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1.  Sildenafil Exposure and Hemodynamic Effect after Fontan Surgery 
Objective
Determine sildenafil exposure and hemodynamic effect in children after Fontan single-ventricle surgery.
Design
Prospective, dose-escalation trial.
Setting
Single-center, pediatric catheterization laboratory.
Patients
9 children post Fontan single-ventricle surgical palliation and undergoing elective cardiac catheterization: Median (range) age and weight: 5.2 years (2.5–9.4) and 16.3 kg (9.5–28.1). Five children (55%) were male, and 6/9 (67%) had a systemic right ventricle.
Interventions
Catheterization and echocardiography performed before and immediately after single-dose intravenous sildenafil (0.25, 0.35, or 0.45 mg/kg over 20 minutes).
Measurements
Peak sildenafil and des-methyl sildenafil concentration, change in hemodynamic parameters measured by cardiac catheterization and echocardiography.
Main Results
Maximum sildenafil concentrations ranged from 124–646 ng/ml and were above the in vitro threshold needed for 77% phosphodiesterase type-5 (PDE-5) inhibition in 8/9 children and 90% inhibition in 7/7 of children with doses ≥0.35 mg/kg. Sildenafil improved stroke volume (+22%, p=0.05) and cardiac output (+10%, p=0.01) with no significant change in heart rate in 8/9 children. Sildenafil also lowered systemic (-16%, p=0.01) and pulmonary vascular resistance index (PVRI) in all 9 children (median baseline PVRI 2.4 [range: 1.3, 3.7]; decreased to 1.9 [0.8, 2.7] WU x m2; p=0.01) with no dose-response effect. Pulmonary arterial pressures decreased (−10%, p=0.02) and pulmonary blood flow increased (9%, p=0.02). There was no change in myocardial performance index and no adverse events.
Conclusions
After Fontan surgery, sildenafil infusion acutely improves cardiopulmonary hemodynamics, increasing cardiac index. For the range of doses studied, exposure was within the acute safety range reported in adult subjects.
doi:10.1097/PCC.0000000000000007
PMCID: PMC3887448  PMID: 24201857
single ventricle; sildenafil; Fontan; pulmonary hypertension; pulmonary vascular resistance; pharmacokinetics
2.  Population Pharmacokinetics of Intravenous Acyclovir in Preterm and Term Infants 
Background
Acyclovir is used to treat herpes infections in preterm and term infants; however, the influence of maturation on drug disposition and dosing requirements is poorly characterized in this population.
Methods
We administered intravenous acyclovir to preterm and term infants <31 days postnatal age and collected plasma samples. We performed a population pharmacokinetic analysis. The primary pharmacodynamic target was acyclovir concentration ≥3 mg/L for ≥50% of the dosing interval. The final model was simulated using infant data from a clinical database.
Results
The analysis included 28 infants (median 30 weeks gestation). Acyclovir pharmacokinetics was described by a 1-compartment model: clearance (L/h/kg) = 0.305 × (postmenstrual age [PMA]/31.3 weeks)3.02. This equation predicts a 4.5-fold increase in clearance from 25 to 41 weeks PMA. With proposed dosing, the pharmacodynamic target was achieved in 91% of infants: 20 mg/kg every 12 hours in infants <30 weeks PMA; 20 mg/kg every 8 hours in infants 30 to <36 weeks PMA; 20 mg/kg every 6 hours in infants 36–41 weeks PMA.
Conclusions
Acyclovir clearance increased with infant maturation. A dosing strategy based on PMA accounted for developmental changes in acyclovir disposition to achieve the surrogate pharmacodynamic target in the majority of infants.
doi:10.1097/01.inf.0000435509.75114.3d
PMCID: PMC3904301  PMID: 24346595
herpes simplex virus; preterm infants; acyclovir
3.  Intestinal Fatty-Acid Binding Protein and Metronidazole Response in Premature Infants 
Objectives
In premature infants with suspected intra-abdominal infection, biomarkers for treatment response to antimicrobial therapy are lacking. Intestinal fatty acid-binding protein (I-FABP) is specific to the enterocyte and is released in response to intestinal mucosal injury. I-FABP has not been evaluated as a surrogate marker of disease response to antimicrobial therapy. We examined the relationship between metronidazole exposure and urinary I-FABP concentrations in premature infants with suspected intra-abdominal infection.
Study design
We conducted an intravenous metronidazole pharmacokinetic study, collecting ≤3 urine samples per infant for I-FABP concentration measurements. We analyzed the relationship between I-FABP concentrations and measures of metronidazole exposure and pharmacokinetics, maturational factors, and other covariates.
Results
Twenty-six samples from 19 premature infants were obtained during metronidazole treatment. When analyzed without regard to presence of necrotic gastrointestinal disease, there were no significant associations between predictor variables and I-FABP concentrations. However, when the sample was limited to premature infants with necrotic gastrointestinal disease, an association was found between average predicted metronidazole concentration and I-FABP concentration (p=0.006).
