Pharmacokinetic considerations for anti-epileptic drugs in children

Pharmacokinetic variability and use of therapeutic drug monitoring of cannabidiol in patients with refractory epilepsy

OBJECTIVE

Cannabidiol (CBD) (Epidyolex) is a new antiseizure medication (ASM) for rare and severe epileptic syndromes. We aimed to investigate the pharmacokinetic variability of CBD to elucidate relationships between doses, serum concentrations, metabolites, and biochemical markers of toxicity by using therapeutic drug monitoring (TDM) data.

METHODS

Data on serum concentrations of all ASMs, CBD, and the active metabolite 7-hydroxy-cannabidiol (7-OH-CBD) were collected (January 2022 to June 2023) at the Section for Clinical Pharmacology, National Centre for Epilepsy, Oslo University Hospital.

RESULTS

Data from 52 patients were included: 122 serum concentration measurements (1-7 per patient); 48% female, mean age 23 (range 3-55) years. At maintenance (n = 34), the mean daily dose was 535 (SD 224) mg, that is, 10.03 (standard deviation [SD] .49) mg/kg/day, serum concentration .26 (SD .14) for CBD and .13 (SD .10) μmol/L for 7-OH-CBD. Reference ranges of .15-.50 μmol/L for CBD and .04-.25 μmol/L for 7-OH-CBD are proposed, which included 80% of measurements. There was a linear correlation between CBD dose to concentration and CBD to CBD-7-OH concentrations (r2 = .39 and .38) (p < .05). The hepatic marker alanine aminotransferase (ALT) increased on average 37%, demonstrating a moderate effect on liver function. Intra-individual coefficients of variation (CVs) were 32% (SD 17) for CBD and 48% (SD 24) for 7-OH-CBD (n = 15, ≥3 measurements). Twenty different ASMs were used: clobazam (n = 24), valproate (n = 17), and stiripentol (n = 8) were most common. The mean concentration ratio of desmethyl-clobazam/clobazam increased by 140% (7.29-17.5; p < .05) but was variable, pointing to enzyme inhibition by CBD.

SIGNIFICANCE

This observational study with TDM data revealed extensive pharmacokinetic variability of CBD in patients with refractory epilepsy. The results demonstrate the need for close follow-up and use of TDM, including biochemical markers of toxicity, for individualized treatment with CBD.

Persistent low concentrations of antiepileptics in a critically ill paediatric patient: an example of multiple potential drug interactions

A middle childhood boy with epilepsy exhibited persistent low concentrations of valproic acid, lamotrigine and topiramate for over 1 month, primarily due to pharmacokinetic interactions involving fosphenytoin, meropenem and phenobarbital. Awareness of these clinically significant interactions is crucial for ensuring effective seizure control. However, further research is needed to establish optimal evidence-based treatment strategies in complex paediatric cases.

Pharmacokinetic variability of everolimus and impact of concomitant antiseizure medications in patients with tuberous sclerosis complex: A retrospective study of therapeutic drug monitoring data in Denmark and Norway

The mTOR-inhibitor everolimus is a precision drug with antiepileptogenic properties approved for treatment of epilepsy in persons with tuberous sclerosis complex (TSC) in combination with other antiseizure medications (ASMs). However, the pharmacokinetic variability of everolimus is scarcely described, and the available information on pharmacokinetic interactions is scarce. The purpose of this study was to investigate pharmacokinetic variability of everolimus in patients with TSC, and the impact of age, sex and comedication. In this retrospective observational study we used anonymized data from medical records of patients with TSC using everolimus in Norway and Denmark, 2012 to 2020. Long-term therapeutic drug monitoring (TDM) identified inter-patient and intra-patient variability. The study included 59 patients, (36 females (61%)), median age 22 (range 3-59 years). Polytherapy was used in 50 patients (85%). The most frequently used ASMs were lamotrigine (n = 21), valproate (n = 17), and levetiracetam (n = 13). Blood concentrations of everolimus were measured in all patients. Pharmacokinetic variability of everolimus between patients was extensive, as demonstrated by a 24-fold variability from minimum-maximum concentration/dose (C/D)-ratios. The coefficient of variation (CV) for intra-patient (n = 59) and inter-patient variability (n = 47, ≥3 measurements) was 40% and 43%, respectively. The C/D-ratio of everolimus was 50% lower in 13 patients (22%) using enzyme-inducing ASMs compared to the 30 patients who did not (0.7 vs 1.4 ng/mL mg, P < .05). Age and sex were not significantly associated with changes in C/D-ratios of everolimus. Long-term TDM identified extensive variability in concentrations over time for everolimus both within and between patients, where comedication with enzyme-inducing ASMs was an important contributing factor. The findings suggest a need for TDM in patients with TSC treated with everolimus.

