons).

CONCLUSIONS

The revised empiric dosing regimen was more effective in achieving target serum trough concentrations.

Exploring the Use of C-Reactive Protein to Estimate the Pharmacodynamics of Vancomycin

BACKGROUND

C-reactive protein (CRP) pharmacodynamic (PD) models have the potential to provide adjunctive methods for predicting the individual exposure response to antimicrobial therapy. We investigated CRP PD linked to a vancomycin pharmacokinetic (PK) model using routinely collected data from noncritical care adults in secondary care.

METHODS

Patients receiving intermittent intravenous vancomycin therapy in secondary care were identified. A 2-compartment vancomycin PK model was linked to a previously described PD model describing CRP response. PK and PD parameters were estimated using a Non-Parametric Adaptive Grid technique. Exposure-response relationships were explored with vancomycin area-under-the-concentration-time-curve (AUC) and EC50 (concentration of drug that causes a half maximal effect) using the index, AUC:EC50, fitted to CRP data using a sigmoidal Emax model.

RESULTS

Twenty-nine individuals were included. Median age was 62 (21-97) years. Fifteen (52%) patients were microbiology confirmed. PK and PD models were adequately fitted (r 0.83 and 0.82, respectively). There was a wide variation observed in individual Bayesian posterior EC50 estimates (6.95-48.55 mg/L), with mean (SD) AUC:EC50 of 31.46 (29.22). AUC:EC50 was fitted to terminal CRP with AUC:EC50 >19 associated with lower CRP value at 96-120 hours of therapy (100 mg/L versus 44 mg/L; P < 0.01).

CONCLUSIONS

The use of AUC:EC50 has the potential to provide in vivo organism and host response data as an adjunct for in vitro minimum inhibitory concentration data, which is currently used as the gold standard PD index for vancomycin therapy. This index can be estimated using routinely collected clinical data. Future work must investigate the role of AUC:EC50 in a prospective cohort and explore linkage with direct patient outcomes.

Delivering precision antimicrobial therapy through closed-loop control systems

Sub-optimal exposure to antimicrobial therapy is associated with poor patient outcomes and the development of antimicrobial resistance. Mechanisms for optimizing the concentration of a drug within the individual patient are under development. However, several barriers remain in realizing true individualization of therapy. These include problems with plasma drug sampling, availability of appropriate assays, and current mechanisms for dose adjustment. Biosensor technology offers a means of providing real-time monitoring of antimicrobials in a minimally invasive fashion. We report the potential for using microneedle biosensor technology as part of closed-loop control systems for the optimization of antimicrobial therapy in individual patients.

Prospective Trial on the Use of Trough Concentration versus Area under the Curve To Determine Therapeutic Vancomycin Dosing

We hypothesized that dosing vancomycin to achieve trough concentrations of >15 mg/liter overdoses many adults compared to area under the concentration-time curve (AUC)-guided dosing. We conducted a 3-year, prospective study of vancomycin dosing, plasma concentrations, and outcomes. In year 1, nonstudy clinicians targeted trough concentrations of 10 to 20 mg/liter (infection dependent) and controlled dosing. In years 2 and 3, the study team controlled vancomycin dosing with BestDose Bayesian software to achieve a daily, steady-state AUC/MIC ratio of ≥400, with a maximum AUC value of 800 mg · h/liter, regardless of trough concentration. For Bayesian estimation of AUCs, we used trough samples in years 1 and 2 and optimally timed samples in year 3. We enrolled 252 adults who were ≥18 years old with ≥1 available vancomycin concentration. Only 19% of all trough concentrations were therapeutic versus 70% of AUCs (P < 0.0001). After enrollment, median trough concentrations by year were 14.4, 9.7, and 10.9 mg/liter (P = 0.005), with 36%, 7%, and 6% over 15 mg/liter (P < 0.0001). Bayesian AUC-guided dosing in years 2 and 3 was associated with fewer additional blood samples per subject (3.6, 2.0, and 2.4; P = 0.003), shorter therapy durations (8.2, 5.4, and 4.7 days; P = 0.03), and reduced nephrotoxicity (8%, 0%, and 2%; P = 0.01). The median inpatient stay was 20 days among nephrotoxic patients versus 6 days (P = 0.002). There was no difference in efficacy by year, with 42% of patients having microbiologically proven infections. Compared to trough concentration targets, AUC-guided, Bayesian estimation-assisted vancomycin dosing was associated with decreased nephrotoxicity, reduced per-patient blood sampling, and shorter length of therapy, without compromising efficacy. These benefits have the potential for substantial cost savings. (This study has been registered at ClinicalTrials.gov under registration no. NCT01932034.).

Challenges and strategies to facilitate formulation development of pediatric drug products: Safety qualification of excipients

A public workshop entitled "Challenges and strategies to facilitate formulation development of pediatric drug products" focused on current status and gaps as well as recommendations for risk-based strategies to support the development of pediatric age-appropriate drug products. Representatives from industry, academia, and regulatory agencies discussed the issues within plenary, panel, and case-study breakout sessions. By enabling practical and meaningful discussion between scientists representing the diversity of involved disciplines (formulators, nonclinical scientists, clinicians, and regulators) and geographies (eg, US, EU), the Excipients Safety workshop session was successful in providing specific and key recommendations for defining paths forward. Leveraging orthogonal sources of data (eg. food industry, agro science), collaborative data sharing, and increased awareness of the existing sources such as the Safety and Toxicity of Excipients for Paediatrics (STEP) database will be important to address the gap in excipients knowledge needed for risk assessment. The importance of defining risk-based approaches to safety assessments for excipients vital to pediatric formulations was emphasized, as was the need for meaningful stakeholder (eg, patient, caregiver) engagement.

