Inadvertent relaxation of the ductus arteriosus by pharmacologic agents that are commonly used in the neonatal period

Prenatal Exposure to Acid Suppressor Medications and Development of Ductus Arteriosus in Term Newborns

OBJECTIVE

 The ductus arteriosus normally closes after birth. Histamine 2 receptor antagonist (H2RA) has been associated with patent ductus arteriosus (PDA). We aimed to study the characteristics of term infants with PDA and their possible association with prenatal exposure to antacids-proton pump inhibitors (PPIs) and H2RA.

STUDY DESIGN

 This was a population-based matched case-control study of mothers registered at "Clalit" Health Maintenance Organization (HMO) and their infants born at "Soroka" University Medical Center (SUMC) between 2001 and 2018. Cases are defined as term infants born with PDA diagnosed by echocardiography and registered in the postdelivery discharge form. Each case was matched with four term newborns without PDA diagnosis. Exposure window was defined by the timing of first purchase of H2RA or PPI during pregnancy and based on information from a computerized medication database (Clalit HMO, SUMC).

RESULTS

 PDA was diagnosed in 1,884 term infants (4.9%). Characteristics included a significantly higher percentage of lack of prenatal care, cesarean section, in vitro fertilization, polyhydramnios, oligohydramnios, Apgar 1 minute <5, and prenatal exposure to H2RA (odds ratio [OR] 4.18) and PPIs (OR 3.50; all p < 0.001). PDA association with exposure window was similar in each trimester (1.5-2%) for both H2RA and PPI.

CONCLUSION

 PDA incidence in term infants in our population was greater than previously reported. PPI and H2RA are both antiacids with different mechanisms of action. The similar OR for exposure to one as well as the other, and the lack of influence of the initial exposure period, are compatible with bias.

KEY POINTS

· Term newborns with PDA have different characteristics than newborns without PDA.. · Prenatal exposure to PPIs or H2RA is associated with greater risk of PDA in term newborns.. · The possible effect mechanism of PPIs on the ductus is unclear and understudied..

Association of patent ductus arteriosus with fetal factors and endotypes of prematurity

During fetal life, the ductus arteriosus (DA) acquires the mechanisms for its postnatal closure following a thorough developmental program. This program can be interrupted by preterm birth and is also susceptible to alteration during fetal life by numerous physiological and pathological stimuli. In this review, we aim to summarize the evidence on how physiological and pathological factors affect DA development, eventually leading to patent DA (PDA). Specifically, we reviewed the associations of sex, race, and pathophysiological pathways leading to very preterm birth (endotypes) with PDA incidence and pharmacological closure. Summary of evidence suggests that there are no male-female differences in the incidence of PDA among very preterm infants. In contrast, risk of developing PDA appears to be higher in infants exposed to chorioamnionitis or who are small for gestational age. Finally, hypertensive disorders of pregnancy may be associated with a better response to pharmacological treatment of PDA. All of this evidence comes from observational studies and therefore associations do not imply causation. The current trend for many neonatologists is to wait for the natural evolution of preterm PDA. Continued research is needed to identify which fetal and perinatal factors modulate the eventual late closure of PDA in very and extremely preterm infants.

Mouse models of patent ductus arteriosus (PDA) and their relevance for human PDA

The ductus arteriosus (DA) is a unique fetal vascular shunt, which allows blood to bypass the developing lungs in utero. After birth, changes in complex signaling pathways lead to constriction and permanent closure of the DA. The persistent patency of the DA (PDA) is a common disorder in preterm infants, yet the underlying causes of PDA are not fully defined. Although limits on the availability of human DA tissues prevent comprehensive studies on the mechanisms of DA function, mouse models have been developed that reveal critical pathways in DA regulation. Over 20 different transgenic models of PDA in mice have been described, with implications for human DA biology. Similarly, we enumerate 224 human single-gene syndromes that are associated with PDA, including a small subset that consistently feature PDA as a prominent phenotype. Comparison and functional analyses of these genes provide insight into DA development and identify key regulatory pathways that may serve as potential therapeutic targets for the management of PDA.

