Current Pharmaceutical Design - Volume 21, Issue 39, 2015

The critical need for pediatric research on drugs and biological products underscores the responsibility to ensure that children are enrolled in clinical research that is both scientifically necessary and ethically sound. In this chapter, we review key ethical considerations concerning the participation of children. We review a basic ethical framework to guide pediatric research, and suggest how this framework might be operationalized in linking science and ethics. Topics examined include: the status of children as a vulnerable population; the appropriate balance of risk and potential benefit in research; and parental permission and child assent to participate in research.

Over the past 30 years, much has been learned about the impact of development on drug disposition (i.e., pharmacokinetics). This is not true concerning drug action (i.e., pharmacodynamics). As a consequence, in clinical therapeutics and the drug development process, assumptions are often times made that a specific systemic drug exposure that is associated with desired drug action in adults will produce the same response in children. A review of the literature would suggest that this assumption may, in some cases, be an errant one. The relative paucity of information concerning developmental pharmacodynamics is associated with the challenge of assessing and quantitating drug response in vivo in infants and children. An approach to overcome these difficulties has been the evolution of biomarkers that are functional in nature in that they are capable of measuring drug response in both a time and age dependent fashion. The purpose of this review is to illustrate how functional biomarkers capable of assessing drug response/ effect in the developing child are developed and being evaluated for their clinical utility.

Severe adverse drug reactions (ADRs) cause 5-7% of all hospital admissions, an estimated 2,000,000 severe reactions, and over 100,000 deaths each year in the USA. A recent systematic review indicated that the overall incidence of ADRs was 11% in hospitalized children and 1% in outpatients. Detecting ADRs in neonates and children is challenging, particularly because there are fewer clinical trials involving children than adults and drug use in children is common without a labeled indication. Ontogeny and significant physiological changes related to age have an impact on metabolic drug clearance and pharmacodynamics in children compared to adults, as well as on drug action. A variety of strategies have been developed for the identification and further evaluation of ADRs, starting from case reports and advancing into more structured methodologies, such as active surveillance, for accumulating the necessary information. While each approach has merit, a comprehensive surveillance approach with different methods is required to monitor drug safety in the post-market period. Among the methods that have shown value in neonates and children are anecdotal reporting, voluntary organized reporting, prescription event monitoring, pharmacoepidemiology using administrative databases, and active surveillance. There is an urgent need to improve the evaluation of paediatric drug safety in the pre- and post-market phases of drug evaluation in order to better predict in whom serious harm may occur and better ensure the safe use of drugs for neonates and children.

Obesity represents one of the most important public health issues according to the World Health Organization. Additionally, in a recent National Health and Nutrition Survey of 2011-2012, approximately 17 % of children and adolescents in the United States were considered obese. The obesity rate is higher within the adolescent age group as compared to preschool children. Childhood obesity is particularly problematic, because the co-morbid disease states which accompany obesity may require frequent pharmacotherapy and/ or surgical intervention. Despite the potential for increased pharmacotherapy among obese patients, there is a paucity of dosing guidelines for this special population. Optimal drug dosing in obese pediatric patients has not been sufficiently explored as the present data available are mostly specific for obese adults. In this review, we present an overview concerning what is currently known about the pharmacokinetics and pharmacogenetics of frequently used drugs including midazolam, fentanyl and its newer derivatives, morphine, ketamine, acetaminophen, dexmedetomidine and enoxaparin in obese adolescents undergoing bariatric surgery. We will also summarize the current dosing recommendations of anesthetic drugs in bariatric anesthesia.

Sickle cell disease (SCD) is a potentially devastating and life threatening condition that is caused by an autosomal recessive inherited hemoglobinopathy which results in vaso-occlusive phenomena and hemolysis. The severity of this disorder is widely variable, but overall mortality is increased and life expectancy decreased when compared to the general population. Care of patients with sickle cell disease is largely supportive. In fact, hydroxyurea is the only drug used that modifies disease pathogenesis. Painful vaso-occlusive events are the most common complication experienced by both children and adults with sickle cell disease and hydroxyurea is the only treatment option available to prevent the development of these events. Most events are managed with traditional supportive care measures (i.e. aggressive hydration, antiinflammatory and narcotic analgesics) that have not changed in decades. As such, there is an overwhelming need for both the development of new agents and new approaches to treatment with existing modalities for patients with sickle cell disease.

