Antiepileptic drug treatment in children

The reference range of lamotrigine in the treatment of epilepsy in children: a systematic review

PURPOSE

This study intends to assess the reference range of lamotrigine concentration for treating childhood epilepsy.

METHODS

PubMed, Ovid-Embase, The Cochrane Library, CNKI, WanFang data and VIP databases were searched from database inception to January 2022. RCT, cohort study, case-control study, cross-sectional study that estimated the reference range of lamotrigine for children epilepsy treatment were included. The data extracted included basic information, statistical methods, data type, and results of reference range. Descriptive analysis was performed for them.

RESULTS

8 studies were included and estimated the reference range, and all of them were calculated based on efficacy data and/or concentration data. Statistical methods including ROC curve, concentration-effect curve, mean ± standard deviation, 95% confidence interval and percentile interval were utilized. For lamotrigine monotherapy, the lower limits ranged from 2.06 mg/L to 3.99 mg/L, and the upper limits ranged from 8.43 mg/L to 9.08 mg/L, showing basic consistency. However, for lamotrigine concomitant with valproate, the lower limits ranged from 2.00 mg/L to 8.00 mg/L, and the upper limit was 11.50 mg/L, for lamotrigine concomitant with other antiepileptics, the lower limits ranged from 1.00 mg/L to 3.09 mg/L, and the upper limits varied from 5.90 mg/L to 16.24 mg/L, indicating inconsistency.

CONCLUSION

Several studies have estimated the reference range of lamotrigine for childhood epilepsy, while controversy exist and no studies have determined the upper limit of the range based on safety data. To establish the optimal reference range, further high-quality studies are necessary that consider both efficacy and safety data.

Therapeutic Drug Monitoring of Perampanel in Children With Refractory Epilepsy: Focus on Influencing Factors on the Free-Perampanel Concentration

BACKGROUND

This study aimed to assess the effect of perampanel dose, age, sex, and antiseizure medication cotherapy on steady-state free-perampanel concentration in children with refractory epilepsy, as well as the relationship between inflammation and the pharmacokinetics of perampanel.

METHODS

This prospective study in China included 87 children with refractory epilepsy treated with adjunctive perampanel therapy. Free and total perampanel concentrations in plasma were determined using liquid chromatography-tandem mass spectrometry. Free-perampanel concentration was compared among patients with various potential influencing factors.

RESULTS

A total of 87 pediatric patients (44 female children) aged 2-14 years were enrolled. The mean free-perampanel concentration and free concentration-to-dose (CD) ratio in plasma were 5.7 ± 2.7 ng/mL (16.3 ± 7.7 nmol/L) and 45.3 ± 21.0 (ng/mL)/(mg/kg) [129.6 ± 60.1 (nmol/L)/(mg/kg)], respectively. The protein binding of perampanel in plasma was 97.98%. A linear relationship was observed between perampanel dose and free concentration in plasma, and a positive relationship was found between the total and free-perampanel concentrations. Concomitant use of oxcarbazepine reduced the free CD ratio by 37%. Concomitant use of valproic acid increased the free CD ratio by 52%. Five patients had a plasma high-sensitivity C-reactive protein (Hs-CRP) level of >5.0 mg/L (Hs-CRP positive). The total and free CD ratios of perampanel were increased in patients with inflammation. Two patients with inflammation developed adverse events, which disappeared as the Hs-CRP level returned to normal, and neither required perampanel dose reduction. Age and sex did not influence the free-perampanel concentration.

CONCLUSIONS

This study found complex drug interactions between perampanel and other concomitant antiseizure medications, providing valuable information to enable clinicians to apply perampanel in the future reasonably. In addition, it may be important to quantify both the total and free concentrations of perampanel to assess complex pharmacokinetic interactions.

