Joseph F. Standing

Poor Formulation Information in Published Pediatric Drug Trials

Objective. The International Conference on Harmonisation Steering Committee recommends that appropriate formulations be used in pediatric drug trials. However, a lack of formulation research and/or economic constraints means that appropriate formulations are not always used. It is important for investigators who report the results of pediatric drug trials to provide sufficient information on the formulation and method of administration to ensure that the results can be reproduced in other clinical studies (reliability) and, more important, implemented in clinical practice (validity). The objective of this study was to evaluate whether pediatric formulation information was adequately reported in recent published trials of oral medicines that included children who were younger than 12 years. Methods. Studies that were published between July 2002 and June 2004 in 10 highly cited journals (5 pediatric and 5 general medicine) were hand-searched and data were extracted independently by 2 reviewers according to a protocol. Papers that reported oral medication studies that included children who were younger than 12 years were classified as containing adequate, some, or no information on drug formulation. Results. Of 3992 papers reviewed, 76 fulfilled the inclusion criteria. Only 28 (37%) gave adequate information for the study to be reproduced accurately, and 20 (26%) did not state the formulation used. When the formulation was reported, only 37 (49%) studies used a pediatric formulation (liquid, chewable tablet, granules). No significant differences between pediatric and general medical journals were seen, and no single journal consistently met the criteria for adequate information. Conclusion. Highly cited journals seem to permit inadequate formulation information in pediatric drug trials that they publish, impairing their validity and reliability. Authors should provide full formulation information in all pediatric clinical trial reports.

Prospective observational study of adverse drug reactions to diclofenac in children.

AIM The aim of this study was to investigate the type of common (occurring in >1% of patients) adverse reactions caused by diclofenac when given to children for acute pain. METHODS A prospective observational study was undertaken on paediatric surgical patents aged < or =12 years at Great Ormond Street and University College London Hospitals. All adverse events were recorded, and causality assessment used to judge the likelihood of them being due to diclofenac. Prospective recruitment meant not all patients were prescribed diclofenac, allowing an analysis of utilization. Causality of all serious adverse events was reviewed by an expert panel. RESULTS Children prescribed diclofenac were significantly older, and stayed in hospital for shorter periods than those who were not. Diclofenac was not avoided in asthmatic patients. Data on 380 children showed they suffer similar types of nonserious adverse reactions to adults. The incidence (95% confidence interval) of rash was 0.8% (0.016, 2.3); minor central nervous system disturbance 0.5% (0.06, 1.9); rectal irritation with suppositories 0.3% (0.009, 1.9); and diarrhoea 0.3% (0.007, 1.5). No serious adverse event was judged to be caused by diclofenac, meaning the incidence of serious adverse reactions to diclofenac in children is <0.8%. CONCLUSION Children given diclofenac for acute pain appeared to suffer similar types of adverse reactions to adults; the incidence of serious adverse reaction is <0.8%.

Short versus Long Infusion of Meropenem in Very-Low-Birth-Weight Neonates

ABSTRACT Prolonged infusion of meropenem has been suggested in studies with population pharmacokinetic modeling but has not been tested in neonates. We compared the steady-state pharmacokinetics (PK) of meropenem given as a short (30-min) or prolonged (4-h) infusion to very-low-birth-weight (gestational age, <32 weeks; birth weight, <1,200 g) neonates to define the appropriate dosing regimen for a phase 3 efficacy study. Short (n = 9) or prolonged (n = 10) infusions of meropenem were given at a dose of 20 mg/kg every 12 h. Immediately before and 0.5, 1.5, 4, 8, and 12 h after the 4th to 7th doses of meropenem, blood samples were collected. Meropenem concentrations were measured by ultrahigh-performance liquid chromatography. PK analysis was performed with WinNonlin software, and modeling was performed with NONMEM software. A short infusion resulted in a higher mean drug concentration in serum (Cmax) than a prolonged infusion (89 versus 54 mg/liter). In all but two patients in the prolonged-infusion group, the free serum drug concentration was above the MIC (2 mg/liter) 100% of the time. Meropenem clearance (CL) was not influenced by postnatal or postmenstrual age. In population PK analysis, a one-compartment model provided the best fit and the steady-state distribution volume (Vss) was scaled with body weight and CL with a published renal maturation function. The covariates serum creatinine and postnatal and gestational ages did not improve the model fit. The final parameter estimates were a Vss of 0.301 liter/kg and a CL of 0.061 liter/h/kg. Meropenem infusions of 30 min are acceptable as they balance a reasonably high Cmax with convenience of dosing. In very-low-birth-weight neonates, no dosing adjustment is needed over the first month of life.

Population pharmacokinetics of oral diclofenac for acute pain in children

AIMS To develop a population pharmacokinetic model for a new diclofenac suspension (50 mg 5 ml(-1)) in adult volunteers and paediatric patients, and recommend a dose for acute pain in children. METHODS Blood samples were drawn at the start and end of surgery, and on removal of the venous cannula from 70 children (aged 1 to 12 years, weight 9 to 37 kg) who received a preoperative oral 1 mg kg(-1) dose; these were pooled with rich (14 post-dose samples) data from 30 adult volunteers. Population pharmacokinetic modelling was undertaken with NONMEM. The optimum adult dose of diclofenac for acute pain is 50 mg. Simulation from the final model was performed to predict a paediatric dose to achieve a similar AUC to 50 mg in adults. RESULTS A total of 558 serum diclofenac concentrations from 100 subjects was used in the pooled analysis. A single disposition compartment model with first order elimination and dual absorption compartments was used. The estimates of CL/F and V(D)/F were 53.98 l h(-1) 70 kg(-1) and 4.84 l 70 kg(-1) respectively. Allometric size models appeared to predict adequately changes in CL and V(D) with age. Of the simulated doses investigated, 1 mg kg(-1) gave paediatric AUC((0,12 h)) to adult 50 mg AUC((0,12 h)) ratios of 1.00, 1.08 and 1.18 for ages 1-3, 4-6 and 7-12 years respectively. CONCLUSIONS This study has shown 1 mg kg(-1) diclofenac to produce similar exposure in children aged 1 to 12 years as 50 mg in adults, and is acceptable for clinical practice; patients are unlikely to obtain further benefit from higher doses.