Conclusion
While a predictive association between urinary I-FABP and metronidazole systemic exposure was not observed, the data suggest the potential of this endogenous biomarker to serve as a pharmacodynamic surrogate for antimicrobial treatment of serious abdominal infections in neonates and infants.
doi:10.3233/NPM-1477013
PMCID: PMC4225165  PMID: 25318626
necrotizing enterocolitis; biomarkers; pharmacokinetics; premature infants; antimicrobial agents
4.  Characterization of the Population Pharmacokinetics of Ampicillin in Neonates Using an Opportunistic Study Design 
Although ampicillin is the most commonly used drug in neonates, developmental pharmacokinetic (PK) data to guide dosing are lacking. Ampicillin is primarily renally eliminated, and developmental changes are expected to influence PK. We conducted an open-label, multicenter, opportunistic, prospective PK study of ampicillin in neonates stratified by gestational age (GA) (≤34 or >34 weeks) and postnatal age (PNA) (≤7 or >7 days). Drug concentrations were measured by tandem mass spectrometry. PK data were analyzed using population nonlinear mixed-effects modeling in NONMEM 7.2. Monte Carlo simulations were conducted to determine the probability of target attainment for the time in which the total steady-state ampicillin concentrations remained above the MIC (T>MIC) for 50%, 75%, and 100% of the dosing interval. A total of 142 PK samples from 73 neonates were analyzed (median [range] GA, 36 [24 to 41] weeks; PNA, 5 [0 to 25] days). The median ampicillin dose was 200 (100 to 350) mg/kg/day. Postmenstrual age and serum creatinine were covariates for ampicillin clearance (CL). A simplified dosing regimen of 50 mg/kg every 12 h for GA of ≤34 weeks and PNA of ≤7 days, 75 mg/kg every 12 h for GA of ≤34 weeks and PNA of ≥8 and ≤28 days, and 50 mg/kg every 8 h for GA of >34 weeks and PNA of ≤28 days achieved the prespecified surrogate efficacy target in 90% of simulated subjects. Ampicillin CL was associated with neonatal development. A simplified dosing regimen stratified by GA and PNA achieves the desired surrogate therapeutic target in the vast majority of neonates.
doi:10.1128/AAC.02374-13
PMCID: PMC4068432  PMID: 24614374
5.  Developmental Pharmacokinetics of Piperacillin and Tazobactam Using Plasma and Dried Blood Spots from Infants 
Piperacillin-tazobactam is often given to infants with severe infection in spite of limited pharmacokinetics (PK) data. We evaluated piperacillin-tazobactam PK in premature and term infants of ages <61 days with suspected systemic infection. Infants received intravenous piperacillin-tazobactam (80 to 100 mg/kg of body weight every 8 h [q 8 h]) based on gestational and postnatal age. Sparse plasma samples were obtained after first and multiple doses. Drug concentrations were measured by tandem mass spectrometry. PK data were analyzed using population nonlinear mixed-effect modeling. Target attainment rates for the time unbound piperacillin concentrations remained above the MIC for 50% and 75% of the dosing interval at steady state were evaluated. Bias in population PK parameter estimates was assessed for dried blood spot (DBS) samples, and a comparability analysis was performed for DBS and plasma drug concentrations using linear regression. We obtained 128 plasma samples from 32 infants, median gestational age of 30 weeks (range, 23 to 40 weeks) and postnatal age of 8 days (range, 1 to 60). Piperacillin and tazobactam PK models included body weight (WT) and postmenstrual age (PMA) as covariates for clearance and WT for volume of distribution and were used to optimize dosing in infants. DBS drug concentrations were 50 to 60% lower than those in plasma, but when combined with plasma concentrations and a matrix effect, the data generated PK model parameters similar to those for plasma alone. With PMA-based dosing (100 mg/kg q 8 h, 80 mg/kg q 6 h, and 80 mg/kg q 4 h for PMA of ≤30, 30 to 35, and 35 to 49 weeks, respectively), 90% of simulated infants achieved the surrogate therapeutic target of time above the MIC (≤32 mg/liter) for 75% of the dosing interval.
doi:10.1128/AAC.02139-13
PMCID: PMC3993246  PMID: 24614369
6.  Thromboprophylaxis with fondaparinux in high-risk postoperative patients with renal insufficiency 
Thrombosis research  2013;133(4):629-633.
