Bidirectional Transfer of Raltegravir in an Ex Vivo Human Cotyledon Perfusion Model.

Placental transfer of the HIV integrase inhibitor raltegravir (RLT) was investigated in term human cotyledons in the maternal-to-fetal (n = 3) and fetal-to-maternal (n = 6) directions. In the maternal-to-fetal direction, the mean ± standard deviation (SD) fetal transfer rate (FTR) was 9.1% ± 1.4%, and the mean ± SD clearance index (IC), i.e., RLT FTR/antipyrine FTR, was 0.28 ± 0.05. In the fetal-to-maternal direction, the mean ± SD CI was 0.31 ± 0.09. Placental transfer of RLT was high in both directions.

Transplacental transfer of oseltamivir and its metabolite using the human perfused placental cotyledon model.

OBJECTIVE: Given the lack of data regarding the use of oseltamivir (Tamiflu) during pregnancy, we aimed to evaluate the placental transfer of oseltamivir phosphate and its active metabolite oseltamivir carboxylate, using the perfused placental cotyledon model. STUDY DESIGN: Cotyledons were coperfused with oseltamivir phosphate and oseltamivir carboxylate using the maximal concentrations described with a 75 mg, twice-daily oral dose. Main transfer parameters such as fetal transfer rate (FTR) and clearance index (CI) were assessed. RESULTS: Five placentas were coperfused with oseltamivir phosphate and oseltamivir carboxylate. The median FTR of oseltamivir phosphate was 8.5% (range, 5.0-11.6%) and the median CI was 0.3 (range, 0.2-0.6). Regarding oseltamivir carboxylate transplacental transfer, the median FTR was 6.6% (range, 3.9-9.7%), whereas the median CI was 0.2 (range, 0.2-0.5). CONCLUSION: A transplacental transfer of oseltamivir phosphate and its metabolite oseltamivir carboxylate was detected and might have clinical relevance. Clinicians should be encouraged to report oseltamivir treatment outcomes during pregnancy.

High levels and safety of oseltamivir carboxylate plasma concentrations after nasogastric administration in critically ill children in a pediatric intensive care unit.

During the 2009 H1N1 influenza pandemics, the concentrations of oseltamivir (O) and its active metabolite (oseltamivir carboxylate [OC]) were determined in 11 children (1 month to 16 years of age) admitted to intensive care units for presumed severe H1N1 infection. They received oseltamivir phosphate (OP) nasogastrically at doses between 1.5 and 6.8 mg/kg of body weight. High OC concentrations were found, with a mean level of 678 ± 535 µg/liter. The mean OP concentration was 27 ± 52 µg/liter. No marked side effect was reported.

Lopinavir/ritonavir population pharmacokinetics in neonates and infants.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: • Lopinavir/ritonavir pharmacokinetics have been fully investigated in adults and children. WHAT THIS STUDY ADDS: • Lopinavir/ritonavir population pharmacokinetics in 96 neonates and infants from birth to less than 2 years (1.16 to 10.4 kg) showed that CL/F and V/F were dependent on body weight on an allometric basis and post-menstrual age. AIMS: Because of immature hepatic metabolism, lopinavir could present specific pharmacokinetics in the first weeks of life. We aimed at determining the optimal dosing regimen in neonates and infants weighing 1 to 10.5 kg. METHODS: Lopinavir/ritonavir (LPV/r) pharmacokinetics were studied in 96 infants using a population approach. RESULTS A one-compartment model described LPV/r pharmacokinetics. Normalized to a 70 kg adult using allometry, clearance (CL/F) and distribution volume (V/F) estimates were 5.87|h(-1) 70 kg(-1) and 91.7|70 kg(-1). The relative bioavailabilty, F, increased with post-menstrual age (PMA) and reached 50% of the adult value at 39.7 weeks. CONCLUSIONS: Size and PMA explained some CL/F and V/F variability in neonates/infants. Based upon trough concentration limitations, suggested LPV/r dosing regimens were 40 mg 12 h(-1), 80 mg 12 h(-1) and 120 mg 12 h(-1) in the 1-2 kg, 2-6 kg and 6-10 kg group, respectively.

Comparison of a morphine and midazolam combination with morphine alone for paediatric displaced fractures: a randomized study.