Extrapolation of a Brivaracetam Exposure-Response Model from Adults to Children with Focal Seizures

Introduction

Prediction of brivaracetam effects in children was obtained by scaling an existing adult pharmacokinetic/pharmacodynamic (PK/PD) model for brivaracetam to children, using an existing population PK model for brivaracetam in children. The scaling was supported by estimating the change from adults to children in the concentration–effect relationship parameters for levetiracetam, a compound interacting with the same target protein (synaptic vesicle protein SV2A).

Methods

The existing adult PK/PD model for brivaracetam was applied to a combined adult–pediatric dataset of levetiracetam. This model was then used to predict the effective oral twice-daily dose of brivaracetam in children aged ≥4 to <16 years as adjunctive treatment for focal (partial onset) seizures. The existing model described daily seizure counts using a negative binomial distribution, taking previous-day seizure frequencies into account, and using a mixture model to separate ‘placebo-like’ and ‘responder’ subpopulations. The model was adapted to describe aggregated monthly seizure counts for adult patients in the levetiracetam studies: daily seizure counts were only available for children in the levetiracetam studies.

Results

The levetiracetam PK/PD model successfully described both the adult and pediatric data using the same drug effect parameters, and using a model structure similar to the existing adult brivaracetam PK/PD model.

Conclusion

Simulation with the adult brivaracetam PK/PD model in combination with an existing pediatric brivaracetam population PK model allowed characterization of the dose–response curve, suggesting maximum response at brivaracetam 4 mg/kg/day dosing (capped at 200 mg/day, the maximum adult dose) in children aged ≥4 years.

Electronic supplementary material

The online version of this article (doi:10.1007/s40262-017-0597-2) contains supplementary material, which is available to authorized users.

Safety and tolerability of adjunctive lacosamide in a pediatric population with focal seizures - An open-label trial

PURPOSE

To evaluate safety and tolerability of adjunctive lacosamide in children with focal seizures.

METHODS

Patients were eligible for this open-label, fixed-titration trial (SP0847; NCT00938431) if aged 1 month-17 years with focal seizures taking 1-3 antiepileptic drugs. Findings from Cohort 1, aged 5-11 years, who received lacosamide ≤8 mg/kg/day, informed dosing for age-based cohorts 2-5, who then received ≤12 mg/kg/day (≤600 mg/day). Oral lacosamide was initiated at 2 mg/kg/day (1 mg/kg bid) and uptitrated by 2 mg/kg/day/week to the maximum cohort-defined dose (maximum trial duration: 13 weeks). Patients who did not achieve the maximum cohort-defined dose were discontinued.

RESULTS

Forty-seven patients (aged 6 months-≤17 years) enrolled (≥1 month-<4 years: n = 15; ≥4-<12 years: n = 23; ≥12-≤17 years: n = 9). 24/47 (51.1%) patients completed the trial at the maximum cohort-defined dose and 40/47 (85.1%) continued lacosamide in the extension trial. Treatment-emergent adverse events (TEAEs) were reported by 42/47 (89.4%) patients. The most common TEAEs (≥10% of patients) were vomiting (21.3%), diarrhea (14.9%), somnolence (12.8%), irritability, dizziness, and pyrexia (10.6% each). Twenty (42.6%) patients discontinued due to TEAEs, most commonly vomiting (8.5%), gait disturbance, dizziness, and somnolence (6.4% each). Six (12.8%) patients reported serious TEAEs, most commonly status epilepticus (3/47; 6.4%).

CONCLUSION

This fixed-titration trial supports the safety of adjunctive lacosamide in children (aged 6 months-≤17 years) with focal seizures. The TEAE profile was generally consistent with that observed in trials in adults, and no new safety concerns were identified.

