Development of a safe and effective pediatric dosing regimen for sotalol based on population pharmacokinetics and pharmacodynamics in children with supraventricular tachycardia

Characterizing Associations of QTc Interval with Nocturnal Glycemic Control in Children with Type 1 Diabetes

An association between QT prolongation (Bazett's corrected QT interval, QTcB) of 7 milliseconds and nocturnal hypoglycemia, compared with euglycemia, has been observed in children with type 1 diabetes (T1D). The objective of this pharmacometric analysis was to understand this association and other sources of QTc variability quantitatively. Data originate from a prospective observational study (25 cardiac healthy children with T1D, aged 8.1-17.6 years) with continuous subcutaneous glucose and electrocardiogram measurements for 5 consecutive nights. Mixed-effect modeling was used to compare QTcB with individual heart-rate correction (QTcI). Covariate models accounting for circadian variation, age, and sex were evaluated, followed by an investigation of glucose-QTc relationships (with univariable and combined adjusted analysis). Factors potentially modifying sensitivity to QTc lengthening were explored. Random inter-individual variability was reduced in the QTcI versus QTcB model (±12.6 vs 14.1 milliseconds), and was further reduced in the adjusted covariate model (±9.7 milliseconds), accounting for the significantly (P < .01) shortened QTc in adolescent boys (-14.6 milliseconds), circadian variation (amplitude, 19.2 milliseconds; shift, 2.9 hours), and linear glucose-QTc relationship (delay rate, 0.56-h ; slope, 0.76 milliseconds [95%CI 0.67- 0.85 milliseconds] per 1 mmol/L decrease in glucose). Differing sensitivity was suggested to depend upon hemoglobin A1c (HbA1c), T1D duration, and time spent in nocturnal hypoglycemia. In conclusion, a clinically mild association of QTc prolongation with nocturnal hypoglycemia was confirmed and quantified in this pharmacometric analysis, and the longest QTc interval was around 03:00 a.m. The characterized delayed association with glucose highlights the relevance of both the extent and the duration of hypoglycemia. Further clinical studies are warranted to investigate whether these factors contribute to increased risk of hypoglycemia-associated cardiac arrhythmia in children with T1D.

Informing a Comprehensive Risk Assessment of Infant Drug Exposure From Human Milk: Application of a Physiologically Based Pharmacokinetic Lactation Model for Sotalol

Characterization of infant drug exposure through human milk is important and underexplored. Because infant plasma concentrations are not frequently collected in clinical lactation studies, modeling and simulation approaches can integrate physiology, available milk concentrations, and pediatric data to inform exposure in breastfeeding infants. A physiologically based pharmacokinetic model was built for sotalol, a renally eliminated drug, to simulate infant drug exposure from human milk. Intravenous and oral adult models were built, optimized, and scaled to an oral pediatric model for a breastfeeding-relevant age group (<2 years). Model simulations captured the data that were put aside for verification. The resulting pediatric model was applied to predict the impacts of sex, infant body size, breastfeeding frequency, age, and maternal dose (240 and 433 mg) on drug exposure during breastfeeding. Simulations suggest a minimal effect of sex or frequency on total sotalol exposure. Infants in the 90th percentile in height and weight have predicted exposures ≈20% higher than infants of the same age in the 10th percentile due to increased milk intake. The simulated infant exposures increase throughout the first 2 weeks of life and are maintained at the highest concentrations in weeks 2-4, with a consistent decrease observed as infants age. Simulations suggest that breastfeeding infants will have plasma concentrations in the lower range observed in infants administered sotalol. With further validation on additional drugs, physiologically based pharmacokinetic modeling approaches could use lactation data to a greater extent and provide comprehensive information to support decisions regarding medication use during breastfeeding.

Sotalol in neonates for arrhythmias: Dosing, safety, and efficacy

INTRODUCTION

Various agents may be utilized to manage supraventricular tachycardia (SVT) in neonates and infants. Recently, sotalol has piqued interest given its reported success in managing neonates and infants with SVTs, especially with the intravenous formulation. While the manufacturer recommends using an age-related nomogram in neonates and young infants to guide doses, clinical reports describe various dosing based on weight (mg/kg) or on body surface area (BSA) in mg/m2 . Given the reported variation in clinical practice with regard to dosing in neonates, there is a gap in the literature and translation into clinical practice regarding applicability of the nomogram into clinical practice. The purpose of this study was to describe sotalol doses based on body weight and BSA in neonates for SVT.

METHODS

This is a single center retrospective study evaluating effective sotalol dosing from January 2011 and June 2021 (inclusive). Neonates who received intravenous (IV) or oral (PO) sotalol for SVT were eligible for inclusion. The primary outcome was to describe sotalol doses based on body weight and BSA. Secondary outcomes include comparison of doses to the manufacturer nomogram, description of dose titrations, reported adverse outcomes, and change in therapy. Two-sided Wilcoxon signed-rank tests were used to determine statistically significant differences.

RESULTS

Thirty-one eligible patients were included in this study. The median (range) age and weight were 16.5 (1-28) days and 3.2 (1.8-4.9) kg, respectively. The median initial dose was 7.3 (1.9-10.8) mg/kg or 114.3 (30.9-166.7) mg/m2 /day. Fourteen (45.2%) of patients required a dose increase for SVT control. The median dose required for rhythm control was 8.5 (2-14.8) mg/kg/day or 120.7 (30.9-225) mg/m2 /day. Of note, the median recommended dose per manufacturer nomogram for our patients would have been 51.3 (16.2-73.8) mg/m2 /day, which is significantly lower than both the initial dose (p < .001) and final doses (p < .001) utilized in our study. A total of 7 (22.9%) patients were uncontrolled on sotalol monotherapy using our dosing regimen. Two patients (6.5%) had reports of hypotension and one patient (3.3%) had a report of bradycardia requiring discontinuation of therapy. The average change in baseline QTC following sotalol initiation was 6.8%. Twenty-seven (87.1%), 3 (9.7%), 1 (3.3%) experienced prolongation, no change, or a decrease in QTc, respectively.

CONCLUSIONS

This study demonstrates that a sotalol strategy significantly higher than the manufacture dose recommendations are required for rhythm control in neonates with SVT. There were few adverse events reported with this dosing. Further prospective studies would be advantageous to confirm these findings.