AIM: To compare the efficacy of sublingual midazolam with oral morphine versus that of oral morphine with placebo in a paediatric population attending an emergency department (ED) with acute long-bone fractures. METHODS: A sample of children aged 5-16 years with clinically deformed closed long-bone fractures was randomized to groups receiving either oral morphine (0.5 mg/kg)/sublingual placebo or oral morphine (0.5 mg/kg)/sublingual midazolam (0.2 mg/kg). The main exclusion criteria were narcotic or benzodiazepine use, significant head injury, multiple organ failure, femoral fracture and allergy. Pain scores were rated on a 100-mm visual analogue scale (VAS) at 0, 15, 30, 60, 90 and 120 min. RESULTS: Fifty-eight children were enrolled (mean age: 10.5 years, SD 2.7). Fractures concerned the radius or ulna in 43 cases (74.1%), the humerus (22.4%) and the tibia or fibula (3.5%). No significant difference in VAS scores was observed between the two treatment arms (p = 0.72). Drowsiness was significantly more frequent in the midazolam group (p = 0.007) during the first 2 h after administration. No serious adverse event was observed. CONCLUSION: The analgesic performances of morphine and the combination of morphine with midazolam assessed by VAS were similar in children presenting at the ED with a long-bone fracture.

Rapid identification of HEXA mutations in Tay-Sachs patients.

Tay-Sachs disease (TSD) is a recessively inherited neurodegenerative disorder due to mutations in the HEXA gene resulting in a beta-hexosaminidase A (Hex A) deficiency. The purpose of this study was to characterize the molecular abnormalities in patients with infantile or later-onset forms of the disease. The complete sequencing of the 14 exons and flanking regions of the HEXA gene was performed with a unique technical condition in 10 unrelated TSD patients. Eleven mutations were identified, including five splice mutations, one insertion, two deletions and three single-base substitutions. Four mutations were novel: two splice mutations (IVS8+5G>A, IVS2+4delAGTA), one missense mutation in exon 6 (c.621T>G (p.D207E)) and one small deletion (c.1211-1212delTG) in exon 11 resulting in a premature stop codon at residue 429. The c.621T>G missense mutation was found in a patient presenting an infantile form. Its putative role in the pathogenesis of TSD is suspected as residue 207 is highly conserved in human, mouse and rat. Moreover, structural modelling predicted changes likely to affect substrate binding and catalytic activity of the enzyme. The time-saving procedure reported here could be useful for the characterization of Tay-Sachs-causing mutations, in particular in non-Ashkenazi patients mainly exhibiting rare mutations.

Human bocavirus infection in hospitalized children during winter.

Human bocavirus (HBoV) has recently been described as a common agent of acute upper and lower respiratory tract infections in children. We screened by polymerase chain reaction for HBoV nucleic acid nasopharyngeal aspirates from hospitalized children with negative culture and immunofluorescence assay for respiratory syncytial virus, influenza viruses, adenovirus, and parainfluenza viruses. HBoV was detected in 32 children (5.5%) and was the second virus identified in nasopharyngeal aspirates after respiratory syncytial virus. Most of the children had severe disease.

High exposure to zidovudine during the first 2 weeks of life and concentration-toxicity relationships.

OBJECTIVES: The aims of the study were in a large group of neonates to identify the relative effect of bodyweight, postnatal age, and gestational age on zidovudine (ZDV) pharmacokinetics; to link concentrations with lactate and hemoglobin levels; and to find the more appropriate neonatal ZDV dose. METHODS: In 484 neonates aged 3-30 days, born to HIV-infected mothers, 767 ZDV and 417 ZDV glucuronide concentrations were collected. RESULTS: Using a population approach, ZDV clearance per kilogram increased with postnatal age but not with gestational age. High neonatal exposures were found as follows: 14,025 ng/mL·h the first week and 6528 ng/mL·h the second week in comparison to 3000 ng/mL·h in adults. At month 1, median lactate level was 2.8 mmol/L (60%, ≥2.5 mmol/L) and median hemoglobin was 10.1 g/dL (90%, <12 g/dL). ZDV trough concentrations at first sampling (days 3-7) or at last sampling (day 20 ± 10) were significantly negatively correlated to hemoglobin at months 1, 3, and 6 (P < 0.02). ZDV maximal or trough concentrations at days 3-7 and at day 20 ± 10 were significantly positively correlated to lactate levels at months 3 and 6, respectively. CONCLUSIONS: To obtain an exposure comparable to adults, which should reduce neonatal toxicity, doses should to be decreased during the first 2 weeks of life.

Expression and induction by dexamethasone of ABC transporters and nuclear receptors in a human T-lymphocyte cell line.

The efficacy of drugs acting within lymphocytes, like antiretroviral drugs in the treatment of HIV infection, depends on their intracellular concentrations modulated by efflux proteins like ABCB1 (P-glycoprotein). In lymphocytes, two glucocorticoids, prednisone and prednisolone, have been shown to induce ABCB1 activity. Yet, no data exist regarding dexamethasone (DEX). We report the modulation of ABC transporters and nuclear receptors' expression by DEX in a commonly used model of human lymphocytes. CCRF-CEM cells were exposed to DEX (100 nM, 2 µM) for 24 to 72 hours. ABCB1 activity was measured using DiOC(6) efflux in flow cytometry. Gene expression levels were quantified by qRT-PCR. ABCB1 activity and mRNA expression increased with DEX concentrations and incubation times. DEX (1 µM, 24 h) increased significantly ABCB1 and GR mRNA expression levels by around 8- and 3.5-fold, respectively (P<10(-6)). ABCB1 induction by DEX in CCRF-CEM cells suggests a potential risk of interaction in lymphocytes when associating DEX to ABCB1 substrates in antiretroviral multitherapies in vivo.

