Pediatric pharmacology in the first year of life

Allogeneic hematopoietic stem cell transplantation in infants is associated with significant morbidity and mortality

BACKGROUND

Infants are subjected to hematopoietic stem cell transplantation (HSCT) due to malignant and non-malignant diseases. However, specific data concerning the outcome and transplantation-related complications in infants, as a separate age group, are limited. Our aim was to evaluate the impact of infancy on the outcome, toxicity, and complications after HSCT.

METHODS

We retrospectively analyzed data of 55 infants that underwent HSCT in our unit from May 1997 until February 2020, emphasizing on the probability of overall survival (OS) and the cumulative incidence (CI) of transplantation-related mortality (TRM) and complications.

RESULTS

We report a probability of OS of 61%, a CI of TRM at day 100 and 365 post transplantation of 22% and 30%, respectively, and additionally a CI of graft failure, acute graft-versus-host disease (GvHD), and infectious complications, 18%, 44%, and 39%, respectively. No statistically significant association was detected between the above mentioned parameters and diagnosis, the use of myeloablative or non-myeloablative/reduced toxicity conditioning regimens or the type of donor.

CONCLUSIONS

We conclude that HSCT in infancy is associated with significant mortality and morbidity. This is possibly attributed to endogenous, age-related factors. More specifically, infants may be at a higher risk of toxicities due to the immaturity of developing vital organs and the deficiency of the newly adopted immune system that predisposes them to infectious complications. The development of GvHD further augments the danger of infections, in a potential vice-versa relationship. Moreover, there are few data on pharmacokinetics of chemotherapy agents, making safe and efficacious drug administration hard.

Pharmacokinetic modeling and simulation to understand diamorphine dose-response in neonates, children, and adolescents

Pharmacokinetic-pharmacodynamic modeling and simulation can facilitate understanding and prediction of exposure-response relationships in children with acute or chronic pain. The pharmacokinetics of diamorphine (diacetylmorphine, heroin), a strong opioid, remain poorly quantified in children and dose is often guided by clinical acumen. This tutorial demonstrates how a model to describe intranasal and intravenous diamorphine pharmacokinetics can be fashioned from a model for diamorphine disposition in adults and a model describing morphine disposition in children. Allometric scaling and maturation models were applied to clearances and volumes to account for differences in size and age between children and adults. The utility of modeling and simulation to gain insight into the analgesic exposure-response relationship is demonstrated. The model explains reported observations, can be used for interrogation, interpolated to determine equianalgesia and inform future clinical studies. Simulation was used to illustrate how diamorphine is rapidly metabolized to morphine via its active metabolite 6-monoacetylmorphine, which mediates an early dopaminergic response accountable for early euphoria. Morphine formation is then responsible for the slower, prolonged analgesic response. Time-concentration profiles of diamorphine and its metabolites reflected disposition changes with age and were used to describe intravenous and intranasal dosing regimens. These indicated that morphine exposure in children after intranasal diamorphine 0.1 mg.kg-1 was similar to that after intranasal diamorphine 5 mg in adults. A target concentration of morphine 30 μg.L-1 can be achieved by a diamorphine intravenous infusion in neonates 14 μg.kg-1 .h-1 , in a 5-year-old child 42 μg.kg-1 .h-1 and in an 15 year-old-adolescent 33 μg.kg-1 .h-1 .

Effect of Caffeine on the Acceleration of Emergence from General Anesthesia with Inhalation Anesthetics in Children Undergoing Inguinal Herniorrhaphy: A Randomized Clinical Trial

Background

Awakening following general anesthesia (GA) is one of the most important concerns of anesthesiologists in their daily work. Previous studies on adult humans found that caffeine could accelerate awakening after anesthesia. This study aimed to determine whether or not caffeine can accelerate awakening after anesthesia in children undergoing inguinal herniorrhaphy under GA.

