Understanding pharmacokinetics/pharmacodynamics in managing neonatal sepsis

Pharmacokinetic and Pharmacodynamic Considerations of Antibiotic Use in Neonates

The selection of an appropriate dose of a given antibiotic for a neonate not only requires knowledge of the drug's basic pharmacokinetic (PK) and pharmacodynamic (PD) properties but also the profound effects that organ development might have on the volume of distribution and clearance, both of which may affect the PK/PD of a drug. Interest has grown in alternative antibiotic dosing strategies that are better aligned with the antibiotic's PK and PD properties. These strategies should be used in conjunction with minimum inhibitory concentration measurements and therapeutic drug monitoring to measure their potential success. They can also guide the clinician in tailoring the delivery of antibiotics to suit an individual patient's needs. Model-informed precision dosing, such as Bayesian forecasting dosing software (which incorporates PK/PD population models), may be utilized to optimize antibiotic exposure in neonatal populations. Consequently, optimizing the antibiotic dose and exposure in each newborn requires expertise in different fields. It drives the collaboration of physicians together with lab technicians and quantitative clinical pharmacologists.

Impact of Extracorporeal Membrane Oxygenation in an Infant Treated with Vancomycin: A Case Report

Vancomycin is a glycopeptide antibiotic used for prophylaxis and treatment of infections caused by methicillin-resistant Staphylococcus aureus. Although major organ sizes and functions mature during infancy, pharmacokinetic studies, especially those focused on infants, are limited. Changes in extracorporeal membrane oxygenation-related drug disposition largely contribute to changes in pharmacokinetics. Here, pharmacokinetic profiles of vancomycin in an infant receiving extracorporeal membrane oxygenation therapy are presented. A two-month-old Japanese infant with moderately decreased renal function was started on 12.0 mg/kg vancomycin every 8 h from day X for prophylaxis of pneumonia during extracorporeal membrane oxygenation therapy. As the trough concentration of vancomycin observed on day X+3 was 27.1 μg/mL, vancomycin was then discontinued. The trough concentration decreased to 18.6 μg/mL 24 h after discontinuation, and 9.0 mg/kg vancomycin every 12 h was restarted from day X+5. On day X+6, the trough concentration increased to 36.1 μg/mL, and vancomycin therapy was again discontinued. On day X+7, the trough concentration decreased to 22.4 μg/mL. The pharmacokinetic profiles of vancomycin based on first-order conditional estimation in this infant were as follows: plasma clearance = 0.053 L/kg/hour, distribution volume = 2.19 L/kg, and half-life = 29.5 h. This research reported the prolonged half-life of vancomycin during extracorporeal membrane oxygenation in infants with moderately decreased renal function.

Ampicillin dosing in premature infants for early-onset sepsis: exposure-driven efficacy, safety, and stewardship

OBJECTIVE

Define optimal ampicillin dosing for empiric early-onset sepsis (EOS) therapy in preterm neonates.

STUDY DESIGN

We simulated ampicillin concentrations in newborns (birthweight < 1500 g; gestational age 22-27 weeks), summarizing three 48 h regimens: high 100 mg/kg Q8hr, medium 100 mg/kg Q12hr, and standard 50 mg/kg Q12hr. Concentration data were analyzed for concentration above minimum inhibitory concentration (MIC), below neurotoxicity threshold (Cmax ≤ 140 mcg/mL), and duration limited to 48 h.

RESULTS

Among 34,689 newborns, all dosing regimens provided concentrations above MIC through 48 h, but Cmax exceeded the neurotoxicity threshold. With the 4-dose standard regimen, >90% maintained concentrations >MIC beyond 48 h. With the 2-dose regimen, newborns maintained the mean concentration >MIC within the 48 h culture window and below neurotoxicity level. Infants 22-24 weeks' gestation had higher drug concentrations and more prolonged exposure duration than 25-27 weeks' gestation.

CONCLUSIONS

For EOS in preterm infants, two ampicillin doses (50 mg/kg) provided optimal bactericidal exposures, while minimizing potential toxicity.

Population Pharmacokinetics of Teicoplanin in Preterm and Term Neonates: Is It Time for a New Dosing Regimen?