Readability of the written study information in pediatric research in France.

BACKGROUND: The aim was to evaluate the readability of research information leaflets (RIL) for minors asked to participate in biomedical research studies and to assess the factors influencing this readability. METHODS AND FINDINGS: All the pediatric protocols from three French pediatric clinical research units were included (N = 104). Three criteria were used to evaluate readability: length of the text, Flesch's readability score and presence of illustrations. We compared the readability of RIL to texts specifically written for children (school textbooks, school exams or extracts from literary works). We assessed the effect of protocol characteristics on readability. The RIL had a median length of 608 words [350 words, 25(th) percentile; 1005 words, 75(th) percentile], corresponding to two pages. The readability of the RIL, with a median Flesch score of 40 [30; 47], was much poorer than that of pediatric reference texts, with a Flesch score of 67 [60; 73]. A small proportion of RIL (13/91; 14%) were illustrated. The RIL were longer (p<0.001), more readable (p<0.001) and more likely to be illustrated (p<0.009) for industrial than for institutional sponsors. CONCLUSION: Researchers should routinely compute the reading ease of study information sheets and make greater efforts to improve the readability of written documents for potential participants.

Developmental pharmacokinetics of etoposide in 67 children: lack of dexamethasone effect.

PURPOSE: A randomized clinical trial examined whether dexamethasone administration prior to ondansetron followed by etoposide and carboplatin infusions, and single-nucleotide polymorphisms (SNPs) of CYP3A4, CYP3A5 and MDR1 genes could modify etoposide pharmacokinetics in pediatric patients. METHODS: Patients, 67 children, aged 14 weeks to 16.7 years, were treated for various malignancies and received either 3- or 5-day courses of etoposide and carboplatin: these two drugs were always administered after ondansetron infusion but combined or not with dexamethasone 5 mg/m²/day 30 min prior to etoposide infusion. Population pharmacokinetics was modeled using a non-linear mixed effect model program (Monolix version 31 s). RESULTS: Etoposide pharmacokinetics was ascribed to a 2-compartment model. The most significant covariate effect was bodyweight (BW), so the parameters were standardized to a 70-kg BW using the allometric ¾ or 1 power model for clearance (CL, Q) or volume terms (V), respectively. The population means for clearance and central volume of distribution were 2.05 l/h/70 kg and 9.21 l/70 kg with the corresponding between-subject variabilities, 0.26 and 0.28. Dexamethasone treatment had no effect on CL, either at the first or at the last administration occasion. CYP3A and MDR1 examined SNPs had no significant effect. CONCLUSION: Pharmacokinetics of etoposide was influenced by BW on an allometric basis in this pediatric population. Dexamethasone did not influence etoposide pharmacokinetics during these 3-5 days courses. These results should allow a better individualization of etoposide dosing in children.

ABC transporters in human lymphocytes: expression, activity and role, modulating factors and consequences for antiretroviral therapies.

IMPORTANCE OF THE FIELD: ATP-binding cassette (ABC) transporters are a superfamily of efflux pumps that transport numerous compounds across cell membranes. These transporters are located in various human tissues including peripheral blood cells, in particular lymphocytes, and present a high variability of expression and activity. This variability may affect the intracellular concentrations and efficacy of drugs acting within lymphocytes, such as antiretroviral drugs. AREAS COVERED IN THIS REVIEW: This review focuses on the current knowledge about the expression, activity, roles and variability of ABC drug transporters in human lymphocytes. The identified modulating factors and their impact on the intracellular pharmacokinetics and efficacy of antiretroviral drugs are also detailed. WHAT THE READER WILL GAIN: Controversial data regarding the expression, activity and sources of variability of ABC transporters in lymphocytes are discussed. The modulating factors and their pharmacological consequences regarding antiretroviral therapies are also provided. TAKE HOME MESSAGE: Numerous studies have reported conflicting results regarding the expression and activity of ABC drug transporters in lymphocytes. Despite these discrepancies, which may partly result from heterogeneous analytical methods, ABCC1 appears to have the highest expression in lymphocytes and may thus play a predominant role in the resistance to antiretroviral drugs, particularly to protease inhibitors.

Influence of development, HIV infection, and antiretroviral therapies on the gene expression profiles of ABC transporters in human lymphocytes.

