Kelly C. Wade

Population Pharmacokinetics of Fluconazole in Young Infants

ABSTRACT Fluconazole is being increasingly used to prevent and treat invasive candidiasis in neonates, yet dosing is largely empirical due to the lack of adequate pharmacokinetic (PK) data. We performed a multicenter population PK study of fluconazole in 23- to 40-week-gestation infants less than 120 days of age. We developed a population PK model using nonlinear mixed effect modeling (NONMEM) with the NONMEM algorithm. Covariate effects were predefined and evaluated based on estimation precision and clinical significance. We studied fluconazole PK in 55 infants who at enrollment had a median (range) weight of 1.02 (0.440 to 7.125) kg, a gestational age at birth (BGA) of 26 (23 to 40) weeks, and a postnatal age (PNA) of 2.3 (0.14 to 12.6) weeks. The final data set contained 357 samples; 217/357 (61%) were collected prospectively at prespecified time intervals, and 140/357 (39%) were scavenged from discarded clinical specimens. Fluconazole population PK was best described by a one-compartment model with covariates normalized to median values. The population mean clearance (CL) can be derived for this population by the equation CL (liter/h) equals 0.015 · (weight/1)0.75 · (BGA/26)1.739 · (PNA/2)0.237 · serum creatinine (SCRT)−4.896 (when SCRT is >1.0 mg/dl), and using a volume of distribution (V) (liter) of 1.024 · (weight/1). The relative standard error around the fixed effects point estimates ranged from 3 to 24%. CL doubles between birth and 28 days of age from 0.008 to 0.016 and from 0.010 to 0.022 liter/kg/h for typical 24- and 32-week-gestation infants, respectively. This population PK model of fluconazole discriminated the impact of BGA, PNA, and creatinine on drug CL. Our data suggest that dosing in young infants will require adjustment for BGA and PNA to achieve targeted systemic drug exposures.

Fluconazole dosing for the prevention or treatment of invasive candidiasis in young infants.

Background: Young infants are susceptible to developmental factors influencing the pharmacokinetics of drugs. Fluconazole is increasingly used to prevent and treat invasive candidiasis in infants. Dosing guidance remains empiric and variable because limited pharmacokinetic data exist. Methods: Our population pharmacokinetic model derived from 357 fluconazole plasma concentrations from 55 infants (23–40 week gestation) illustrates expected changes in fluconazole clearance based upon gestational age, postnatal age, weight, and creatinine. We used a Monte Carlo simulation approach based on parametric description of a patient populations pharmacokinetic response to fluconazole to predict fluconazole exposure (median: 10th and 90th percentile population variability range) after 3, 6, and 12 mg/kg dosing. Results: For the treatment of invasive candidiasis, a dose of at least 12 mg/kg/d in the first 90 days after birth is needed to achieve an area under the concentration curve (AUC) of >400 mg*h/L and an AUC/minimum inhibitory concentration (MIC) >50 for Candida species with MIC <8 &mgr;g/mL in ≥90% of <30 week gestation infants and 80% of 30 to 40 week gestation infants. The more preterm infants achieve a higher median AUC (682 mg*hr/L) compared with more mature infants (520 mg*hr/L). For early prevention of candidiasis in 23 to 29 week infants, a dose of 3 or 6 mg/kg twice weekly during the first 42 days of life is equivalent to an AUC of 50 and 100 mg*hr/L, respectively, and maintains fluconazole concentrations ≥2 or 4 &mgr;g/mL, respectively, for half of the dosing interval. For late prevention, the 6 mg/kg dose every 72 hours provides similar exposure to 3 mg/kg daily dose. Infants with serum creatinine ≥1.3 mg/dL have delayed drug clearance and dose adjustment is indicated if creatinine does not improve within 96 hours. Conclusions: A therapeutic concentration of fluconazole in premature infants with invasive candidiasis requires dosing substantially greater than commonly recommended in most reference texts. To prevent invasive candidiasis, twice weekly prophylaxis regimens can provide adequate exposure when unit specific MICs are taken into account.

