Therapeutic Drug Monitoring of Newer Antiepileptic Drugs: A Randomized Trial for Dosage Adjustment

A Simulation-Based Assessment of Levetiracetam Concentrations Following Fixed and Weight-Based Loading Doses: A Meta-Regression and Pharmacokinetic Modeling Analysis

Current recommendations for refractory status epilepticus (SE) unresponsive to benzodiazepines suggest a loading dose of levetiracetam (LEV) of 60 mg/kg to a maximum of 4500 mg. LEV therapeutic drug monitoring can help guide therapy and is garnering increasing attention. The objective of this study is to simulate the probability of target attainment (PTA) of fixed dose and weight-based loading doses of LEV with respect to established therapeutic target concentrations. Meta-regression of the current literature was performed to evaluate the relationship between intravenous LEV loading dose and seizure cessation in refractory SE patients. A previously published pharmacokinetic model was used to simulate the PTA capacity of competing single intravenous dosing schemes (fixed vs weight-based dosing) to achieve maximum (Cpeak) and 12-h (C12h) plasma concentrations that exceed 12 mg/L. The meta-regression indicated that dosage was not a statistically significant modulator of seizure control at dosages between 20 and 60 mg/kg. Stochastic simulations showed all dosing schemes achieved plasma Cpeak >12 mg/L, but C12h levels were <12 mg/L in subjects over 60 kg with a fixed dose ≤2000 mg or in subjects <60 kg with a weight-based dose <30 mg/kg. Dosages of 40 and 60 mg/kg provided ≥90% PTAs across all weights. Using a weight-based loading dose of 40 mg/kg, up to a suggested maximum of 4500 mg, improves the likelihood of achieving a sustained therapeutic drug concentration after the initial LEV dose, whereas fixed <3000 mg may not achieve the desired concentration before maintenance dosing.

Value of drug level concentrations of brivaracetam, lacosamide, and perampanel in care of people with epilepsy

OBJECTIVE

The aim of this study was to determine whether clinical efficacy and reported adverse effects (AEs) of the newer antiseizure medications (ASMs) brivaracetam (BRV), lacosamide (LCM), and perampanel (PER) have been associated with plasma levels of these ASMs. We also investigated whether plasma levels outside the reference range has led to dose adjustments.

METHODS

Plasma levels of 300 people with epilepsy (PWE) seen at our tertiary epilepsy center were determined by liquid chromatography-tandem mass spectrometry. PWE received BRV (n = 100), LCM (n = 100), or PER (n = 100), in most cases in polytherapy. Demographic and clinical data were retrospectively analyzed and related to plasma levels. Clinical efficacy of BRV, LCM, or PER was assessed retrospectively by comparing seizure frequency at the time of current blood draw with seizure frequency at the time of first administration. AEs were also recorded and, if reported, compared retrospectively with the time of first administration.

RESULTS

No significant associations were found between plasma levels of BRV, LCM, or PER and seizure freedom (BRV, p = 1.000; LCM, p = .243; PER, p = .113) or responder status (BRV, p = .118; LCM, p = .478; PER, p = .069) at presentation. There was also no pattern between plasma levels and the occurrence of AEs. In the majority of cases, drug levels outside the reference ranges have not led to adjustments in the daily doses of BRV (93.5%), LCM (93.9%), or PER (89.1%).

SIGNIFICANCE

Plasma levels at a given time point did not allow conclusions to be drawn about seizure control or the occurrence of AEs. Our findings indicate that efficacy and tolerability cannot be predicted based on averaged data from a single plasma measurement due to high interindividual variability. Instead, individual reference values should be established when sufficient clinical data are available, in line with the 2008 International League Against Epilepsy position paper on therapeutic drug monitoring.

Clinical impact of therapeutic drug monitoring for newer anti-seizure medications in patients with epilepsy: A real-world observation study

BACKGROUND

The clinical value of therapeutic drug monitoring (TDM) for newer anti-seizure medications (ASMs) remains uncertain. This study aimed to assess the impact of newer ASM TDM on clinical decision making in patients with epilepsy.

METHODS

We retrospectively identified all plasma requests for newer ASM level measurement as part of routine clinical management in the outpatient departments of seven medical institutes across Taiwan between September 2016 and May 2019. Data collected from reviewed medical records included clinical and medication details, indications for TDM request, test results, interpretation, and impact on patient management.

