Matthew W. Linakis

Characteristics and publication patterns of obstetric studies registered in ClinicalTrials.gov

Physiologic changes during pregnancy alter the pharmacokinetics, safety, and efficacy of many drugs. For clinicians, there is often uncertainty regarding the safety of these drugs due to a scarcity of published data. This study aimed to comprehensively evaluate the characteristics and publication patterns of obstetric studies registered in ClinicalTrials.gov from 2007 to 2012. Primary outcome measures, funding sources, inclusion criteria, and the reporting of study results were evaluated. A manual review of Medline/PubMed was performed to identify publications associated with studies registered in ClinicalTrials.gov. Of 93,709 total studies, there were 5,203 (6%) obstetric studies registered in ClinicalTrials.gov. Interventional studies accounted for 70% and 30% were observational. Clinical trials of drugs (49%), procedures (13%), and behavioral interventions (12%) were most common. Among interventional drug trials, 84% featured randomized allocation to study arms and 93% included measures of safety and/or efficacy as primary endpoints. Of 946 (18%) studies completed more than 2 years ago, only 11% had reported results and <7% had been published. In an area with a great need for evidence of safe and effective therapies, the low publication rate of completed studies incorporating elements of high‐quality trial design is concerning. The sources of this trend should be closely investigated.

A propensity-matched cohort study of vancomycin-associated nephrotoxicity in neonates

Background The incidence of nephrotoxicity among vancomycin-treated neonates has been reported to range from 2% to 20%. These widely varying estimates have led to confusion and controversy regarding the safety of vancomycin among neonates. Objective Evaluate the incidence of nephrotoxicity among neonates receiving vancomycin concomitantly with gentamicin. Design Retrospective observational cohort study using propensity score matching to provide covariate balance between neonates who did or did not receive vancomycin based on factors known to be related to the development of renal dysfunction. Setting Hospitals (n=22) throughout the Intermountain West, including a quaternary care childrens hospital. Patients Neonates ≤44 postmenstrual weeks (median gestational age: 31 (IQR 28–36) weeks) receiving intravenous gentamicin with or without exposure to vancomycin from January 2006 to December 2012. Main outcome measures Nephrotoxicity based on the modified Acute Kidney Injury Network criteria for acute kidney injury (AKI) or serum creatinine concentration ≥1.5 mg/dL persisting for ≥48 h. Results The final cohort was comprised of 1066 neonates (533 receiving vancomycin and gentamicin vs 533 receiving gentamicin). In a propensity score-matched cohort that was well balanced across 16 covariates, AKI was not associated with vancomycin use (16 neonates receiving vancomycin vs 7 controls experienced AKI; OR 1.5; 95% CI 0.6 to 4.0). However, the presence of a patent ductus arteriosus, concomitant non-steroidal anti-inflammatory drug use, ≥1 positive blood cultures, low birth weight and higher severity of illness and risk of mortality scores were associated with an increased risk of nephrotoxicity. Conclusions These results corroborate several earlier reports and much anecdotal evidence describing the infrequent occurrence of nephrotoxicity in neonates receiving concomitant vancomycin and gentamicin.

Challenges Associated with Route of Administration in Neonatal Drug Delivery

Abstract The administration of drugs to neonates poses significant challenges. The aim of this review was to provide insight into some of these challenges and resolutions that may be encountered with several of the most commonly used routes of administration and dosage forms in neonatal care, including oral, parenteral, transdermal, intrapulmonary, and rectal. Important considerations include fluctuations in stomach pH hours to years after birth, the logistics of setting up an intravenous infusion, the need for reduced particle size for aerosol delivery to the developing neonatal lung, and variation in perirectal venous drainage. Additionally, some of the recently developed technologies for use in neonatal care are described. While the understanding of neonatal drug delivery has advanced over the past several decades, there is still a deficiency of technologies and formulations developed specifically for this population.