Model-Based Exposure-Response Assessment for Spectinamide 1810 in a Mouse Model of Tuberculosis

Despite decades of research, tuberculosis remains a leading cause of death from a single infectious agent. Spectinamides are a promising novel class of antituberculosis agents, and the lead spectinamide 1810 has demonstrated excellent efficacy, safety, and drug-like properties in numerous in vitro and in vivo assessments in mouse models of tuberculosis. In the current dose ranging and dose fractionation study, we used 29 different combinations of dose level and dosing frequency to characterize the exposure-response relationship for spectinamide 1810 in a mouse model of Mycobacterium tuberculosis infection and in healthy animals. The obtained data on 1810 plasma concentrations and counts of CFU in lungs were analyzed using a population pharmacokinetic/pharmacodynamic (PK/PD) approach as well as classical anti-infective PK/PD indices. The analysis results indicate that there was no difference in the PK of 1810 in infected compared to healthy, uninfected animals. The PK/PD index analysis showed that bacterial killing of 1810 in mice was best predicted by the ratio of maximum free drug concentration to MIC (fC_max/MIC) and the ratio of the area under the free concentration-time curve to the MIC (fAUC/MIC) rather than the cumulative percentage of time that the free drug concentration is above the MIC (f%T_MIC). A novel PK/PD model with consideration of postantibiotic effect could adequately describe the exposure-response relationship for 1810 and supports the notion that the in vitro observed postantibiotic effect of this spectinamide also translates to the in vivo situation in mice. The obtained results and pharmacometric model for the exposure-response relationship of 1810 provide a rational basis for dose selection in future efficacy studies of this compound against M. tuberculosis.

Supraventricular tachycardias in neonates and infants: factors associated with fatal or near-fatal outcome

Prognosis of supraventricular tachycardias in neonates and infants is thought to be excellent with rare fatal outcomes. Nevertheless, initial management can be challenging. The aim of this study was to perform a retrospective analysis in neonates/infants with non-pos-toperative supraventricular tachycardias regarding risk factors for clinical outcome and type of antiarrhythmic drug therapy. The data of 157 patients aged < 1 year who presented between 2000 and 2015 with symptomatic tachycardias were retrospectively reviewed. Pharmacological therapy was successful in 151 patients (96%); 1 patient (1%) required catheter ablation and 5 patients (3%) died (1 death linked to hemodynamical reasons after effective arrhythmia control). Serious complications following acute medical therapy occurred in 4 patients of survivors. Patients with complications or death had a lower bodyweight, more frequent intrauterine tachycardia, transplacental therapy, urgent caesarian section, higher PRISM II score, longer period to control tachycardia, more frequent proarrhythmia, and major adverse event-defined as life-threatening event without a documented new arrhythmia-compared to the group without complications. There was no significant difference between the groups regarding prematurity, structural heart disease, and type of tachycardia. Proarrhythmia occurred in 6 cases and was related to intravenous drug use with class IC antiarrhythmics in 3/6 cases, digoxin in 2/6 cases, and amiodarone in 1/6 cases. ECG signs of impending proarrhythmia without new-onset arrhythmia requiring cessation of therapy were detected in 6 patients.Conclusion: Although rare, non-post-operative supraventricular tachycardia in neonates and infants might be a serious disease. Acute intravenous pharmacological treatment to control tachycardia might pose a risk for fatal or near-fatal outcome. Detection of proarrhythmia related to class IC antiarrhythmics in neonates might be especially difficult and requires alertness. What is Known • Prognosis of supraventricular tachycardias in children are thought to be excellent with fatal outcomes being rare. • Mortality is increased in the very young and in those with structural heart disease. What is New • Complicated outcome of non-post-operative supraventricular tachycardias in neonates is associated with lower bodyweight, age, prenatal tachycardia, higher PRISM II score, longer period to control tachycardia, and proarrhythmia. • Detection of class IC proarrhythmic effect is especially difficult in neonates because of their narrow QRS and warrants alertness.

Intravenous Sotalol for the Treatment of Ventricular Dysrhythmias in an Infant on Extracorporeal Membrane Oxygenation

Sotalol is a class III anti-arrhythmic agent with beta receptor blocking properties. Intravenous (IV) sotalol may be useful to treat refractory atrial and ventricular arrhythmias. A report on the efficacy and safety of IV sotalol in an infant on extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT), who developed refractory ventricular arrhythmias following surgery for congenital heart disease. A 10-day old infant with severe pulmonary valve stenosis underwent surgical pulmonary valvectomy and enlargement of the main pulmonary artery. Post-operatively, the patient developed hemodynamically significant accelerated idioventricular rhythm which was not responsive to a combination of amiodarone, lidocaine, and procainamide leading to 2 cardiac arrest events and placement on ECMO. The amiodarone infusion was uptitrated to 20 mcg/kg/min, but episodes of the hemodynamically compromising arrhythmia continued. Amiodarone was discontinued and IV sotalol was initiated at 42 mg/m²/day, divided to 3 doses, and administered every 8 h, which completely suppressed the arrhythmia. The initial sotalol dose was calculated based on a daily dose of 90 mg/m² and reduced by an age-related factor as recommended by the FDA approved prescribing information. Subsequently, acute kidney injury requiring CRRT developed. The patient remained on IV sotalol for 3 weeks and then transitioned to oral sotalol. The oral dose was increased to 44 mg/m²/day (3.5 mg every 8 h) to account for the difference in bioavailability between the IV and oral formulations. Serial sotalol levels during IV and PO therapy remained therapeutic on ECMO and CRRT. The patient maintained normal sinus rhythm on sotalol without adverse events. IV sotalol in the setting of ECMO and CRRT was safe and effective in controlling refractory hemodynamically compromising accelerated idioventricular rhythm unresponsive to amiodarone.

Receiver Operating Characteristic Analysis and Clinical Trial Simulation to Inform Dose Titration Decisions

Optimal dose selection in clinical trials is problematic when efficacious and toxic concentrations are close. A novel quantitative approach follows for optimizing dose titration in clinical trials. A system of pharmacokinetics (PK), pharmacodynamics, efficacy, and toxicity was simulated for scenarios characterized by varying degrees of different types of variability. Receiver operating characteristic (ROC) and clinical trial simulation (CTS) were used to optimize drug titration by maximizing efficacy/safety. The scenarios included were a low-variability base scenario, and high residual (20%), interoccasion (20%), interindividual (40%), and residual plus interindividual variability scenarios, and finally a shallow toxicity slope scenario. The percentage of subjects having toxicity was reduced by 87.4% to 93.5%, and those having efficacy was increased by 52.7% to 243%. Interindividual PK variability may have less impact on optimal cutoff values than other sources of variability. ROC/CTS methods for optimizing dose titration offer an individualized approach that leverages exposure-response relationships.