Use of Prostaglandin E1 in the Management of Congenital Diaphragmatic Hernia-A Review

Congenital diaphragmatic hernia (CDH) is a rare congenital anomaly, whose presentation is complicated by pulmonary hypertension (PH), pulmonary hypoplasia, and myocardial dysfunction, each of which have significant impact on short-term clinical management and long-term outcomes. Despite many advances in therapy and surgical technique, optimal CDH management remains a topic of debate, due to the variable presentation, complex pathophysiology, and continued impact on morbidity and mortality. One of the more recent management strategies is the use of prostaglandin E1 (PGE1) infusion in the management of PH associated with CDH. PGE1 is widely used in the NICU in critical congenital cardiac disease to maintain ductal patency and facilitate pulmonary and systemic blood flow. In a related paradigm, PGE1 infusion has been used in situations of supra-systemic right ventricular pressures, including CDH, with the therapeutic intent to maintain ductal patency as a "pressure relief valve" to reduce the effective afterload on the right ventricle (RV), optimize cardiac function and support pulmonary and systemic blood flow. This paper reviews the current evidence for use of PGE1 in the CDH population and the opportunities for future investigations.

Early closure mechanisms of the ductus arteriosus in immature infants

AIM

According to experimental studies, cardiopulmonary distress decreases after closure of patent ductus arteriosus. However, early closure of the ductus using ibuprofen or indomethacin has failed to increase survival without serious morbidity. We review relevant data aiming to define optimal early management strategies that promote early closure of ductus arteriosus without serious adverse effects.

METHODS

Literature in English was searched selectively focusing on the potential of using acetaminophen for early closure of the ductus.

RESULTS

Prophylactic ibuprofen or indomethacin intended to close the ductus, predisposes infants to ischaemia, bleeding and immune dysfunction. Acetaminophen appears to have a similar efficacy as indomethacin or ibuprofen, and all three dose-dependently constrict the ductus. Ibuprofen and indomethacin cause non-specific inhibition of prostaglandin synthesis, while acetaminophen predominantly inhibits prostaglandin E synthesis. Owing to low CYP450 activity in infancy, acetaminophen toxicity has been rarely evident. However, increasing the dosage increases the oxidative stress. We review prophylactic treatments that may increase the safety and efficacy of acetaminophen. These include vitamin A, cysteine and glutamine, and low-dose corticosteroid supplementation.

CONCLUSION

The current challenge is to define a safe perinatal management practice that promotes cardiorespiratory adaptation in immature infants, particularly the seamless closure of the ductus before significant cardiopulmonary distress develops.

Aminoglycosides were associated with higher rates of surgical patent ductus arteriosus closure in preterm infants

AIM

In animal studies, aminoglycosides induced ductus arteriosus relaxation in a dose-dependent fashion. We tested the hypothesis that antibiotic treatment of preterm infants with aminoglycosides is associated with higher rates of surgical patent ductus arteriosus (PDA) closure.

METHODS

Preterm infants (birthweight <1000 grams or gestational age <29 weeks) enrolled in 62 German neonatal intensive care units (NICUs) were analysed. NICUs were stratified according to the use of aminoglycosides as first-line antibiotics.

RESULTS

Baseline data were not different when NICUs using aminoglycosides (n = 9965 infants) were compared to NICUs using other antibiotics (n = 1948 infants). Rates of surgical PDA closure were 5.9% for NICUs using aminoglycosides; 6.2% for units using gentamicin; and 5.0% for NICUs using tobramycin compared to 4.1% in NICUs using other antibiotics (P < .001, P < .001 and P = .140, respectively, Fisher's exact test). Indomethacin and ibuprofen use was more common in NICUs using aminoglycosides (41% vs 33%, P < .001, Fisher's exact test). Gentamicin trough levels were higher in NICUs with surgical closure rates above the mean (median 2.0 µg/mL, inter-quartile range 0.8-4.0 µg/mL vs 1.2 µg/mL, IQR 0.8-1.7, P < .001, Mann-Whitney U test).

CONCLUSION

First-line antibiotic treatment of preterm infants with aminoglycosides was associated with higher rates of surgical PDA closure.

