Maturation of hepatosomal mono-oxygenation and glucuronidation activities in pre- and full-term infants as studied using the [15N]methacetin urine test

The dark side of ibuprofen in the treatment of patent ductus arteriosus: could paracetamol be the solution?

INTRODUCTION

Patent ductus arteriosus (PDA) persistence is associated, in prematures, to several complications. The optimal PDA management is still under debate, especially regarding the best therapeutic approach and the time to treat. The available drugs are not exempt from contraindications and side effects; ibuprofen itself, although representing the first-choice therapy, can show nephrotoxicity and other complications. Paracetamol seems a valid alternative to classic nonsteroidal anti-inflammatory Drugs, with a lower toxicity. Areas covered: Through an analysis of the published literature on ibuprofen and paracetamol effects in preterm neonates, this review compares the available treatments for PDA, analyzing the mechanisms underlining ibuprofen-associated nephrotoxicity and the eventual paracetamol-induced hepatic damage, also providing an update of what has been yet demonstrated and a clear description of the still open issues. Expert Opinion: Paracetamol is an acceptable alternative in case of contraindication to ibuprofen; its toxicity, in this setting, is very low. Lower doses may be effective, with even fewer risks. In the future, paracetamol could represent an efficacious first-line therapy, although its safety, optimal dosage, and global impact have to be fully clarified through long-term trials, also in the perspective of an individualized and person-based therapy taking into account the extraordinary individual variability.

Prenatal diagnosis of Bartter syndrome: amniotic fluid aldosterone

OBJECTIVE

Bartter syndrome is a severe inherited tubulopathy characterized by postnatal salt wasting, severe polyuria, dehydration, failure to thrive and secondary hyperaldosteronism. Prenatally, the disease is usually discovered following the onset of severe polyhydramnios in the second trimester. We studied amniotic fluid aldosterone concentration in Bartter syndrome and in controls.

METHODS

Amniotic fluid aldosterone was assayed by radioimmunoassay. We undertook a retrospective case-control study based on 36 cases of prenatally suspected and postnatally confirmed Bartter syndrome (22 with identified mutations): and 72 gestational age matched controls presenting with polyhydramnios and 72 without polyhydramnios. Amniotic fluid aldosterone was compared between the three groups.

RESULTS

The median amniotic fluid aldosterone concentration in the Bartter syndrome group (90 pg/mL) was not different from that in the controls with polyhydramnios (90 pg/mL, P = 0.33) or without polyhydramnios (87 pg/mL, P = 0.41).

CONCLUSION

Amniotic fluid aldosterone assay cannot be used for prenatal diagnosis of Bartter syndrome. © 2015 John Wiley & Sons, Ltd.

Paracetamol to induce ductus arteriosus closure: is it valid?

There remains a need for alternative medical treatments for patent ductus arteriosus (PDA) closure in extreme preterm neonates because of therapeutic failure and adverse effects associated with non-selective cyclo-oxygenase inhibitors. Reports of an association between paracetamol exposure and PDA closure in a limited number of extreme preterm neonates have been published. However, causality cannot be taken for granted because a link between the current knowledge of the clinical pharmacology of paracetamol and (patho)physiology of ductal closure is not known. In contrast to non-selective cyclo-oxygenase inhibitors, paracetamol has limited effects at peripheral sites, is a poor antithrombotic and anti-inflammatory drug and exerts its effects primarily within the central nervous system. Although paracetamol appears an effective and safe analgesic in term and near term neonates, its effectiveness and safety for PDA closure are uncertain because the drug is administered in high doses and there remain a limited number of observations in this specific subpopulation so far. Prospective comparative trials are reasonable and are urgently needed to establish both the effectiveness and safety data of paracetamol when used for this indication.

Continuous 13C-methacetin breath test differentiates biliary atresia from other causes of neonatal cholestasis

BACKGROUND AND AIM

Distinguishing biliary atresia (BA) from other causes of neonatal cholestasis (NC) is challenging. Continuous BreathID C-methacetin breath test (MBT) is a novel method that determines liver function. Methacetin is metabolized uniquely by the liver and CO2 is measured passively, through a nasal cannula in the exhaled breath. The aim of this study was to assess the ability of MBT to differentiate BA from other causes of NC.