The efficacy of drugs acting on lymphocytes like anticancer, immunosuppressive, and antiretroviral drugs depends on their intracellular concentrations, which could be modulated by membrane efflux pumps belonging to the ABC transporter superfamily. The gene expression profiles of 6 main ABC transporters (MDR1, MRP1, MRP3, MRP4, MRP5, and BCRP) were established in lymphocytes from birth to adulthood using blood samples from 57 children and 15 adults (34 and 5 HIV-infected, respectively). Gene expression levels were quantified by quantitative RT-PCR. In adults, the MRP1 gene had the highest expression, followed by the MRP5 gene. BCRP and MRP4 genes were significantly higher expressed at birth than after 1 month of life. Neither HIV infection nor antiretroviral therapies modulated the gene expression profiles of ABC transporters. In conclusion, drugs that are substrates of BCRP and MRP4, like zidovudine, may have an altered efficacy in newborns.

In vitro and in vivo inhibitory effect of stiripentol on clobazam metabolism.

A metabolic interaction between stiripentol (STP), an anticonvulsant agent that inhibits the activity of several cytochromes P450 (P450s), and clobazam (CLB), a 1,5-benzodiazepine, used in association with STP in severe myoclonic epilepsy in infancy was observed in vivo. This interaction was characterized in vitro using cDNA-expressed CYP3A4 and CYP2C19 (main P450 involved in CLB metabolism) to calculate K(i) and IC(50) of stiripentol in comparison with ketoconazole (CYP3A4 inhibitor) and omeprazole (CYP2C19 inhibitor). STP inhibited N-demethylation of CLB to N-desmethylclobazam (NCLB) mediated by CYP3A4 (noncompetitively) and CYP2C19 (competitively) with K(i) = 1.59 +/- 0.07 and 0.516 +/- 0.065 microM and IC(50) = 1.58 microM [95% confidence interval (CI95%) = 1.20-2.08] and 3.29 microM (CI95% = 1.87-5.79), respectively. STP inhibited also more strongly the 4'-hydroxylation of NCLB to 4'-hydroxy-N-desmethylclobazam by CYP2C19 [competitive interaction with K(i) = 0.139 +/- 0.025 microM and IC(50) = 0.276 microM (CI95% = 0.206-0.371)]. The inhibitory effect of STP on CLB demethylation by CYP3A4 was much weaker than that of ketoconazole [IC(50) = 0.023 microM (CI95% = 0.016-0.033)], whereas its effect on NCLB hydroxylation by CYP2C19 was much higher than that of omeprazole [IC(50) = 2.99 microM (CI95% = 2.11-4.24)]. The major in vitro inhibitory effect of STP on CLB metabolism and mostly on NCLB biotransformation is consistent with the changes in vivo in CLB and NCLB plasma concentrations in children treated by the association CLB/STP.

In vitro characterization of clobazam metabolism by recombinant cytochrome P450 enzymes: importance of CYP2C19.

The specific cytochrome P450 (P450) isoforms mediating the biotransformations of clobazam (CLB) and those of its major metabolites, N-desmethylclobazam (NCLB) and 4'-hydroxyclobazam were identified using cDNA-expressed P450 and P450-specific chemical inhibitors. Among the 13 cDNA-expressed P450 isoforms tested, CLB was mainly demethylated by CYP3A4, CYP2C19, and CYP2B6 and 4'-hydroxylated by CYP2C19 and CYP2C18. CYP2C19 and CYP2C18 catalyzed the 4'-hydroxylation of NCLB. The kinetics of the major biotransformations were studied: CYP3A4, CYP2C19, and CYP2B6 mediated the formation of NCLB with Km = 29.0, 31.9, and 289 microM, Vmax = 6.20, 1.15, and 5.70 nmol/min/nmol P450, and intrinsic clearance (CLint) = 214, 36.1, and 19.7 microl/min/nmol P450, respectively. NCLB was hydroxylated to 4'-hydroxydesmethylclobazam by CYP2C19 with Km = 5.74 microM, Vmax = 0.219 nmol/min/nmol P450, and CLint = 38.2 microl/min/nmol P450 (Hill coefficient = 1.54). These findings were supported by chemical inhibition studies in human liver microsomes. Indeed, ketoconazole (1 microM) inhibited the demethylation of CLB by 70% and omeprazole (10 microM) by 19%; omeprazole inhibited the hydroxylation of NCLB by 26%. Twenty-two epileptic patients treated with CLB were genotyped for CYP2C19. The NCLB/CLB plasma metabolic ratio was significantly higher in the subjects carrying one CYP2C19*2 mutated allele than in those carrying the wild-type genotype. CYP3A4 and CYP2C19 are the main P450s involved in clobazam metabolism. Interactions with other drugs metabolized by these P450s can occur; moreover, the CYP2C19 genetic polymorphism could be responsible for interindividual variations of plasma concentrations of N-desmethylclobazam and thus for occurrence of adverse events.