Association of chorioamnionitis and patent ductus arteriosus in a national U.S. cohort

OBJECTIVE

To estimate the effect of clinical chorioamnionitis on the risk of patent ductus arteriosus (PDA).

STUDY DESIGN

A secondary analysis of all deliveries >23 gestational weeks from the U.S. Consortium on Safe Labor (CSL) study. The primary exposure was a clinical diagnosis of chorioamnionitis, and the outcome was a diagnosis of PDA. Generalized estimating equations with estimated error variance for women with multiple deliveries were utilized. Models adjusted for age, race, region, delivery year, body mass index, infant sex, multiple gestation, mode of delivery, and antenatal corticosteroid exposure.

RESULTS

Among 228,438 deliveries, a diagnosis of PDA was more frequent with chorioamnionitis exposure versus without (9.2% vs. 3.0%; OR: 3.25; 95% CI: 2.92-3.62). Chorioamnionitis was associated with higher adjusted odds of PDA (AOR: 2.18; 95% CI: 1.93-2.45). In sensitivity analyses, the association between chorioamnionitis and PDA held after adjustment for gestational age at delivery (AOR: 1.28; 95% CI: 1.13-1.44).

CONCLUSIONS

Chorioamnionitis was associated with increased odds of PDA. Robust exposure and outcome ascertainment with careful assessment of confounding is needed to further investigate this epidemiologic association.

Early Urinary Metabolomics in Patent Ductus Arteriosus Anticipates the Fate: Preliminary Data

Introduction: In premature neonates, the persistence of hemodynamically significant ductus arteriosus (hsPDA) can be associated with short- and long-term consequences, impairing their outcome. The correct strategy of management for such condition is under debate, especially regarding contraindications and/or side effects. In recent years, metabolomics was applied to several perinatal, pediatric, and adult conditions to investigate potential biomarkers of disease, which have become useful for early diagnosis and/or therapeutic management. Aim of the Study: The main purpose of our exploratory study was to asses, through ¹H-NMR metabolomics analysis of urinary samples at birth, possible metabolic pathways differentiating, with a significant predictive power, those preterm neonates who will subsequently develop hsPDA and neonates of comparable gestational age (GA) who will undergo spontaneous ductal closure or the persistence of an irrelevant PDA (no-hsPDA). Moreover, we investigated potential prenatal or perinatal clinical factors potentially influencing the development of hsPDA. Materials and Methods: We enrolled n = 35 preterm neonates with GA between 24 and 32 weeks; urinary samples were collected within the first 12 h of life. Patients were closely monitored regarding intensive care, respiratory support, fluid balance and administered drugs; an echocardiogram was performed at 48-72 h. Results: Our results reported a significant correlation between lower GA at birth and the development of hsPDA. Moreover, neonates with GA ≤ 30w developing hsPDA were characterized by lower Apgar scores at 1' and 5', higher rates of perinatal asphyxia, higher need of delivery room resuscitation and subsequent surfactant administration. Interestingly, metabolomics analysis at birth detected a clear separation between the ¹H-NMR urinary spectra of subjects GA ≤ 30w not developing hsPDA (n = 19) and those of subjects born at GA ≤ 30w in which hsPDA was confirmed at 48-72 h of life (n = 5). Conclusions: This is the first study applying metabolomics to investigate the PDA condition. Although preliminary and conducted on a limited sample, our results reveal that metabolomics could be a promising tool in the early identification of hsPDA, potentially superior to the clinical or laboratory predictive tools explored to date and even to the clinical observations and correlations in our sample, through the detection of specific urinary metabolites.

Hemodynamic assessment of the patent ductus arteriosus: Beyond ultrasound

Assessment and management of a patent ductus arteriosus (PDA) in premature infants remains problematic. The more immature the infant, the more likely a PDA is to be present, due to lower spontaneous PDA closure rates. Clinicians now recognize that not all PDAs require treatment and that selection of the group of infants with a more hemodynamically relevant PDA, often manifesting as an increasing systemic-to-pulmonary shunt, is increasingly important. Ultrasound is the mainstay of diagnosis and physiological assessment of the PDA; however, there are other methodologies used to assess hemodynamic importance of the PDA. These range from assessment of clinical signs through biomarkers and finally to physiological assessment of the end-organ effect of the PDA, using methods such as cerebral Doppler or near infra-red spectroscopy. Extended assessment of a PDA's physiological effect may lead to a more individualized approach to PDA treatment.