Our objective was to develop a population pharmacokinetic (PK) model in order to evaluate the currently recommended dosing regimen in term and preterm neonates. By using an optimal design approach, a prospective PK study was designed and implemented in 60 neonates with postmenstrual ages (PMA) of 26 to 43 weeks. A loading dose of 16 mg/kg was administered at day 1, followed by a maintenance dose of 8 mg/kg daily. Plasma concentrations were quantified by high-pressure liquid chromatography-mass spectrometry. Population PK (popPK) analysis was performed using NONMEM software. Monte-Carlo (MC) simulations were performed to evaluate currently recommended dosing based on a pharmacodynamic index of area under the concentration-time curve (AUC)/MIC ratio of ≥400. A two-compartment model with linear elimination best described the data by the following equations: clearance (CL) = 0.0227 × (weight [wt]/1,765)^0.75 × (estimated creatinine clearance [eCRCL]/22)^0.672, central compartment volume of distribution (V1) = 0.283 (wt/1,765), intercompartmental clearance (Q) = 0.151 (wt/1,765)^0.75, and peripheral compartment volume (V2) = 0.541 (wt/1,765). The interindividual variability estimates for CL, V1, and V2 were 36.5%, 45.7%, and 51.4%, respectively. Current weight (wt) and estimated creatinine clearance (eCRCL) significantly explained the observed variability. MC simulation demonstrated that, with the current dosing regimen, an AUC/MIC ratio of ≥400 was reached by only 68.5% of neonates with wt of <1 kg when the MIC was equal to 1 mg/kg, versus 82.2%, 89.7%, and 92.7% of neonates with wt of 1 to <2, 2 to <3, or ≥3 kg, respectively. Augmentation of a maintenance dose up to 10 or 11 mg/kg for preterm neonates with wt of 1 to <2 or <1 kg, respectively, increases the probability of reaching the therapeutic target; the recommended doses seem to be adequate for neonates with wt of ≥2 kg. Teicoplanin PK are variable in neonates, with wt and eCRCL having the most significant impact. Neonates with wt of <2 kg need higher doses, especially for Staphylococcus spp. with an MIC value of ≥1 mg/liter.

Oral antibiotics for neonatal infections: a systematic review and meta-analysis

BACKGROUND

Worldwide many neonates suffer from bacterial infections. Adequate treatment is important but is associated with prolonged hospitalization for intravenous administration. In older children, oral switch therapy has been proven effective and safe for several indications and is now standard care.

OBJECTIVES

To evaluate the currently available evidence on pharmacokinetics, safety and efficacy of oral antibiotics and oral switch therapy in neonates (0-28 days old).

METHODS

We performed systematic searches in Medline, Embase.com, Cochrane, Google Scholar and Web of Science. Studies were eligible if they described the use of oral antibiotics in neonates (0-28 days old), including antibiotic switch studies and pharmacological studies.

RESULTS

Thirty-one studies met the inclusion criteria. Compared with parenteral administration, oral antibiotics generally reach their maximum concentration later and have a lower bioavailability, but in the majority of cases adequate serum levels for bacterial killing are reached. Furthermore, studies on efficacy of oral antibiotics showed equal relapse rates (OR 0.95; 95% CI 0.79-1.16; I2 0%) or mortality (OR 1.11; 95% CI 0.72-1.72; I2 0%). Moreover, a reduction in hospital stay was observed.

CONCLUSIONS

Oral antibiotics administered to neonates are absorbed and result in adequate serum levels, judged by MICs of relevant pathogens, over time. Efficacy studies are promising but robust evidence is lacking, most importantly because in many cases clinical efficacy and safety are not properly addressed. Early oral antibiotic switch therapy in neonates could be beneficial for both families and healthcare systems. There is a need for additional well-designed trials in different settings.

Plasma and CSF pharmacokinetics of meropenem in neonates and young infants: results from the NeoMero studies

Background

Sepsis and bacterial meningitis are major causes of mortality and morbidity in neonates and infants. Meropenem, a broad-spectrum antibiotic, is not licensed for use in neonates and infants below 3 months of age and sufficient information on its plasma and CSF disposition and dosing in neonates and infants is lacking.

Objectives

To determine plasma and CSF pharmacokinetics of meropenem in neonates and young infants and the link between pharmacokinetics and clinical outcomes in babies with late-onset sepsis (LOS).

Methods

Data were collected in two recently conducted studies, i.e. NeoMero-1 (neonatal LOS) and NeoMero-2 (neonatal meningitis). Optimally timed plasma samples (n = 401) from 167 patients and opportunistic CSF samples (n = 78) from 56 patients were analysed.