Therapeutic Drug Monitoring of Antiepileptic Drugs in Epilepsy: A 2018 Update

BACKGROUND

Antiepileptic drugs (AEDs) are the mainstay of epilepsy treatment. Since 1989, 18 new AEDs have been licensed for clinical use and there are now 27 licensed AEDs in total for the treatment of patients with epilepsy. Furthermore, several AEDs are also used for the management of other medical conditions, for example, pain and bipolar disorder. This has led to an increasingly widespread application of therapeutic drug monitoring (TDM) of AEDs, making AEDs among the most common medications for which TDM is performed. The aim of this review is to provide an overview of the indications for AED TDM, to provide key information for each individual AED in terms of the drug's prescribing indications, key pharmacokinetic characteristics, associated drug-drug pharmacokinetic interactions, and the value and the intricacies of TDM for each AED. The concept of the reference range is discussed as well as practical issues such as choice of sample types (total versus free concentrations in blood versus saliva) and sample collection and processing.

METHODS

The present review is based on published articles and searches in PubMed and Google Scholar, last searched in March 2018, in addition to references from relevant articles.

RESULTS

In total, 171 relevant references were identified and used to prepare this review.

CONCLUSIONS

TDM provides a pragmatic approach to epilepsy care, in that bespoke dose adjustments are undertaken based on drug concentrations so as to optimize clinical outcome. For the older first-generation AEDs (carbamazepine, ethosuximide, phenobarbital, phenytoin, primidone, and valproic acid), much data have accumulated in this regard. However, this is occurring increasingly for the new AEDs (brivaracetam, eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, piracetam, pregabalin, rufinamide, stiripentol, sulthiame, tiagabine, topiramate, vigabatrin, and zonisamide).

Brivaracetam population pharmacokinetics in children with epilepsy aged 1 month to 16 years

Purpose

The aims of the study were to develop a population pharmacokinetic model of orally administered brivaracetam in paediatric patients and to provide dosing suggestions.

Methods

Analysis included 600 brivaracetam plasma concentrations from a phase 2a study (NCT00422422; N01263) in 96 paediatric patients with epilepsy aged 1 month to 16 years, taking one to three concomitant antiepileptic drugs (AEDs). Pharmacokinetic analysis was performed using non-linear mixed effects modelling, and a stepwise covariate search was used to determine factors influencing brivaracetam clearance. Simulations were performed to investigate dosing regimens.

Results

The final model consisted of first-order absorption, single compartment distribution and first-order elimination components with allometric scaling of clearance and volume using lean body weight and fixed allometric exponents. Co-administration with phenobarbital or carbamazepine was associated with a 29% (95%CI 17%/39%) and 32% (22%/42%) decrease in exposure, respectively. Co-administration with valproate was associated with an 11% (1%/23%) increase in exposure. Simulations demonstrated that the majority of children were predicted to have an exposure similar to that in adults, using an age-independent dosing regimen of 2.0 mg/kg bid with a maximum of 100 mg bid for body weight >50 kg.

Conclusions

A paediatric dose adaptation of 2.0 mg/kg twice daily with a maximum of 100 mg twice daily for body weight >50 kg is predicted to ensure steady-state plasma concentrations in the same range as in adult patients receiving 100 mg twice daily (highest recommended dose). Data suggest no need to change brivaracetam dosing when used concomitantly with carbamazepine, phenobarbital or valproate.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-017-2230-6) contains supplementary material, which is available to authorized users.

The Impact of Anti-Epileptic Drugs on Growth and Bone Metabolism

Epilepsy is a common neurological disorder worldwide and anti-epileptic drugs (AEDs) are always the first choice for treatment. However, more than 50% of patients with epilepsy who take AEDs have reported bone abnormalities. Cytochrome P450 (CYP450) isoenzymes are induced by AEDs, especially the classical AEDs, such as benzodiazepines (BZDs), carbamazepine (CBZ), phenytoin (PT), phenobarbital (PB), and valproic acid (VPA). The induction of CYP450 isoenzymes may cause vitamin D deficiency, hypocalcemia, increased fracture risks, and altered bone turnover, leading to impaired bone mineral density (BMD). Newer AEDs, such as levetiracetam (LEV), oxcarbazepine (OXC), lamotrigine (LTG), topiramate (TPM), gabapentin (GP), and vigabatrin (VB) have broader spectra, and are safer and better tolerated than the classical AEDs. The effects of AEDs on bone health are controversial. This review focuses on the impact of AEDs on growth and bone metabolism and emphasizes the need for caution and timely withdrawal of these medications to avoid serious disabilities.