Genetics of the patent ductus arteriosus (PDA) and pharmacogenetics of PDA treatment

Patent ductus arteriosus (PDA) is a frequent, complex, and difficult to treat clinical syndrome among preterm infants in the neonatal intensive care unit. In addition to known clinical risk factors, there are emerging data about genetic predisposition to PDA in both animal and human models. Clinical response and toxicity from drugs used to treat PDA are highly variable. Developmental and genetic aspects of pharmacokinetics and pharmacodynamics influence exposure and response to pharmacologic therapies. Given the variable efficacy and toxicity of known drug therapies, novel therapeutic targets for PDA treatment offer the promise of precision medicine. This review addresses the known genetic contributions to prolonged ductal patency, variability in response to drug therapy for PDA, and potential novel drug targets for future PDA treatment discovery.

Diagnosis and Management of Patent Ductus Arteriosus

Preterm infants are at increased risk for patent ductus arteriosus (PDA). Prolonged exposure to PDA may be deleterious and has been associated with neonatal morbidity and mortality. Although the molecular mechanisms underlying regulation of postnatal ductus arteriosus closure are not fully understood, clinical experience and research trials have informed recent changes in PDA management strategies and refocused treatment strategies on smaller subsets of infants who require intervention. This review examines current diagnostic and management approaches to PDA in preterm neonates.

Prostaglandin E1 for maintaining ductal patency in neonates with ductal-dependent cardiac lesions

BACKGROUND

Prostaglandin E1 (PGE1) is used to keep the ductus arteriosus patent and can be life-saving in neonates with ductal-dependent cardiac lesions. PGE1 is used to promote mixing of pulmonary and systemic blood flow or improve pulmonary or systemic circulations, prior to balloon atrial septostomy or surgery. PGE1 therapy may cause several short-term and long-term adverse effects. The efficacy and safety of PGE1 in neonates with ductal-dependent cardiac lesions has not been systematically reviewed.

OBJECTIVES

To determine the efficacy and safety of both short-term (< 120 hours) and long-term (≥120 hours) PGE1 therapy in maintaining patency of the ductus arteriosus and decreasing mortality in ductal-dependent cardiac lesions.

SEARCH METHODS

We searched the literature in October 2017, using the search strategy recommended by Cochrane Neonatal. We searched electronic databases (CENTRAL (in the Cochrane Library), MEDLINE, CINAHL, Embase); abstracts of the Pediatric Academic Societies; websites for registered trials at www.clinicaltrials.gov and www.controlled-trials.com; and in the reference list of identified articles.

SELECTION CRITERIA

Randomized or quasi-randomized trials using PGE1 at any dose or duration to maintain ductal patency in term or late preterm (≥ 34 weeks' gestation) infants with ductal-dependent cardiac lesions and which reported effectiveness and safety in the short term or long term.

DATA COLLECTION AND ANALYSIS

We followed the standard Cochrane methods for conducting a systematic review. Two review authors (SA and MP) independently assessed the titles and abstracts of studies identified by the search strategy to determine eligibility for inclusion. We obtained the full-text version if eligibility could not be done reliably by title and abstract. We resolved any differences by discussion. We designed electronic forms for trial inclusion/exclusion, data extraction, and for requesting additional published information from authors of the original reports.

MAIN RESULTS

Our search did not identify any completed or ongoing trials that met our inclusion criteria.

AUTHORS' CONCLUSIONS

There is insufficient evidence from randomized controlled trials to determine the safety and efficacy of PGE1 in neonates with ductal-dependent cardiac lesions. Evidence from observational trials have informed clinical practice on the use of PGE, which is now considered the standard of care for ductal-dependent cardiac lesions. It is unlikely that randomized controlled studies will be performed for this indication but comparative efficacy of newer formulations of PGE1, different doses of PGE1 and studies comparing PGE with PDA stents or other measures to keep the ductus open may be ethical and necessary.