Results

A one-compartment model with allometric scaling and fixed maturation gave adequate fit to both plasma and CSF data; the CL and volume (standardized to 70 kg) were 16.7 (95% CI 14.7, 18.9) L/h and 38.6 (95% CI 34.9, 43.4) L, respectively. CSF penetration was low (8%), but rose with increasing CSF protein, with 40% penetration predicted at a protein concentration of 6 g/L. Increased infusion time improved plasma target attainment, but lowered CSF concentrations. For 24 patients with culture-proven Gram-negative LOS, pharmacodynamic target attainment was similar regardless of the test-of-cure visit outcome.

Conclusions

Simulations showed that longer infusions increase plasma PTA but decrease CSF PTA. CSF penetration is worsened with long infusions so increasing dose frequency to achieve therapeutic targets should be considered.

Evaluation of vancomycin target trough attainment with published dosing regimens in the neonatal intensive care unit population

BACKGROUND

Study aims to evaluate whether vancomycin dosing from published dosing algorithms correlate with the attainment of target troughs of 10 to 20 mg/L.

METHODS

NICU patients who received minimum three doses of vancomycin and had a trough level met inclusion criteria. Dosing information was retrospectively evaluated to determine which published dosing regimen was followed. Dosing algorithms used were matched to NeoFax/Harriet Lane, renal-function directed dosing, and weight-directed dosing, in which the latter two can be found in Pediatric and Neonatal Lexi-Drugs. Primary outcome was percentage of troughs within therapeutic (10 to 20 mg/L) and subtherapeutic (less than 10 mg/L) levels.

RESULTS

Of 97 troughs evaluated, NeoFax/Harriet Lane accounted for 86.6%, renal-function directed accounted for 5.1%, and weight-directed dosing accounted for 18.5% of dosing algorithms. NeoFax/Harriet Lane, renal-function directed, and weight-directed dosing attained therapeutic levels between 10 to 20 mg/L at a rate of 60.7%, 60%, and 50% of the time, respectively. With respect to initiation of therapy, a higher dose of 15 mg/kg versus 10 mg/kg attained therapeutic levels (p < 0.001; OR 11.22; 95% CI, 3.96 to 31.81), while a serum creatinine value below 0.5 mg/dL attained subtherapeutic levels (p = 0.028; OR 0.068; 95% CI, 0.006 to 0.74).

CONCLUSIONS

NeoFax, Harriet Lane, and renal-directed dosing from Pediatric and Neonatal Lexi-Drugs achieved target troughs within the 10 to 20 mg/L range more often than weight-directed dosing from Pediatric and Neonatal Lexi-Drugs. Initiating therapy at a higher dose and patient serum creatinine value above 0.5 mg/dL were factors significantly associated with a 10 to 20 mg/L range.

A Phase 3 Study of Micafungin Versus Amphotericin B Deoxycholate in Infants With Invasive Candidiasis

BACKGROUND

Amphotericin B deoxycholate (AmB-D) is standard of care treatment for neonatal invasive candidiasis (IC). Micafungin (MCA) has broad-spectrum fungicidal activity against Candida spp. We compared the efficacy and safety of intravenous MCA with intravenous AmB-D and assessed the pharmacokinetics of MCA in infants >2-120 days of age with proven IC in a phase 3, randomized, double-blind, multicenter, parallel-group, noninferiority study (NCT00815516).

METHODS

Infants were randomized 2:1 to MCA (10 mg/kg/d) or AmB-D (1 mg/kg/d) for ≥21 days. Primary efficacy endpoint was fungal-free survival (FFS) 1 week after last study drug dose. MCA population pharmacokinetics included simulated area under the curve (AUC) at steady state and maximum plasma concentration after 2-hour infusion. AUC pharmacodynamic target exposure was 170 µg·h/mL.

RESULTS

Thirty infants received MCA (n = 20) or AmB-D (n = 10). The trial was terminated early because of slow recruitment. FFS was observed in 12 of 20 [60%; 95% confidence interval (CI): 36%-81%] MCA-group infants and in 7 of 10 (70%; 95% CI: 35%-93%) AmB-D-group infants. The most common treatment-emergent adverse events were anemia [MCA: n = 9 (45%); AmB-D: n = 3 (30%)] and thrombocytopenia [n = 2 (10%) and n = 3 (30%), respectively]. Model-derived mean AUC at steady state for MCA was 399.3 ± 163.9 µg·h/mL (95% prediction interval: 190.3-742.3 µg/mL); steady state and maximum plasma concentration after 2-hour infusion was 31.1 ± 10.5 µg/mL (95% prediction interval: 17.0-49.7 µg/mL). MCA exposures were above the AUC pharmacodynamic target exposure.