Innovative Study Designs Optimizing Clinical Pharmacology Research in Infants and Children

Almost half of recent pediatric trials failed to achieve labeling indications, in large part because of inadequate study design. Therefore, innovative study methods are crucial to optimizing trial design while also reducing the potential harms inherent with drug investigation. Several methods exist to optimize the amount of pharmacokinetic data collected from the smallest possible volume and with the fewest number of procedures, including the use of opportunistic and sparse sampling, alternative and noninvasive matrices, and microvolume assays. In addition, large research networks using master protocols promote collaboration, reduce regulatory burden, and increase trial efficiency for both early- and late-phase trials. Large pragmatic trials that leverage electronic health records can capitalize on central management strategies to reduce costs, enroll patients with rare diseases on a large scale, and augment study generalizability. Further, trial efficiency and safety can be optimized through Bayesian adaptive techniques that permit planned protocol changes based on analyses of prior and accumulated data. In addition to these trial design features, advances in modeling and simulation have paved the way for systems-based and physiologically based models that individualize pediatric dosing recommendations and support drug approval. Last, given the low prevalence of many pediatric diseases, collecting deidentified genetic and clinical data on a large scale is a potentially transformative way to augment clinical pharmacology research in children.

Population Pharmacokinetics: Some Observations in Pediatric Modeling for Drug Clearance

The objective of this study is to evaluate the predictive performance of several models to predict drug clearance in preterm and term neonates. Five models using different types of allometric and linear models were developed. Two sets of data were used to develop these models (data from preterm neonates to adults and data from preterm and term neonates). Models were also developed with (normalized to 70 kg) or without body weight normalization (body weight 1 kg). From the literature, clearance values for four drugs from neonates to adults were obtained. External data were used to evaluate the predictive performance of these models in preterm and term neonates. The results of the study indicated that (1) normalization to a standard body weight had no impact on the predictive performance of the models, (2) the model developed from preterm neonates to adults using fixed exponent 0.75 provided inaccurate estimate (overestimation) of drug clearance in neonates, (3) a far superior prediction of clearance was observed with the model when the exponents of allometry were estimated than the model using exponent 0.75, (4) linear models with the exception of the model with intercept provided comparable results to the estimated exponent model and were superior in their predictive performance to the model using exponent 0.75, and (5) when the models were developed from neonate data, the predictive performance of all models were similar. Overall, the study indicated that body weight normalization had no impact on the performance of model prediction, the exponents of allometry in pharmacostatistical models should be estimated rather than fixed, and more studies are needed to evaluate the suitability of linear models for the prediction of drug clearance in neonates.

Predictors of Pharmacological Therapy of Ectopic Atrial Tachycardia in Children

Ectopic atrial tachycardia (EAT) is a relatively common type of supraventricular tachycardia in the pediatric population, and it can be resistant to antiarrhythmic drugs and lead to tachycardia-induced cardiomyopathy (TIC) if not properly managed. The purpose of this study was to determine the predictors of the response to pharmacological therapy in children with EAT. From January 2009 to April 2014, 115 children were admitted to our hospital with a diagnosis of EAT and placed on antiarrhythmic drugs. We examined the clinical history, response to therapy, and follow-up of the children. The incidence of TIC secondary to EAT was 22.6% (n = 26) in children. Incessant EAT accounted for 44.3% of all patients. Control of EAT with antiarrhythmic therapy was achieved in 73.9% (n = 85) of the children. The combination of sotalol and propafenone performed well in controlling EAT in children [complete control in 35 (49.3%) of 71]. The mean time of conversion to sinus rhythm was 24 days, and the mean duration of therapy was 11 months in children with resolution. Multivariate predictors of the control of EAT were age at presentation (OR 0.289, P = 0.038) and tachycardia type (OR 0.276, P = 0.006). TIC occurs in 22.6% of children with EAT. Incessant EAT is more frequently complicated by TIC. Independent factors associated with a good response to pharmacological therapy include a younger age at presentation and non-incessant tachycardia in children with EAT.

Impact of disease, drug and patient adherence on the effectiveness of antiviral therapy in pediatric HIV

INTRODUCTION

Maintaining effective antiretroviral treatment for life is a major problem in both resource-limited and resource-rich countries. Despite the progress observed in paediatric antiretroviral therapy, approximately 12% of children still experience treatment failure due to drug resistance, inadequate dosing and poor adherence. We explore the current status of antiretroviral therapy in children with focus on the interaction between disease, drug pharmacokinetics and patient behavior, all of which are strongly interconnected and determine treatment outcome. Areas covered: An overview is provided of the viral characteristics and available drug combinations aimed at the prevention of resistance. In this context, the role of patient adherence is scrutinized. A detailed assessment of factors affecting adherence is presented together with the main strategies to enhance treatment response in children. Expert opinion: Using modeling and simulation, a framework for characterizing the forgiveness of non-adherence for specific antiretroviral drugs in children is proposed in which information on pharmacokinetics, pharmacokinetic-pharmacodynamic relationships and viral dynamics is integrated. This approach represents an opportunity for the simplification of dosing regimens taking into account the interaction between these factors. Based on clinical trial simulation scenarios, we envisage the possibility of assessing the impact of variable adherence to antiretroviral drug combinations in HIV-infected children.

Pediatric Dosing of Intravenous Sotalol Based on Body Surface Area in Patients with Arrhythmia

In a recently published study, we evaluated the efficacy and safety of intravenous sotalol in pediatric patients with incessant tachyarrhythmias and we have found that intravenous sotalol is effective and safe. Our dosing regimen was based on the body weight of the patients. In the US, the recommendation for intravenous sotalol dosing in pediatric patients is based on body surface area (BSA) while taking into consideration the patients' age. The purpose of this paper is to show the correspondence of a body weight-based dosing regimen when expressed for BSA as mg/m². We evaluated the similarity of a body weight-based dose to that calculated based on BSA using the US labeling recommendations. Of the 83 patients, 5 were newborns (age: 0-30 days), 39 infants and toddlers (age: 1-24 month), 26 young children (age: >2-6 years), 11 older children (age: 6-12 years), and 2 adolescents (age: 14 years). Each received a loading dose of 1 mg/kg intravenous sotalol administered over 10 min followed by a maintenance dose of 4.5 mg/kg/day. There was a close correlation between the sotalol loading doses calculated based on body weight and BSA across the entire age range (r = 0.977, p < 0.001). In most of the age groups, the body weight-based loading doses were lower or equal to the BSA-based doses. Only in the adolescents were the body weight-based doses higher. The maintenance doses given in our study were significantly higher than the BSA-based dose in newborns: 75 ± 6 versus 53 ± 8 mg/m², p < 0.05; infants/toddlers: 88 ± 14 versus 77 ± 7 mg/m², p < 0.001; younger children: 113 ± 12 versus 85 mg/m², p < 0.001; older children: 123 ± 16 versus 85 mg/m², p < 0.01; and adolescents 157 ± 30 versus 85.5 mg/m². Despite the rapid administration of the loading dose and the increased maintenance doses, our body weight-based dosing regimen was safe. Only one newborn had significant adverse event (AV block) that resolved spontaneously after discontinuation of the infusion.