Methods

In this randomized clinical trial, we enrolled 18 children undergoing inguinal herniorrhaphy under GA with inhaled anesthetics from June 2019 to September 2019 in the tertiary hospital affiliated with Shiraz University of Medical Sciences (Shiraz, Iran). These children were randomly allocated to two groups. In group A, the children received intravenous caffeine (10 mg/Kg) at the end of the surgery, and in group B, the children received intravenous normal saline at the end of the surgery. The primary outcome was laryngeal mask airway (LMA) removal time at the end of anesthesia. Intra-operative hemodynamic data and side effects such as nausea, vomiting, dysrhythmia, cyanosis, and seizures in the recovery room were recorded and compared between the two groups. We used the independent-samples t test, Fisher's exact test, and repeated measures ANOVA for analyzing the data. P values<0.05 were considered statistically significant.

Results

There were no significant differences in terms of demographic characteristics and hemodynamic data between the two groups. Furthermore, the time from the induction of anesthesia to laryngeal mask removal was 44.77±7.87 min in the placebo group and 44.55±10.68 min in the caffeine group. Therefore, there was no significant difference between the two groups (P=0.961).

Conclusion

In children undergoing inguinal herniorrhaphy under GA, 10 mg/Kg of caffeine could not accelerate awakening from GA. However, caffeine did not increase the blood pressure and heart rate in the children, and no significant side effects were observed.

Trial Registration Number

IRCT20190511043550N1.

Propofol context-sensitive decrement times in children

Plasma drug concentration is the variable linking dose to effect. The decrement time required for plasma concentration of anesthetic agents to decrease by 50% (context-sensitive half-time) correlates with the time taken to regain consciousness. However, the decrement time to consciousness may not be 50%. An effect compartment concentration is associated more closely with return of consciousness than plasma concentration. An alternative decrement time, the time required for propofol to decrease to a predetermined effect compartment concentration associated with movement (eg, 2 µg.ml^-1 ), was used to simulate time for the concentration to decrease from steady state at a typical targeted effect compartment concentration 3.5 µg.ml^-1 in children. These times were short and reflected a decrement time to consciousness (CST_AWAKE ) increase that was small with longer infusion time. CST_AWAKE ranged from 7.5 min in 1-year-old infant given propofol for 15 min to 13.5 min in a 15-year-old adolescent given a 2-hour infusion. Changes in decrement time with age reflect maturation of drug clearance. Neonates had prolonged increment times, 10 min after 15 min infusion and 18 min after 120 min infusion using a target concentration of 3.5 µg.ml^-1 . Decrement times to a targeted arousal concentration are context-sensitive. Use of a higher target concentration of 6 µg.ml^-1 doubled decrement times. Decrement times are associated with variability: delayed recovery beyond these simulated times is likely more attributable to the use of adjuvant drugs or the child's clinical status. An understanding of propofol decrement times can be used to guide recovery after anesthesia.

Premature birth: topics in physiology and pharmacological characteristics

OBJECTIVE

To review the main physiological and pharmacological changes related to prematurity, to promote the evidence-based clinical practice.

METHODS

This is a narrative review whose research was carried out in the ScienceDirect and Medline databases via PubMed, searching for articles in any language from January 2000 to February 2020.

RESULTS

Premature newborns are born before completing the maturation process that prepares them for extrauterine life, which occurs especially in the last weeks of pregnancy. Therefore, they have their own characteristics in development. Several physiological peculiarities stand out, such as disturbances in glucose regulation, adrenal function, thermoregulation, immunity, in addition to changes in liver, renal and respiratory functions. Pharmacological aspects were also highlighted, involving pharmacokinetics and pharmacodynamics.

CONCLUSIONS

Despite the recent advances in prematurity, it is still an area with many uncertainties, since several changes occur quickly and there are ethical issues that make studies difficult. Thus, it is clear that the therapeutic management of premature infants is still very much based on clinical practice.

Biomarkers for Diagnosis and Prognosis of AKI in Children: One Size Does Not Fit All

Pediatric AKI has become a significant health concern due to its rising incidence and association with adverse outcomes. Because of the limitations of serum creatinine, ongoing research has evaluated multiple novel biomarkers for the early detection of AKI. Identifying biomarkers that precede changes in serum creatinine is vital, because these biomarkers provide opportunities to improve outcomes through early diagnosis and timely disease management. In this review, we discuss salient findings on 16 candidate biomarkers and their association with AKI. We explore the differences in biomarker distribution by age and discuss why adult biomarker research findings cannot be directly extrapolated to children. With future research, more consideration needs to be given to how the maturing kidney affects biomarker levels and how we interpret biomarker performance in children. A comprehensive approach using age-specific biomarker reference ranges is required to develop pediatric biomarkers and improve outcomes for children with kidney disease.

