Hitesh Pandya

Facilitating pharmacokinetic studies in children: a new use of dried blood spots.

Pharmacokinetic data are used to develop dosing regimens for medicines. The dose regimens of many drugs administered to children have historically been based on pharmacokinetic data generated in adults. The ‘adult’ dose was simply adjusted to the childs body weight or surface area. This practice is potentially unsafe and not acceptable to drug regulatory agencies. Obtaining pharmacokinetic data in children is beset with ethical issues and technical challenges as pharmacokinetic studies require repeated measurement of drug levels in blood. Dried blood spot (DBS) samples used in conjunction with population pharmacokinetic modelling techniques is one potential method for performing pharmacokinetic studies in children. In this article, we review the DBS technique for performing pharmacokinetic studies and highlight issues that still need to be addressed to establish DBS as a method for performing pharmacokinetic studies in children.

Toxic additives in medication for preterm infants

Background: Little is known about exposure of preterm infants to excipients during routine clinical care. Objective: To document excipient exposure in vulnerable preterm babies in a single centre, taking into account chronic lung disease (CLD) as a marker of illness severity. Design: Excipient exposure after treatment with eight oral liquid medications was determined by retrospectively analysing the drug charts of infants admitted to a neonatal unit. Setting: The Leicester Neonatal Service. Participants: 38 infants born between June 2005 and July 2006 who were less than 30 weeks’ gestation and 1500 g in weight at birth and managed in Leicester to discharge. Results: The 38 infants represented 53% of the eligible target group; 7/38 infants had CLD. During their in-patient stay, infants were exposed to over 20 excipients including ethanol and propylene glycol, chemicals associated with neurotoxicity. Infants with CLD were exposed to higher concentrations of these toxins. Infants were also exposed to high concentrations of sorbitol, with some infants being exposed to concentrations in excess of recommended guidelines for maximum exposure in adults. Conclusions: Preterm infants are commonly exposed to excipients, some of which are potentially toxic. Strategies aimed at reducing excipient load in preterm infants are urgently required

Dexamethasone quantification in dried blood spot samples using LC–MS: The potential for application to neonatal pharmacokinetic studies

A high-performance liquid chromatography (LC-MS) method has been developed and validated for the determination of dexamethasone in dried blood spot (DBS) samples. For the preparation of DBS samples whole blood spiked with analyte was used to produce 30μl blood spots on specimen collection cards. An 8mm disc was cut from the DBS sample and extracted using a combination of methanol: water (70:30, v/v) containing the internal standard, triamcinolone acetonide. Extracts were centrifuged and chromatographic separation was achieved using a Zorbax Eclipse Plus C18 column using gradient elution with a mobile phase of acetonitrile and water with formic acid at a flow rate of 0.2ml/min. LC-MS detection was conducted with single ion monitoring using target ions at m/z 393.1 for dexamethasone and 435.1 for the internal standard. The developed method was linear within the tested calibration range of 15-800ng/ml. The overall extraction recovery of dexamethasone from DBS samples was 99.3% (94.3-105.7%). The accuracy (relative error) and precision (coefficient of variation) values were within the pre-defined limits of ≤15% at all concentrations. Factors with potential to affect drug quantification measurements such as blood haematocrit, the volume of blood applied onto the collection card and spotting device were investigated. Although a haematocrit related effect was apparent, the assay accuracy and precision values remained within the 15% variability limit with fluctuations in haematocrit of ±5%. Variations in the volume of blood spotted did not appear to affect the performance of the developed assay. Similar observations were made regarding the spotting device used. The methodology has been applied to determine levels of dexamethasone in DBS samples collected from premature neonates. The measured concentrations were successfully evaluated using a simple 1-compartment pharmacokinetic model. Requiring only a microvolume (30μl) blood sample for analysis, the developed assay is particularly suited to pharmacokinetic studies involving paediatric populations.

Neonatal extracorporeal membrane oxygenation: practice patterns and predictors of outcome in the UK

Objective: To review the UK neonatal extracorporeal membrane oxygenation (ECMO) service and identify predictors of outcome. Design: Retrospective review of the national cohort. Patients and interventions: 718 neonates received ECMO for respiratory failure between 1993 and 2005. Measurements and results: Diagnoses were: 48.0% meconium aspiration syndrome (97.1% survivors), 15.9% congenital diaphragmatic hernia (CDH; 57.9% survivors), 15.9% sepsis (62.3% survivors), 9.5% persistent pulmonary hypertension (79.4% survivors), 5.6% respiratory distress syndrome (92.5% survivors) and 5.1% congenital lung abnormalities (24.3% survivors). The overall survival rate of 79.7% compared favourably with the worldwide Extracorporeal Life Support Organization (ELSO) Registry. Over the period of review, pre-ECMO use of advanced respiratory therapies increased (p<0.001), but ECMO initiation was not delayed (p = 0.61). The use of veno-venous (VV) ECMO increased (p<0.001) and average run time fell (p = 0.004). Patients treated with VV ECMO had a survival rate of 87.7% compared with 73.4% in the veno-arterial (VA) ECMO group; only 42.4% of those needing conversion from VV to VA ECMO survived. In non-CDH neonates, lower birth weight, lower gestational age, older age at ECMO and higher oxygenation index (OI) were associated with increased risk of death. In CDH neonates, lower birth weight and younger age at ECMO were identified as risk factors for death. Conclusion: The UK neonatal ECMO service achieves good outcomes and with overall survival rate reaching 80% compares favourably with international results. Advanced respiratory therapies are used widely in UK ECMO patients. Identification of higher OI and older age at ECMO as risk factors in non-CDH neonates reinforces the importance of timely referral for ECMO.