Pharmacodynamic studies of voriconazole: informing the clinical management of invasive fungal infections

ABSTRACT Introduction: Voriconazole is a broad-spectrum antifungal agent commonly used to treat invasive fungal infections (IFI), including aspergillosis, candidiasis, Scedosporium infection, and Fusarium infection. IFI often occur in immunocompromised patients, leading to increased morbidity and mortality. Areas covered: The objective of this review is to summarize the pharmacodynamic properties of voriconazole and to provide considerations for potential optimal dosing strategies. Studies have demonstrated superior clinical response when an AUC/MIC >25 or Cmin/MIC >1 is attained in adult patients, correlating to a trough concentration range as narrow as 2–4.5 mg/L; however, these targets are poorly established in the pediatric population. Topics in this discussion include voriconazole use in multiple age groups, predisposing patient factors for IFI, and considerations for clinicians managing IFI. Expert commentary: The relationship between voriconazole dosing and exposure is not well defined due to the large inter- and intra-subject variability. Development of comprehensive decision support tools for individualizing dosing, particularly in children who require higher dosing, will help to increase the probability of achieving therapeutic efficacy and decrease sub-therapeutic dosing and adverse events.

Use of Oxandrolone to Promote Growth in Neonates following Surgery for Complex Congenital Heart Disease: An Open‐Label Pilot Trial

OBJECTIVE Malnutrition and poor weight gain, common in neonates following repair of complex congenital heart disease (CHD), are associated with increased morbidity and mortality. Oxandrolone, an anabolic steroid, improves weight gain in older children at high-risk for growth failure. We sought to determine feasibility, safety, and efficacy of oxandrolone therapy in neonates following surgery for complex CHD. DESIGN Neonates with RACHS-1 score >3 were eligible to receive open-label oxandrolone for 28 days in this prospective pilot trial. There were 3 cohorts of 5 subjects receiving oxandrolone therapy under 3 specified dosage and preparation protocols: 0.1 mg/kg/day aqueous solution, 0.2 mg/kg/day aqueous solution, and 0.1 mg/kg/day preparation in medium chain triglyceride (MCT) oil. Age- and diagnosis-matched neonates who underwent surgery, but received no oxandrolone, served as a control cohort. Anthropometric measurements, physical examination for virilization, safety labs, and adverse events were monitored. RESULTS Of 25 eligible patients, 15 consented (60%, 13/15 with Norwood procedure). There was no evidence of virilization, no changes in safety labs, and no serious adverse events related to oxandrolone among subjects receiving therapy. No subject met criteria for termination of study drug. There was a significant difference in change in weight-for-age z-score among the four cohorts, with subjects receiving 0.1 mg/kg/day in MCT oil having the lowest decline during the study period (-1.8 ± 0.5 for controls, -1.7 ± 0.4 for 0.1 mg/kg/day aqueous, -1.0 ± 0.4 for 0.2 mg/kg/day aqueous, and -0.6 ± 0.7 for 0.1 mg/kg/day MCT oil, P = .012). CONCLUSIONS Oxandrolone therapy at the doses studied appears safe in neonates after surgery for complex CHD. The decline in weight-for-age z-score was lowest in those receiving the MCT oil preparation suggesting better bioavailability of this preparation and a potential growth benefit with oxandrolone therapy. Further investigation is needed to define optimal dosing and assess efficacy.

Pharmacokinetic considerations in the use of antivirals in neonates

Introduction: Neonatal patients, because of the inability of their immune system to properly respond to microbial challenge, are highly susceptible to viral infections. Immunoglobulins, monoclonal antibody and antiviral drugs are used for prophylaxis and treatment of viral diseases in neonates. Neonates and, especially, preterm infants differ in drug absorption, distribution, metabolism and excretion from adults and older children. Areas covered: This review will evaluate deficiencies of neonatal immune responses to microbial challenge that predispose newborns to viral infections, clinical manifestations and the treatment of viral diseases in neonates. We focus on published studies describing antiviral drug pharmacokinetics in neonates and make recommendations on the dosing of these drugs, allowing achievement of maximal clinical benefits in neonates. Expert opinion: While some efforts were undertaken to study pharmacokinetics and pharmacodynamics of antiviral drugs, much more needs to be done. Current data indicate that the pharmacokinetics of antiviral drugs may vary significantly depending on gestational age, maturation processes of drug-metabolizing enzymes and renal clearance. Specifics of pharmacokinetics of antiviral drugs need to be taken into consideration when they are prescribed to neonates and infants.