Fondaparinux is an antithrombin-dependent factor Xa inhibitor that is used for thromboprophylaxis of patients undergoing hip fracture surgery, hip or knee replacement, or abdominal surgery. It is cleared by the kidney and should be used with caution in patients with renal impairment and avoided in patients with severe renal insufficiency. Recently, several studies have demonstrated that a lower dose of fondaparinux in patients with moderate renal impairment appears to be safe and effective. The purpose of this study was to obtain pharmacokinetic and clinical data on the use of prophylactic fondaparinux inpatients with renal insufficiency undergoing major abdominal surgery for cancer (n=8) or orthopedic surgery (n=1). Anti-factor Xa levels were obtained, and a published population pharmacokinetic model for fondaparinux was fit to the data. The data were analyzed using NONMEM software. Fondaparinux did not appear to accumulate in these patients, even when the drug was administered for up to twelve days. Pharmacokinetic analysis revealed thatthe apparent clearance in this population, who were primarily undergoing cancer surgery, was similar to prior studies in orthopedic surgery patients. In contrast, lower estimates were obtained for volume of distribution and absorption rate constant parameters.None of the patients sustained a hemorrhagic complication attributable to fondaparinux. One patient developed hypoxia in the setting of transient atrial fibrillation and clinical suspicion for pulmonary embolism, but this was not confirmed radiographically. These results support the use of 1.5 mg of fondaparinux every 24 hours for thromboprophylaxis in patients with renal insufficiency undergoing high-risk surgical procedures.
doi:10.1016/j.thromres.2013.11.019
PMCID: PMC4156854  PMID: 24508189
thromboprophylaxis; renal failure; fondaparinux
7.  Determining Population and Developmental Pharmacokinetics of Metronidazole Using Plasma and Dried Blood Spot Samples from Premature Infants 
Background
Limited pharmacokinetic (PK) data of metronidazole in premature infants has led to various dosing recommendations. Surrogate efficacy targets for metronidazole are ill-defined and therefore aimed to exceed minimum inhibitory concentration of organisms responsible for intra-abdominal infections.
Methods
We evaluated the PK of metronidazole using plasma and dried blood spot (DBS) samples from infants ≤32 weeks gestational age in an open-label, PK, multicenter (N=3) study using population PK modeling (NONMEM). Monte Carlo simulations (N=1000 virtual subjects) were used to evaluate the surrogate efficacy target. Metabolic ratios of parent and metabolite were calculated.
Results
Twenty-four premature infants (111 plasma and 51 DBS samples) were enrolled: median (range) gestational age at birth 25 (23–31) weeks, postnatal age 27 (1–82) days, postmenstrual age (PMA) 31 (24–39) weeks, and weight 740 (431–1466) g. Population clearance (CL, L/h/kg) was 0.038 × (PMA/30)2.45 and volume of distribution (L/kg) of 0.93. PK parameter estimates and precision were similar between plasma and DBS samples. Metabolic ratios correlated with CL.
Conclusion
Simulations suggested the majority of infants in the neonatal intensive care unit (>80%) would meet the surrogate efficacy target using PMA-based dosing.
doi:10.1097/INF.0b013e3182947cf8
PMCID: PMC3769518  PMID: 23587979
neonate; drug; pharmacokinetics; metronidazole; dried blood spots
8.  Adverse Events Associated with Meropenem versus Imipenem/Cilastatin Therapy in a Large Retrospective Cohort of Hospitalized Infants 
Background
Carbapenems are commonly used in hospitalized infants despite a lack of complete safety data and associations with seizures in older children. We compared the incidence of adverse events in hospitalized infants receiving meropenem versus imipenem/cilastatin.
Methods
We conducted a retrospective cohort study of 5566 infants treated with meropenem or imipenem/cilastatin in neonatal intensive care units managed by the Pediatrix Medical Group between 1997 and 2010. Multivariable conditional logistic regression was performed to evaluate the association between carbapenem therapy and adverse events, controlling for infant factors and severity of illness.
Results
Adverse events were more common with use of meropenem compared with imipenem/cilastatin (62.8/1000 infant days vs. 40.7/1000 infant days, P<0.001). There was no difference in seizures with meropenem vs. imipenem/cilastatin (adjusted odds ratio [OR] 0.96; 95% confidence interval 0.68, 1.32). The incidence of death, as well as the combined outcome of death or seizure, was lower with meropenem use—OR 0.68 (0.50, 0.88) and OR 0.77 (0.62, 0.95), respectively.
Conclusion
In this cohort of infants, meropenem was associated with more frequent but less severe adverse events when compared with imipenem/cilastatin.
doi:10.1097/INF.0b013e31828be70b
PMCID: PMC3708263  PMID: 23838776
meropenem; imipenem/cilastatin; adverse events; infant
9.  Sildenafil exposure and hemodynamic effect after stage II single-ventricle surgery 
Objective
To determine sildenafil exposure and hemodynamic effect in children after stage II single-ventricle surgery.
Design
Prospective, dose escalation trial.
Setting
Single-center, pediatric catheterization laboratory.
