Levetiracetam in children with refractory epilepsy: lack of correlation between plasma concentration and efficacy

Application of Physiologically Based Pharmacokinetic Modeling to Characterize the Effects of Age and Obesity on the Disposition of Levetiracetam in the Pediatric Population

BACKGROUND

Levetiracetam is an antiseizure medication used for several seizure types in adults and children aged 1 month and older; however, due to a lack of data, pharmacokinetic (PK) variability of levetiracetam is not adequately characterized in certain populations, particularly neonates, children younger than 2 years of age, and children older than 2 years of age with obesity.

OBJECTIVE

This study aimed to address the gap by leveraging PK data from two prospective standard-of-care pediatric trials (n = 88) covering an age range from 1 month to 19 years, including those with obesity (64%), and applying a physiologically based PK (PBPK) modeling framework.

METHODS

A published PBPK model of levetiracetam for children aged 2 years and older was extended to pediatric patients younger than 2 years of age and patients older than 2 years of age with obesity by accounting for the obesity and age-related changes in PK using PK-Sim® software. The prospective pediatric data, along with the literature data for neonates and children younger than 2 years of age, were used to evaluate the extended PBPK models.

RESULTS

Overall, 82.4% of data fell within the 90% interval of model-predicted concentrations, with an average fold error within twofold of the accepted criteria. PBPK modeling revealed that children with obesity had lower weight-normalized clearances (0.053 L/h/kg) on average than children without obesity (0.063 L/h/kg). The effect of maturation was well-characterized, resulting in comparable PBPK-simulated, weight-normalized clearances for neonates and children younger than 2 years of age reported from the literature.

CONCLUSIONS

PBPK modeling simulations revealed that the current US FDA-labeled pediatric dosing regimen listed in the prescribing information can produce the required exposure of levetiracetam in these target populations with dose adjustments for children with obesity aged 4 years to younger than 16 years.

Therapeutic drug monitoring and the therapeutic reference range of levetiracetam for Chinese patients: Problems and issues

BACKGROUND

Levetiracetam (LEV) is widely used in the clinical monotherapy or multi-drug combination treatment of seizures due to its good tolerability and efficacy. Due to a lack of large-scale clinical studies, the relationship between levetiracetam concentrations, disease activity and adverse is unclear, limiting the usefulness of therapeutic drug monitoring (TDM) based LEV plasma levels. This study was intended to investigate factors influencing the pharmacokinetics of and the appropriate reference range of LEV concentration using available LEV TDM data.

METHODS

A rapid, accurate and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) method was established to determine LEV plasma concentrations. In this study, the levetiracetam plasma concentration monitoring data from 352 samples (taken from 248 patients) were used to explore the relationship between levetiracetam dose, age, combined administration with other antiseizure medications in patients with epilepsy.

RESULTS

Age and combined administration emerged as important affecting factors for the correlation of LEV concentration and dose. The correlation between concentration and dose was better in monotherapy. Combined administration may affect LEV concentration, especially when LEV is combined with oxcarbazepine, which might decrease the LEV concentration.

CONCLUSION

These findings emphasize the need to monitor LEV routinely LEV, especially among children and older adults when other antiseizure comedications are prescribed in the treatment regimen. LEV TDM is a well-established tool for the management of patients with epilepsy.

The Pharmacokinetics of Crushed Levetiracetam Tablets Administered to Neonates

BACKGROUND

Intravenous phenobarbital remains the first-line therapy in the management of neonatal seizures. Shortages of intravenous phenobarbital in South Africa necessitated the addition of oral levetiracetam as part of management of neonatal seizures.

OBJECTIVE

We evaluated the pharmacokinetics of crushed immediate-release levetiracetam tablets administered to neonates to terminate seizures.

METHODS

A prospective, observational study of neonates admitted with seizures to Tygerberg Hospital. Participants received crushed levetiracetam (diluted in saline) given orally or via naso-/orogastric tube. At steady-state, pharmacokinetic sampling was performed at pre-dose, 1.5, 2.5 and 4 h post-dose. Maximum concentration (Cmax), time to Cmax (Tmax), trough concentrations (Ctrough) and area under the concentration-time curve (AUC0-12) were calculated using non-compartmental analysis. Seizure termination and safety profiles were documented.

RESULTS

Nineteen participants were grouped into three dosing ranges: (i) 5-15 mg/kg/12-hourly, (ii) 15-25 mg/kg/12-hourly and (iii) 25-35 mg/kg/12-hourly. Range 1 demonstrated AUC0-12 167.0 ± 45.6 h*μg/mL, Cmax 19.19 ± 4.12 μg/mL and Ctrough 9.99 ± 3.86 µg/mL. Range 2, AUC0-12 316.5 ± 108.4 h*μg/mL, Cmax 35.12 ± 10.54 µg/mL and Ctrough 19.25 ± 8.48 µg/mL. Range 3, AUC0-12 290.9 (range 176.14-405.59) h*μg/mL, Cmax 36.11 (range 27.58-44.64) µg/mL and Ctrough 13.03 (2.98-23.07) µg/mL. Seizures terminated in 17/19 (90%) neonates by day 3 and 19/19 (100%) by day 4 post-levetiracetam initiation.