Initiating antiepileptic drug treatment and characteristics of drugs

This chapter covers the main steps involved in the initiation of antiepileptic drug therapy. Aspects covered specifically include the decision whether or not to initiate treatment, the selection process of a drug of first choice for a given patient with a particular seizure type or epilepsy syndrome, and the process of initiating therapy with the selected drug of first choice. Suggested choices of antiepileptic drugs by seizure type or epilepsy syndrome are summarized in a table. In an appendix, these drugs are reviewed individually with regard to their clinical use. The emphasis is on initial dose, dosage escalation, common and serious adverse effects, baseline evaluation, monitoring of therapy, and relevant drug interactions.

Identification and prevention of antiepileptic drug noncompliance: the collaborative use of state-supplied pharmaceutical data

Background. Antiepileptic drugs (AEDs) noncompliance is associated with increased risk of seizures and morbidity in seizure disorder patients. Objective. To identify risk factors that correlated to higher levels of morbidity, measured by emergency room (ER) utilization by seizure disorder members taking AED. Methods. Patients with primary or secondary diagnosis of seizures, convulsions, and/or epilepsy and prescribed AEDs during an 11-month period were included in the study. Variables were analyzed using multivariate statistical analysis including logistic regression. Results. The study identified 201 members. No statistical significance (NS) between age, gender, number of tablets, type of drug, or other risk factors was associated with increased mortality. Statistical significance resulted with medication compliance review of 0–14 days, 15–60 days, and 61+ days between refills. 68% of patients with ER visit had noncompliance refill between 0 and 14 days compared to 52% of patients in non-ER group (P = 0.04). Contrastingly, 15% of ER group had refills within 15–60 days compared with 33% of non-ER group (P = 0.01). There was NS difference between two groups when noncompliance was greater than 60 days (P = 0.66). Conclusions. The study suggests that careful monitoring of pharmaceutical refill information could be used to identify AED noncompliance in epileptic patients.

Therapeutic drug monitoring of antiepileptic drugs by use of saliva

Blood (serum/plasma) antiepileptic drug (AED) therapeutic drug monitoring (TDM) has proven to be an invaluable surrogate marker for individualizing and optimizing the drug management of patients with epilepsy. Since 1989, there has been an exponential increase in AEDs with 23 currently licensed for clinical use, and recently, there has been renewed and extensive interest in the use of saliva as an alternative matrix for AED TDM. The advantages of saliva include the fact that for many AEDs it reflects the free (pharmacologically active) concentration in serum; it is readily sampled, can be sampled repetitively, and sampling is noninvasive; does not require the expertise of a phlebotomist; and is preferred by many patients, particularly children and the elderly. For each AED, this review summarizes the key pharmacokinetic characteristics relevant to the practice of TDM, discusses the use of other biological matrices with particular emphasis on saliva and the evidence that saliva concentration reflects those in serum. Also discussed are the indications for salivary AED TDM, the key factors to consider when saliva sampling is to be undertaken, and finally, a practical protocol is described so as to enable AED TDM to be applied optimally and effectively in the clinical setting. Overall, there is compelling evidence that salivary TDM can be usefully applied so as to optimize the treatment of epilepsy with carbamazepine, clobazam, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, phenobarbital, phenytoin, primidone, topiramate, and zonisamide. Salivary TDM of valproic acid is probably not helpful, whereas for clonazepam, eslicarbazepine acetate, felbamate, pregabalin, retigabine, rufinamide, stiripentol, tiagabine, and vigabatrin, the data are sparse or nonexistent.