Patients
12 children post stage II single-ventricle surgical palliation and undergoing elective cardiac catheterization: median age 1.9 years (range: 0.8, 4.0), weight 11 kg (8, 13), 9 females, and 10 with a single right ventricle.
Interventions
Catheterization and echocardiography performed before and immediately after single-dose intravenous sildenafil (0.125, 0.25, 0.35, or 0.45 mg/kg over 20 minutes).
Measurements
Peak sildenafil and des-methyl sildenafil concentration, change in hemodynamic parameters measured by cardiac catheterization and echocardiography including indexed pulmonary vascular resistance, and myocardial performance.
Main Results
Maximum sildenafil concentrations ranged from 92–775 ng/ml and were above the in vitro threshold needed for 77% phosphodiesterase type-5 (PDE-5) inhibition in 80% of subjects and 90% inhibition in 80% of subjects with doses ≥0.35 mg/kg. Sildenafil lowered pulmonary vascular resistance index (PVRI) in all 12 subjects (median PVRI 2.2 [range: 1.6, 7.9]; decreased to 1.7 [1.2, 5.4] WU x m2; p<0.01) with no dose-response effect. Sildenafil improved pulmonary blood flow (+8% [0, 20], p=0.04) and saturations (+2% [0, 16], p=0.04) in those with baseline PVRI ≥2 WU x m2 (n=7). Change in saturations correlated inversely with change in PVRI (r2 = 0.74 p<0.01). Sildenafil also lowered mean blood pressure (−12% [−20, +10]; p=0.04). There was no change in cardiac index and no effect on myocardial performance. There were no adverse events.
Conclusions
Sildenafil demonstrated non-linear exposure with high inter-individual variability but was well tolerated and effectively lowered PVRI in all subjects. Sildenafil did not acutely improve myocardial performance or increase cardiac index.
doi:10.1097/PCC.0b013e31828aa5ee
PMCID: PMC3782306  PMID: 23823195
Single ventricle; sildenafil; bidirectional Glenn anastomosis; pulmonary hypertension; pulmonary vascular resistance; pharmacokinetics
10.  Urinary tract infection concordance with positive blood and cerebrospinal fluid cultures in the neonatal intensive care unit 
Objective
Urinary tract infections (UTI) are common in the neonatal intensive care unit (NICU). Blood, urine, and cerebrospinal fluid (CSF) cultures are frequently obtained to evaluate for infection. We sought to determine the concordance between positive urine cultures and blood or CSF cultures.
Study design
Infants <121 days of age with a UTI admitted to 322 NICUs managed by the Pediatrix Medical Group from 1997–2010 were identified. UTIs were defined by isolation of a single pathogenic organism in a urine sample obtained by catheterization or suprapubic tap. The UTI was concordant if the same organism was identified in the blood or CSF within 3 days of the urine culture.
Results
Of 5681 infants with a urine culture, 984 had 1162 UTIs. Nine hundred seventy-six UTIs (84%) had a blood culture collected within 3 days, and 127 (13%) were concordant. Of the 1162 UTIs, 77 (7%) had a CSF culture collected within 3 days, and 2 (3%) were concordant.
Conclusion
Collection of a urine culture in infants evaluated for late-onset sepsis is important. Concordance was observed in 13% of blood cultures and 3% of CSF cultures. These findings may be related to the initiation of empirical antimicrobial therapy before evaluation for disseminated infection or poor blood culture sensitivity.
doi:10.1038/jp.2012.111
PMCID: PMC3549035  PMID: 22935772
infant; sepsis
11.  Group B Streptococcus and Escherichia coli Infections in the Intensive Care Nursery in the Era of Intrapartum Antibiotic Prophylaxis 
Background
Group B Streptococcus (GBS) and Escherichia coli (E. coli) cause serious bacterial infections (SBIs) and are associated with morbidity and mortality in newborn infants. Intrapartum antibiotic prophylaxis (IAP) reduces early-onset SBIs caused by GBS. The effect of IAP on late-onset SBIs caused by these organisms is unknown.
Methods
We examined all blood, urine, and cerebrospinal fluid culture results from infants admitted from 1997–2010 to 322 neonatal intensive care units managed by the Pediatrix Medical Group. We identified infants with positive cultures for GBS or E. coli and compared the incidence of early- and late-onset SBI for each organism in the time period before (1997–2001) and after (2002–2010) universal IAP recommendations.
Results
We identified 716,407 infants with cultures, 2520 (0.4%) with cultures positive for GBS and 2476 (0.3%) with cultures positive for E. coli. The incidence of GBS early-onset SBI decreased between 1997–2001 and 2002–2010 from 3.5 to 2.6 per 1000 admissions, and the incidence for E. coli early-onset SBI remained stable (1.4 per 1000 admissions in both time periods). Over the same time period, the incidence of GBS late-onset SBI increased from 0.8 to 1.1 per 1000 admissions, and incidence of E. coli late-onset SBI increased from 2.2 to 2.5 per 1000 admissions.