Fluconazole Loading Dose Pharmacokinetics and Safety in Infants

Background: Invasive candidiasis is a leading cause of morbidity and mortality in critically ill infants. Prompt administration of fluconazole and achievement of the therapeutic target (area under the curve 0 to 24 hours >400 mg*h/L) improve outcomes in candidemic patients. A loading dose of fluconazole is advised for older patients but has not been evaluated in infants. We sought to determine the pharmacokinetics and safety of a fluconazole loading dose in infants at risk for invasive fungal infection. Methods: We enrolled 10 hospitalized infants <60 days old with suspected systemic fungal infection in this open-label study; 9 received a 25-mg/kg fluconazole loading dose followed by a maintenance dose of 12 mg/kg every 24 hours for 4 additional days. Plasma samples were obtained following the loading and steady-state doses (doses 3–5). We used a 1-compartment model to fit the data to estimate pharmacokinetic indices. Results: Data from 57 drug concentrations obtained from 8 infants (median postnatal age, 16 days [interquartile range, 13–32] and median gestational age, 37 weeks [35–38]) showed that the median fluconazole area under the curve 0 to 24 hours (mg*h/L) in this population was 479 (347–496). Of the 8 infants who received the loading dose, 5 (63%) achieved the therapeutic target on the first day of dosing, and all infants achieved a fluconazole 24-hour trough concentration >8 &mgr;g/mL. No adverse events were thought to be related to fluconazole therapy. Conclusions: A loading dose of fluconazole (25 mg/kg) was safe in this small cohort of young infants and achieved the therapeutic target more rapidly than traditional dosing.

Innovative clinical trial design for pediatric therapeutics

Until approximately 15 years ago, sponsors rarely included children in the development of therapeutics. US and European legislation has resulted in an increase in the number of pediatric trials and specific label changes and dosing recommendations, although infants remain an understudied group. The lack of clinical trials in children is partly due to specific challenges in conducting trials in this patient population. Therapeutics in special populations, including premature infants, obese children and children receiving extracorporeal life support, are even less studied. National research networks in Europe and the USA are beginning to address some of the gaps in pediatric therapeutics using novel clinical trial designs. Recent innovations in pediatric clinical trial design, including sparse and scavenged sampling, population pharmacokinetic analyses and ‘opportunistic’ studies, have addressed some of the historical challenges associated with clinical trials in children.

Effect of Fluconazole Prophylaxis on Candidiasis and Mortality in Premature Infants: A Randomized Clinical Trial

IMPORTANCE Invasive candidiasis in premature infants causes death and neurodevelopmental impairment. Fluconazole prophylaxis reduces candidiasis, but its effect on mortality and the safety of fluconazole are unknown. OBJECTIVE To evaluate the efficacy and safety of fluconazole in preventing death or invasive candidiasis in extremely low-birth-weight infants. DESIGN, SETTING, AND PATIENTS This study was a randomized, blinded, placebo-controlled trial of fluconazole in premature infants. Infants weighing less than 750 g at birth (N = 361) from 32 neonatal intensive care units (NICUs) in the United States were randomly assigned to receive either fluconazole or placebo twice weekly for 42 days. Surviving infants were evaluated at 18 to 22 months corrected age for neurodevelopmental outcomes. The study was conducted between November 2008 and February 2013. INTERVENTIONS Fluconazole (6 mg/kg of body weight) or placebo. MAIN OUTCOMES AND MEASURES The primary end point was a composite of death or definite or probable invasive candidiasis prior to study day 49 (1 week after completion of study drug). Secondary and safety outcomes included invasive candidiasis, liver function, bacterial infection, length of stay, intracranial hemorrhage, periventricular leukomalacia, chronic lung disease, patent ductus arteriosus requiring surgery, retinopathy of prematurity requiring surgery, necrotizing enterocolitis, spontaneous intestinal perforation, and neurodevelopmental outcomes-defined as a Bayley-III cognition composite score of less than 70, blindness, deafness, or cerebral palsy at 18 to 22 months corrected age. RESULTS Among infants receiving fluconazole, the composite primary end point of death or invasive candidiasis was 16% (95% CI, 11%-22%) vs 21% in the placebo group (95% CI, 15%-28%; odds ratio, 0.73 [95% CI, 0.43-1.23]; P = .24; treatment difference, -5% [95% CI, -13% to 3%]). Invasive candidiasis occurred less frequently in the fluconazole group (3% [95% CI, 1%-6%]) vs the placebo group (9% [95% CI, 5%-14%]; P = .02; treatment difference, -6% [95% CI, -11% to -1%]). The cumulative incidences of other secondary outcomes were not statistically different between groups. Neurodevelopmental impairment did not differ between the groups (fluconazole, 31% [95% CI, 21%-41%] vs placebo, 27% [95% CI, 18%-37%]; P = .60; treatment difference, 4% [95% CI, -10% to 17%]). CONCLUSIONS AND RELEVANCE Among infants with a birth weight of less than 750 g, 42 days of fluconazole prophylaxis compared with placebo did not result in a lower incidence of the composite of death or invasive candidiasis. These findings do not support the universal use of prophylactic fluconazole in extremely low-birth-weight infants. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00734539.