Risk of nonsteroidal anti-inflammatory drug-associated renal dysfunction among neonates diagnosed with patent ductus arteriosus and treated with gentamicin

OBJECTIVE

To evaluate the risk of nonsteroidal anti-inflammatory drug (NSAID) therapy-associated acute kidney injury (AKI) among neonates diagnosed with patent ductus arteriosus (PDA) who are treated with gentamicin.

STUDY DESIGN

Multicenter retrospective observational study of patients ⩽44 postmenstrual weeks of age diagnosed with PDA who received gentamicin during hospitalization between January 2006 and December 2014. Patients with and without NSAID exposure were matched on covariates associated with AKI and NSAID therapy. The primary end point, AKI, was defined according to Kidney Disease Improving Global Outcomes neonatal criteria.

RESULTS

The rate of AKI for the entire cohort (n=594) was 12% (n=71). Among neonates receiving NSAIDS, 14.8% (n=44) experienced an AKI as compared to 9.1% (n=27) for those who were not exposed (relative risk, 1.6; 95% confidence interval, 1.0 to 2.6). Therefore, the attributable risk of NSAID use was 5.7% (95% confidence interval, 0.5 to 11.0).

CONCLUSION

Among neonates with PDA and receiving gentamicin, NSAID therapy increases the risk of AKI by about 6%.

Chorioamnionitis appears not to be a Risk Factor for Patent Ductus Arteriosus in Preterm Infants: A Systematic Review and Meta-Analysis

The contribution of chorioamnionitis (CA) to mortality and morbidity in preterm infants is difficult to assess because observational studies frequently present significant differences in baseline characteristics of the infants exposed or non-exposed to CA. In an attempt to perform a thorough assessment of the possible association between CA and patent ductus arteriosus (PDA) in preterm infants, we conducted a meta-analysis in which adjusted odds ratios (ORs) were pooled and we analyzed the effects of potential confounders, such as gestational age (GA) or birth weight (BW). We identified 45 relevant studies (27186 patients, 7742 CA cases). Random effects meta-analysis of crude ORs showed a significant positive association between CA and PDA (OR 1.352, 95% CI 1.172 to 1.560). Adjusted ORs were reported in 11 studies (19577 infants). Meta-analysis of these studies showed a significant negative association between CA and PDA (OR 0.802, 95% CI 0.751 to 0.959). Meta-regression showed that the differences in GA or BW between the CA-exposed and non-exposed groups were significantly correlated with the effect size of the association between PDA and CA. In conclusion, our study confirms that confounders need to be taken into account when assessing the association between CA and clinical outcomes in preterm infants.

Congenital Heart Disease Requiring Maintenance of Ductus Arteriosus in Critically Ill Newborns Admitted at a Tertiary Neonatal Intensive Care Unit

Introduction

Congenital heart diseases (CHD) have been reported to be responsible for 30 to 50% of infant mortality caused by congenital disabilities. In critical cases, survival of newborns with CHD depends on the patency of the ductus arteriosus (PDA), for maintaining the systemic or pulmonary circulation. The aim of the study was to assess the efficacy and side effects of PGE (prostaglandin E) administration in newborns with critical congenital heart disease requiring maintenance of the ductus arteriosus.

Material and method

All clinical and paraclinical data of 66 infants admitted to one referral tertiary level academic center and treated with Alprostadil were analyzed. Patients were divided into three groups: Group 1: PDA dependent pulmonary circulation (n=11) Group 2: PDA dependent systemic circulation (n=31) Group 3: PDA depending mixed circulation (n=24).

Results

The mean age of starting PGE1 treatment was 2.06 days, 1.91 (+/-1.44) days for PDA depending pulmonary flow, 2.39 (+/-1.62) days for PDA depending systemic flow and 1.71 (+/1.12) for PDA depending mixing circulation. PEG1 initiation was commenced 48 hours after admission for 72%, between 48-72 hours for 6%, and after 72 to 120 hours for 21% of newborns detected with PDA dependent circulation. Before PEG1 initiation the mean initial SpO2 was 77.89 (+/- 9.2)% and mean initial oxygen pressure (PaO2) was 26.96(+/-6.45) mmHg. At the point when stable wide open PDA was achieved their mean SpO2increased to 89.73 (+/-8.4)%, and PaO2 rose to 49 (+/-7.2) mmHg. During PGE1 treatment, eleven infants (16.7%) had apnea attacks, five children (7.5%) had convulsions, 33 (50%) had fever, 47 (71.2%) had leukocytosis, 52 (78.8%) had edema, 25.8% had gastrointestinal intolerance, 45.5% had hypokalemia, and 63.6% had irritability.