Conclusions
In our cohort, the incidence of early-onset GBS SBI decreased, while the incidence of late-onset SBI for E. coli and GBS increased.
doi:10.1097/INF.0b013e318275058a
PMCID: PMC3572304  PMID: 23011013
infection; infant; sepsis; group B Streptococcus; Escherichia coli
12.  Risk Factors for Invasive Candidiasis in Infants >1500 g Birth Weight 
Background
We describe the incidence, risk factors, and outcomes of invasive candidiasis in infants >1500 g birth weight.
Methods
We conducted a retrospective cohort study of infants >1500 g birth weight discharged from 305 NICUs in the Pediatrix Medical Group from 2001–2010. Using multivariable logistic regression, we identified risk factors for invasive candidiasis.
Results
Invasive candidiasis occurred in 330/530,162 (0.06%) infants. These were documented from positive cultures from ≥1 of these sources: blood (n=323), cerebrospinal fluid (n=6), or urine from catheterization (n=19). Risk factors included day of life >7 (OR 25.2; 95% CI 14.6–43.3), vaginal birth (OR 1.6 [1.2–2.3]), exposure to broad-spectrum antibiotics (OR 1.6 [1.1–2.4]), central venous line (OR 1.8 [1.3–2.6]), and platelet count <50,000/mm3 (OR 3.7 [2.1–6.7]). All risk factors had poor sensitivities, low positive likelihood ratios, and low positive predictive values. The combination of broad-spectrum antibiotics and low platelet count had the highest positive likelihood ratio (46.2), but the sensitivity of this combination was only 4%. Infants with invasive candidiasis had increased mortality (OR 2.2 [1.3–3.6]).
Conclusions
Invasive candidiasis is uncommon in infants >1500 g birth weight. Infants at greatest risk are those exposed to broad-spectrum antibiotics and with platelet counts of <50,000/mm3.
doi:10.1097/INF.0b013e3182769603
PMCID: PMC3578110  PMID: 23042050
candidiasis; candidemia; neonates; neonatal intensive care unit
13.  Triazole use in the nursery: fluconazole, voriconazole, posaconazole, and ravuconazole 
Current drug metabolism  2013;14(2):193-202.
Invasive fungal infections in infants admitted to the neonatal intensive care unit are common and often fatal. The mainstay of therapy against invasive fungal infections is antifungal agents. Over the last two decades, the development and approval of these drugs evolved tremendously, and the azole class emerged as important agents in the treatment and prevention of invasive fungal infections. Among the azoles, fluconazole has been used extensively due to its favorable pharmacokinetics, excellent activity against Candida spp, and safety profile. This drug has been well studied in children but data for its use in infants are largely limited to Candida prophylaxis studies. Voriconazole, a second generation triazole, has excellent activity against Candida and Aspergillus spp. However, data on its use in neonates are extremely limited. Posaconazole and Ravuconazole are the newest agents of the triazole family. The antimicrobial spectrum of posaconazole is similar to voriconazole, but with additional activity against zygomycetes. Experience with posaconazole in children is very limited, and there are no reports of its use in infants. Ravuconazole is not approved for use by the FDA but studies in animals and humans show that it is often fungicidal and has favorable pharmacokinetics. In conclusion, the management of invasive fungal infections has progressed greatly over the last two decades with the azole antifungals playing a significant role. Related to this class, future research is needed in order to better assess dosing, safety, schedules and areas of use of these agents in infants admitted to the neonatal intensive care unit.
PMCID: PMC3541435  PMID: 22935068
antifungal agents; triazole; prematurity; infection; candida; aspergillosis
14.  Safety and Effectiveness of Meropenem in Infants With Suspected or Complicated Intra-abdominal Infections 
The safety and effectiveness of meropenem in young infants with suspected or confirmed intra-abdominal infections were evaluated. was well tolerated in this cohort of critically-ill infants, and the majority of infants treated with meropenem (84%) met the definition of therapeutic success.
Background. Intra-abdominal infections are common in young infants and lead to significant morbidity and mortality. Meropenem is a broad-spectrum antimicrobial with excellent activity against pathogens associated with intra-abdominal infections. The purpose of this study was to determine the safety and effectiveness of meropenem in young infants with suspected or complicated intra-abdominal infections.
Methods. Preterm and term infants <91 days of age with suspected or confirmed intra-abdominal infections hospitalized in 24 neonatal intensive care units were studied in an open-label, multiple-dose study. Adverse events and serious adverse events were collected through 3 and 30 days following the last meropenem dose, respectively. Effectiveness was assessed by 3 criteria: death, bacterial cultures, and presumptive clinical cure score.