Application of a systems pharmacology model for translational prediction of hERG-mediated QTc prolongation

Drug‐induced QTc interval prolongation (ΔQTc) is a main surrogate for proarrhythmic risk assessment. A higher in vivo than in vitro potency for hERG‐mediated QTc prolongation has been suggested. Also, in vivo between‐species and patient populations’ sensitivity to drug‐induced QTc prolongation seems to differ. Here, a systems pharmacology model integrating preclinical in vitro (hERG binding) and in vivo (conscious dog ΔQTc) data of three hERG blockers (dofetilide, sotalol, moxifloxacin) was applied (1) to compare the operational efficacy of the three drugs in vivo and (2) to quantify dog–human differences in sensitivity to drug‐induced QTc prolongation (for dofetilide only). Scaling parameters for translational in vivo extrapolation of drug effects were derived based on the assumption of system‐specific myocardial ion channel densities and transduction of ion channel block: the operational efficacy (transduction of hERG block) in dogs was drug specific (1–19% hERG block corresponded to ≥10 msec ΔQTc). System‐specific maximal achievable ΔQTc was estimated to 28% from baseline in both dog and human, while %hERG block leading to half‐maximal effects was 58% lower in human, suggesting a higher contribution of hERG‐mediated potassium current to cardiac repolarization. These results suggest that differences in sensitivity to drug‐induced QTc prolongation may be well explained by drug‐ and system‐specific differences in operational efficacy (transduction of hERG block), consistent with experimental reports. The proposed scaling approach may thus assist the translational risk assessment of QTc prolongation in different species and patient populations, if mediated by the hERG channel.

Comparison of Drug Use Between Clinical Practice and Regulatory Approval: Results in Older Japanese Patients With Rheumatoid Arthritis, Diabetes, High Blood Pressure, or Depression

BACKGROUND

In this study, differences in older patients between drug use as reported in clinical practice and in clinical trials for regulatory approval were examined.

METHODS

Electronic medical record (EMR) data such as patient background (age, sex), concomitant drugs, data on laboratory tests, and prescribed doses of drugs from outpatients with rheumatoid arthritis, diabetes, high blood pressure, or depression at Chiba University Hospital were obtained for the period from January 2003 to December 2012. These data were compared with data from relevant clinical trials for regulatory approval in order to examine differences in drug use.

RESULTS

There were 5134 eligible patients. The prescribed doses of drugs were lower than the standard approved doses for depression and rheumatoid arthritis but were generally within the approved dose range for type 2 diabetes mellitus and hypertension. When comparing the characteristics of older patients taking tacrolimus, 5.6% to 17.0% of those would not be able to participate in clinical trials because of liver or renal abnormality, and the incidence rates of some adverse drug events (ADEs) differed significantly between clinical practice and clinical trials.

CONCLUSIONS

Appropriate doses of drugs for older patients may differ from approved doses in certain diseases. Complex situations such as a lot of polypharmacy, comorbidity, and functional impairment in older patients in clinical practice make it difficult to evaluate safety based on data from clinical trials. In the future, utilization of a database created from the EMR of older patients should be considered for assessment of drug safety in older patients in clinical practice.

Cardiovascular Safety Assessment in Early-Phase Clinical Studies: A Meta-Analytical Comparison of Exposure-Response Models

Exposure‐response analysis of QT interval in clinical studies has been proposed as a thorough QT study alternative. Many exposure‐response model structures have been proposed for cardiovascular (CV) safety markers, but few studies have compared models across multiple drugs. To recommend preferred drug‐effect exposure‐response models on vital signs and electrocardiogram (ECG) intervals, an individual‐level model‐based meta‐analysis (39 studies and 1,291 subjects) compared 90 model structures. Models were selected to describe the data and cross‐validate studies on the same drug. The most commonly selected baseline model was an unstructured model (estimation of a value at each study nominal time) for all measures but blood pressure. The unstructured model estimated a better cross‐validated drug‐effect when considering all markers. A linear model was the most commonly selected to characterize drug‐effect on all markers. We propose these models as a starting point assisting with CV safety exposure‐response assessment in nondedicated small studies with healthy subjects.

Sotalol

Sotalol is effective for treating atrial fibrillation (AF), ventricular tachycardia, premature ventricular contractions, and supraventricular tachycardia. Racemic (DL) sotalol inhibits the rapid component of the delayed rectifier potassium current. There is a near linear relationship between sotalol dosage and QT interval prolongation. However, in dose ranging trials in patients with AF, low-dose sotalol was not more effective than placebo. Orally administered sotalol has a bioavailability of nearly 100%. The only significant drug interactions are the need to avoid or limit use of concomitant drugs that cause QT prolongation, bradycardia, and/or hypotension.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Antiarrhythmics

OBJECTIVE

Arrhythmias are a common occurrence in critically ill pediatric patients. Pharmacotherapy is a usual modality for treatment and prevention of arrhythmias in this patient population. This review will highlight particular arrhythmias in the pediatric critical care population and discuss salient points of pharmacotherapy of these arrhythmias. The mechanisms of action for the various agents, potential adverse events, place in therapy, and evidence for their use will be summarized.

DATA SOURCES

The literature was searched for articles related to the topic. Expertise of the authors and a consensus of the editors were additional sources of data in the article.

DATA SYNTHESIS

The author team synthesized the current pharmacology and recommendations and present them in this review. Tables were generated to summarize the state of the art evidence-based practice.

CONCLUSION

Specialized knowledge as to the safe and effective use of the antiarrhythmic pharmacotherapy in the intensive care setting can lead to safe and effective rhythm management in patients with complex heart disease.

Extemporaneous sotalol hydrochloride oral solutions for use in paediatric cardiology: formulation and stability study

Objectives

Sotalol hydrochloride (SOT) is an antiarrhythmic β-blocker which is highly effective for the treatment of supraventricular tachycardia in children. However, a licensed paediatric dosage form with sotalol is not currently available in Europe. The aim of this work was to formulate paediatric oral solutions with SOT 5 mg/mL for extemporaneous preparation in a hospital pharmacy with the lowest possible amount of excipients and to determine their stability.