The latest advances in the pharmacological management of focal epilepsies in children: a narrative review

INTRODUCTION

Focal epilepsy constitutes the most common epilepsy in children, and medical treatment represents the first-line therapy in this condition. The main goal of medical treatment for children and adolescents with epilepsy is the achievement of seizure freedom or, in drug-resistant epilepsies, a significant seizure reduction, both minimizing antiseizure medications (ASM)-related adverse events, thus improving the patient's quality of life. However, up to 20-40% of pediatric epilepsies are refractory to drug treatments. New ASMs came to light in the pediatric landscape, improving the drug profile compared to that of the preexisting ones. Clinicians should consider several factors during the drug choice process, including patient and medication-specific characteristics.

AREAS COVERED

This narrative review aims to summarize the latest evidence on the effectiveness and tolerability of the newest ASMs administered as monotherapy or adjunctive therapy in pediatric epilepsies with focal onset seizures, providing a practical appraisal based on the existing evidence.

EXPERT OPINION

The latest ASMs have the potential to be effective in the pharmacological management of focal onset seizures in children, and treatment choice should consider several drug- and epilepsy-related factors. Future treatments should be increasingly personalized and targeted on patient-specific pathways. Future research should focus on discovering new chemical compounds and repurposing medications used for other indications.

UGT1A polymorphism rs4148324 associated with topiramate plasma concentration to dose ratio in children with epilepsy

PURPOSE

The objective of this study is to evaluate the association between genetic polymorphisms and the concentration to dose ratio of topiramate in children with epilepsy.

METHODS

A cohort of 163 pediatric patients with epilepsy receiving topiramate therapy were enrolled. The ultra-performance liquid chromatography-tandem mass spectrometry method was employed to measure the trough plasma concentration of topiramate at steady-state. These concentrations were normalized by dividing them by the ratio of total daily dose to body weight, yielding the concentration to dose ratio (CDR) of topiramate. MassArray system identified 30 single nucleotide polymorphisms associated with the pharmacokinetics and pharmacodynamics of topiramate. The CDR values were logarithmic transformed (lnCDR) for normal distribution. The association between the identified genetic polymorphisms and lnCDR was assessed using the PLINK software, employing linear regression analysis with adjustments by epilepsy types, estimated glomerular filtration rate, alanine aminotransferase, valproic acid, phenobarbital, and oxcarbazepine.

RESULTS

Variant rs4148324 (UGT1A1/3/4/5/6/7/8/9/10, BETA = 0.182, P = 0.010) was significantly associated with lnCDR of topiramate. Patients carrying the G allele exhibited higher normalized topiramate plasma concentrations. No other significant associations were found.

CONCLUSIONS

In pediatric patients receiving topiramate therapy, rs4148324 was associated with normalized topiramate plasma concentration. Further studies are warranted to validate and confirm the findings.

Pharmacological aspects of antiseizure medications: From basic mechanisms to clinical considerations of drug interactions and use of therapeutic drug monitoring

Antiseizure medications (ASMs) are the cornerstone of treatment for patients with epilepsy. Several new ASMs have recently been introduced to the market, making it possible to better tailor the treatment of epilepsy, as well as other indications (psychiatry and pain disorders). For this group of drugs there are numerous pharmacological challenges, and updated knowledge on their pharmacodynamic and pharmacokinetic properties is, therefore, crucial for an optimal treatment outcome. This review focuses on educational approaches to the following learning outcomes as described by the International League Against Epilepsy (ILAE): To demonstrate knowledge of pharmacokinetics and pharmacodynamics, drug interactions with ASMs and with concomitant medications, and appropriate monitoring of ASM serum levels (therapeutic drug monitoring, TDM). Basic principles in pharmacology, pharmacokinetic variability, and clinically relevant approaches to manage drug interactions are discussed. Furthermore, recent improvements in analytical technology and sampling are described. Future directions point to the combined implementation of TDM with genetic panels for proper diagnosis, pharmacogenetic tests where relevant, and the use of biochemical markers that will all contribute to personalized treatment. These approaches are clinically relevant for an optimal treatment outcome with ASMs in various patient groups.