Characterization of the supplementary motor area syndrome and seizure outcome after medial frontal lobe resections in pediatric epilepsy surgery

BACKGROUND

In adults, resection of the medial frontal lobe has been shown to result in supplementary motor area (SMA) syndrome, a disorder characterized by transient motor impairment. Studies examining the development of SMA syndrome in children, however, are wanting.

OBJECTIVE

To characterize the development of SMA syndrome and to analyze seizure outcomes after surgery in the medial frontal lobe for medically intractable epilepsy.

METHODS

Thirty-nine patients with medically intractable epilepsy who underwent surgery in the medial frontal lobe were reviewed retrospectively. The progression of neurological impairment and seizure outcome after surgery was recorded, and the extent of cortex resected was analyzed.

RESULTS

After resection in the region of the SMA, 23 patients (59%) developed postoperative neurological impairment; 17 (74%) were identified as SMA syndrome. No neurological impairment was found after surgery in 16 patients (41%). Six patients (15%) experienced permanent neurological impairment. The majority of patients (82%) who developed SMA syndrome had resolution of their symptoms by 1 month postoperatively. Preoperative magnetic resonance imaging finding of lesional cases was associated with a significantly decreased likelihood of developing SMA syndrome (P = .02). Seizure outcome was favorable after surgery in most patients.

CONCLUSION

Surgery for medically intractable epilepsy in the region of the medial frontal cortex is effective and associated with reversible neurological impairment in children. All patients had resolution of their SMA syndrome by 6 months postoperatively.

Host factors affecting antiepileptic drug delivery-pharmacokinetic variability

Antiepileptic drugs (AEDs) are the mainstay in the treatment of epilepsy, one of the most common serious chronic neurological disorders. AEDs display extensive pharmacological variability between and within patients, and a major determinant of differences in response to treatment is pharmacokinetic variability. Host factors affecting AED delivery may be defined as the pharmacokinetic characteristics that determine the AED delivery to the site of action, the epileptic focus. Individual differences may occur in absorption, distribution, metabolism and excretion. These differences can be determined by genetic factors including gender and ethnicity, but the pharmacokinetics of AEDs can also be affected by age, specific physiological states in life, such as pregnancy, or pathological conditions including hepatic and renal insufficiency. Pharmacokinetic interactions with other drugs are another important source of variability in response to AEDs. Pharmacokinetic characteristics of the presently available AEDs are discussed in this review as well as their clinical implications.

Pharmacotherapy for children and adolescents with epilepsy

INTRODUCTION

Childhood epilepsies are the most frequent neurological problems that occur in children. Despite the introduction of new antiepileptic drugs (AEDs) 25-30% of children with epilepsy remain refractory to medical therapy.

AREAS COVERED

This review aims to highlight the main published data on the treatment of childhood epilepsy. The electronic database, PubMed, and abstract proceedings were used to identify studies. The aim of antiepileptic therapy should be to provide complete seizure control, if possible without the burden of any side effect. Since 1993, new agents have been approved for use as an antiepileptic. Although there are few published data (especially in pediatric populations) to establish that the second-generation AEDs are more efficacious than the older AEDs, they appear to have better tolerability.

EXPERT OPINION

Old AEDs are efficacious agents that continue to play a major role in the current treatment of epilepsy. These agents actually remain the first-line treatment for many specific seizure types or epileptic syndromes. The new AEDs were initially approved as adjunct agents and--subsequently--as monotherapy for various seizure types in the adult and children. Despite these improvements, few AEDs are now considered to be a first-choice for the treatment of epilepsy in children.

Oral health status in epileptic children

BACKGROUND

The aim of the present study was to evaluate the oral hygiene status and dental treatment requirements in children with epilepsy.

METHODS

The treatment group consisted of 211 children with epilepsy (120 boys and 91 girls, 4-15 years old, mean age 7.85 + or - 2.98 years). The control group consisted of healthy children, matched by age and gender. Clinical features of the patients were obtained from hospital records. Clinical examinations were conducted, under standard light, using a plane buccal mirror, a dental probe and air drying to evaluate caries experience and to record the periodontal health of each child. Statistical analysis was performed using chi(2) test, Fisher exact test and anova.