Population pharmacokinetics of meropenem in plasma and cerebrospinal fluid of infants with suspected or complicated intra-abdominal infections

Background: Suspected or complicated intra-abdominal infections are common in young infants and lead to significant morbidity and mortality. Meropenem is a broad-spectrum antimicrobial agent with excellent activity against pathogens associated with intra-abdominal infections in this population. The purpose of this study was to determine the pharmacokinetics (PK) of meropenem in young infants as a basis for optimizing dosing and minimizing adverse events. Methods: Premature and term infants <91 days old hospitalized in 24 neonatal intensive care units were studied. Limited PK sampling was performed following single and multiple doses of meropenem 20 to 30 mg/kg of body weight every 8 to 12 hours based on postnatal and gestational age at birth. Population and individual patient (Bayesian) PK parameters were estimated using NONMEM. Results: In this study, 200 infants were enrolled and received the study drug. Of them, 188 infants with 780 plasma meropenem concentrations were analyzed. Their median (range) gestational age at birth and postnatal age at PK evaluation were 28 (23–40) weeks and 21 (1–92) days, respectively. In the final PK model, meropenem clearance was strongly associated with serum creatinine and postmenstrual age (clearance [L/h/kg] = 0.12*[(0.5/serum creatinine)**0.27]*[(postmenstrual age/32.7)**1.46]). Meropenem concentrations remained >4 &mgr;g/mL for 50% of the dose interval and >2 &mgr;g/mL for 75% of the dose interval in 96% and 92% of patients, respectively. The estimated penetration of meropenem into the cerebrospinal fluid was 70% (5–148). Conclusions: Meropenem dosing strategies based on postnatal and gestational age achieved therapeutic drug exposure in almost all infants.

Pediatric care for preterm infants after NICU discharge: high number of office visits and prescription medications.

Objective:To determine the frequency and risk factors for clinic and pharmacy use in preterm infants during the first year after neonatal intensive care unit (NICU) discharge.Study Design:We analyzed clinic visits and prescriptions in a cohort of 23 to 32 weeks infants. We constructed multivariable regression models to determine risk factors for high use.Result:The 892 preterm infants experienced 18 346 pediatric visits (mean 20 visits per infant per year) and filled 2100 prescriptions (mean 5.5 prescriptions per year among infants taking medications). Most visits were non-well child care visits to pediatric primary care providers. Prematurity and bronchopulmonary dysplasia (BPD) are important risk factors: infants at 23 to 26 weeks gestation or infants with BPD had an average 29 visits per year and 9 prescriptions per year among infants taking medication. However, half of the highest using infants were relatively healthy infants at 27 to 32 weeks gestation who escaped BPD, NEC or grade 3 to 4 intraventricular hemorrhage.Conclusion:Premature infants had frequent pediatric visits and prescription medications. Extreme prematurity and neonatal morbidities are important risk factors; however, half of the highest using infants are moderately preterm without neonatal morbidities.