CONCLUSION

Crushed levetiracetam has comparable pharmacokinetics to historical data. No pharmacokinetic differences were observed between oral vs. naso-/orogastric administration. Crushed levetiracetam tablets can be considered for neonates in low-resource settings where intravenous and syrup access is limited.

LAY SUMMARY

Intravenous preparations of antiepileptic medications are used in the management of neonatal seizures. Various established standard of care intravenous antiepileptic medicines are unavailable nationally and internationally due to reasons outside our control. This stock shortage included intravenous phenobarbitone which is the first-line treatment for paediatric seizures. Due to phenobarbital shortage, levetiracetam has been identified by the neonatologists at Tygerberg Hospital, Cape Town, South Africa, as a suitable treatment option due to its efficacy and safety profile. However, intravenous levetiracetam and oral syrup is not registered in South Africa. Levetiracetam tablets are being crushed, dissolved and administered to neonates. There are no data available on the absorption of crushed levetiracetam tablets administered to neonates via a nasogastric tube. This study characterized the pharmacokinetic profile of crushed levetiracetam administered to neonates. We selected neonates receiving levetiracetam from the neonatal wards at Tygerberg hospital and drew blood to analyse the levetiracetam concentrations at 4 different time points. We found that the overall exposure of crushed levetiracetam tablets were comparable to the exposures achieved in historical data of the unaltered formulations. We concluded that crushed levetiracetam tablets can be considered for neonates in low resource settings where intravenous and syrup access is limited.

The efficacy of levetiracetam for focal seizures and its blood levels in children

AIM

To evaluate the efficacy of levetiracetam (LEV) and the usefulness of measurement of its blood levels during the follow-up of patients with focal seizures.

METHODS

Twenty-four patients (13 cases without impairment of consciousness or awareness and 11 cases with them or evolving to a bilateral, convulsive seizure) treated with LEV had their peak blood levels measured. The blood concentrations were measured at 2 weeks, 1 year and 2 years after reaching the LEV maintenance dosage. The efficacy of LEV was evaluated with repeated blood sampling to determine the seizure reduction rate. The patients were classified as effective cases (seizure reduction rate>50%) and ineffective cases (⩽50%).

RESULTS

In Japanese children treated with LEV, the dosage and blood level showed positive correlations. The blood levels were higher in effective cases than in ineffective cases at all time points (p<0.05). In effective cases, the blood concentration was 23.26±6.88 μg/mL (mean±SD) 2 weeks later, 23.59±8.23 μg/mL 1 year later, and 24.46±7.57 μg/mL 2 years later. However, the blood levels and efficacies showed positive correlations only at 2 weeks and 1 year later. No patients had any side effects.

CONCLUSIONS

No precise definition of the therapeutic range was possible because of the incomplete correlation between the blood level and seizure frequency. Instead of a therapeutic range, we recommend an optimal range for LEV of 20-30 μg/mL as a therapeutic target without any side effects.

Correlation between efficacy of levetiracetam and serum levels among children with refractory epilepsy

BACKGROUND

Levetiracetam is used as adjunctive therapy in various types of seizures. Studies evaluating the effect of levetiracetam on children with refractory epilepsy are scarce. The aim of this study was to evaluate the correlation between serum concentration of levetiracetam and either efficacy or tolerability in children with refractory epilepsy, and to determine the value of levetiracetam blood level monitoring.

METHODS

Medical records of 50 children with refractory epilepsy treated with levetiracetam and regularly followed at Assaf Harofeh Medical Center were retrospectively reviewed. Trough serum levetiracetam concentration was determined using high-performance liquid chromatography and correlated with the administered dose and clinical report.

RESULTS

No correlation between levetiracetam serum levels and clinical efficacy, tolerability or administered dosage was found. The average dose of levetiracetam was 43.7 ± 20.0 (range 14-100) mg/kg/day and the average serum concentration was 16.0 ± 9.5 (range 2.5-38.5) μg/mL. Forty-five patients (95%) had more than a 50% reduction of seizure frequency, with 22 (44%) patients becoming seizure-free for at least 6 months. Adverse events related to levetiracetam were reported in 15 (30%) patients. No correlation between serum concentrations and adverse events was found. These results were not affected by gender, age, type of seizure, and other drugs.

CONCLUSIONS

Determination of serum concentration is not needed in all children treated with levetiracetam. Serum concentrations may be valuable either in patients with refractory epilepsy for compliance evaluation or in patients with satisfactory control of seizures for determination of their therapeutic baseline.