Conclusions

For those infants with severe cyanosis or shock caused by PDA dependent heart lesions, the initiation and maintenance of PGE1 infusion is imperative. The side effects of this beneficial therapy were transient and treatable.

Aminoglycoside-mediated relaxation of the ductus arteriosus in sepsis-associated PDA

Sepsis is strongly associated with patency of the ductus arteriosus (PDA) in critically ill newborns. Inflammation and the aminoglycoside antibiotics used to treat neonatal sepsis cause smooth muscle relaxation, but their contribution to PDA is unknown. We examined whether: 1) lipopolysaccharide (LPS) or inflammatory cytokines cause relaxation of the ex vivo mouse DA; 2) the aminoglycosides gentamicin, tobramycin, or amikacin causes DA relaxation; and 3) newborn infants treated with aminoglycosides have an increased risk of symptomatic PDA (sPDA). Changes in fetal mouse DA tone were measured by pressure myography in response to LPS, TNF-α, IFN-γ, macrophage-inflammatory protein 2, IL-15, IL-13, CXC chemokine ligand 12, or three aminoglycosides. A clinical database of inborn patients of all gestations was analyzed for association between sPDA and aminoglycoside treatment. Contrary to expectation, neither LPS nor any of the inflammatory mediators caused DA relaxation. However, each of the aminoglycosides caused concentration-dependent vasodilation in term and preterm mouse DAs. Pretreatment with indomethacin and N-(G)-nitro-L-arginine methyl ester did not prevent gentamicin-induced DA relaxation. Gentamicin-exposed DAs developed less oxygen-induced constriction than unexposed DAs. Among 488,349 infants who met the study criteria, 40,472 (8.3%) had sPDA. Confounder-adjusted odds of sPDA were higher in gentamicin-exposed infants, <25 wk and >32 wk. Together, these findings suggest that factors other than inflammation contribute to PDA. Aminoglycoside-induced vasorelaxation and inhibition of oxygen-induced DA constriction support the paradox that antibiotic treatment of sepsis may contribute to DA relaxation. This association was also found in newborn infants, suggesting that antibiotic selection may be an important consideration in efforts to reduce sepsis-associated PDA.

Ductal spasm during performance of transcatheter ductal occlusion

OBJECTIVES

Transcatheter patent ductus arteriosus (PDA) occlusion is a staple of pediatric catheterization laboratories. We present the phenomenon of significant PDA spasm to prevent failure to occlude a hemodynamically significant duct.

BACKGROUND

Transcatheter techniques have evolved, allowing safe and effective occlusion of PDAs in younger and smaller patients. Neonatal care is evolving with increasing survival at younger gestational ages. Premature infants often have PDAs, so the proportion of formerly premature children referred for transcatheter ductal occlusion will likely rise.

METHODS

We reviewed all transcatheter PDA occlusions performed at our institution since 2001 (N = 331). Retrospective data included: gestational age, age at catheterization, precatheterization echocardiographic parameters, PDA size (after spasm relief), device specifications, and most recent follow-up data.

RESULTS

Seven cases were identified. Median age was 12 months, median gestational age was 28 weeks. All were born prematurely. All PDAs were restrictive and six had left-heart volume overload. All patients were examined by the interventional cardiologist and had ductal murmurs. When reauscultated (three of seven), murmurs were absent during spasm. Once spasm relieved, PDA diameters ranged from 1.5 to 8 (median 2) mm. All patients accommodated a 6-mm-or larger-Amplatzer device. No significant complications occurred and all patients were well at follow-up.