CONCLUSIONS

Within the study limitations, infants with IC treated with MCA achieved similar FFS compared with AmB-D. Both agents were safe and well tolerated.

Population pharmacokinetics and dosing optimization of cefathiamidine in children with hematologic infection

Purpose

Cefathiamidine, a first-generation cephalosporin, has approval from the China Food and Drug Administration for the treatment of infections caused by susceptible bacteria in both adults and children. As pharmacokinetic data are limited in the pediatric population, we aimed to evaluate the population pharmacokinetics of cefathiamidine in children and to define the appropriate dose in order to optimize cefathiamidine treatment.

Methods

Blood samples were collected from children treated with cefathiamidine, and concentrations were quantified by high-performance liquid chromatography and tandem mass spectrometry. Population pharmacokinetic analysis was conducted using NONMEM software.

Results

Fifty-four children (age range: 2.0-11.8 years) were included. Sparse pharmacokinetic samples (n=120) were available for analysis. A two-compartment model with first-order elimination showed the best fit with the data. A covariate analysis identified that bodyweight had a significant impact on cefathiamidine pharmacokinetics. Monte Carlo simulation demonstrated that the currently used dosing regimen of 100 mg/kg/day q12h was associated with a high risk of underdosing in pediatric patients. To reach the target 70% fT>MIC, a dose of 100 mg/kg/day cefathiamidine q6h is required for effective treatment against Haemophilus influenzae.

Conclusion

A population pharmacokinetics model of cefathiamidine in children with hematologic disease was established. A dosing regimen of 100 mg/kg/day cefathiamidine q6h should be used in clinical practice against H. influenza infections.

A Population and Developmental Pharmacokinetic Analysis To Evaluate and Optimize Cefotaxime Dosing Regimen in Neonates and Young Infants

Cefotaxime is one of the most frequently prescribed antibiotics for the treatment of Gram-negative bacterial sepsis in neonates. However, the dosing regimens routinely used in clinical practice vary considerably. The objective of the present study was to conduct a population pharmacokinetic study of cefotaxime in neonates and young infants in order to evaluate and optimize the dosing regimen. An opportunistic sampling strategy combined with population pharmacokinetic analysis using NONMEM software was performed. Cefotaxime concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry. Developmental pharmacokinetics-pharmacodynamics, the microbiological pathogens, and safety aspects were taken into account to optimize the dose. The pharmacokinetic data from 100 neonates (gestational age [GA] range, 23 to 42 weeks) were modeled with an allometric two-compartment model with first-order elimination. The median values for clearance and the volume of distribution at steady state were 0.12 liter/h/kg of body weight and 0.64 liter/kg, respectively. The covariate analysis showed that current weight, GA, and postnatal age (PNA) had significant impacts on cefotaxime pharmacokinetics. Monte Carlo simulations demonstrated that the current dose recommendations underdosed older newborns. A model-based dosing regimen of 50 mg/kg twice a day to four times a day, according to GA and PNA, was established. The associated risk of overdose for the proposed dosing regimen was 0.01%. We determined the population pharmacokinetics of cefotaxime and established a model-based dosing regimen to optimize treatment for neonates and young infants.

[Dosing regimens of antibiotics in neonates: Variations in clinical practice and what should be done?]

There is wide variation in neonatal dosages of antibiotics in clinical practice, both nationally and internationally. This reflects the lack of evaluation of drugs in this therapeutic class, although widely prescribed. Given this situation, optimization of antibiotic prescription is required to ensure efficacy and safety of neonatal treatment and reduce microbial resistance. Rational prescription should be based on the knowledge of developmental pharmacokinetics and pharmacodynamics. Rigorous studies, conducted in collaboration between neonatologists and pharmacologists, are essential to develop and validate evidence-based neonatal dosage regimens.