A comprehensive review on pharmacological applications and drug-induced toxicity of valproic acid

Valproic acid, a branching short chain fatty acid, is a popular drug to treat epilepsy and acts as a mood-stabilizing drug. The obstruction of ion channels and Gamma Amino Butyrate transamino butyrate GABA has been linked to antiepileptic effects. Valproic acid has been characterized as a Histone deacetylase inhibitor, functioning directly transcription of gene levels by blocking the deacetylation of histones and increasing the accessibility of transcription sites. Study has been extensively focused on pharmaceutical activity of valproic acid through various pharmacodynamics activity from absorption, distribution and excretion particularly in patients who are resistant to or intolerant of lithium or carbamazepine, as well as those with mixed mania or rapid cycling.

Use of lacosamide in children: experience of a tertiary medical care center in Brazil

BACKGROUND

Lacosamide (LCM) is a third-generation anti-seizure drug approved in Europe and the United States, either as a monotherapy or adjunctive therapy, to treat partial-onset seizures in adults, adolescents, and children. In Brazil, LCM is licensed for treatment only in patients older than 16 years of age.

OBJECTIVE

To evaluate a cohort of children presenting with refractory epilepsy who received LCM as an add-on therapy and observe the response and tolerability to the LCM treatment.

METHODS

A retrospective cohort study conducted in a tertiary health care facility, which included 26 children, aged up to 16 years, who presented with refractory epilepsy and received LCM as an add-on treatment. The follow-up visits were scheduled every 3 months until 9 months of treatment with LCM.

RESULTS

After 3 months of LCM administration, in 73.1% of the children, there was a reduction of > 50% in the frequency of seizures, and this clinical improvement was maintained in most patients (73.9%) for the following 9 months. Mild (such as, somnolence and behavioral changes) or severe (seizure worsening) adverse effects were observed in two and three children respectively. Among responders to LCM, there was a higher prevalence of males, fewer concomitant anti-seizure drugs, and lower percentage of patients using sodium channel blockers.

CONCLUSIONS

Lacosamide should be considered as an early treatment option in pediatric patients with refractory epilepsy, mainly focal seizures.

Correlation between Level of Serum Transaminases and Duration of Antiepileptic Drugs in Epilepsy Children in Sanglah Hospital

BACKGROUND: Some antiepileptic drugs (AEDs), particularly sodium valproate, phenytoin, phenobarbital, and carbamazepine induce and increase production of hepatic enzymes. The adverse metabolic effects of AEDs treatments have become main concern, however data about evaluation of serum transaminases and duration of AEDs in Indonesia still limited. AIM: The aim of the study was to investigate correlation of AEDs and serum transaminases in children with epilepsy. METHODS: This cross-sectional research was conducted in pediatric neurology outpatient clinic in Sanglah Hospital. The target was children with epilepsy who had taken AEDs for at least 6 months. Data were collected from January 2020 to the number of samples were achieved. The exclusion criteria were concomitant liver disease, taking drugs which induce elevated serum transaminase or alcohol abuse. Data including age, gender, nutritional status, type, and duration of AEDs were obtained from medical record. Correlation was analyzed by Pearson’s or Spearman’s correlation, p < 0.05 was considered significant. RESULTS: Total 148 epileptic children enrolled in this study. Aspartate transaminase (AST) and alanine aminotransferase (ALT) level were highest in the group receiving combination therapy (34.37 ± 24.9 U/L and 35.96 ± 23.3 U/L). There was a significant negative correlation between duration of carbamazepine and AST (r = –0.723, p = 0.0001) and ALT (r = –0.457, p = 0.009), as well as duration of valproic acid with AST and ALT (r = –0.689 and –0.677, p = 0.0001). Duration of phenobarbital administration was positively correlated with AST and ALT (r = 0.546 and 0.425, p = 0.0001). Combination therapy also had positive correlation with AST and ALT (r = 0.815 and 0.781, p = 0.0001, respectively). CONCLUSION: Duration administration of carbamazepine and valproic acid had negative correlation with AST and ALT; however, phenobarbital and combination therapy were positively correlated with AST and ALT.