CONCLUSIONS

Ductal spasm occurs during transcatheter occlusion and may be an unrecognized cause of procedural failure. The phenomenon seems to occur in children born prematurely, and can occur after infancy. Loss of a continuous murmur confirms the diagnosis. Care should be taken to avoid device under-sizing when spasm occurs.

Pharmacogenetics in clinical pediatrics: challenges and strategies

The use of genetic information to guide medication decisions holds great promise to improve therapeutic outcomes through increased efficacy and reduced adverse events. As in many areas of medicine, pediatric research and clinical implementation in pharmacogenetics lag behind corresponding adult discovery and clinical applications. In adults, genotype-guided clinical decision support for medications such as clopidogrel, warfarin and simvastatin are in use in some medical centers. However, research conducted in pediatric populations demonstrates that the models and practices developed in adults may be inaccurate in children, and some applications lack any pediatric research to guide clinical decisions. To account for additional factors introduced by developmental considerations in pediatric populations and provide pediatric patients with maximal benefit from genotype-guided therapy, the field will need to develop and employ creative solutions. In this article, we detail some concerns about research and clinical implementation of pharmacogenetics in pediatrics, and present potential mechanisms for addressing them.

Pharmacogenetics in clinical pediatrics: challenges and strategies

The use of genetic information to guide medication decisions holds great promise to improve therapeutic outcomes through increased efficacy and reduced adverse events. As in many areas of medicine, pediatric research and clinical implementation in pharmacogenetics lag behind corresponding adult discovery and clinical applications. In adults, genotype-guided clinical decision support for medications such as clopidogrel, warfarin and simvastatin are in use in some medical centers. However, research conducted in pediatric populations demonstrates that the models and practices developed in adults may be inaccurate in children, and some applications lack any pediatric research to guide clinical decisions. To account for additional factors introduced by developmental considerations in pediatric populations and provide pediatric patients with maximal benefit from genotype-guided therapy, the field will need to develop and employ creative solutions. In this article, we detail some concerns about research and clinical implementation of pharmacogenetics in pediatrics, and present potential mechanisms for addressing them.

Results of a two-center, before and after study of piperacillin-tazobactam versus ampicillin and gentamicin as empiric therapy for suspected sepsis at birth in neonates ≤ 1500 g

OBJECTIVE

We changed from ampicillin and gentamicin (AG) to piperacillin-tazobactam (PT) for routine treatment of suspected early-onset sepsis. The rationale for this change included ototoxic and renal toxic effects of gentamicin, resistance to gentamicin in late-onset infections and emergence of ampicillin resistant Escherichia coli. A before and after study was designed before the start of PT administration to monitor whether PT was associated with altered outcomes within the 501 to 1500 g birth weight (Very Low Birth Weight) population.

METHOD

Both unmatched and matched comparisons of AG (2007 to 2009) and PT (2010 to 2011) exposed infants are reported. Cohorts were evaluated for initial effectiveness for congenital infections, subsequent morbidities and mortality.

RESULTS

Data from 714 patients were collected (499 AG and 215 PT in the unmatched and 301 AG and 183 PT in the matched cohorts). No significant differences in demographics or initial Apgar scores were noted in the unmatched or matched comparisons. There were significant differences in many of the outcomes of interest in both the matched and unmatched comparisons including less necrotizing enterocolitis (NEC) and less diaper rash with PT versus AG. The only adverse finding with PT was a small, but statistically significant elevation in alkaline phosphatase.

CONCLUSIONS

Use of PT as the initial empiric antibiotic for very low birth weight infants was not associated with adverse microbiological outcomes. There was no increase in major morbidities. Although outcomes were superior in ≤ 1500 g infants treated with PT when compared with AG, the study design does not allow us to conclude that others will see a reduction in NEC or diaper rash if they implement this alternative.