Methods

Three aqueous solutions were formulated. One preparation without any additives for neonates and two preparations for children from 1 month of age were compounded using citric acid to stabilise the pH value, potassium sorbate 0.1% w/v as a preservative, and simple syrup or sodium saccharin as a sweetener. The samples were stored at room temperature and in a refrigerator, respectively, and the content of SOT and potassium sorbate was determined simultaneously using a validated high performance liquid chromatography method at different time points over 180 days.

Results

At least 95% of the initial sotalol concentration remained throughout the 180-day study period in all three preparations at both temperatures. The content of potassium sorbate decreased by 17% with sodium saccharin stored at room temperature.

Conclusions

The three proposed oral aqueous solutions of SOT for neonates and infants were stable for 180 days. Storage in a refrigerator is preferred, particularly with sodium saccharin. The additive-free solution of SOT can be autoclaved to ensure microbiological stability and used particularly for neonates and in emergency situations.

The role of concentration-effect relationships in the assessment of QTc interval prolongation

Population pharmacokinetic and pharmacokinetic-pharmacodynamic (PKPD) modelling has been widely used in clinical research. Yet, its application in the evaluation of cardiovascular safety remains limited, particularly in the evaluation of pro-arrhythmic effects. Here we discuss the advantages of disadvantages of population PKPD modelling and simulation, a paradigm built around the knowledge of the concentration-effect relationship as the basis for decision making in drug development and its utility as a guide to drug safety. A wide-ranging review of the literature was performed on the experimental protocols currently used to characterize the potential for QT interval prolongation, both pre-clinically and clinically. Focus was given to the role of modelling and simulation for design optimization and subsequent analysis and interpretation of the data, discriminating drug from system specific properties. Cardiovascular safety remains one of the major sources of attrition in drug development with stringent regulatory requirements. However, despite the myriad of tests, data are not integrated systematically to ensure accurate translation of the observed drug effects in clinically relevant conditions. The thorough QT study addresses a critical regulatory question but does not necessarily reflect knowledge of the underlying pharmacology and has limitations in its ability to address fundamental clinical questions. It is also prone to issues of multiplicity. Population approaches offer a paradigm for the evaluation of drug safety built around the knowledge of the concentration-effect relationship. It enables quantitative assessment of the probability of QTc interval prolongation in patients, providing better guidance to regulatory labelling and understanding of benefit/risk in specific populations.

Effect of Kidney Function on Drug Kinetics and Dosing in Neonates, Infants, and Children

Neonates, infants, and children differ from adults in many aspects, not just in age, weight, and body composition. Growth, maturation and environmental factors affect drug kinetics, response and dosing in pediatric patients. Almost 80% of drugs have not been studied in children, and dosing of these drugs is derived from adult doses by adjusting for body weight/size. As developmental and maturational changes are complex processes, such simplified methods may result in subtherapeutic effects or adverse events. Kidney function is impaired during the first 2 years of life as a result of normal growth and development. Reduced kidney function during childhood has an impact not only on renal clearance but also on absorption, distribution, metabolism and nonrenal clearance of drugs. 'Omics'-based technologies, such as proteomics and metabolomics, can be leveraged to uncover novel markers for kidney function during normal development, acute kidney injury, and chronic diseases. Pharmacometric modeling and simulation can be applied to simplify the design of pediatric investigations, characterize the effects of kidney function on drug exposure and response, and fine-tune dosing in pediatric patients, especially in those with impaired kidney function. One case study of amikacin dosing in neonates with reduced kidney function is presented. Collaborative efforts between clinicians and scientists in academia, industry, and regulatory agencies are required to evaluate new renal biomarkers, collect and share prospective pharmacokinetic, genetic and clinical data, build integrated pharmacometric models for key drugs, optimize and standardize dosing strategies, develop bedside decision tools, and enhance labels of drugs utilized in neonates, infants, and children.

Predicting neonatal pharmacokinetics from prior data using population pharmacokinetic modeling

Selection of the first dose for neonates in clinical trials is very challenging. The objective of this analysis was to assess if a population pharmacokinetic (PK) model developed with data from infants to adults is predictive of neonatal clearance and to evaluate what age range of prior PK data is needed for informative modeling to predict neonate exposure. Two sources of pharmacokinetic data from 8 drugs were used to develop population models: (1) data from all patients > 2 years of age, and (2) data from all nonneonatal patients aged > 28 days. The prediction error based on the models using data from subjects > 2 years of age showed bias toward overprediction, with median average fold error (AFE) for CL predicted/CLobserved greater than 1.5. The bias for predicting neonatal PK was improved when using all prior PK data including infants as opposed to an assessment without infant PK data, with the median AFE 0.91. As an increased number of pediatric trials are conducted in neonates under the Food and Drug Administration Safety and Innovation Act, dose selection should be based on the best estimates of neonatal pharmacokinetics and pharmacodynamics prior to conducting efficacy and safety studies in neonates.

Treatment of supraventricular tachycardia in infants: Analysis of a large multicenter database

OBJECTIVE

Supraventricular tachycardia (SVT) is the most common arrhythmia in infants. Infants are typically treated with antiarrhythmic medications, but there is a lack of evidence guiding management, thus exposing infants to risks of both inadequate therapy and medication adverse events. We used data from a large clinical database to better understand current practices in SVT management, safety of commonly used medications, and outcomes of hospitalized infants treated for SVT.

METHODS

This retrospective data analysis included all infants discharged from Pediatrix Medical Group neonatal intensive care units between 1998 and 2012 with a diagnosis of SVT who were treated with antiarrhythmic medications. We categorized infants by the presence of congenital heart disease other than patent ductus arteriosus. Medications were categorized as abortive, acute, or secondary prevention therapies. We used descriptive statistics to describe medication use, adverse events, and outcomes including SVT recurrence and mortality.

RESULTS

A total of 2848 infants with SVT were identified, of whom 367 (13%) had congenital heart disease. Overall, SVT in-hospital recurrence was high (13%), and almost one fifth of our cohort (18%) experienced an adverse event. Mortality was 2% in the overall cohort and 6% in the congenital heart disease group (p<0.001). Adenosine was the most commonly used abortive therapy, but there was significant practice variation in therapies used for acute treatment and secondary prevention of SVT.

CONCLUSION AND PRACTICE IMPLICATION

Significant variation in SVT treatment and suboptimal outcomes warrant future clinical trials to determine best practices in treating SVT in infants.