Intermittent montelukast in children aged 10 months to 5 years with wheeze (WAIT trial): a multicentre, randomised, placebo-controlled trial

Summary Background The effectiveness of intermittent montelukast for wheeze in young children is unclear. We aimed to assess whether intermittent montelukast is better than placebo for treatment of wheeze in this age group. Because copy numbers of the Sp1-binding motif in the arachidonate 5-lipoxygenase (ALOX5) gene promoter (either 5/5, 5/x, or x/x, where x does not equal 5) modifies response to montelukast in adults, we stratified by this genotype. Methods We did this multicentre, parallel-group, randomised, placebo-controlled trial between Oct 1, 2010, and Dec 20, 2013, at 21 primary care sites and 41 secondary care sites in England and Scotland. Children aged 10 months to 5 years with two or more wheeze episodes were allocated to either a 5/5 or 5/x+x/x ALOX5 promoter genotype stratum, then randomly assigned (1:1) via a permuted block schedule (size ten), to receive intermittent montelukast or placebo given by parents at each wheeze episode over a 12 month period. Clinical investigators and parents were masked to treatment group and genotype strata. The primary outcome was number of unscheduled medical attendances for wheezing episodes. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01142505. Findings We randomly assigned 1358 children to receive montelukast (n=669) or placebo (n=677). Consent was withdrawn for 12 (1%) children. Primary outcome data were available for 1308 (96%) children. There was no difference in unscheduled medical attendances for wheezing episodes between children in the montelukast and placebo groups (mean 2·0 [SD 2·6] vs 2·3 [2·7]; incidence rate ratio [IRR] 0·88, 95% CI: 0·77–1·01; p=0·06). Compared with placebo, unscheduled medical attendances for wheezing episodes were reduced in children given montelukast in the 5/5 stratum (2·0 [2·7] vs 2·4 [3·0]; IRR 0·80, 95% CI 0·68–0·95; p=0·01), but not in those in the 5/x+x/x stratum (2·0 [2·5] vs 2·0 [2·3]; 1·03, 0·83–1·29; p=0·79, pinteraction=0·08). We recorded one serious adverse event, which was a skin reaction in a child allocated to placebo. Interpretation Our findings show no clear benefit of intermittent montelukast in young children with wheeze. However, the 5/5 ALOX5 promoter genotype might identify a montelukast-responsive subgroup. Funding Medical Research Council (UK) and National Institute for Health Research.

Oxygen dose responsiveness of human fetal airway smooth muscle cells

Maintenance of blood oxygen saturation dictates supplemental oxygen administration to premature infants, but hyperoxia predisposes survivors to respiratory diseases such as asthma. Although much research has focused on oxygen effects on alveoli in the setting of bronchopulmonary dysplasia, the mechanisms by which oxygen affects airway structure or function relevant to asthma are still under investigation. We used isolated human fetal airway smooth muscle (fASM) cells from 18-20 postconceptual age lungs (canalicular stage) to examine oxygen effects on intracellular Ca(2+) ([Ca(2+)](i)) and cellular proliferation. fASM cells expressed substantial smooth muscle actin and myosin and several Ca(2+) regulatory proteins but not fibroblast or epithelial markers, profiles qualitatively comparable to adult human ASM. Fluorescence Ca(2+) imaging showed robust [Ca(2+)](i) responses to 1 μM acetylcholine (ACh) and 10 μM histamine (albeit smaller and slower than adult ASM), partly sensitive to zero extracellular Ca(2+). Compared with adult, fASM showed greater baseline proliferation. Based on this validation, we assessed fASM responses to 10% hypoxia through 90% hyperoxia and found enhanced proliferation at <60% oxygen but increased apoptosis at >60%, effects accompanied by appropriate changes in proliferative vs. apoptotic markers and enhanced mitochondrial fission at >60% oxygen. [Ca(2+)](i) responses to ACh were enhanced for <60% but blunted at >60% oxygen. These results suggest that hyperoxia has dose-dependent effects on structure and function of developing ASM, which could have consequences for airway diseases of childhood. Thus detrimental effects on ASM should be an additional consideration in assessing risks of supplemental oxygen in prematurity.

Continuous venovenous hemofiltration with or without extracorporeal membrane oxygenation in children.