Levetiracetam in neonatal seizures: a review

Phenobarbital and phenytoin have been the mainstay treatment modalities for neonatal seizures. Studies have revealed these agents control seizures in less than half of neonates, can cause neuronal apoptosis in vitro, and have highly variable pharmacokinetics in neonates. In contrast, there have been no reports of levetiracetam causing these neurotoxic effects. Due to its favorable side effect and pharmacokinetic profiles and positive efficacy outcomes in neonatal studies to date, there is great interest in the use of levetiracetam for neonatal seizures. This article reviews the literature regarding the safety of levetiracetam in neonates and its efficacy in neonatal seizures.

Efficacy and safety of IV levetiracetam in children with acute repetitive seizures

BACKGROUND

Levetiracetam has been proven to be effective in both partial and generalized seizures in children. However, few studies have reported its efficacy in the treatment of acute repetitive seizures. We aimed to investigate the efficacy and safety of levetiracetam in children with acute repetitive seizures.

METHODS

The medical records of children from the age of 1 month-18 years who received levetiracetam because of acute repetitive seizures in the pediatric intensive care unit between 2010 and 2013 were reviewed retrospectively.

RESULTS

Of the 133 patients, levetiracetam terminated seizures in 104 (78.2%). Side effects such as agitation and aggression were observed in three patients (2.2%). The likelihood of treatment failure was increased by four times by younger age at seizure onset; by six times in the individuals with neurological abnormalities; and by 22 times in the patients with West syndrome. The patients who used levetiracetam as the first treatment option for acute repetitive seizures had a longer duration of epilepsy, a higher rate of neurological abnormality, and a higher proportion of medically resistant epilepsy compared with the individuals who used levetiracetam as an add-on treatment to the other intravenous antiepileptic drugs. However, no differences were detected between these two groups in terms of treatment response.

CONCLUSIONS

Intravenous levetiracetam appears to be effective and safe in the treatment of acute repetitive seizures. Randomized clinical trials are needed to determine whether intravenous levetiracetam may replace other antiepileptic drugs as the first-line therapy in the management of acute repetitive seizures.

Levetiracetam use in the critical care setting

Intravenous (IV) levetiracetam (LEV) is currently approved as an alternative or replacement therapy for patients unable to take the oral form of this antiepileptic drug (AED). The oral form has Food and Drug Administration (FDA) indications for adjunctive therapy in the treatment of partial onset epilepsy ages 1 month or more, myoclonic seizures associated with juvenile myoclonic epilepsy starting with the age of 12 and primary generalized tonic-clonic seizures in people 6 years and older. Since the initial introduction, oral and IV LEV has been evaluated in various studies conducted in the critical care setting for the treatment of status epilepticus, stroke-related seizures, seizures following subarachnoid or intracerebral hemorrhage, post-traumatic seizures, tumor-related seizures, and seizures in critically ill patients. Additionally, studies evaluating rapid infusion of IV LEV and therapeutic monitoring of serum LEV levels in different patient populations have been performed. In this review we present the current state of knowledge on LEV use in the critical care setting focusing on the IV uses and discuss future research needs.

Safety and efficacy of levetiracetam for the treatment of partial onset seizures in children from one month of age

Epilepsy is a common neurological disorder in the pediatric population, affecting up to one percent of children, and for which the mainstay of treatment is anticonvulsant medication. Despite the frequent use of anticonvulsant drugs, remarkably little is known about the safety and efficacy of most of these medications in the pediatric epilepsy population. Of 34 anticonvulsants currently approved for use by the US Food and Drug Administration (FDA), only 13 have been approved for use in children. Although infants and young children are disproportionately affected by epilepsy, there are currently only three anticonvulsant medications that have been specifically evaluated and approved for use in children younger than 2 years of age. In 2012, the FDA approved levetiracetam as an adjunctive treatment for partial onset seizures in infants and children from one month of age. Here we review the available data on levetiracetam in the pediatric epilepsy population. We first discuss the pharmacological profile of levetiracetam, including its mechanism of action, formulations and dosing, and pharmacokinetics in children. We then review the available efficacy, safety, and tolerability data in children from one month of age with partial onset seizures. We conclude that the current data leading to the approval of levetiracetam for use in infants and children with partial onset seizures is encouraging, although more work needs to be done before definitive conclusions can be drawn about the efficacy of levetiracetam across different pediatric age groups.

Levetiracetam for treatment of neonatal seizures

Neonatal seizures are often refractory to treatment with initial antiseizure medications. Consequently, clinicians turn to alternatives such as levetiracetam, despite the lack of published data regarding its safety, tolerability, or efficacy in the neonatal population. We report a retrospectively identified cohort of 23 neonates with electroencephalographically confirmed seizures who received levetiracetam. Levetiracetam was considered effective if administration was associated with a greater than 50% seizure reduction within 24 hours. Levetiracetam was initiated at a mean conceptional age of 41 weeks. The mean initial dose was 16 ± 6 mg/kg and the mean maximum dose was 45 ± 19 mg/kg/day. No respiratory or cardiovascular adverse effects were reported or detected. Levetiracetam was associated with a greater than 50% seizure reduction in 35% (8 of 23), including seizure termination in 7. Further study is warranted to determine optimal levetiracetam dosing in neonates and to compare efficacy with other antiseizure medications.