Background: The paucity of marketed drug products that have been adequately studied in infants and children and subsequently, licensed (or labeled) for pediatric use has caused abundant use of off-label and unauthorized products in this patient population. In those instances where insufficient pharmacologic or therapeutic information exists for children, the potential for off-label use of medicines to result in therapeutic misadventure does as well. In the USA, a series of regulatory measures have been introduced since 1997 which have increased both the number and scope of pediatric drug trials and also, fostered the development of ageappropriate drug formulations by pharmaceutical companies. Provisions of these regulations for previously marketed drugs include the potential for a company to be granted 6 months of marketing exclusivity, thereby providing them with a financial incentive. For new drugs being developed that have potential pediatric use, the regulations mandate the inclusion of children in the drug development process. In the EU comparable measures have been very recently (Jan 2007) signed into European law to overcome the therapeutic orphan status of the infants and children of Europe. Method: The aims of this study was to compare the availability of age-appropriate oral formulations labeled for use in children less than 12 years of age in Serbia, Germany and USA in 2007, and to investigate if certain drug groups of therapeutic importance to children had fewer medicines appropriately labeled for pediatric patients available. The primary sources of information for determining the ageappropriate oral dosage forms, and their licensing and labeling status were the official manuals on drug information and national formularies in 2007. Finding: The general availability of oral drugs was the highest in the USA (304), followed by Germany (235) and Serbia (156). From all these oral drugs the availability of labeled age-appropriate pediatric dosage formulations was only between 21.2% and 47.7%. Moreover, there were striking differences between the three countries in the availability of labeled age-appropriate formulations for certain drug groups such as cardiovascular (absent in Serbia) and antiparasitic drugs (absent in Serbia and Germany). Interpretation: Our data suggest that significant country-to-country differences continue to exist in both the number and type of oral drug formulations that have pediatric labeling. Potential contributing factors include country-specific differences in the drug regulatory process, capacity for pharmaceutical development and the regulatory lag time associated with the implementation of drug regulation specifically addressing pediatric product development and labeling. We hypothesize that the new European regulation concerning medicines and children will improve the current unacceptable situation.

To attain effective and safe pharmacotherapy in neonates, caregivers have to consider both the clinical characteristics of the newborn and the pharmacokinetic estimates of a given compound during prescription and administration. Overall, clearance in neonates is low when compared to other pediatric subpopulations. Despite this overall low clearance, there is already extensive between individual variability in clearance in early life. As a consequence, neonates are in urgent need of tailored drug product development that considers the need for both low and flexible dosing to maintain dose accuracy. During the development of such formulations tailored for neonates, there is also a need for guidance on excipient exposure. The available knowledge on the safety or toxicity of excipients is limited and difficult to retrieve, but there are initiatives (e.g. Safety and Toxicity of Excipients for Pediatrics [STEP] database initiative) to improve the present situation. In addition, population focussed studies on aspects of clinical pharmacology of excipients in neonates should be conducted. The propylene glycol research project and the European Study for Neonatal Excipient Exposure (ESNEE) initiative illustrate its feasibility. Finally, until tailored formulations make it to the market, compounding practices for drug formulations in neonates should be evaluated to guarantee correct dosing, product stability, safety and to support pharmacists in their daily practice.

Neonates are given many medicines. A significant proportion of these medicines contain excipients. Excipients are used to facilitate the manufacture and use of medicines. Without excipients, it would not be feasible to formulate some drugs into appropriate medicinal products. For others the removal of excipients would reduce the shelf life and make them uneconomic to produce or too expensive for users to purchase. Excipients are also important because some of them can cause harm. Accordingly, it is important to minimize excipient exposure when possible and to only use them when there is a clear pharmaceutical requirement. On balance it is generally safe to use medicines containing excipients. This review introduces physicians and nurses to the functions of excipients in medicines and describes some potential adverse effects of excipients in neonates. The review also provides pharmaceutical scientists with an insight to issues that arise when excipients are administered to neonates. The review answers some key questions about excipients, addresses some case studies of excipient use, proposes approaches for clinicians who prescribe and administer medicines containing excipients and identifies areas for research that seeks to establish the safety profiles of excipients in neonates."

Among pediatric patients, preterm neonates and newborns are the most vulnerable subpopulation. Rapid developmental changes of physiological factors affecting the pharmacokinetics of drug substances in newborns require extreme care in dose and dose regimen decisions. These decisions could be supported by in silico methods such as physiologically-based pharmacokinetic (PBPK) modeling. In a comprehensive literature search, the physiological information of preterm neonates that is required to establish a PBPK model has been summarized and implemented into the database of a generic PBPK software. Physiological parameters include the organ weights and blood flow rates, tissue composition, as well as ontogeny information about metabolic and elimination processes in the liver and kidney. The aim of this work is to evaluate the model’s accuracy in predicting the pharmacokinetics following intravenous administration of two model drugs with distinct physicochemical properties and elimination pathways based on earlier reported in vivo data. To this end, PBPK models of amikacin and paracetamol have been set up to predict their plasma levels in preterm neonates. Predicted plasma concentration-time profiles were compared to experimentally obtained in vivo data. For both drugs, plasma concentrationtime profiles following single and multiple dosing were appropriately predicted for a large range gestational and postnatal ages. In summary, PBPK simulations in preterm neonates appear feasible and might become a useful tool in the future to support dosing decisions in this special patient population.