Objectives: We report the frequency of usage, patient demographics, and outcomes in children treated with continuous venovenous hemofiltration (CVVH) in three pediatric intensive care units (PICUs), with one unit providing combined extracorporeal membrane oxygenation (ECMO) and CVVH. Design: Prospective database analysis. Setting: Three regional PICUs in the Trent Haemofiltration Network with two general PICUs admitting 450–500 patients annually and the other providing regional cardiac support and a supraregional service for ECMO (600–650 admissions annually with 50 ECMO patients). Patients: Children who underwent CVVH alone or in combination with ECMO or other therapies between January 2000 and December 2002. Interventions: None. Measurements and Main Results: There were 115 children (58 male) treated, with a median age of 18 months (range 1 day to 17 yrs) and median weight of 12 kg (range 1.8–119 kg). In the two PICUs without ECMO, CVVH was undertaken in 2.5% of admissions annually compared with 3% of annual admissions to the PICU with an ECMO service. Fifty-five patients received CVVH alone (group 1), while 53 patients underwent CVVH in conjunction with ECMO (group 2). In addition, five patients received plasmafiltration followed by CVVH, and two patients were treated with combined CVVH and molecular adsorbents recirculating system. Mean duration of therapy in group 1 was 142 hrs (1–840 hrs) and in group 2,231 hrs (3–1104 hrs). Overall patient survival was 43% with 29 of 55 (53%) CVVH patients surviving and 18 of 53 (34%) of those treated with ECMO plus CVVH. Conclusions: Performing CVVH in a heterogeneous population with large age and weight ranges poses significant clinical and technical challenges. The low frequency of CVVH use, as well as the use of other extracorporeal therapies, also raises problems with maintaining nursing skills. Objective clinical and biochemical markers for commencing CVVH alone or in combination with ECMO remain to be defined.

Developmental outcome in newborn infants treated for acute respiratory failure with extracorporeal membrane oxygenation: present experience

Objective: To describe the later health status of newborn infants who received extracorporeal membrane oxygenation (ECMO) for acute respiratory failure in the era after the UK ECMO trial. Design: Prospective follow up study of newborn infants who received ECMO at a single centre between January 1997 and January 2001. Setting: Departments of ECMO and Paediatric Intensive Care, University Hospitals of Leicester. Patients: All babies who received ECMO within 14 days of birth. Interventions: Neurodevelopment screening using the schedule for growing skills-II (SGS-II) assessment tool. Main outcome measures: Survival at 12 months of age by disease and functional development at follow up. Results: A total of 145 neonates received ECMO for treatment of respiratory failure. Of these, 108 (75%) were alive at 1 year of age. There were no deaths in children treated for respiratory failure secondary to meconium aspiration syndrome (73/145). Ninety three (86% of survivors) infants attended a follow up visit at 11–19 months postnatal age. Eighty two were classed as normal, seven as having “impairment”, and four as having “severe disability”. Conclusions: Most newborn infants with acute respiratory failure treated with ECMO will have a normal neurodevelopment screening assessment at 11–19 months of postnatal age. There is no evidence to suggest that changes in neonatal practice since the UK ECMO trial have led to changes in outcome of infants undergoing ECMO therapy.

Risk assessment of neonatal excipient exposure: Lessons from food safety and other areas

Newborn babies can require significant amounts of medication containing excipients intended to improve the drug formulation. Most medicines given to neonates have been developed for adults or older children and contain excipients thought to be safe in these age groups. Many excipients have been used widely in neonates without obvious adverse effects. Some excipients may be toxic in high amounts in which case they need careful risk assessment. Alternatively, it is conceivable that ill-founded fears about excipients mean that potentially useful medicines are not made available to newborn babies. Choices about excipient exposure can occur at several stages throughout the lifecycle of a medicine, from product development through to clinical use. Making these choices requires a scalable approach to analysing the overall risk. In this contribution we examine these issues.

Vitamin D Attenuates Cytokine-Induced Remodeling in Human Fetal Airway Smooth Muscle Cells

Asthma in the pediatric population remains a significant contributor to morbidity and increasing healthcare costs. Vitamin D3 insufficiency and deficiency have been associated with development of asthma. Recent studies in models of adult airway diseases suggest that the bioactive Vitamin D3 metabolite, calcitriol (1,25‐dihydroxyvitamin D3; 1,25(OH)2D3), modulates responses to inflammation; however, this concept has not been explored in developing airways in the context of pediatric asthma. We used human fetal airway smooth muscle (ASM) cells as a model of the early postnatal airway to explore how calcitriol modulates remodeling induced by pro‐inflammatory cytokines. Cells were pre‐treated with calcitriol and then exposed to TNFα or TGFβ for up to 72 h. Matrix metalloproteinase (MMP) activity, production of extracellular matrix (ECM), and cell proliferation were assessed. Calcitriol attenuated TNFα enhancement of MMP‐9 expression and activity. Additionally, calcitriol attenuated TNFα and TGFβ‐induced collagen III expression and deposition, and separately, inhibited proliferation of fetal ASM cells induced by either inflammatory mediator. Analysis of signaling pathways suggested that calcitriol effects in fetal ASM involve ERK signaling, but not other major inflammatory pathways. Overall, our data demonstrate that calcitriol can blunt multiple effects of TNFα and TGFβ in developing airway, and point to a potentially novel approach to alleviating structural changes in inflammatory airway diseases of childhood. J. Cell. Physiol. 230: 1189–1198, 2015.