Population pharmacokinetics of teicoplanin and attainment of pharmacokinetic/pharmacodynamic targets in adult patients with haematological malignancy

OBJECTIVES

To describe the population pharmacokinetics of teicoplanin in adult patients with haematological malignancies receiving higher than standard doses, and to perform Monte Carlo simulations to determine dosing regimens associated with optimal teicoplanin concentrations.

METHODS

This was a hospital-based clinical trial (EudraCT 2013-004535-72). Nine blood samples were collected on Day 3, plus single trough samples on Days 7 and 10, and 24 and 48 hours after the last dose. Teicoplanin minimum inhibitory concentrations were determined for Gram-positive isolates from study patients. Population pharmacokinetic analyses and Monte Carlo dosing simulations were undertaken using Pmetrics.

RESULTS

Thirty adult haematological malignancy patients were recruited with a mean (SD) loading dose, age, total body weight, and creatinine clearance of 9.5 (1.9) mg/kg, 63 (12) years, 69.1 (15.8) kg, and 72 (41) mL/min, respectively. A three-compartment linear pharmacokinetic model best described the teicoplanin concentration data. Covariates supported for inclusion in the final model were creatinine clearance for clearance and total body weight for volume of the central compartment. The median (IQR) area under the concentration-time curve from 48 to 72 hours (AUC_48-72h) was 679 (319) mg.h/L. There was a strong correlation between the AUC_48-72h and trough concentration at 72 hours (Pearson correlation coefficient 0.957, p <0.001). Dosing simulations showed that administration of five loading doses at 12-hourly intervals, stratified by total body weight and creatinine clearance, increased the probability of achieving target concentrations within 72 hours.

CONCLUSIONS

To increase the number of patients achieving optimal teicoplanin concentrations an individualized dosing approach, based on body weight and creatinine clearance, is recommended.

Coagulase negative staphylococcal sepsis in neonates: do we need to adapt vancomycin dose or target?

Background

Despite differences in types of infection and causative organisms, pharmacokinetic-pharmacodynamic (PKPD) targets of vancomycin therapy derived from adult studies are suggested for neonates. We aimed to identify doses needed for the attainment of AUC/MIC > 400 and AUC/MIC > 300 in neonates with sepsis and correlate these targets with recommended doses and treatment outcome.

Methods

Neonates who had Vancomycin therapeutic drug monitoring (TDM) performed between January 1, 2010 and December 31, 2012 were studied. Clinical characteristics, episodes of Gram-positive sepsis with outcomes and all neonatal blood culture isolates in hospital were collected from medical records. To estimate probability of target attainment of AUC/MIC >400 and AUC/MIC >300 a 1000-subject Monte Carlo simulation was performed by calculating AUC using Anderson’s (Anderson et al. 2006) and TDM trough concentrations (C_trough) based population PK models.

Results

Final dataset included 76 patients; 57 with confirmed Gram-positive sepsis. TDM was taken after the 1^st to 44^th dose. 84.1% of C_trough were within the range 5–15 mg/L. Currently recommended doses achieved probability of the targets (PTA) of AUC/MIC >400 and AUC/MIC >300 in less than 25% and 40% of cases, respectively. Doses required for 80% PTA of AUC/MIC > 400 for MIC ≥2 mg/L resulted in C_trough values ≥14 mg/L. Mean AUC/MIC values were similar in treatment failure and success groups.

Conclusion

With currently recommended vancomycin dosing the therapeutic target of AUC/MIC > 400 is achieved only by 25% of neonates. Appropriate PKPD targets and respective dosing regimens need to be defined in prospective clinical studies in this population.

Quantitative clinical pharmacology practice for optimal use of antibiotics during the neonatal period

INTRODUCTION

For safe and effective neonatal antibiotic therapy, knowledge of the pharmacokinetic parameters of antibacterial agents in neonates is a prerequisite. Fast maturational changes during the neonatal period influence pharmacokinetic and pharmacodynamic parameters and their variability. Consequently, the need for applying quantitative clinical pharmacology and determining optimal drug dosing regimens in neonates has become increasingly recognized.

AREAS COVERED

Modern quantitative approaches, such as pharmacometrics, are increasingly utilized to characterize, understand and predict the pharmacokinetics of a drug and its effect, and to quantify the variability in the neonatal population. Individual factors, called covariates in modeling, are integrated in such approaches to explain inter-individual pharmacokinetic variability. Pharmacometrics has been shown to be a relevant tool to evaluate, optimize and individualize drug dosing regimens.

EXPERT OPINION

Challenges for optimal use of antibiotics in neonates can largely be overcome with quantitative clinical pharmacology practice. Clinicians should be aware that there is a next step to support the clinical decision-making based on clinical characteristics and therapeutic drug monitoring, through Bayesian-based modeling and simulation methods. Pharmacometric modeling and simulation approaches permit us to characterize population average, inter-subject and intra-subject variability of pharmacokinetic parameters such as clearance and volume of distribution, and to identify and quantify key factors that influence the pharmacokinetic behavior of antibiotics during the neonatal period.