Evident bias in a paracetamol metabolite population pharmacokinetic model applied to an external dataset

Division of Clinical Pharmacology, Department of Pediatrics, School of Medicine, University of Utah, Salt Lake City, Utah, USA, Department of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, University of Utah, Salt Lake City, Utah, USA, Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt Lake City, Utah, USA, Division of Clinical Pharmacology, Children’s National Health System,Washington, DC, USA, Department of Pediatrics, Pharmacology and Physiology, School of Medicine and Health Sciences, GeorgeWashington University, Washington, DC, USA, Intensive Care and Department of Pediatric Surgery, Erasmus Medical Center–Sophia Children’s Hospital, Rotterdam, The Netherlands, and Division of Paediatric Pharmacology and Pharmacometrics, University Children’s Hospital Basel, Basel, Switzerland

Antibiotic Dosing in Pediatric Critically Ill Patients

Despite being some of the most frequently utilized drugs in children, caregivers still commonly prescribe antibiotics in neonates and children based on dosing regimens linearly extrapolated from adults. Although this practice is not limited to antibiotics, specific concerns related to dosing inaccuracy for antibiotics are treatment failure, antimicrobial resistance, and maturational toxicity.

Riding (High) into the danger zone: a review of potential differences in chemical exposures in fighter pilots resulting from high altitude and G-forces

ABSTRACT Introduction: When in flight, pilots of high performance aircraft experience conditions unique to their profession. Training flights, performed as often as several times a week, can expose these pilots to altitudes in excess of 15 km (~50,000 ft, with a cabin pressurized to an altitude of ~20,000 ft), and the maneuvers performed in flight can exacerbate the G-forces felt by the pilot. While the pilots specifically train to withstand these extreme conditions, the physiologic stress could very likely lead to differences in the disposition of chemicals in the body, and consequently, dangerously high exposures. Unfortunately, very little is known about how the conditions experienced by fighter pilots affects chemical disposition. Areas covered: The purpose of this review is to present information about the effects of high altitude, G-forces, and other conditions experienced by fighter pilots on chemical disposition. Using this information, the expected changes in chemical exposure will be discussed, using isopropyl alcohol as an example. Expert opinion: There is a severe lack of information concerning the effects of the fighter pilot environment on the pharmacokinetics and pharmacodynamics of chemicals. Given the possibility of exposure prior to or during flight, it is important that these potential effects be investigated further.

Population pharmacokinetic model of transdermal nicotine delivered from a matrix-type patch

AIMS Nicotine addiction is an issue faced by millions of individuals worldwide. As a result, nicotine replacement therapies, such as transdermal nicotine patches, have become widely distributed and used. While the pharmacokinetics of transdermal nicotine have been extensively described using noncompartmental methods, there are few data available describing the between-subject variability in transdermal nicotine pharmacokinetics. The aim of this investigation was to use population pharmacokinetic techniques to describe this variability, particularly as it pertains to the absorption of nicotine from the transdermal patch. METHODS A population pharmacokinetic parent-metabolite model was developed using plasma concentrations from 25 participants treated with transdermal nicotine. Covariates tested in this model included: body weight, body mass index, body surface area (calculated using the Mosteller equation) and sex. RESULTS Nicotine pharmacokinetics were best described with a one-compartment model with absorption based on a Weibull distribution and first-order elimination and a single compartment for the major metabolite, cotinine. Body weight was a significant covariate on apparent volume of distribution of nicotine (exponential scaling factor 1.42). After the inclusion of body weight in the model, no other covariates were significant. CONCLUSIONS This is the first population pharmacokinetic model to describe the absorption and disposition of transdermal nicotine and its metabolism to cotinine and the pharmacokinetic variability between individuals who were administered the patch.