Pharmacokinetics of doripenem during high volume hemodiafiltration in patients with septic shock

Pharmacokinetics (PK) of doripenem was determined during high volume hemodiafiltration (HVHDF) in patients with septic shock. A single 500 mg dose of doripenem was administered as a 1 hour infusion during HVHDF to 9 patients. Arterial blood samples were collected before and at 30 or 60 minute intervals over 8 hours (12 samples) after study drug administration. Doripenem concentrations were determined by ultrahigh performance liquid chromatography‐tandem mass spectrometry. Population PK analysis and Monte Carlo simulation of 1,000 subjects were performed. The median convective volume of HVHDF was 10.3 L/h and urine output during the sampling period was 70 mL. The population mean total doripenem clearance on HVHDF was 6.82 L/h, volume of distribution of central compartment 10.8 L, and of peripheral compartment 12.1 L. Doses of 500 mg every 8 hours resulted in 88.5% probability of attaining the target of 50% time over MIC for bacteria with MIC = 2 µg/mL at 48 hours, when doubling of MIC during that time was assumed. Significant elimination of doripenem occurs during HVHDF. Doses of 500 mg every 8 hours are necessary for treatment of infections caused by susceptible bacteria during extended HVHDF.

Useful pharmacodynamic endpoints in children: selection, measurement, and next steps

Pharmacodynamic (PD) endpoints are essential for establishing the benefit-to-risk ratio for therapeutic interventions in children and neonates. This article discusses the selection of an appropriate measure of response, the PD endpoint, which is a critical methodological step in designing pediatric efficacy and safety studies. We provide an overview of existing guidance on the choice of PD endpoints in pediatric clinical research. We identified several considerations relevant to the selection and measurement of PD endpoints in pediatric clinical trials, including the use of biomarkers, modeling, compliance, scoring systems, and validated measurement tools. To be useful, PD endpoints in children need to be clinically relevant, responsive to both treatment and/or disease progression, reproducible, and reliable. In most pediatric disease areas, this requires significant validation efforts. We propose a minimal set of criteria for useful PD endpoint selection and measurement. We conclude that, given the current heterogeneity of pediatric PD endpoint definitions and measurements, both across and within defined disease areas, there is an acute need for internationally agreed, validated, and condition-specific pediatric PD endpoints that consider the needs of all stakeholders, including healthcare providers, policy makers, patients, and families.

Pharmacokinetics and Pharmacodynamics of Oseltamivir in Neonates, Infants and Children

Pharmacokinetic-pharmacodynamic (PKPD) studies have the potential to yield useful information on whether and how a drug works, and what dose to use. This approach is often best suited to situations where dose-response relationships need to be elucidated and where randomisation is not feasible. Children make up around one third of cases during influenza outbreaks, and are more susceptible to certain complications such as otitis media. Despite this, high-quality randomised controlled trials (RCT) of antiviral therapies such as oseltamivir have not been performed, leaving open the question of whether and at what dose to use. This review therefore focusses on the available PKPD data in children. Oseltamivir has complex PK which requires modelling to properly understand the relationship between dose and concentration with time, and there is a lack of clarity on appropriate pharmacodynamic endpoints. Following a general overview of oseltamivir PKPD, this review seeks to summarise the available paediatric PKPD data, identify gaps in our knowledge and priorities for future research.

Scaling beta‐lactam antimicrobial pharmacokinetics from early life to old age

Beta‐lactam dose optimization in critical care is a current priority. We aimed to review the pharmacokinetics (PK) of three commonly used beta‐lactams (amoxicillin ± clavulanate, piperacillin–tazobactam and meropenem) to compare PK parameters reported in critically and noncritically ill neonates, children and adults, and to investigate whether allometric and maturation scaling principles could be applied to describe changes in PK parameters through life.

Pharmacokinetic studies in children: recommendations for practice and research

Optimising the dosing of medicines for neonates and children remains a challenge. The importance of pharmacokinetic (PK) and pharmacodynamic (PD) research is recognised both in medicines regulation and paediatric clinical pharmacology, yet there remain barriers to undertaking high-quality PK and PD studies. While these studies are essential in understanding the dose–concentration–effect relationship and should underpin dosing recommendations, this review examines how challenges affecting the design and conduct of paediatric pharmacological studies can be overcome using targeted pharmacometric strategies. Model-based approaches confer benefits at all stages of the drug life-cycle, from identifying the first dose to be used in children, to clinical trial design, and optimising the dosing regimens of older, off-patent medications. To benefit patients, strategies to ensure that new PK, PD and trial data are incorporated into evidence-based dosing recommendations are needed. This review summarises practical strategies to address current challenges, particularly the use of model-based (pharmacometric) approaches in study design and analysis. Recommendations for practice and directions for future paediatric pharmacological research are given, based on current literature and our joint international experience. Success of PK research in children requires a robust infrastructure, with sustainable funding mechanisms at its core, supported by political and regulatory initiatives, and international collaborations. There is a unique opportunity to advance paediatric medicines research at an unprecedented pace, bringing the age of evidence-based paediatric pharmacotherapy into sight.