In silico optimization of pharmacokinetic properties and receptor binding affinity simultaneously: a 'parallel progression approach to drug design' applied to β-blockers

The present work exploits the potential of in silico approaches for minimizing attrition of leads in the later stages of drug development. We propose a theoretical approach, wherein 'parallel' information is generated to simultaneously optimize the pharmacokinetics (PK) and pharmacodynamics (PD) of lead candidates. β-blockers, though in use for many years, have suboptimal PKs; hence are an ideal test series for the 'parallel progression approach'. This approach utilizes molecular modeling tools viz. hologram quantitative structure activity relationships, homology modeling, docking, predictive metabolism, and toxicity models. Validated models have been developed for PK parameters such as volume of distribution (log Vd) and clearance (log Cl), which together influence the half-life (t1/2) of a drug. Simultaneously, models for PD in terms of inhibition constant pKi have been developed. Thus, PK and PD properties of β-blockers were concurrently analyzed and after iterative cycling, modifications were proposed that lead to compounds with optimized PK and PD. We report some of the resultant re-engineered β-blockers with improved half-lives and pKi values comparable with marketed β-blockers. These were further analyzed by the docking studies to evaluate their binding poses. Finally, metabolic and toxicological assessment of these molecules was done through in silico methods. The strategy proposed herein has potential universal applicability, and can be used in any drug discovery scenario; provided that the data used is consistent in terms of experimental conditions, endpoints, and methods employed. Thus the 'parallel progression approach' helps to simultaneously fine-tune various properties of the drug and would be an invaluable tool during the drug development process.

A population pharmacokinetic model of remifentanil in pediatric patients using body-weight-dependent allometric exponents

BACKGROUND

Allometric exponents in population pharmacokinetic analysis are regularly used but the issue of fixing or estimating an allometric exponent remains controversial. The objective of the current analysis is to evaluate the performance of a body-weight-dependent allometric exponent (BDE) model of remifentanil.

METHODS

The study was conducted in 34 patients (neonates to 17 years and 2.5 to 97 kg body weight) following a single intravenous (IV) infusion of remifentanil (5 μg/kg). A population pharmacokinetic approach was taken to describe drug clearance by the following BDE equation: CL=CLpop(BW/14.6 kg)L×BW(-M). Three allometric models were used to explore the impact of allometric exponents on the total clearance of remifentanil.

RESULTS

All model-fitted structural, covariate, and statistical parameters were estimated with good to excellent precision (%RSE). However, on the basis of calculated Akaike weights (0.000 for model 1, 0.004 for model 2, and 0.996 for model 3), model 3 is the most robust model to describe individual clearance estimates.

CONCLUSIONS

The BDE model performed best for the estimation of remifentanil clearance and is realistic and of practical value. Further investigation should be conducted for such models.

[Non-invasive treatment of tachycardias during childhood]

In principle tachycardias during childhood do not differ from those in adulthood but they present with a significant age-dependency. Additionally the clinical presentation has a broad spectrum related to the different ages, from the neonatal period until adolescence. If congenital heart disease is present the hemodynamic compromise may be accentuated. This paper describes the diagnostic and therapeutic approaches to pediatric tachycardias with focus upon the age dependent aspects and the presense of congenital heart disease, either native or postoperative.

Physiologically based pharmacokinetic models in the prediction of oral drug exposure over the entire pediatric age range-sotalol as a model drug

In recent years, the increased interest in pediatric research has enforced the role of physiologically based pharmacokinetic (PBPK) models in pediatric drug development. However, an existing lack of published examples contributes to some uncertainties about the reliability of their predictions of oral drug exposure. Developing and validating pediatric PBPK models for oral drug application shall enrich our knowledge about their limitations and lead to a better use of the generated data. This study was conducted to investigate how whole-body PBPK models describe the oral pharmacokinetics of sotalol over the entire pediatric age. Two leading software tools for whole-body PBPK modeling: Simcyp® (Simcyp Ltd, Sheffield, UK) and PK-SIM® (Bayer Technology Services GmbH, Leverkusen, Germany), were used. Each PBPK model was first validated in adults before scaling to children. Model input parameters were collected from the literature and clinical data for 80 children were used to compare predicted and observed values. The results obtained by both models were comparable and gave an adequate description of sotalol pharmacokinetics in adults and in almost all pediatric age groups. Only in neonates, the mean ratio_(Obs/Pred) for any PK parameter exceeded a twofold error range, 2.56 (95% confidence interval (CI), 2.10–3.49) and 2.15 (95% CI, 1.77–2.99) for area under the plasma concentration-time curve from the first to the last concentration point and maximal concentration (C_max) using SIMCYP® and 2.37 (95% CI, 1.76–3.25) for time to reach C_max using PK-SIM®. The two PBPK models evaluated in this study reflected properly the age-related pharmacokinetic changes and predicted adequately the oral sotalol exposure in children of different ages, except in neonates.

Computational methods in drug discovery

Computer-aided drug discovery/design methods have played a major role in the development of therapeutically important small molecules for over three decades. These methods are broadly classified as either structure-based or ligand-based methods. Structure-based methods are in principle analogous to high-throughput screening in that both target and ligand structure information is imperative. Structure-based approaches include ligand docking, pharmacophore, and ligand design methods. The article discusses theory behind the most important methods and recent successful applications. Ligand-based methods use only ligand information for predicting activity depending on its similarity/dissimilarity to previously known active ligands. We review widely used ligand-based methods such as ligand-based pharmacophores, molecular descriptors, and quantitative structure-activity relationships. In addition, important tools such as target/ligand data bases, homology modeling, ligand fingerprint methods, etc., necessary for successful implementation of various computer-aided drug discovery/design methods in a drug discovery campaign are discussed. Finally, computational methods for toxicity prediction and optimization for favorable physiologic properties are discussed with successful examples from literature.

Strategic biomarkers for drug development in treating rare diseases and diseases in neonates and infants

There are similar challenges in developing a product designed to treat patients with a rare disease and drugs to treat critically ill neonates and infants. Part of the challenge in developing such products as well as identifying the optimal dosing regimen for the treatment of young children arises from the complex interrelationship between developmental changes and changes in biomarkers responsive to drug therapy. These difficulties are further compounded by our lack of understanding of the key physiological factors that cause the differences in clinical responses between adults and neonates and infants. Regulatory efforts have succeeded in overcoming these challenges in many areas of pediatric and orphan drug development. Strategic applications of biomarkers and surrogate endpoints for the development and approval of a product used to treat an orphan disease will be highlighted with examples of approved products. Continued efforts are still needed to fill in our knowledge gap and to strategically link biomarkers and surrogate endpoints to clinical responses for rare diseases and diseases affecting neonates and infants.