METHODS

MBT was performed in infants with NC before any invasive procedure. Percent dose recovered (PDR) peak and time to peak (TTPP) of C recovered were correlated with blood test results and degree of fibrosis on liver biopsy.

RESULTS

Fifteen infants were enrolled in the study. Eight were eventually diagnosed as having BA. MBT showed that infants with NC from various causes reached the PDR peak after 44.5 ± 6.7 minutes, whereas infants with BA reached the PDR peak value after 54.7 ± 4.3 minutes (P < 0.005). This suggested low cytochrome P450 1A2 activity in the BA group. The area under the curve (AUC) was 0.95 (95% confidence interval [CI] 0.83-1), sensitivity of 88%, and specificity of 100%.

CONCLUSIONS

This pilot study shows that MBT can differentiate between BA and other causes of NC by time to peak of methacetin metabolism. The results suggest that MBT may be used as part of the diagnostic algorithm in infants with liver disease. Larger-scale studies should be conducted to confirm these initial observations.

Exposure to di(2-ethylhexyl) phthalate in premature neonates in a neonatal intensive care unit in Taiwan

OBJECTIVE

Neonates are exposed to high levels of di(2ethylhexyl) phthalate through numerous medical procedures in the neonatal intensive care unit. Our aim was to assess the contribution of specific medical devices to the di(2-ethylhexyl) phthalate exposure of neonates.

DESIGN

Prospective.

SETTING

University hospital.

PATIENTS

We recruited 32 premature neonates, 20 with very low birth weight (<1500 g) and 12 with low birth weight (<2500 g), and 31 controls at a neonatal intensive care unit from a medical center in central Taiwan.

INTERVENTIONS

Interventions were based on a clinical need and used standard materials and devices, including endotracheal tubes, continuous positive airway pressure, oxygen hood, intravenous injection, intralipid injection, blood transfusion, orogastric tubes, nasogastric tubes, umbilical venous catheterization, umbilical arterial catheterization, chest tube, and isolate.

MEASUREMENTS AND MAIN RESULTS

We recorded the medical procedures of each subject, collected their urine samples, and determined the urinary concentration of three metabolites of di(2-ethylhexyl) phthalate using reversed-phase high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry. Median levels of di(2-ethylhexyl) phthalate metabolites in premature neonates treated with an endotracheal tube and orogastric tube or nasogastric tube were significantly higher than those not treated with an endotracheal tube, orogastric tube, or nasogastric tube. Median levels of di(2-ethylhexyl) phthalate metabolites in premature neonates treated with intravenous injection were ≥ 2-fold higher than those of healthy controls who received intravenous injections (p = .01). Median levels of three di(2-ethylhexyl) phthalate metabolites were similar in very-low-birth-weight and low-birth-weight neonates.

CONCLUSIONS

These data suggest that polyvinyl chloride-containing devices are the major defining factor in di(2-ethylhexyl) phthalate exposure levels in neonates in the neonatal intensive care unit. We urge the use of polyvinyl chloride-free or alternative materials in medical devices, especially for endotracheal tubes, orogastric tubes, nasogastric tubes, and intravenous tubing in the neonatal intensive care unit. The health effects of high di(2-ethylhexyl) phthalate exposure on premature neonates in the neonatal intensive care unit is worthy of further investigation.

In vivo glucuronidation activity of drugs in neonates: extensive interindividual variability despite their young age

Compared with phase I isoenzymes, data on isoenzyme-specific phenotypic activity of uridine diphosphate glucuronosyltransferase (UGT) and its covariates in neonates are limited. In vivo observations on morphine, paracetamol (acetaminophen), and propofol disposition throughout childhood confirm the overall low-glucuronidation activity in neonates observed in in vitro studies. In addition to the phenotypic low-glucuronidation activity, in vivo observations of bilirubin (UGT1A1), morphine (UGT2B7), paracetamol (UGT1A6), and propofol (UGT1A9) glucuronidation in neonates display extensive interindividual variability, only in part explained by postmenstrual and postnatal age. Covariates like disease state characteristics (decreased morphine metabolism during therapeutic head cooling), genetic polymorphisms (UGT1A1 genetic variants and differences in bilirubin metabolism), or environmental factors (increased urinary excretion of paracetamol-glucuronide by repeated administration of paracetamol) further contribute to this variability. A focused approach to unveil covariates of the interindividual range is needed to improve our knowledge on drug disposition in early life.