Results. Of 200 subjects enrolled in the study, 99 (50%) experienced an adverse event, and 34 (17%) had serious adverse events; no adverse events were probably or definitely related to meropenem. The most commonly reported adverse events were sepsis (6%), seizures (5%), elevated conjugated bilirubin (5%), and hypokalemia (5%). Only 2 of the serious adverse events were determined to be possibly related to meropenem (isolated ileal perforation and an episode of fungal sepsis). Effectiveness was evaluable in 192 (96%) subjects, and overall treatment success was 84%.
Conclusions. Meropenem was well tolerated in this cohort of critically ill infants, and the majority of infants treated with meropenem met the definition of therapeutic success.
Clinical Trials Registration. NCT00621192.
doi:10.1093/cid/cis758
PMCID: PMC3491861  PMID: 22955430
15.  Pharmacokinetics and Safety of Fluconazole in Young Infants Supported with Extracorporeal Membrane Oxygenation 
Background
Candida infections are a leading cause of infectious disease-related death in infants supported with extracorporeal membrane oxygenation (ECMO). The ECMO circuit can alter drug pharmacokinetics (PK), thus standard fluconazole dosing in children on ECMO may result in suboptimal drug exposure. This study determined the PK of fluconazole in infants on ECMO.
Methods
Infants <120 days old received either intravenous fluconazole prophylaxis (25 mg/kg once a week) or treatment (12 mg/kg daily) while on ECMO. Paired plasma samples were collected pre- and post-oxygenator around doses 1 and 2 to calculate PK indices and describe oxygenator extraction. A 1-compartment model was fit to the data using non-linear regression. Surrogate pharmacodynamic targets for efficacy were evaluated.
Results
Ten infants were enrolled. After dose 1 (n=9), the median clearance was 17 mL/kg/h, the median volume of distribution was 1.5 L/kg, and the median exposure in the first 24 hours (AUC0–24) was 322 h*mg/L. After multiple doses (n=7), the median clearance was 22 mL/kg/h, the median volume of distribution was 1.9 L/kg, and the AUC0–24 was 352 h*mg/L. After dose 1, 78% of infants achieved the prophylaxis target, while only 11% achieved the therapeutic target. Oxygenator extraction of fluconazole was minimal (−2.0%, standard deviation 15.0), and extraction was not correlated with age of the ECMO circuit (rho= − 0.05). There were no adverse events related to fluconazole.
Conclusions
Infants on ECMO had higher volume of distribution but similar clearance when compared with historical controls not on ECMO. In infants on ECMO, a fluconazole dose of 25 mg/kg weekly provides adequate exposure for prophylaxis against Candida infections. However, higher doses may be needed for treatment.
doi:10.1097/INF.0b013e31825d3091
PMCID: PMC3444624  PMID: 22627870
fluconazole; Candida; extracorporeal membrane oxygenation; pharmacokinetics; infants
16.  Pharmacokinetics and Tolerability of Single-Dose Daptomycin in Young Infants 
Background
Daptomycin is approved for the treatment of complicated skin and skin structure infections and Staphylococcus aureus bacteremia. We sought to characterize daptomycin single-dose pharmacokinetics and tolerability in young infants.
Methods
Subjects <120 days of age with suspected systemic infections were eligible for inclusion. Each subject was given a single 6 mg/kg intravenous dose of daptomycin. An average of 4 post-dose concentrations per infant was obtained.
Results
Data from 20 infants are presented. Median gestational age at birth and postnatal age were 32 weeks (range 23, 40) and 3 days (1, 85), respectively. The median area under the concentration curve at 24 hours, volume of distribution, total body clearance, and half-life of daptomycin were 262.4 mg*h/L (166.7, 340.2), 0.21 L/kg (0.11, 0.34), 0.021 L/hr/kg (0.016, 0.034), and 6.2 hours (3.7, 9.0), respectively. No adverse events related to daptomycin were observed, including changes in creatine phosphokinase concentrations.
Conclusions
Daptomycin clearance in young infants was similar to that in 2–6-year-olds and higher than that observed in adolescents and adults.
doi:10.1097/INF.0b013e31825d2fa2
PMCID: PMC3421038  PMID: 22627869
daptomycin; complicated skin and skin structure infections; Staphylococcus aureus; pharmacokinetics
18.  Use of the Complete Blood Cell Count in Early-Onset Neonatal Sepsis 
Background
Early-onset sepsis is an important cause of morbidity and mortality in neonates, and its diagnosis remains challenging. The complete blood cell count and differential have been previously evaluated as diagnostic tools for early-onset sepsis in small, single-center reports. We evaluated the diagnostic accuracy of the complete blood count and differential in early-onset sepsis in a large, multicenter population of neonates admitted to the neonatal intensive care unit.
Methods
Using a cohort of 166,092 neonates with suspected early-onset sepsis with cultures admitted to 293 neonatal intensive care units, we calculated odds ratios and receiver operating characteristic curves for complete blood cell count indices and prediction of a positive culture. We determined sensitivity, specificity, and likelihood ratios for various commonly used cut-off values from the complete blood cell count.