High-dose sotalol is safe and effective in neonates and infants with refractory supraventricular tachyarrhythmias

Our objective was to assess the efficacy and safety of high-dose sotalol in neonates and infants with refractory supraventricular tachycardia (SVT). SVT in neonates and infants can be refractory to primary therapies; therefore, secondary agents, e.g., sotalol, are often required to obtain control of SVT. Age-factor nomogram dosing of sotalol is widely used; however, our institution uses greater doses based on body surface area (approximately 150-200 mg/m(2)/d). A retrospective review of 78 inpatients receiving sotalol, after failing another antiarrthymic medication, at our institution from 2001 to 2008 was performed. Corrected QT intervals (QTc), 24-h Holter-monitoring results, and outpatient records were reviewed to assess safety and efficacy for patients ≤ 2 years of age. Median patient age at the time of initiation of therapy was 24 days (range 3-728). Forty-eight patients (62%) were neonates, and 36 (46%) had congenital heart disease. The median sotalol dosage was 152 mg/m(2)/day (range 65-244). The SVT of 70 patients (90%) was controlled with sotalol. No patients experienced significant QTc prolongation or proarrhythmia. Mean duration of follow-up was 3.3 ± 0.24 years. High-dose sotalol allows for safe and rapid control of refractory tachyarrhythmias in this young age group.

Primary HHV 6 infection after liver transplantation with acute graft rejection and multi-organ failure: successful treatment with a 2.5-fold dose of cidofovir and reduction of immunosuppression

HHV type 6 has been reported with enhanced pathogenicity in immunocompromised patients. Herein, we report about a two-yr-old girl who experienced primary HHV 6 infection after liver transplantation. She clinically presented with graft rejection and necrotic hepatitis as well as high fever, pneumonitis with respiratory failure and a rash. Therapy with cidofovir of 5 mg/kg per wk did not show improvement, so that a full pharmacokinetic profile of cidofovir was performed. It demonstrated enhanced body weight normalized clearance of cidofovir and cidofovir dosage was augmented to 12 mg/kg per wk to reach adequate drug exposure. With additional reduction of immunosuppression, the patient dramatically improved and liver function stabilized.

Pediatric cardiovascular drug development and research: integration of modeling and simulation as one future direction

The integration of the needs of children into the legal drug development process since 1997 in the United States and since 2007 in the European Union has improved health and stimulated innovative approaches in the design of clinical trials and will benefit both current and future populations. According to the US Food and Drug Administration, to date, 394 pediatric labels together with safer medicines and better dosing practices have provided a sound basis for the safer and more effective use of drugs in a pediatric population. This may be measurable with fewer medication errors and perhaps shorter hospital stays in the future. Although relevant data have been generated by clinical trials in pediatric populations, challenges, such as nonefficacy and safety issues, have arisen. Heterogeneity in the physiological maturation and growth processes and differences in the etiology and pathogenesis of disease in patients from birth to 18 years of age may explain these results. The use of cutting-edge technology, such as modeling and simulation of "in silico" pediatric populations, may allow the integration of data from previous trials and experiments into the design of future clinical trials and allow exploration in other areas that have the potential to enhance the outcome of clinical trials in children.

Knowledge-driven approaches for the guidance of first-in-children dosing

Pediatric pharmacokinetic and pediatric safety and efficacy studies are, in most cases, a mandatory activity during the drug development process in North America and Europe. Pharmacokinetic modeling in anticipation of the pediatric clinical trial should take a data or knowledge-driven approach by employing either top-down or bottom-up approaches to assessing differential age-related dosing. These two approaches depend on different starting information and are likely to be used in conjunction with each other for the purposes of defining pediatric dosing guidelines. This review primarily focuses on the available bottom-up, mechanistic models for predicting age-dependent drug absorption, distribution and elimination, and their integration through the whole-body physiologically based pharmacokinetic (PBPK) model. The bottom-up approach incorporating adult and pediatric whole-body PBPK models for optimizing age-related dosing is detailed for a drug currently undergoing pediatric development.

Modelling and simulation as research tools in paediatric drug development

Purpose

Although practical and ethical constraints impose special requirements for the evaluation of treatment safety and efficacy in children, the main issue remains the empirical basis for patient stratification and dose selection at the early stage of the development of new chemical and biological entities. The aim of this review is to highlight the advantages and limitations of modelling and simulation (M&S) in supporting decision making during paediatric drug development.

Methods

A literature search on Pubmed’s database Medical Subject Headings (MeSH) has been performed to retrieve relevant publications on the use of model-based approaches in paediatric drug development and therapeutics.

Results

M&S enable the assessment of the impact of different regimens as well as of different populations on a drug’s safety and efficacy profile. It has been widely used in the last two decades to support pre-clinical and early clinical drug development. In fact, M&S have been applied to drug development as decision tools, as study optimization tools and as data analysis tools. In particular, this approach can be used to support dose adjustment in specific subgroups of a population. M&S may therefore allow the individualisation of drug therapy in children, improving the risk–benefit ratio in this population.

Conclusions

The lack of consensus on how to assess the impact of developmental factors on pharmacokinetics, pharmacodynamics, efficacy and safety has so far prevented a broader use of M&S. This problem is compounded by the limited collaboration between stakeholders, which prevents data sharing in this field. In this article, we emphasise the need for a concerted effort to promote the effective use of this technology in paediatric drug development and avoid unnecessary exposure of children to clinical trials.

Study design and simulation approach

Modeling and simulation techniques are a mainstay of clinical drug development and are particularly useful to support clinical trials in children. If a pediatrician wants to use these tools most efficiently, a basic understanding of the principles and methods of classical and novel techniques of modeling and simulation is essential. Key elements comprise the definition and description of terms like deterministic simulation, Monte Carlo simulation, classical "top down" or novel "bottom up" approach, as well as the term "virtual world simulation." The illustrated examples in this chapter from pediatric clinical trials will help to understand and demonstrate these key elements. The importance of the understanding of developmental physiology and pharmacokinetics will become visible when explaining novel "bottom up" approaches like physiologically based pharmacokinetic simulations which also bridge to current research tools from other areas such as systems biology using mathematical models to describe biological systems.