Cimetidine-associated patent ductus arteriosus is mediated via a cytochrome P450 mechanism independent of H2 receptor antagonism

Persistent patency of the ductus arteriosus (PDA) is a common problem in preterm infants. The antacid cimetidine is a potent antagonist of the H2 histamine receptor but it also inhibits certain cytochrome P450 enzymes (CYPs), which may affect DA patency. We examined whether cimetidine contributes to PDA and is mediated by CYP inhibition rather than H2 blockade. Analysis of a clinical trial to prevent lung injury in premature infants revealed a significant association between cimetidine treatment and PDA. Cimetidine and ranitidine, both CYP inhibitors as well as H2 blockers, caused relaxation of the term and preterm mouse DA. CYP enzymes that are inhibited by cimetidine were expressed in DA subendothelial smooth muscle. The selective CYP3A inhibitor ketoconazole induced greater DA relaxation than cimetidine, whereas famotidine and other H2 antagonists with less CYP inhibitory effects caused less dilation. Histamine receptors were developmentally regulated and localized in DA smooth muscle. However, cimetidine caused DA relaxation in histamine-deficient mice, consistent with CYP inhibition, not H2 antagonism, as the mechanism for PDA. Oxygen-induced DA constriction was inhibited by both cimetidine and famotidine. These studies show that antacids and other compounds with CYP inhibitory properties pose a significant and previously unrecognized risk for PDA in critically ill newborn infants.

Antenatal calcium channel blocker exposure and subsequent patent ductus arteriosus in extremely low-birth-weight infants

This study aimed to assess whether tocolytic fetal exposure to antenatal calcium channel blockers (aCCB) increases the risk for hemodynamically significant patent ductus arteriosus (hsPDA) in extremely low-birth-weight (ELBW) infants. This case-control study investigated ELBW infants (<1,000 g) without cardiac defects in a level 3 neonatal intensive care unit who had survived at least 7 days. Nifedipine was the only aCCB used for this study population. The measurements included the history of aCCB exposure, selected maternal data, hsPDA diagnosis, gestational age at birth, birth weight, mode of delivery, sex, maternal race, location of birth, Apgar scores, and selected neonatal morbidities. The end point of the study was hsPDA, defined as an echocardiographically confirmed PDA with clinical symptoms. A total of 180 infants met the study criteria. The diagnosis was hsPDA for 56% of these patients, 20% of whom had aCCB exposure. Of the infants without hsPDA, 11% had aCCB exposure (p = 0.09). No statistically significant associations were found between aCCB exposure and hsPDA after adjustment for gestational age (odds ratio [OR], 1.5; 95% confidence interval [CI], 0.6-3.7) or for gestational age and cumulative aCCB exposure of 100 mg or more (OR, 2.0; 95% CI, 0.6-6.5). A history of aCCB exposure does not appear to increase hsPDA risk in ELBW infants. Studies using neonatal serum nifedipine concentrations after antenatal exposure should be performed to confirm this conclusion.

High-dose ibuprofen for patent ductus arteriosus in extremely preterm infants: a randomized controlled study

Our aim was to assess the hypothesis that a high-dose regimen of ibuprofen is more effective than the standard-dose regimen in closing patent ductus arteriosus (PDA) without increasing adverse effects. Infants of gestational age <29 weeks, with respiratory distress syndrome (RDS) and echocardiographic evidence of significant PDA at 12-24 h of life, were randomized to receive a standard (10-5-5 mg/kg/day) or high-dose (20-10-10 mg/kg/day) course of ibuprofen. We studied 70 infants, 35 of whom received the standard dose of ibuprofen and the other 35 the high dose. Of the infants treated with the standard-dose regimen, 37% had persistent PDA as compared with 14% of those treated with the high-dose regimen (P = 0.03). No differences in the occurrence of adverse effects were observed between the two groups. The high-dose ibuprofen regimen is more effective than the standard-dose regimen in closing PDA in preterm infants <29 weeks of gestation without increasing the adverse effect rate.

New therapeutic strategies for the treatment of patent ductus arteriosus in preterm infants

A high percentage of preterm infants fails to respond to a single course of indomethacin or ibuprofen. Thus, it has been suggested that the actual dose regimens of these drugs could be inadequate because of large interindividual pharmacokinetics variations in premature infants. We tested the hypothesis that a high-dose regimen of ibuprofen was more effective than the current regimen in closing PDA. We demonstrated that a single course of ibuprofen at 20-10-10 mg/kg/day is more effective than a 10-5-5 mg/kg/day course in closing PDA without significant adverse effects. Many other questions regarding the pharmacological treatment of PDA are still debated.