Pediatric pharmacology in the first year of life

PURPOSE OF REVIEW

Toxicity concerns and awareness during anesthesia issues continue to concern pediatric anesthesiologists. Most developmental pharmacokinetic, pharmacodynamic and pharmacogenomic changes occur within the first year of life. Understanding these early changes can improve drug use in this cohort.

RECENT FINDINGS

Growth and development are two major aspects of children not readily apparent in adults. Clearance in the pediatric population should be investigated using models that describe size, maturation and organ function influences. Glucuronide conjugation (hepatic phase II process) mirrors glomerular filtration maturation over the first year of life. Phase 1 processes appear more rapid, and differences attributable to single nuclear polymorphisms may be obvious by the end of the 4-week neonatal period in term infants.Pharmacodynamic differences in infancy remain poorly defined, and neonatal pharmacokinetic-pharmacodynamic analyses that might elucidate such differences are few, partly because of a paucity of effective pharmacodynamic measures.

SUMMARY

Mechanistic models create a framework for the study of pharmacokinetic changes in infancy. Understanding these changes allows a target concentration approach to therapy and potential for reduced toxicity. The target concentration may be undefined because of a paucity of effect measures.

I.V. acetaminophen pharmacokinetics in neonates after multiple doses

BACKGROUND

Pharmacokinetics of an i.v. prodrug of acetaminophen (propacetamol) in neonates after repeat dosing are reported, with scant data for i.v. acetaminophen formulation.

METHODS

Neonates from an intensive care unit received 6-hourly prn i.v. acetaminophen dosed according to postmenstrual age (PMA): 28-32 weeks, 10 mg kg(-1); 32-36 weeks, 12.5 mg kg(-1); and > or =36 weeks, 15 mg kg(-1). A maximum of five blood samples for assay and liver function tests (LFTs) were collected. A one-compartment linear disposition model (zero-order input; first-order elimination) was used to describe time-concentration profiles using population modelling (NONMEM).

RESULTS

Fifty neonates, median (range) PMA 38.6 (32-45) weeks, mean (SD) weight 2.9 (0.7) kg, received a mean of 15 doses over a median 4 days with 189 serum acetaminophen and 231 LFT measurements. Standardized population parameter estimates for a term neonate were clearance (CL) 5.24 (CV 30.5%) litre h(-1) 70 kg(-1) and volume of distribution (V) 76 (29.6%) litre 70 kg(-1). CL increased with PMA from 4.4 litre h(-1) 70 kg(-1) at 34 weeks to 6.3 litre h(-1) 70 kg(-1) at 46 weeks. The presence of unconjugated hyperbilirubinaemia was associated with reduced CL: 150 micromol litre(-1) associated with 40% CL reduction. Acetaminophen concentrations between 10 and 23 mg litre(-1) at steady state are predicted after 15 mg kg(-1) 6-hourly for a neonate of PMA 40 weeks. Hepatic enzyme analysis of daily samples changed significantly for one patient whose alanine aminotransferase concentration tripled.

CONCLUSIONS

The parameter estimates are similar to those described for propacetamol. There was no evidence of hepatotoxicity. Unconjugated hyperbilirubinaemia impacts upon CL, dictating dose reduction.

Both postnatal and postmenstrual age contribute to the interindividual variability in tramadol glucuronidation in neonates

INTRODUCTION

Although of pharmacokinetic and -dynamic relevance, data on ontogeny of UDP-glucuronosyltransferase (UGT) activity in neonates are scant. We therefore wanted to assess the impact of both postnatal and postmenstrual age (PNA/PMA) on the interindividual variability of glucuronidation to overall tramadol urinary elimination in neonates.