RESULTS

A total of 682 visits with 1051 plasma samples were included. The most frequently analyzed ASMs were levetiracetam (36.1%), oxcarbazepine (18.4%), and lamotrigine (12.0%). Reasons for TDM included poorly controlled seizures (55.3%), concerns about drug-drug interactions (12.3%), and suspicion of drug overdose (10.6%). 68.8% of samples were within the orienting therapeutic range, even for patients with poorly controlled seizures. TDM for non-adherence concerns showed 54.3% below the orienting therapeutic range, while ASM-related adverse events assessment only 8.9% showed levels exceeding the orienting therapeutic range. Following TDM results, 64.2% of cases had medication adjustments, mainly dosage increases. Overall, 55.9% of newer ASM TDM visit showed improved outcomes, including reduced seizures (47.5%) and fewer ASM-related side effects (8.4%).

CONCLUSIONS

These findings suggest that appropriate utilization of TDM for newer ASMs provides clinical benefits in adjunct to complement clinical decision making in the management of epilepsy patients in a real-world clinical setting.

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.

Precision Oncology by Point-of-Care Therapeutic Drug Monitoring and Dosage Adjustment of Conventional Cytotoxic Chemotherapies: A Perspective

Therapeutic drug monitoring (TDM) of conventional cytotoxic chemotherapies is strongly supported yet poorly implemented in daily practice in hospitals. Analytical methods for the quantification of cytotoxic drugs are instead widely presented in the scientific literature, while the use of these therapeutics is expected to keep going for longer. There are two main issues hindering the implementation of TDM: turnaround time, which is incompatible with the dosage profiles of these drugs, and exposure surrogate marker, namely total area under the curve (AUC). Therefore, this perspective article aims to define the adjustment needed from current to efficient TDM practice for cytotoxics, namely point-of-care (POC) TDM. For real-time dose adjustment, which is required for chemotherapies, such POC TDM is only achievable with analytical methods that match the sensitivity and selectivity of current methods, such as chromatography, as well as model-informed precision dosing platforms to assist the oncologist with dose fine-tuning based on quantification results and targeted intervals.

Zonisamide-induced distal renal tubular acidosis and critical hypokalaemia

A woman in her 20s presented with rapidly progressive muscle weakness and a 1-month preceding history of fatigability, nausea and vomiting. She was found to have critical hypokalaemia (K+ 1.8 mmol/L), a prolonged corrected QT interval (581 ms) and a normal anion gap metabolic acidosis (pH 7.15) due to zonisamide-induced distal (type 1) renal tubular acidosis. She was admitted to the intensive care unit for potassium replacement and alkali therapy. Clinical and biochemical improvement ensued, and she was discharged after a 27-day inpatient stay.

Increasing use of newer antiseizure medication during pregnancy: An observational study with special focus on lacosamide

INTRODUCTION

Epilepsy is a common neurological disease requiring long-term therapy also during pregnancy. Most studies on pregnancy outcomes in women with epilepsy are based on antiseizure medication (ASM) in monotherapy. However, about 20-30% of epilepsy patients require polytherapy and newer ASMs are an option, when seizure control is not achieved with first line ASMs.

METHODS

Observational study evaluating the use of newer ASMs with marketing authorization since 2005 reported to the Embryotox Center of Clinical Teratology and Drug Safety in Pregnancy between 2004 and 2019. In addition, course and outcome of lacosamide exposed pregnancies were analysed.

RESULTS

Our study confirms the increasing use of newer ASMs also in pregnant women. This is especially true for lacosamide, eslicarbazepine and brivaracetam with rising numbers of exposed pregnancies soon after marketing authorization. Analysis of 55 prospectively and 10 retrospectively ascertained lacosamide exposed pregnancies does not indicate increased risks of major birth defects or spontaneous abortion. However, bradycardia observed in 3 neonates might be related to prenatal lacosamide exposure.

CONCLUSION

Available data do not support the assumption of lacosamide being a major teratogen. The increasing use of newer ASMs during pregnancy underscores the need for more studies to guide preconception counselling, especially for lacosamide, eslicarbazepine and brivaracetam.

Microneedle-based interstitial fluid extraction for drug analysis: Advances, challenges, and prospects

Similar to blood, interstitial fluid (ISF) contains exogenous drugs and biomarkers and may therefore substitute blood in drug analysis. However, current ISF extraction techniques require bulky instruments and are both time-consuming and complicated, which has inspired the development of viable alternatives such as those relying on skin or tissue puncturing with microneedles. Currently, microneedles are widely employed for transdermal drug delivery and have been successfully used for ISF extraction by different mechanisms to facilitate subsequent analysis. The integration of microneedles with sensors enables in situ ISF analysis and specific compound monitoring, while the integration of monitoring and delivery functions in wearable devices allows real-time dose modification. Herein, we review the progress in drug analysis based on microneedle-assisted ISF extraction and discuss the related future opportunities and challenges.