Basics and dynamics of neonatal and pediatric pharmacology

Understanding the role of ontogeny in the disposition and actions of medicines is the most fundamental prerequisite for safe and effective pharmacotherapeutics in the pediatric population. The maturational process represents a continuum of growth, differentiation, and development, which extends from the very small preterm newborn infant through childhood, adolescence, and to young adulthood. Developmental changes in physiology and, consequently, in pharmacology influence the efficacy, toxicity, and dosing regimen of medicines. Relevant periods of development are characterized by changes in body composition and proportion, developmental changes of physiology with pathophysiology, exposure to unique safety hazards, changes in drug disposition by major organs of metabolism and elimination, ontogeny of drug targets (e.g., enzymes, transporters, receptors, and channels), and environmental influences. These developmental components that result in critical windows of development of immature organ systems that may lead to permanent effects later in life interact in a complex, nonlinear fashion. The ontogeny of these physiologic processes provides the key to understanding the added dimension of development that defines the essential differences between children and adults. A basic understanding of the developmental dynamics in pediatric pharmacology is also essential to delineating the future directions and priority areas of pediatric drug research and development.

Understanding developmental pharmacodynamics: importance for drug development and clinical practice

Developmental pharmacodynamics is the study of age-related maturation of the structure and function of biologic systems and how this affects response to pharmacotherapy. This may manifest as a change in the potency, efficacy, or therapeutic range of a drug. The paucity of studies exploring developmental pharmacodynamics reflects the lack of suitable juvenile animal models and the ethical and practical constraints of conducting studies in children. However, where data from animal models are available, valuable insight has been gained into how response to therapy can change through the course of development. For example, animal neurodevelopmental models have revealed that temporal differences in the maturation of norepinephrine and serotonin neurotransmitter systems may explain the lack of efficacy of some antidepressants in children. GABA(A) receptors that switch from an excitatory to inhibitory mode during early development help to explain paradoxical seizures experienced by infants after exposure to benzodiazepines. The increased sensitivity of neonates to morphine may be due to increased postnatal expression of the mu opioid receptor. An age dependency to the pharmacokinetic-pharmacodynamic relationship has also been found in some clinical studies. For example, immunosuppressive effects of ciclosporin (cyclosporine) revealed markedly enhanced sensitivity in infants compared with older children and adults. A study of sotalol in the treatment of children with supraventricular tachycardia showed that neonates exhibited a higher sensitivity towards QTc interval prolongation compared with older children. However, the data are limited and efforts to increase and establish data on developmental pharmacodynamics are necessary to achieve optimal drug therapy in children and to ensure long-term success of pediatric drug development. This requires a dual 'bottom up' (ontogeny knowledge driven) and 'top down' (pediatric pharmacokinetic-pharmacodynamic studies) approach.

Quantification of cidofovir in human serum by LC-MS/MS for children

A new method for the quantification of cidofovir (CDV), an acyclic nucleotide analogue of cytosine with antiviral activity against a broad-spectrum of DNA viruses, in human serum, using high-performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) has been developed. A strong anion exchange (SAX) solid-phase extraction procedure was applied for the sample preparation. The tandem mass spectrometer was tuned in the multiple reaction monitoring mode to monitor the m/z 278.1-->234.9 and the m/z 288.1-->133.1 transitions for CDV and the internal standard 9-(2-phosphonylmethoxyethyl)guanine (PMEG), respectively, using negative electrospray ionization. The MS/MS response was linear over the concentration range from 78.125 ng/ml to 10,000 ng/ml, with a lower limit of quantification of 78.125 ng/ml. The intra- and inter-day precisions (relative standard deviation (%)) for CDV were less than 7.8% and the accuracies (% of deviation from nominal level) were within +/-12.1% for quality controls. The novel LC-MS/MS method allowed a specific, sensitive and reliable determination of CDV in human serum and was applied to investigate the yet unknown pharmacokinetic properties of CDV in a paediatric cancer patient.

Mechanism-based concepts of size and maturity in pharmacokinetics

Growth and development can be investigated using readily observable demographic factors such as weight and age. Size is the primary covariate and can be referenced to a 70-kg person with allometry using a coefficient of 0.75 for clearance and 1 for volume. The use of these coefficients is supported by fractal geometric concepts and observations from diverse areas in biology. Fat free mass (FFM) might be expected to do better than total body weight when there are wide variations in fat affecting body composition. Clearance pathways develop in the fetus before birth. The use of postnatal age as a descriptor of maturation is unsatisfactory because birth may occur prematurely; therefore postmenstrual age is a superior predictor of elimination function. A sigmoid E(max) model (Hill equation) describes gradual maturation of clearance in early life leading to a mature adult clearance achieved at a later age.

Guidelines on paediatric dosing on the basis of developmental physiology and pharmacokinetic considerations

The approach to paediatric drug dosing needs to be based on the physiological characteristics of the child and the pharmacokinetic parameters of the drug. This review summarises the current knowledge on developmental changes in absorption, distribution, metabolism and excretion and combines this knowledge with in vivo and in vitro pharmacokinetic data that are currently available. In addition, dosage adjustments based on practical problems, such as child-friendly formulations and feeding regimens, disease state, genetic make-up and environmental influences are presented. Modification of a dosage based on absorption, depends on the route of absorption, the physico chemical properties of the drug and the age of the child. For oral drug absorption, a distinction should be made between the very young and children over a few weeks old. In the latter case, it is likely that practical considerations, like appropriate formulations, have much greater relevance to oral drug absorption. The volume of distribution (V(d)) may be altered in children. Hydrophilic drugs with a high V(d) in adults should be normalised to bodyweight in young children (age <2 years), whereas hydrophilic drugs with a low V(d) in adults should be normalised to body surface area (BSA) in these children. For drugs that are metabolised by the liver, the effect of the V(d) becomes apparent in children <2 months of age. In general, only the first dose should be based on the V(d); subsequent doses should be determined by the clearance. Pharmacokinetic studies on renal and liver function clarify that a distinction should be made between maturation and growth of the organs. After the maturation process has finished, the main influences on the clearance of drugs are growth and changes in blood flow of the liver and kidney. Drugs that are primarily metabolised by the liver should be administered with extreme care until the age of 2 months. Modification of dosing should be based on response and on therapeutic drug monitoring. At the age of 2-6 months, a general guideline based on bodyweight may be used. After 6 months of age, BSA is a good marker as a basis for drug dosing. However, even at this age, drugs that are primarily metabolised by cytochrome P450 2D6 and uridine diphosphate glucuronosyltransferase should be normalised to bodyweight. In the first 2 years of life, the renal excretion rate should be determined by markers of renal function, such as serum creatinine and p-aminohippuric acid clearance. A dosage guideline for drugs that are significantly excreted by the kidney should be based on the determination of renal function in first 2 years of life. After maturation, the dose should be normalised to BSA. These guidelines are intended to be used in clinical practice and to form a basis for more research. The integration of these guidelines, and combining them with pharmacodynamic effects, should be considered and could form a basis for further study.