Once daily dosing of aminoglycosides has been introduced and validated in non-neonatal patient cohorts. This is because aminoglycosides display peak concentration dependent bacterial killing, have a postantibiotic effect and adaptive resistance. In addition, this strategy reduces toxicity. Although aminoglycosides are also frequently administered to neonates, there is still debate about how to integrate and extrapolate these extended interval dosing regimens into dosing schedules tailored for neonates. There is a growing body of knowledge on aminoglycoside disposition and its covariates (e.g. asphyxia, ibuprofen or indomethacin exposure, serum creatinine, sepsis, dose accuracy) in neonates. In essence, integration of developmental physiology with clinical pharmacology unveils a discrepancy between aspects related to either body composition (higher distribution volume necessitates higher dose, to attain peak concentration) or to elimination clearance (lower renal clearance necessitates prolonged time interval between administrations). Such discrepancy can be solved by introducing more complex dosing guidelines (based on weight, postnatal age, serum creatinine, ibuprofen, asphyxia) in neonates. However, the introduction of more complex dosing guidelines should be balanced with its clinical feasibility. At least, there are reports that these more complex dosing guidelines result in a higher incidence of dosing errors. Besides errors in prescription, these errors also relate to the number of dilutions or manipulations needed before the prescribed dose can be administered. Since an integrated approach is needed, we discuss in this overview both the available pharmacokinetic data in support of the use of extended dosing regimens in neonates as well as the strategies suggested to reduce dosing errors.

Therapeutic hypothermia (HT) is frequently used in neonates with hypoxic-ischemic encephalopathy and young infants during cardiopulmonary bypass (CPB). Hypothermia and CPB result in physiological changes contributing to pharmacokinetic (PK) and pharmacodynamic (PD) changes. Changes in the absorption, the volume of distribution (Vd) and the total body clearance (CL) of drugs used during hypothermia and CPB might lead to the interindividual PK variability resulting in either insufficient or toxic plasma concentrations and have an impact on the biodisposition and action of drugs. Both under- or overdosing of medicines in these critically ill patients may contribute to a worse overall outcome. Overall, hypothermia decreases CL but may decrease or increase Vd by changing intravascular blood volume, organ perfusion and enzymatic metabolic processes. In addition, maturational as well as organ specific changes may occur during hypothermia superimposed on the underlying disease and/or procedures such as extracorporeal membrane oxygenation (ECMO) or CPB. This paper will provide an overview of variables and potential covariates (e.g., asphyxia, sepsis, multiorgan dysfunction syndrome, cardiac arrest) determining the PK of frequently used drugs. In addition, the effects of hypothermia on individual drugs are described as well as alternative ways for future study designs such as the use of population PK-PD and opportunistic sampling. Ultimately, these investigations are warranted to obtain specific dosing nomograms of medicines for use in clinical practice and to improve the treatment results of this vulnerable group of pediatric patients.

Drug development for neurodegenerative diseases such as Alzheimer’s disease (AD) is a challenge, not only due to the cellular molecular mechanisms involved, but also because of the inherent difficulty of most molecules to cross the blood-brain-barrier (BBB). A promising approach to overcome these drawbacks is developing fluorinated molecules and supramolecular assemblies. This review focuses on the therapeutic potential of new fluorinated molecules, developed as active and selective agents for AD, to meet the desired pharmacokinetic/pharmacodynamic properties and BBB targeting. The methods to fluorinate organic molecules and a brief characterization of the mechanisms of AD progression and therapeutic approaches are described. The paradigm of cell biology knowledge and fluorine biochemistry such as, organofluorine inhibitors of amyloid fibrilogenesis, is highlighted.

Objectives: Sulfonylurea derivatives are widely used for clinical treatment of human subjects with Maturity Onset Diabetes of the Young (MODY) caused by mutations in HNF-1α or HNF-4α despite the mechanism leading to their hypersensitivity is incompletely understood. In Hnf1a-/- mice, serum concentrations and half-life of sulfonylurea derivatives are strongly increased. We thus hypothesized that reduced sulfonylurea derivatives clearance stands behind their therapeutic potential in human HNF1A/HNF4A MODY subjects. Design and Methods: Single doses of 3 mg glipizide and 5 mg glibenclamide/glyburide were administered sequentially to seven HNF1A/HNF4A MODY subjects and six control individuals matched for their age, BMI and CYP2C9 genotype. Pharmacokinetic (plasma concentration levels, Cmax, tmax, t1/2, AUC) and pharmacodynamic parameters (glycemia, C-peptide and insulin plasma levels) were followed for 24 hours after drug administration. Results: We provide the first evidence on the pharmacokinetics and pharmacodynamics of sulfonylurea derivatives in human MODY subjects. The half-life of glipizide did not change, and reached 3.8±0.7 and 3.7±1.8 h in the MODY and control subjects, respectively. The half-life of glibenclamide was increased only in some MODY subjects (t1/2 9.5±6.7 and 5.0±1.4 h, respectively). Importantly, the intra- individual responses of MODY (but control) subjects to glipizide and glibenclamide treatment were highly correlated. With regards to pharmacodynamics, we observed a differential response of control but not MODY subjects to the doses of glipizide and glibenclamide applied. Conclusions: We rejected the hypothesis that all human MODY-associated mutations in HNF1A / HNF4A induce changes in the pharmacokinetics of sulfonylureas in humans analogically to the Hnf1a-/- mouse model.