[Interactions between anti-seizure medications and recommendations for combination treatment]

Pharmacotherapy is the most important pillar in the treatment of epilepsies. In approximately 50% of epilepsy patients monotherapy with anti-seizure medications (ASM) is insufficient. The knowledge of specific drug interactions in combination therapies is essential to recognize and avoid adverse side effects up to relevant therapy risks, including loss of efficiency and intoxication. Interactions can be of a pharmacokinetic or pharmacodynamic nature. Some effects of interactions in combination therapies can also be advantageous. Therapeutic drug monitoring in serum is not necessary for all ASMs and should be used rationally: however, it should be performed consistently if the indications are present. This review article provides fundamental knowledge about the most relevant interactions between ASMs and the indications for therapeutic drug monitoring.

Antiseizure medications (antiepileptic drugs) in adults: starting, monitoring and stopping

Up to 10% of people living to 80 years of age have one or more seizures; and many will not require anti-seizure medication (ASMs). In 85% of patients, the diagnosis comes from the history of the index event. One-third of patients with an apparent "first seizure" have previous events, changing their diagnosis to epilepsy. Targeted investigations are important for classification and risk prediction. Patients with a low risk of seizure recurrence are not usually offered ASM treatment. High-risk patients have multiple seizures, neurological deficits, intellectual disability and/or relevant abnormal investigations; and are offered ASMs. Individual factors modulate this decision-making. Future integrated technologies offer the game-changing potential for seizure monitoring and prediction, but are not yet robust, convenient or affordable. Therapeutic drug monitoring in patients taking ASMs may confirm ASM toxicity, or when non-adherence, malabsorption, or rapid metabolism are suspected causes of breakthrough seizures. They are less useful when these factors are intermittent or irregular. Current evidence does not favour routine monitoring of serum levels, as it neither reliably predicts control, relapse, or adverse effects. The decision to discontinue ASM should follow a full discussion with the patient of risks and benefits. Along with population risk factors for seizure recurrence, the patient's lifestyle and preferences must be considered. ASM are usually discontinued in a slow step-wise fashion, one at a time, after at least two years of remission. Seizure recurrence risk plateaus only after 2 years following ASM discontinuation, and patients need access to specialist follow-up over that period.

Treatment-emergent adverse events and antiseizure medication actual drug load

OBJECTIVE

The correlation between treatment-emergent adverse events (TEAE) and antiseizure medication (ASM) drug load is a controversial topic. Previous studies used daily defined dosage (DDD) to measure drug load. We aim to assess if ASM adjusted to body weight and plasma levels were associated with TEAE.

METHODS

We analyzed clinical visits of a trial on therapeutic drug monitoring in outpatients with epilepsy. TEAE, treatment, and its changes, as well as ASM plasma levels, were recorded at each visit. Each medication level was stratified according to its position in relation to its proposed reference range (below, in the lower half, upper half, or above).

RESULTS

We analyzed 424 visits (151 participants). Treatment-emergent adverse events were reported in 84 (20%) visits. There was no significant difference when comparing visits with TEAE with those without TEAE in terms of ASM drug load (calculated with DDD), corrected for body weight, their changes since the last visit, as well as summed plasma levels compared to reference ranges.

SIGNIFICANCE

Actual drug load seems not to represent a major determinant of TEAE recorded during routine visits, even when accounting thoroughly for the patient's exposure to the treatment. The use of structured questionnaires and neuropsychometric tests may assess more accurately the potential consequences of drug loads.