Neuropathology Evaluation in Juvenile Toxicity Studies in Rodents: Comparison of Developmental Neurotoxicity Studies for Chemicals With Juvenile Animal Studies for Pediatric Pharmaceuticals

The developmental neuropathology examination in juvenile toxicity studies depends on the nature of the product candidate, its intended use, and the exposure scenario (eg, dose, duration, and route). Expectations for sampling, processing, and evaluating neural tissues differ for developmental neurotoxicity studies (DNTS) for chemicals and juvenile animal studies (JAS) for pediatric pharmaceuticals. Juvenile toxicity studies typically include macroscopic observations, brain weights, and light microscopic evaluation of routine hematoxylin and eosin (H&E)-stained sections from major neural tissues (brain, spinal cord, and sciatic nerve) as neuropathology endpoints. The DNTS is a focused evaluation of the nervous system, so the study design incorporates perfusion fixation, plastic embedding of at least one nerve, quantitative analysis of selected brain regions, and sometimes special neurohistological stains. In contrast, the JAS examines multiple systems, so neural tissues undergo conventional tissue processing (eg, immersion fixation, paraffin embedding, H&E staining only). An "expanded neurohistopathology" (or "expanded neuropathology") approach may be performed for JAS if warranted, typically by light microscopic evaluation of more neural tissues (usually additional sections of brain, ganglia, and/or more nerves) or/and special neurohistological stains, to investigate specific questions (eg, a more detailed exploration of a potential neuroactive effect) or to fulfill regulatory requests.

Development, Characterization, and In Vivo Evaluation of a Novel Aptamer (Anti-MUC1/Y) for Breast Cancer Therapy

MUC1, the transmembrane glycoprotein Mucin 1, is usually found to be overexpressed in a variety of epithelial cancers playing an important role in disease progression. MUC1 isoforms such as MUC1/Y, which lacks the entire variable number of tandem repeat region, are involved in oncogenic processes by enhancing tumour initiation. MUC1/Y is therefore considered a promising target for the identification and treatment of epithelial cancers; but so far, the precise role of MUC1/Y remains to be elucidated. In this work, we developed and identified a DNA aptamer that specifically recognizes the splice variant MUC1/Y for the first time. The DNA aptamer could bind to a wide variety of human cancer cells, and treatment of MUC1/Y positive cells resulted in reduced growth in vitro. Moreover, MUC1/Y aptamer inhibited the tumour growth of breast cancer cells in vivo. The present study highlights the importance of targeting MUC1/Y for cancer treatment and unravels the suitability of a DNA aptamer to act as a new therapeutic tool.

Radioactive gold nanocluster (198-AuNCs) showed inhibitory effects on cancer cells lines

Cancer is a global epidemic disease responsible for over ten millions death worldwide. The early diagnosis and the precise treatment with reduced adverse reactions are the main goal worldwide. In this study, we produced, characterized and evaluated (in vitro) in three different cancer cell lines (protaste, breast and melanoma) a radioactive gold nanocluster (R-AuNC) (¹⁹⁸Au25(Capt)18). The pharmacokinetics as the influence in the ABC transporter (MRP1 Efflux Transporter Protein) was also evaluated. The results showed that R-AuNC (¹⁹⁸Au25(Capt)18) are capable to kill the cancer cells lines of protaste, breast and melanoma. The pharmacokinetics showed a fast clearance and great volume of distribution, confirming the use of R-AuNC as nanomedicine for cancer treatment. Finally, the ABC transporter assay corroborated that the R-AuNC (¹⁹⁸Au25(Capt)18) has no risk of being pumped out of cells by this efflux transporter. The results validate the use of gold nanoparticles as therapeutic nanomedicine for cancer treatment.