Results
Low white blood cell counts, low absolute neutrophil counts, and high immature-to-total neutrophil ratios were associated with increasing odds of infection (highest odds ratios: 5.38, 6.84, and 7.97, respectively). Specificity and negative predictive values were high (73.7–99.9% and >99.8%). However, sensitivities were low (0.3–54.5%) for all complete blood cell count indices analyzed.
Conclusion
Low white blood cell count, absolute neutrophil count, and high immature-to-total neutrophil ratio were associated with increasing odds of infection, but no complete blood cell count-derived index possesses the sensitivity to rule out reliably early-onset sepsis in neonates.
doi:10.1097/INF.0b013e318256905c
PMCID: PMC3399972  PMID: 22531231
neonatal; early-onset sepsis; blood cell count
19.  Use of the Complete Blood Cell Count in Late-Onset Neonatal Sepsis 
Background
Late-onset sepsis is an important cause of morbidity and mortality in infants. Diagnosis of late-onset sepsis can be challenging. The complete blood cell count and differential have been previously evaluated as diagnostic tools for late-onset sepsis in small, single-center reports.
Objective
We evaluated the diagnostic accuracy of the complete blood count and differential in late-onset sepsis in a large multicenter population.
Study design
Using a cohort of all infants with cultures and complete blood cell count data from a large administrative database, we calculated odds ratios for infection, as well as sensitivity, specificity, positive and negative predictive values, and likelihood ratios for various commonly used cut-off values.
Results
High and low white blood cell counts, high absolute neutrophil counts, high immature-to-total neutrophil ratios, and low platelet counts were associated with late-onset sepsis. Associations were weaker with increasing postnatal age at the time of the culture. Specificity was highest for white blood cell counts <1000/mm3 and >50,000/mm3 (>99%). Positive likelihood ratios were highest for white blood cell counts <1000/mm3 (4.1) and platelet counts <50,000/mm3 (3.5).
Conclusion
No complete blood count index possessed adequate sensitivity to reliably rule out late-onset sepsis in this population.
doi:10.1097/INF.0b013e31825691e4
PMCID: PMC3399981  PMID: 22531232
neonatal; late-onset sepsis; blood cell count
20.  Evidence-based guidelines for pediatric clinical trials: focus on StaR Child Health 
Clinical trials in children are challenging and filled with important ethical considerations that differ from adults. Given difficulties associated with pediatric clinical trials, off-label prescribing is a common practice in pediatrics, which can lead to adverse safety events and efficacy failures. To overcome these consequences, in the past 15 years, legislation in the USA and Europe has provided incentives to industry and increased government funding to conduct pediatric trials. Pediatric trial networks have also been formed to decrease the knowledge gap. However, challenges to performing pediatric trials and lack of standardization and guidelines regarding studies in children still exist. Standards for Research (StaR) in Child Health, begun in 2009, aims to improve the design, conduct and reporting of pediatric trials. This organization uses a consensus guideline approach involving academic, government and industry stakeholders to identify and disseminate best practices for pediatric trials. Six out of 11 planned standards are currently published.
doi:10.1586/ecp.12.52
PMCID: PMC3566240  PMID: 23121275
clinical trials; guidelines; pediatrics
21.  Population Pharmacokinetics of Piperacillin Using Scavenged Samples from Preterm Infants 
Therapeutic Drug Monitoring  2012;34(3):312-319.
Objectives
Piperacillin is often used in preterm infants for intra-abdominal infections; however, dosing has been derived from small single-center studies excluding extremely preterm infants at highest risk for these infections. We evaluated the population pharmacokinetics (PK) of piperacillin using targeted sparse sampling and scavenged samples obtained from preterm infants ≤32 weeks gestational age at birth and <120 postnatal days.
Materials and Methods
A 5-center study was performed. A population PK model using nonlinear mixed effect modeling was developed. Covariate effects were evaluated based on estimated precision and clinical significance.
Results
Fifty-six preterm infants were evaluated and had a median (range) gestational age at birth of 25 (22–32) weeks, a postnatal age of 17 (1–77) days, a postmenstrual age of 29 (23–40) weeks, and a weight of 867 (400–2580) grams. The final PK data set contained 211 samples; 202/211 (96%) were scavenged from discarded clinical specimens. Piperacillin population PK was best described by a 1-compartment model. The population mean clearance (CL) was derived by the equation CL (liter/h)=0.479 x (weight)0.75 x 0.5/serum creatinine and using a volume of distribution (V) (liter) of 2.91 x (weight). The relative standard errors around parameter estimates ranged from 13.7–32.2%. A trend towards increased CL was observed with increasing gestational age at birth; infants with serum creatinine ≥1.2 mg/dL had a 60% reduction in piperacillin CL. The majority (>70%) of infants did not meet pre-defined pharmacodynamic efficacy targets.