An LC-ESI-MS/MS assay for the therapeutic drug monitoring of 15 anti-seizure medications in plasma of children with epilepsy

Oral anti-seizure medications (ASMs) is the preferred option for the clinical treatment of epilepsy. Therapeutic Drug Monitoring (TDM) has become an important means of individualized treatment of epilepsy. A sensitive, accurate and rapid LC-ESI-MS/MS method was developed and validated for the simultaneous determination of 15 ASMs in human plasma (carbamazepine, gabapentin, prebaglin, phenytoin, zonisamide, oxcarbazepine, tiagabine, lamotrigine, topiramate, phenobarbital, lacosamide, primidone, 10,11-dihydro-10-hydroxycarbamazepine, ethosuximide, and levetiracetam). The sample preparation procedure was an one-step protein precipitation with methanol (MeOH). The mass detection was performed in ionization polarity switching mode (positive-negative-positive) using multiple reaction monitoring mode. A "boot-shaped" gradient elution program was applied to separate and concentrate those target analytes resulting in symmetrical peak shapes within 10 min, without endogenous interference. The method showed great linearity over their concentration ranges with acceptable correlation coefficients (0.9966~0.9996). The precision and accuracy values for intra- and inter-assays were within ±15%. Consequently, the method was successfully implemented on pediatric patients undergoing mono- or polytherapy for epilepsy and provided timely concentration results to ordering clinicians.

Brivaracetam and Levetiracetam Suppress Astroglial L-Glutamate Release through Hemichannel via Inhibition of Synaptic Vesicle Protein

To explore the pathophysiological mechanisms of antiseizure and adverse behavioural/psychiatric effects of brivaracetam and levetiracetam, in the present study, we determined the effects of brivaracetam and levetiracetam on astroglial L-glutamate release induced by artificial high-frequency oscillation (HFO) bursts using ultra-high-performance liquid chromatography. Additionally, the effects of brivaracetam and levetiracetam on protein expressions of connexin43 (Cx43) and synaptic vesicle protein 2A (SV2A) in the plasma membrane of primary cultured rat astrocytes were determined using a capillary immunoblotting system. Acutely artificial fast-ripple HFO (500 Hz) burst stimulation use-dependently increased L-glutamate release through Cx43-containing hemichannels without affecting the expression of Cx43 or SV2A in the plasma membrane, whereas acute physiological ripple HFO (200 Hz) stimulation did not affect astroglial L-glutamate release or expression of Cx43 or SV2A. Contrarily, subchronic ripple HFO and acute pathological fast-ripple HFO (500 Hz) stimulations use-dependently increased L-glutamate release through Cx43-containing hemichannels and Cx43 expression in the plasma membrane. Subchronic fast-ripple HFO-evoked stimulation produced ectopic expression of SV2A in the plasma membrane, but subchronic ripple HFO stimulation did not generate ectopic SV2A. Subchronic administration of brivaracetam and levetiracetam concentration-dependently suppressed fast-ripple HFO-induced astroglial L-glutamate release and expression of Cx43 and SV2A in the plasma membrane. In contrast, subchronic ripple HFO-evoked stimulation induced astroglial L-glutamate release, and Cx43 expression in the plasma membrane was inhibited by subchronic levetiracetam administration, but was not affected by brivaracetam. These results suggest that brivaracetam and levetiracetam inhibit epileptogenic fast-ripple HFO-induced activated astroglial transmission associated with hemichannels. In contrast, the inhibitory effect of therapeutic-relevant concentrations of levetiracetam on physiological ripple HFO-induced astroglial responses probably contributes to the adverse behavioural/psychiatric effects of levetiracetam.

Pregabalin add-on for drug-resistant focal epilepsy

BACKGROUND

This is an updated version of the Cochrane Review last published in Issue 7, 2019; it includes two additional studies. Epilepsy is a common neurological disease that affects approximately 1% of the UK population. Approximately one-third of these people continue to have seizures despite drug treatment. Pregabalin is one of the newer antiepileptic drugs that has been developed to improve outcomes. In this review we summarised the current evidence regarding pregabalin when used as an add-on treatment for drug-resistant focal epilepsy.

OBJECTIVES

To assess the efficacy and tolerability of pregabalin when used as an add-on treatment for drug-resistant focal epilepsy.

SEARCH METHODS

For the latest update we searched the following databases on 16 November 2020: Cochrane Register of Studies (CRS Web), and MEDLINE (Ovid, 1946 to 16 November 2020). CRS Web includes randomised or quasi-randomised, controlled trials from PubMed, Embase, ClinicalTrials.gov, the World Health Organisation International Clinical Trials Registry Platform (ICTRP), the Cochrane Central Register of Controlled Trials (CENTRAL), and the Specialised Registers of Cochrane Review Groups, including Epilepsy. We imposed no language restrictions. We contacted the manufacturers of pregabalin and authors in the field to identify any relevant unpublished studies.