An update on brivaracetam for the treatment of pediatric partial epilepsy

Introduction: Brivaracetam (BRV) is an antiseizure medication (ASM), which has been approved as an adjunctive treatment in adults and pediatric patients aged four years and older with focal onset seizures. It is a second-generation levetiracetam (LEV) derivative, sharing the same mechanism of action, binding synaptic vesicles 2A (SV2A). BRV shows higher binding affinity and selectivity and higher brain permeability than LEV.Areas covered: This article reviews randomized controlled trials, retrospective and prospective studies published up to December 2020, searched in electronic databases MEDLINE, EMBASE and the Clinical Trial Database and provide an overview of efficacy, safety and tolerability of BRV in pediatric patients with partial epilepsy. Furthermore, the authors provide their expert opinion on the drug and give their future perspectives.Expert opinion: The analysis of the literature data has demonstrated the safety and efficacy of BRV in pediatric patients, with more evidence in children aged 4 to 16 years with an onset of focal seizures. However, a positive response was also achieved in patients affected by some encephalopathic epilepsies. Comparative efficacy studies between BRV and other ASMs, in addition to well-designed RCTs that include larger pediatric populations are needed to better define the role and potentiality of this ASM.

A Pharmacokinetic Evaluation of a Pectin-Based Oral Multiparticulate Matrix Carrier of Carbamazepine

Background

Carbamazepine is a drug used in the treatment of neurological disorders such as epilepsy. However, due to its erratic absorption, oral bioavailability is often poor. There is, therefore, the need to develop alternative formulations for carbamazepine with better pharmacokinetic characteristics.

Aim

The aim of this study was to formulate an oral modified-release multiparticulate matrix of carbamazepine from cocoa pod husk (CPH) pectin and evaluate the pharmacokinetic profile of this formulation using in vitro and in vivo models.

Methods

CPH pectin was extracted from cocoa pod husks with hot aqueous and citric acid solutions. Oral multiparticulate carbamazepine matrices were formulated from CPH pectin cross-linked with calcium. The formulation was evaluated for carbamazepine content and release profile in vitro. For in vivo pharmacokinetic profile estimation, rats were put into 4 groups of 5 animals each to receive carbamazepine multiparticulate matrix formulations A and B, carbamazepine powder, and Tegretol CR^®. Animals in each group received 200 mg/kg of each drug via the oral route. Maximum plasma concentration (C_max), area under the concentration-time curve (AUC), elimination rate constant (K_e), and terminal half-life (t_1/2) of the formulations were estimated by noncompartmental analysis.

Results

The pectin extraction from fresh cocoa pod husks using hot aqueous and citric acid solutions gave pectin yields of 9.63% and 11.54%, respectively. The drug content of carbamazepine in CPH pectin formulations A and B was 95% and 96%, respectively. There was controlled and sustained release of carbamazepine for both formulations A and B in vitro. AUC_0⟶36 (176.20 ± 7.97 µg.h/mL), C_max (8.45 ± 0.71 μg/mL), T_max (12 ± 1.28 h), and t_1/2 (13.75 ± 3.28 h) of formulation A showed a moderately enhanced and comparable pharmacokinetic profile to Tegretol CR^® (AUC_0⟶36: 155 ± 7.15 µg.h/mL, C_max: 8.24 ± 0.45 μg/mL, T_max: 8.0 ± 2.23 h, and t_1/2: 13.51 ± 2.87 h).

Conclusion

Findings from the study suggest that formulations of CPH pectin had the potential to control and maintain therapeutic concentrations of carbamazepine in circulation over a period of time in the rat model.