Pharmacokinetics in neonatal prescribing: evidence base, paradigms and the future

Paediatric patients, particularly preterm neonates, present many pharmacological challenges. Due to the difficulty in conducting clinical trials in these populations dosing information is often extrapolated from adult populations. As the processes of absorption, distribution, metabolism and excretion of drugs change throughout growth and development extrapolation presents risk of over or underestimating the doses required. Information about the development these processes, particularly drug metabolism pathways, is still limited with weight based dose adjustment presenting the best method of estimating pharmacokinetic changes due to growth and development. New innovations in pharmacokinetic research, such as population pharmacokinetic modelling, present unique opportunities to conduct clinical trials in these populations improving the safety and effectiveness of the drugs used. More research is required into this area to ensure the best outcomes for our most vulnerable patients.

Developmental pharmacokinetics in pediatric populations

Information on drug absorption and disposition in infants and children has increased considerably over the past 2 decades. However, the impact of specific age-related effects on pharmacokinetics, pharmacodynamics, and dose requirements remains poorly understood. Absorption can be affected by the differences in gastric pH and stomach emptying time that have been observed in the pediatric population. Low plasma protein concentrations and a higher body water composition can change drug distribution. Metabolic processes are often immature at birth, which can lead to a reduced clearance and a prolonged half-life for those drugs for which metabolism is a significant mechanism for elimination. Renal excretion is also reduced in neonates due to immature glomerular filtration, tubular secretion, and reabsorption. Limited data are available on the pharmacodynamic behavior of drugs in the pediatric population. Understanding these age effects provide a mechanistic way to identify initial doses for the pediatric population. The various factors that impact pharmacokinetics and pharmacodynamics mature towards adult values at different rates, thus requiring continual modification of drug dose regimens in neonates, infants, and children. In this paper, the age-related changes in drug absorption, distribution, metabolism, and elimination in infants and children are reviewed, and the age-related dosing regimens for this population are discussed.

Pharmacogenomics and adverse drug reactions in children

Adverse drug reactions are a common and important complication of drug therapy in children. Over the past decade it has become increasingly apparent that genetically controlled variations in drug disposition and response are important determinants of adverse events for many important adverse events associated with drug therapy in children. While this research has been difficult to conduct over the past decade technical and ethical evolution has greatly facilitated the ability of investigators to conduct pharmacogenomic studies in children. Some of this research has already resulted in changes in public policy and clinical practice, for example in the case of codeine use by mothers and children. It is likely that the use of pharmacogenomics to enhance drug safety will first be realized among selected groups of children with high rates of drug use such as children with cancer, but it also likely that this research will be extended to other groups of children who have high rates of drug utilization and as well as providing insights into the mechanisms and pathophysiology of adverse drug reactions in children.

Neonatal clinical pharmacology

Effective and safe drug administration in neonates should be based on integrated knowledge on the evolving physiological characteristics of the infant who will receive the drug and the pharmacokinetics (PK) and pharmacodynamics (PD) of a given drug. Consequently, clinical pharmacology in neonates is as dynamic and diverse as the neonates we admit to our units while covariates explaining the variability are at least as relevant as median estimates. The unique setting of neonatal clinical pharmacology will be highlighted based on the hazards of simple extrapolation of maturational drug clearance when only based on 'adult' metabolism (propofol, paracetamol). Second, maturational trends are not at the same pace for all maturational processes. This will be illustrated based on the differences between hepatic and renal maturation (tramadol, morphine, midazolam). Finally, pharmacogenetics should be tailored to neonates, not just mirror adult concepts. Because of this diversity, clinical research in the field of neonatal clinical pharmacology is urgently needed and facilitated through PK/PD modeling. In addition, irrespective of already available data to guide pharmacotherapy, pharmacovigilance is needed to recognize specific side effects. Consequently, pediatric anesthesiologists should consider to contribute to improved pharmacotherapy through clinical trial design and collaboration, as well as reporting on adverse effects of specific drugs.