RESULTS

The number of decayed and missing teeth, the degree of abrasion and periodontal indexes were significantly worse in patients with epilepsy, compared to the control group (P < 0.001). Gingival enlargement was documented in 42% of patients on valproate monotherapy compared to only in 16% of patients on phenobarbital. Dental caries and halitosis were the most common oral disorders. Generalized tonic-clonic seizures often cause minor oral injuries and traumatized anterior teeth.

CONCLUSIONS

Epileptic children are at an increased risk of developing caries and gingivitis compared with healthy subjects.

New antiepileptic drugs in pediatric epilepsy

New antiepileptic drugs (AEDs), introduced since 1993, provide more diverse options in the treatment of epilepsy. Despite the equivalent efficacy and better tolerability of these drugs, more than 25% of patients remain refractory to treatment. Moreover, the issues for pediatric patients are different from those for adults, and have not been addressed in the development and application of the new AEDs. Recently published evidence-based treatment guidelines have helped physicians to choose the most reasonable AED, although they cannot fully endorse new AEDs because of the lack of well-designed, randomized controlled trials. We review the mechanisms of action, pharmacokinetic properties, adverse reactions, efficacy, and tolerability of eight new AEDs (felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, topiramate, vigabatrin, and zonisamide), focusing on currently available treatment guidelines and expert opinions regarding pediatric epilepsy.

Antiepileptic drugs--best practice guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies

Although no randomized studies have demonstrated a positive impact of therapeutic drug monitoring (TDM) on clinical outcome in epilepsy, evidence from nonrandomized studies and everyday clinical experience does indicate that measuring serum concentrations of old and new generation antiepileptic drugs (AEDs) can have a valuable role in guiding patient management provided that concentrations are measured with a clear indication and are interpreted critically, taking into account the whole clinical context. Situations in which AED measurements are most likely to be of benefit include (1) when a person has attained the desired clinical outcome, to establish an individual therapeutic concentration which can be used at subsequent times to assess potential causes for a change in drug response; (2) as an aid in the diagnosis of clinical toxicity; (3) to assess compliance, particularly in patients with uncontrolled seizures or breakthrough seizures; (4) to guide dosage adjustment in situations associated with increased pharmacokinetic variability (e.g., children, the elderly, patients with associated diseases, drug formulation changes); (5) when a potentially important pharmacokinetic change is anticipated (e.g., in pregnancy, or when an interacting drug is added or removed); (6) to guide dose adjustments for AEDs with dose-dependent pharmacokinetics, particularly phenytoin.

Value of therapeutic drug monitoring in epilepsy

Therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) has made it possible to study the individual variations in drug utilization, to reveal noncompliance in patients and for quality assurance aspects. Even if there is a shortage of data from randomized controlled studies concerning the effectiveness of using TDM as an aid to dosage adjustment, experience from nonrandomized investigations and long-lasting clinical experience have shown that TDM of both older and newer AEDs may be of clinical benefit if used appropriately. The main situations for TDM include: after starting treatment to provide a baseline steady-state concentration for further evaluation of an individual therapeutic concentration; after change in drug dosage, in particular when nonlinear kinetics apply; at therapeutic failure to sort out a pharmacokinetic explanation for uncontrolled seizures or side effects; in case of drug interactions; and when pharmacokinetic changes due to physiological or pathological changes are foreseen (e.g., age-dependent conditions [children, elderly], pregnancy, hepatic disease, renal disease or gastrointestinal conditions potentially affecting drug absorption) and change in drug formulation (brand name/generic). Recently, new terminology and definitions have been suggested by the International League Against Epilepsy. The reference range is a range of drug concentrations quoted by laboratories and is not a therapeutic range. Emphasis should be placed on the concept of an individual therapeutic concentration.