Efficacy and safety of sodium valproate plus lamotrigine in children with refractory epilepsy

Efficacy and safety of sodium valproate (SV) and lamotrigine (LTG) in treating refractory epilepsy (RE) in children and the predictive value of serum neuron-specific enolase (NSE) and central nervous system specific S100β protein (S100β) on efficacy assessment were explored. A total of 110 RE children admitted to Xuzhou Children's Hospital, Xuzhou Medical University were enrolled. Patients treated with SV alone served as the control group (n=51), and those treated with SV plus LTG as the study group (n=59). Serum NSE and S100β expression levels were measured by enzyme-linked immunosorbent assay (ELISA). The efficacy, seizure frequency, adverse reactions, concentration of serum brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF), and expression of serum NSE and S100β were observed and compared. The total effective rate in the study group was significantly higher than that in the control group, and the seizure frequency and incidence of adverse reactions were significantly lower than that in the control group. The study group showed remarkably higher BDNF and NGF than the control group after treatment. The expression of serum NSE and S100β in effectively treated children were significantly lower than that in ineffectively treated children. The area under the curve (AUC) of serum NSE and S100β were 0.828 and 0.814 respectively. SV combined with LTG is better and safer than SV alone in the treatment of RE in children. Serum NSE and S100β are of high value in predicting the efficacy.

Withdrawal seizures: possible risk factors

INTRODUCTION

Most of the patients usually achieve seizure freedom under treatment with antiseizure medications (ASMs). Drug withdrawal in seizure-free patients is still one of the most challenging issues in the management of epilepsy. The decision-making process of whether the treatment should be discontinued must be based on the evaluation of possible long-term side effects of chronic treatment and, on the other hand, the risk of seizure relapse.

AREAS COVERED

This review aims to describe and discuss possible predictors and risk factors for seizure relapse during and after discontinuation, according to the available literature evidence. The most important risk factors for withdrawal failure are the etiology of the epilepsy syndrome and epilepsy-related factors, worsening or persistence of epileptiform abnormalities on EEG recordings at the time of discontinuation or during drug tapering, and brain MRI abnormalities. Each single risk factor should be considered together with possible other concurrent predictors.

EXPERT OPINION

The decision to withdrawal antiseizure medication in seizure-free patients should be carefully planned and based on the evaluation of predictors. A discontinuation program should include tailored discussion with patients and family members and individualized decision, the taper schedule, and plans for monitoring during and after drug tapering.

Understanding Childhood Neuroimmune Diseases of the Central Nervous System

Immune-mediated diseases of the central nervous system (CNS) in childhood are a heterogeneous group of rare conditions sharing the inflammatory involvement of the CNS. This review highlights the growing knowledge of childhood neuroimmune diseases that primarily affect the CNS, outlining the clinical and diagnostic features, the pathobiological mechanisms and genetics, current treatment options, and emerging challenges. The clinical spectrum of these conditions is increasingly expanded, and the underlying mechanisms of dysregulation of the immune system could vary widely. Cell-mediated and antibody-mediated disorders, infection-triggered and paraneoplastic conditions, and genetically defined mechanisms can occur in previously healthy children and can contribute to different stages of the disease. The careful evaluation of the clinical presentation and temporal course of symptoms, the specific neuroimaging and immunological findings, and the exclusion of alternative causes are mandatory in clinical practice for the syndromic diagnosis. A common feature of these conditions is that immunotherapeutic agents could modulate the clinical course and outcomes of the disease. Furthermore, specific symptomatic treatments and comprehensive multidisciplinary care are needed in the overall management. We focus on recent advances on immune-mediated demyelinating CNS disorders, autoimmune encephalitis, interferonopathies, and possible neuroimmune disorders as Rasmussen encephalitis. Better knowledge of these conditions could allow prompt diagnosis and targeted immunotherapy, to decrease morbidity and mortality as well as to improve clinical outcomes, reducing the burden of the disease due to possible long-term neuropsychiatric sequelae. Persisting controversies remain in the rigorous characterization of each specific clinical entity because of the relative rarity in children; moreover, in a large proportion of suspected neuroimmune diseases, the immune "signature" remains unidentified; treatment guidelines are mostly based on retrospective cohort studies and expert opinions; then advances in specific molecular therapies are required. In the future, a better characterization of specific immunological biomarkers may provide a useful understanding of the underlying pathobiological mechanisms of these conditions in order to individualize more tailored therapeutic options and paradigms. Multicenter collaborative research on homogeneous groups of patients who may undergo immunological studies and therapeutic trials could improve the characterization of the underlying mechanisms, the specific phenotypes, and tailored management.