Pharmacometric Approaches to Personalize Use of Primarily Renally Eliminated Antibiotics in Preterm and Term Neonates

Sepsis remains a major cause of mortality and morbidity in neonates, and, as a consequence, antibiotics are the most frequently prescribed drugs in this vulnerable patient population. Growth and dynamic maturation processes during the first weeks of life result in large inter- and intrasubject variability in the pharmacokinetics (PK) and pharmacodynamics (PD) of antibiotics. In this review we (1) summarize the available population PK data and models for primarily renally eliminated antibiotics, (2) discuss quantitative approaches to account for effects of growth and maturation processes on drug exposure and response, (3) evaluate current dose recommendations, and (4) identify opportunities to further optimize and personalize dosing strategies of these antibiotics in preterm and term neonates. Although population PK models have been developed for several of these drugs, exposure-response relationships of primarily renally eliminated antibiotics in these fragile infants are not well understood, monitoring strategies remain inconsistent, and consensus on optimal, personalized dosing of these drugs in these patients is absent. Tailored PK/PD studies and models are useful to better understand relationships between drug exposures and microbiological or clinical outcomes. Pharmacometric modeling and simulation approaches facilitate quantitative evaluation and optimization of treatment strategies. National and international collaborations and platforms are essential to standardize and harmonize not only studies and models but also monitoring and dosing strategies. Simple bedside decision tools assist clinical pharmacologists and neonatologists in their efforts to fine-tune and personalize the use of primarily renally eliminated antibiotics in term and preterm neonates.

Renal Function Descriptors in Neonates: Which Creatinine-Based Formula Best Describes Vancomycin Clearance?

Growth and maturational changes have been identified as significant covariates in describing variability in clearance of renally excreted drugs such as vancomycin. Because of immaturity of clearance mechanisms, quantification of renal function in neonates is of importance. Several serum creatinine (SCr)-based renal function descriptors have been developed in adults and children, but none are selectively derived for neonates. This review summarizes development of the neonatal kidney and discusses assessment of the renal function regarding estimation of glomerular filtration rate using renal function descriptors. Furthermore, identification of the renal function descriptors that best describe the variability of vancomycin clearance was performed in a sample study of a septic neonatal cohort. Population pharmacokinetic models were developed applying a combination of age-weight, renal function descriptors, or SCr alone. In addition to age and weight, SCr or renal function descriptors significantly reduced variability of vancomycin clearance. The population pharmacokinetic models with Léger and modified Schwartz formulas were selected as the optimal final models, although the other renal function descriptors and SCr provided reasonably good fit to the data, suggesting further evaluation of the final models using external data sets and cross validation. The present study supports incorporation of renal function descriptors in the estimation of vancomycin clearance in neonates.

Therapeutic guidelines for prescribing antibiotics in neonates should be evidence-based: a French national survey

OBJECTIVE

This survey aims to describe and analyse the dosage regimens of antibiotics in French neonatal intensive care units (NICUs).

METHODS

Senior doctors from 56 French NICUs were contacted by telephone and/or email to provide their local guidelines for antibiotic therapy.

RESULTS

44 (79%) NICUs agreed to participate in this survey. In total, 444 dosage regimens were identified in French NICUs for 41 antibiotics. The number of different dosage regimens varied from 1 to 32 per drug (mean 9, SD 7.8). 37% of intravenous dosage regimens used a unique mg/kg dose from preterm to full-term neonates. Doses and/or dosing intervals varied significantly for 12 antibiotics (amikacin, gentamicin, netilmicin, tobramycin, vancomycin administered as continuous infusion, ceftazidime, cloxacillin, oxacillin, penicillin G, imipenem/cilastatin, clindamycin and metronidazole). Among these antibiotics, 6 were used in more than 70% of local guidelines and had significant variations in (1) maintenance daily doses for amikacin, imipenem/cilastatin, ceftazidime and metronidazole; (2) loading doses for continuous infusion of vancomycin; and (3) dosing intervals for gentamicin and amikacin.

CONCLUSIONS

A considerable inter-centre variability of dosage regimens of antibiotics exists in French NICUs. Developmental pharmacokinetic-pharmacodynamic studies are essential for the evaluation of antibiotics in order to establish evidence-based dosage regimens for effective and safe administration in neonates.

A sensitive liquid chromatography-tandem mass spectrometry method for monitoring the caspofungin trough plasma concentration and its association with caspofungin efficacy in intensive-care-unit patients

LC-MS/MS method for monitoring the caspofungin trough plasma concentration and its association efficacy in intensive-care-unit patients.