Daptomycin use in infants: report of two cases with peak and trough drug concentrations.

We report two infants treated with daptomycin for methicillin-resistant Staphylococcus aureus infection and describe peak and trough blood concentrations measured during therapy. The peak concentrations were 41.7 and 36.7 mcg ml−1, and the 12-hour trough concentrations were 12.7 and 16.3 mcg ml−1, respectively. Even though the infants received higher doses than adults, their drug concentrations were comparable to those observed in adults treated with regular dosing of daptomycin.

Safety and effectiveness of meropenem in infants with suspected or complicated intra-abdominal infections.

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.

Predictors for the development of referral-warranted retinopathy of prematurity in the telemedicine approaches to evaluating acute-phase retinopathy of prematurity (e-ROP) study.

IMPORTANCE Detection of treatment-requiring retinopathy of prematurity (ROP) involves serial eye examinations. An ROP prediction model using predictive factors could identify high-risk infants and reduce required eye examinations. OBJECTIVE To determine predictive factors for the development of referral-warranted (RW) ROP. DESIGN, SETTING, AND PARTICIPANTS This multicenter observational cohort study included secondary analysis of data from the Telemedicine Approaches to Evaluating Acute-Phase Retinopathy of Prematurity Study. Infants included in the study had a birth weight (BW) of less than 1251 g. EXPOSURES Serial ROP examinations of premature infants who had 2 or more ROP examinations. MAIN OUTCOMES AND MEASURES Incidence of RW-ROP (defined as the presence of plus disease, zone I ROP, or ROP stage 3 or greater in either eye) and associations with predictive factors. RESULTS Among 979 infants without RW-ROP at first study-related eye examination (median postmenstrual age, 33 weeks; range, 29-40 weeks) who underwent at least 2 eye examinations, 149 (15.2%) developed RW-ROP. In a multivariate model, significant predictors for RW-ROP were male sex (odds ratio [OR], 1.80; 95% CI, 1.13-2.86 vs female), nonblack race (OR, 2.76; 95% CI, 1.50-5.08 for white vs black race and OR, 4.81; 95% CI, 2.19-10.6 for other vs black race), low BW (OR, 5.16; 95% CI, 1.12-7.20 for ≤500 g vs >1100 g), younger gestational age (OR, 9.79; 95% CI, 3.49-27.5 for ≤24 weeks vs ≥28 weeks), number of quadrants with preplus disease (OR, 7.12; 95% CI, 2.53-20.1 for 1-2 quadrants and OR, 18.4; 95% CI, 4.28-79.4 for 3-4 quadrants vs no preplus disease), stage 2 ROP (OR, 4.13; 95% CI, 2.13-8.00 vs no ROP), the presence of retinal hemorrhage (OR, 4.36; 95% CI, 1.57-12.1 vs absence), the need for respiratory support (OR, 4.99; 95% CI, 1.89-13.2 for the need for controlled mechanical ventilator; OR, 11.0; 95% CI, 2.26-53.8 for the need for high-frequency oscillatory ventilation vs no respiratory support), and slow weight gain (OR, 2.44; 95% CI, 1.22-4.89 for weight gain ≤12 g/d vs >18 g/d). These characteristics predicted the development of RW-ROP significantly better than BW and gestational age (area under receiver operating characteristic curve, 0.88 vs 0.78; P < .001). CONCLUSIONS AND RELEVANCE When controlling for very low BW and prematurity, the presence of preplus disease, stage 2 ROP, retinal hemorrhage, and the need for ventilation at time of first study-related eye examination were strong independent predictors for RW-ROP. These predictors may help identify infants in need of timely eye examinations.