Pharmacokinetics of nevirapine in HIV-infected infants weighing 3 kg to less than 6 kg taking paediatric fixed dose combination tablets

OBJECTIVES

To evaluate pharmacokinetics of nevirapine, lamivudine and stavudine in HIV-infected Zambian infants receiving fixed dose combination (FDC) antiretroviral tablets (Triomune Baby).

DESIGN

Phase I/II study.

METHODS

Sixteen HIV-infected children at least 1 month, weighing 3 kg to less than 6 kg were enrolled. Blood was sampled at t = 0, 2, 6 and 12 h after observed intake of one FDC tablet (50 mg nevirapine, 6 mg stavudine, 30 mg lamivudine) 4 weeks after starting treatment. Safety and viral load response over 48 weeks were determined.

RESULTS

The median [interquartile range (IQR)] age, body weight and daily nevirapine dose in 15 included children (eight girls) were 4.8 (4.2, 8.4) months, 5.3 (4.3, 5.5) kg and 348 (326 385) mg/m, respectively. The median (IQR) nevirapine area under the concentration-time curve (AUC0-12 h), Cmax and C12 h were 70 (56, 104) h mg/l, 7.5 (6.2, 10) mg/l, and 4.3 (2.9, 6.9) mg/l, respectively. Values were on average higher than reported in adults, but approximately 20% lower than previously reported in children weighing at least 6 kg. Four of 15 (27%) children had a subtherapeutic nevirapine C12 h (defined as <3.0 mg/l) compared to only three of 63 (5%) children weighing at least 6 kg (P = 0.02), whereas children aged less than 5 months [three of six (50%)] may have the highest risk for subtherapeutic nevirapine C12 h (P = 0.24). No association was found between viral load values and nevirapine plasma pharmacokinetic parameters (P > 0.3). Stavudine-lamivudine pharmacokinetic parameters were broadly comparable to heavier children.

CONCLUSION

Exposure to nevirapine in African, HIV-infected infants with low body weight taking FDC tablets appears on average to be adequate, but due to large intersubject variability a relatively high proportion had subtherapeutic nevirapine C12 h levels, particularly those aged less than 5 months.

Population pharmacokinetics of intravenous bolus etomidate in children over 6 months of age

BACKGROUND

Information has been very limited on the population pharmacokinetics (PK) of etomidate in pediatric patients. The purpose of this study was to characterize the PK of etomidate in children.

METHODS

Forty-nine children aged over 6 months undergoing elective surgery received etomidate 0.3 mg·kg(-1) bolus i.v. within 15 s for anesthesia induction. Arterial blood samples were collected for 2 h after injection. A population nonlinear mixed effects modeling approach was used to characterize etomidate PK. Estimates were standardized to a 70-kg adult using allometric size models.

RESULTS

Children had a median age of 4 years (0.53-13.21 years) and weight 15.7 kg (7.5-52 kg). PK of etomidate was best estimated using a three-compartment model with weight on systemic (Cl(1)) and inter-compartmental clearances (Cl(2), Cl(3)), central (V(1)), and peripheral compartment volumes (V(2), V(3)). The most significant PK covariate was age, with increasing age having reduced size-adjusted Cl(1), V(1), and V(3) (all P < 0.01). The estimates of PK parameter (standardized to 70-kg adult) for a typical 4-year-old children were Cl(1) = 1.50 l·min(-1), Cl(2) = 1.95 l·min(-1), Cl(3) = 1.23 l·min(-1), V(1) = 9.51 l, V(2) = 11.0 l, and V(3) = 79.2 l, respectively.

CONCLUSIONS

Owing to enhanced clearance and increased central compartment volume of etomidate, smaller (younger) children will require higher etomidate bolus dose than larger (older) children to achieve equivalent plasma concentrations. The dependence of Cl(1) and V(1) on age does not support weight-based etomidate dosing in smaller children.

Tolerance and addiction; the patient, the parent or the clinician?