Treatment option for sepsis in children in the era of antibiotic resistance

Sepsis caused by multidrug-resistant microorganisms is one of the most serious infectious diseases of childhood and poses significant challenges for pediatricians involved in management of critically ill children. This review discusses the use of pharmacokinetic/dynamic principles (i.e., prolonged infusion of β-lactams and vancomycin, once-daily administration of aminoglycosides and rationale of therapeutic drug monitoring) when prescribing antibiotics to critically ill patients. The potential of 'old' agents (i.e., colistin, fosfomycin) and newly approved antibiotics is critically reviewed. The pros and cons of combination antibacterial therapy are discussed and finally suggestions for the treatment of sepsis caused by multidrug-resistant organisms are provided.

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.

Neonatal pharmacology: extensive interindividual variability despite limited size

Providing safe and effective drug therapy to neonates requires knowledge of the impact of development on the pharmacokinetics and pharmacodynamics of drugs. Although maturational changes are observed throughout childhood, they are most prominent during the first year of life. Several of these processes overlap, making development an extremely dynamic system in the newborn compared with that in infants, children, or adults. Changes in body composition and porportions, liver mass, metabolic activity, and renal function collectively affect the pharmacokinetic behavior of medications. Instead of simply adapting doses by scaling adult or pediatric doses on the basis of a patient's weight and/or body surface area, integrated knowledge of clinical maturation and developmental pharmacology is critical to the safe and effective use of medications in neonates. Unfortunately, the effects of human ontogeny on both pharmacokinetics and pharmacodynamics have not been well established in these early stages of life, and information regarding the influence of developmental changes on the pharmacodynamics of medications is even more limited. Theoretically, age-dependent variations in receptor number and affinity for drugs have significant potential to influence an individual's response to drug therapy. In this review, some of the relevant covariates of pharmacokinetics and pharmacodynamics in neonates are reviewed and illustrated based on the published literature.

Antibiotic dosing in children in Europe: can we grade the evidence from pharmacokinetic/pharmacodynamic studies - and when is enough data enough?

PURPOSE OF REVIEW

Antibiotics are prescribed more frequently to children than any other class of medication. Analysis of the evidence behind antimicrobial dosing regimes is imperative to improve clinical outcomes, minimize antimicrobial resistance development, and to identify priority research areas for the future. This review aims to promote debate amongst paediatricians, pharmacologists, and pharmacists about how to improve antimicrobial prescribing by considering methods to develop and disseminate optimal dosage information.

RECENT FINDINGS

There has been increasing use of population analyses to understand pharmacokinetic/pharmacodynamic (PK/PD) parameters in children. Nonlinear mixed effects modelling is widely accepted to be the method of choice for analyses of PK/PD data. However, communicating the quality of PK/PD studies is an equally important factor to allow clinicians to gauge the robustness of the evidence. The possibility of grading PK/PD studies is discussed, along with using systematic reviews and PK/PD meta-analysis for generating high-quality evidence.Many doses in existing formularies (including the British National Formulary for Children) are based on outdated evidence. The need to update formularies to account for new evidence, population changes (e.g. obesity), and changing patterns of resistance requires a more systematic evaluation of antimicrobial PK/PD relationships in children. The possibility of e-formularies with links directly to the evidence should be considered and regulators must also play a role in supporting the re-evaluation of off-patent dosing guidelines.

SUMMARY

Advancing our understanding of the evidence behind paediatric antimicrobial therapeutic regimens is essential to improve both clinical outcomes and patient safety. Using a combination of international collaboration, electronic communication, and PK/PD modelling techniques, we can now define the gaps in our knowledge base and develop the techniques to answer them.

Clinical pharmacokinetics of vancomycin in the neonate: a review

Neonatal sepsis is common and is a major cause of morbidity and mortality. Vancomycin is the preferred treatment of several neonatal staphylococcal infections. The aim of this study was to review published data on vancomycin pharmacokinetics in neonates and to provide a critical analysis of the literature. A bibliographic search was performed using PubMed and Embase, and articles with a publication date of August 2011 or earlier were included in the analysis. Vancomycin pharmacokinetic estimates, which are different in neonates compared with adults, also exhibit extensive inter-neonatal variability. In neonates, several vancomycin dosing schedules have been proposed, mainly based on age (i.e., postmenstrual and postnatal), body weight or serum creatinine level. Other covariates [e.g., extracorporeal membrane oxygenation (ECMO), indomethacin or ibuprofen, and growth restriction] of vancomycin pharmacokinetics have been reported in neonates. Finally, vancomycin penetrates cerebrospinal fluid (range = 7-42%). Renal function drives vancomycin pharmacokinetics. Because either age or weight is the most relevant covariate of renal maturation, these covariates should be considered first in neonatal vancomycin dosing guidelines and further adjusted by renal dysfunction indicators (e.g., ECMO and ibuprofen/indomethacin). In addition to the prospective validation of available dosing guidelines, future studies should focus on the relevance of therapeutic drug monitoring and on the value of continuous vancomycin administration in neonates.