METHODS

O-demethyl tramadol (M1) and M1-glucuronide (M1G) were determined in 24 hour urine collections during continuous intravenous tramadol administration in neonates. Glucuronidation fraction (%) was calculated by the ratio of M1G to the sum of M1G and M1 free (M1total). Fractions (%) in early (<day 8) or late neonatal life (day 8-28) were compared (Mann-Whitney U) and forward multiple regression was applied to assess the impact of various covariates.

RESULTS

Urine collections were available in 59 neonates with a PNA of 6 (1-28) days and a PMA of 38 (SD 4) weeks. Mean M1G/M1total was 27 (SD 15) % and was significantly lower in early compared to late neonatal life (22 versus 32%, p=0.0001). In a forward multiple regression model, both PMA and early versus late neonatal life remained independent variables to explain the interindividual variability in M1G/M1total.

CONCLUSIONS

Besides PMA, there is an additional, independent impact of PNA since phenotypic glucuronidation activity is significantly lower in the first week of postnatal life. These findings should be taken into account in the assessment of compounds for whom glucuronidation is of pharmacokinetic, pharmacodynamic or toxicological relevance.

Bio-effect monitoring using a [(15)N]methacetin test as diagnostic tool to monitor remediation effects in an industrially polluted region

The classical way to demonstrate the efficiency of remediation is measuring the reduction of toxic compounds in the environment. Nevertheless, more important is the risk reduction in human health. To determine changing health effects, exposure and bio-effects have to be monitored at time of and during remediation. Kindergarten children from a heavily polluted industrial (n=23) and a control area (n=12) were investigated. The region-specific outdoor and indoor exposure [27 volatile organic compounds (VOC), emphasis on tri- and tetrachloroethylene (TRI, TETRA)], the internal load [(trichloroacetic acid-TCA-as urine metabolites of TRI and TETRA and S-phenyl- and S-benzylmercapturic acid (SPMA and SBMA) as metabolites of benzene and toluene], and biological effect assessment ([(15)N]methacetin test-a non-invasive stable isotope test to determine the unspecific liver detoxification capacity of an individual) were measured twice a year during 2 years of remediation (1997/1998). It could be shown that in- and outdoor levels of TRI and TETRA decreased by 47% in the heavily polluted village, Greppin, while the levels remained much the same in the control village, Roitzsch. This trend was reflected in the decreasing elimination of TCA in the urine (41%) by the Greppin children, with no differences in the TCA elimination in Roitzsch probands. As the remediation efforts decreased the burden of exposure, the children's liver detoxification capacity improved as well. Combining different methods, such as exposure-effect (external and internal loads) and bio-effect monitoring, proved to be useful to assess remediation successes including the improvement in human health.

Intra- and interindividual variability of glucuronidation of paracetamol during repeated administration of propacetamol in neonates

BACKGROUND

Major changes in drug clearance and metabolism are observed during infancy, in part based on ontogenic regulation of various metabolic pathways. Since paracetamol provides a good substrate to study UGT (1A6) activity, urinary metabolites of propacetamol were determined in neonates in whom propacetamol was repeatedly administered.

METHODS

Paracetamol glucuronide (APAP-G), paracetamol sulphate (APAP-S) and free paracetamol were determined in urine samples of neonates during repeated administration of propacetamol. Spearman rank and linear multiple regression (MedCalc, Mariakerke, Belgium) were used to study the effect of postnatal age, of postconceptional age and of repeated administration on the relative contribution of APAP-G to overall urine paracetamol (APAP-G+APAP-S+free paracetamol) elimination (G/T ratio).

RESULTS

147 samples were collected in 23 neonates. Molar median G/T ratio was 14% (range 1-53). Besides increasing G/T ratio with increasing postnatal (p<0.0001) and postconceptional age (p<0.01), repeated administration (p<0.01) also correlated with an increasing G/T ratio, and repeated administration remained significant (p<0.01) after correction of postnatal and postconceptional age in a multiple regression model.

CONCLUSION

Major variability in the ontogeny of UGT activity to overall elimination of paracetamol was documented in neonates. Besides postnatal and postconceptional age, a significant effect of repeated administration on UGT activity was documented.