Tolerance has been recognized for some time where chronic exposure to certain drugs, particularly benzodiazepines and opioids, is associated with apparent tachyphylaxis. When these drugs are stopped or progressively reduced as in 'tapering', withdrawal symptoms may result. Tolerance and the flip side of the coin, withdrawal, are the determinants of addiction. It is increasingly apparent that tolerance can occur acutely, even within the time span of a single anesthetic for a surgical procedure. Addiction is caused by agents, foreign to the body, that provoke adaptation by homeostatic biological processes. When these agents are withdrawn, the adaptive mechanisms, devoid of substrate, take time to diminish and produce symptoms recognizable under the term of 'withdrawal'. Children may be exposed to these agents in different ways; in utero, as a result of substances that the mother ingests by enteral, parenteral or inhalational means that are transmitted to the infant via the placenta; as a result of an anesthetic for surgery; or as a result of sedation and analgesia administered to offset the stresses and trauma inherent from intensive care treatment in the neonatal intensive care unit or pediatric intensive care unit. Additionally, anesthetic and intensive care staff are exposed to powerful and addictive drugs as part of everyday practice, not simply by overt access, but also by subliminal environmental exposure.

Developmental pharmacology of tramadol during infancy: ontogeny, pharmacogenetics and elimination clearance

AIMS AND OBJECTIVES

To illustrate the complex interaction between ontogeny, i.e., age-dependent maturation, genetic polymorphisms and renal elimination clearance during infancy, based on developmental disposition of intravenous tramadol during infancy.

BACKGROUND

Tramadol (M) is metabolized by O-demethylation (cytochrome P450 [CYP] 2D6) to the pharmacodynamic active metabolite O-demethyl tramadol (M1). This metabolite is subsequently eliminated by renal route while M1 formation will in part depend on ontogeny, i.e., age-dependent activity and CYP2D6 polymorphisms. However, these pathways do not mature simultaneously.

METHODS

A pooled pharmacokinetic analysis of earlier reported time-concentration profiles in neonates and infants was performed with subsequent simulation of the impact of ontogeny, polymorphisms and renal elimination clearance during infancy.

RESULTS

Tramadol plasma time-concentration profile changes with postmenstrual age. The highest metabolite concentrations occur in the 52-week infant, where M1 formation clearance (hepatic, CYP2D6) is already mature but metabolite elimination clearance (through glomerular filtration rate) is immature.

DISCUSSION

The phenotypic observations might in part explain unanticipated (side-)effects of tramadol. In addition to the compound-specific clinical implications, it is important to stress that the maturational trends in the elimination processes described can be considered for other compounds (e.g., codeine) that undergo similar elimination routes.

Pediatric models for adult target-controlled infusion pumps

Target-controlled infusion (TCI) pumps currently do not satisfactorily cater for the pediatric population, particularly for those under 5 years. Growth and development are two major aspects of children not readily apparent in adults, and these two aspects influence clearance (CL) and volume of distribution (V). In simple terms, V determines initial dose, and CL determines infusion rate at steady state. Three major covariates (size, age, and organ function) contribute to parameter variability in children. Size can be standardized for clearance in a 70-kg person using the allometric (3/4) power model. Remifentanil, a drug cleared by hydrolysis, can be modeled in all age groups by simple application of this model using a standardized clearance of 2790 ml x min(-1) for a 70-kg person. Allometry alone is insufficient to predict clearance in neonates and infants from adult parameters for most drugs used in anesthesia. The addition of a model describing maturation is required. The sigmoid Emax or Hill model has been found useful for describing this maturation process. Propofol maturation has been described with a mature clearance of 1.83 l x min(-1) x 70 kg(-1), a maturation half-time (TM(50)) of 44 weeks and a Hill coefficient of 4.9. Organ function also affects clearance, and propofol clearance is reduced in neonates and infants after cardiac surgery. Although pharmacokinetics (PK) in children is receiving increasing attention and is eminently programmable into a TCI device, pharmacodynamic (PD) measures in children remain poorly defined, partly because the depth of anesthesia monitoring are inadequate. Both PK and PD are necessary for safe use of TCI pumps.