Conclusions
Scavenged PK sampling is a minimal-risk approach that can provide meaningful information related to development of PK models but not dosing recommendations for piperacillin. The utility of scavenged sampling in providing definitive dosing recommendations may be drug-dependent and needs to be further explored.
doi:10.1097/FTD.0b013e3182587665
PMCID: PMC3354042  PMID: 22569355
neonate; drug; pharmacokinetics; piperacillin
23.  Therapeutic Monitoring of Voriconazole in Children Less Than 3 Years of Age: A Case Report and Summary of Voriconazole Concentrations for 10 Children 
Voriconazole is the treatment of choice for invasive aspergillosis and its use is increasing in pediatrics. Minimal pharmacokinetic data exist in young children. We report voriconazole concentrations for 10 children less than <3 years of age and pharmacokinetic parameters for one infant who had therapeutic drug monitoring performed. Trough concentrations were unpredictable based on dose, highlighting the need to follow values during therapy.
doi:10.1097/INF.0b013e31824acc33
PMCID: PMC3356483  PMID: 22301479
invasive aspergillosis; pediatric; voriconazole; pharmacokinetic; therapeutic drug monitoring
24.  Antifungal Therapy and Outcomes in Infants with Invasive Candida Infections 
Background
Invasive candidiasis is a leading cause of mortality and morbidity in neonatal intensive care units. Treatment recommendations are limited by a lack of comparative outcomes data.
Methods
We identified all infants ≤120 days of age with positive blood, urine, or cerebrospinal fluid cultures for Candida sp. who received amphotericin B deoxycholate, fluconazole, amphotericin B lipid products, or combination therapy admitted to 1 of 192 neonatal intensive care units in the United States between 1997 and 2003. Primary outcome measures included overall mortality and therapeutic failure (combined outcome of duration of infection >7 days, need for additional antifungal therapy, or death prior to discharge). We compared outcomes by antifungal therapy using logistic regression, controlling for gestational age, day of life at start of antifungal therapy, delay in therapy, and site of infection.
Results
Overall, 138/730 (19%) infants died. On multivariable logistic regression, we observed higher overall mortality for infants receiving amphotericin B lipid products compared with infants receiving amphotericin B deoxycholate (OR 1.96 [95% CI: 1.16, 3.33]; p=0.01) or fluconazole (OR 2.39 [1.18, 4.83]; p=0.02).
Conclusions
Infants treated with amphotericin B lipid products had higher mortality than infants treated with either amphotericin B deoxycholate or fluconazole. This finding may be related to inadequate penetration of amphotericin B lipid products into the kidneys, inappropriate dosing in premature infants, or unknown differences in acuity of illness in infants treated with amphotericin B lipid products.
doi:10.1097/INF.0b013e3182467a72
PMCID: PMC3329577  PMID: 22189522
invasive candidiasis; infants; amphotericin B deoxycholate; fluconazole; amphotericin B lipid products
25.  Early and Late Onset Sepsis in Very-Low-Birth-Weight Infants from a Large Group of Neonatal Intensive Care Units 
Early human development  2012;88(Suppl 2):S69-S74.
Background
Very-low-birth-weight (VLBW, <1500 g birth weight) infants are at high risk for both early- and late-onset sepsis. Prior studies have observed a predominance of gram-negative organisms as a cause of early-onset sepsis and gram-positive organisms as a cause of late-onset sepsis. These reports are limited to large, academic neonatal intensive care units (NICUs) and may not reflect findings in other units. The purpose of this study was to determine the risk factors for sepsis, the causative organisms, and mortality following infection in a large and diverse sample of NICUs.
Methods
We analyzed the results of all cultures obtained from VLBW infants admitted to 313 NICUs from 1997 to 2010.
Results
Over 108,000 VLBW infants were admitted during the study period. Early-onset sepsis occurred in 1032 infants, and late-onset sepsis occurred in 12,204 infants. Gram-negative organisms were the most commonly isolated pathogens in early-onset sepsis, and gram-positive organisms were most commonly isolated in late-onset sepsis. Early- and late-onset sepsis were associated with increased risk of death controlling for other confounders (odds ratio 1.45 [95% confidence interval 1.21, 1.73], and OR 1.30 [95% CI 1.21, 1.40], respectively).
Conclusions
This is the largest report of sepsis in VLBW infants to date. Incidence for early-onset sepsis and late-onset sepsis has changed little over this 14-year period, and overall mortality in VLBW infants with early- and late-onset sepsis is higher than in infants with negative cultures.
doi:10.1016/S0378-3782(12)70019-1
PMCID: PMC3513766  PMID: 22633519
early-onset sepsis; late-onset sepsis; very-low-birth-weight infants

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