Meropenem vs standard of care for treatment of late onset sepsis in children of less than 90 days of age: study protocol for a randomised controlled trial

Background

Late onset neonatal sepsis (LOS) with the mortality of 17 to 27% is still a serious disease. Meropenem is an antibiotic with wide antibacterial coverage. The advantage of it over standard of care could be its wider antibacterial coverage and thus the use of mono-instead of combination therapy.

Methods

NeoMero-1, an open label, randomised, comparator controlled, superiority trial aims to compare the efficacy of meropenem with a predefined standard of care (ampicillin + gentamicin or cefotaxime + gentamicin) in the treatment of LOS in neonates and infants aged less than 90 days admitted to a neonatal intensive care unit.

A total of 550 subjects will be recruited following a 1:1 randomisation scheme. The trial includes patients with culture confirmed (at least one positive culture from normally sterile site except coagulase negative staphylococci in addition to one clinical or laboratory criterion) or clinical sepsis (at least two laboratory and two clinical criteria suggestive of LOS in subjects with postmenstrual age < 44 weeks or fulfilment of criteria established by the International Pediatric Sepsis Consensus Conference in subjects with postmenstrual age ≥ 44 weeks). Meropenem will be given at a dose of 20 mg/kg q12h or q8h depending on the gestational- and postnatal age. Comparator agents are administered as indicated in British National Formulary for Children. The primary endpoint measured at the test of cure visit (2 days after end of study therapy) is graded to success (all baseline symptoms and laboratory parameters are resolved or improved with no need to continue antibiotics and the baseline microorganisms are eradicated and no new microorganisms are identified and the patient has received allocated treatment for 11 ± 3 days with no modification) or a failure (all remaining cases). Secondary outcome measures include comparison of survival, relapse rates or new infections by Day 28, clinical response at Day 3 and end of therapy, duration of hospitalisation, population pharmacokinetic analysis of meropenem and effect of antibiotics on mucosal colonisation and development of antibacterial resistance.

The study will start recruitment in September 2011; the total duration is of 24 months.

Trial registration

EudraCT 2011-001515-31

Accuracy of Empiric Gentamicin Dosing Guidelines in Neonates

OBJECTIVE

To evaluate the accuracy of a neonatal gentamicin nomogram to achieve therapeutic gentamicin serum concentrations without further adjustment, allowing for decreased serum drug monitoring

METHODS

Retrospective single center review of all gentamicin pharmacokinetic evaluations in patients ≤ 30 days of life from July 2005 – June 2007. Patients were evaluated for postnatal age, gestational age, weight, serum creatinine, dose/interval, serum drug peaks and troughs, results of discharge hearing test and recent use of indomethacin. Logistic regression was utilized to determine potential factors impacting overall dosing accuracy, potentially allowing for decreased therapeutic drug monitoring. Factors found to be significant were incorporated into new guidelines which were evaluated through pharmacokinetic modeling.

RESULTS

Overall accuracy rate was 84% when empiric dosing guidelines were utilized; 16% of all doses were changed due to supratherapeutic troughs and 1% were changed due to subtherapeutic peaks. Variables found to impact the necessity for dose changes incuded gestational age (p≤0.001), weight (p≤0.001), indomethacin use (p≤0.001), number of indomethacin doses used (p≤0.001 and p=0.009 for 1–3 and 4–6 doses, respectively), and SCr in patients ≥ 7 days old (p=0.028); however, only gestational age remained a significant predictor when all other factors were considered (p=0.008). The current guidelines were changed to account for increased troughs in patients ≤ 28 weeks gestation and examined through pharmacokinetic modeling. Pharmacokinetic modeling of the new guidelines predicted an overall accuracy of 94%.

CONCLUSIONS

From the data gathered regarding the accuracy in patients ≥ 35 weeks gestation, we recommend to decrease therapeutic drug monitoring within this cohort. Utilizing the results of regression analysis, the current guidelines have been adjusted to allow for increased clearance in patients ≤ 28 weeks gestation, although they still need to be prospectively evaluated.