SELECTION CRITERIA

We included randomised controlled trials comparing pregabalin with placebo or an alternative antiepileptic drug as an add-on for people of any age with drug-resistant focal epilepsy. Double-blind and single-blind trials were eligible for inclusion. The primary outcome was 50% or greater reduction in seizure frequency; secondary outcomes were seizure freedom, treatment withdrawal for any reason, treatment withdrawal due to adverse effects, and proportion of individuals experiencing adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and extracted the relevant data. Primary analyses were intention-to-treat (ITT). We presented summary risk ratios (RRs) and odds ratios (ORs) with 95% confidence intervals (CIs). We evaluated dose response in regression models. We carried out a risk of bias assessment for each included study using the Cochrane risk of bias tool and assessed the overall certainty of evidence using the GRADE approach.

MAIN RESULTS

We included 11 randomised controlled trials (3949 participants). Nine trials compared pregabalin to placebo. For the primary outcome, participants randomised to pregabalin were significantly more likely to attain a 50% or greater reduction in seizure frequency compared to placebo (RR 1.95, 95% CI 1.40 to 2.72, 9 trials, 2663 participants, low-certainty evidence). The odds of response doubled with an increase in dose from 300 mg/day to 600 mg/day (OR 1.99, 95% CI 1.74 to 2.28), indicating a dose-response relationship. Pregabalin was significantly associated with seizure freedom (RR 3.94, 95% CI 1.50 to 10.37, 4 trials, 1125 participants, moderate-certainty evidence). Participants were significantly more likely to withdraw from pregabalin treatment than placebo for any reason (RR 1.33, 95% CI 1.10 to 1.60; 9 trials, 2663 participants; moderate-certainty evidence) and for adverse effects (RR 2.60, 95% CI 1.86 to 3.64; 9 trials, 2663 participants; moderate-certainty evidence). Three trials compared pregabalin to three active-control drugs: lamotrigine, eventrate and gabapentin. Participants allocated to pregabalin were significantly more likely to achieve a 50% or greater reduction in seizure frequency than those allocated to lamotrigine (RR 1.47, 95% CI 1.03 to 2.12; 1 trial, 293 participants) but not those allocated to eventrate (RR 0.94, 95% CI 0.80 to 1.11; 1 trial, 509 participants) or gabapentin (RR 0.96, 95% CI 0.82 to 1.12; 1 trial, 484 participants). We found no significant differences between pregabalin and lamotrigine for seizure freedom (RR 1.39, 95% CI 0.40 to 4.83). However, significantly fewer participants achieved seizure freedom with add-on pregabalin compared to eventrate (RR 0.50, 95% CI 0.30 to 0.85). No data were reported for this outcome for pregabalin versus gabapentin. We detected no significant differences in treatment withdrawal rate for any reason or due to adverse effects, specifically, during either pooled analysis or subgroup analysis. Ataxia, dizziness, somnolence, weight gain, headache and fatigue were significantly associated with pregabalin than in active control. We rated the overall risk of bias in the included studies as low or unclear due to the possibility of publication bias and lack of methodological details provided. We assessed all the studies to be at a high risk of funding bias as they were all sponsored by Pfizer. We rated the certainty of the evidence as very low to moderate using the GRADE approach.

AUTHORS' CONCLUSIONS

For people with drug-resistant focal epilepsy, pregabalin when used as an add-on treatment was significantly more effective than placebo at producing a 50% or greater seizure reduction and seizure freedom. Results demonstrated efficacy for doses from 150 mg/day to 600 mg/day, with increasing effectiveness at 600 mg doses, although there were issues with tolerability at higher doses. However, the trials included in this review were of short duration, and longer-term trials are needed to inform clinical decision-making. This review focused on the use of pregabalin in drug-resistant focal epilepsy, and the results cannot be generalised to add-on treatment for generalised epilepsies. Likewise, no inference can be made about the effects of pregabalin when used as monotherapy.

Plasma lacosamide monitoring in children with epilepsy: Focus on reference therapeutic range and influencing factors

BACKGROUND

Lacosamide (LCM) is a newer anti-seizure medication (ASM) that was approved in China in 2018, but its real-world clinical data and plasma concentrations in Chinese children with epilepsy are very limited. Of note, the reference range for routine LCM therapeutic drug monitoring is still unknown. The purpose of this study was to investigate the efficacy and safety of LCM as a monotherapy or an adjunctive treatment with other ASMs and to evaluate the potential factors affecting its efficacy and variable LCM plasma concentrations in Chinese children with epilepsy.

METHODS

Children with epilepsy (<18 years) with routine plasma LCM monitoring from March 2019 to December 2021 at the Department of Pharmacy, Children's Hospital of Nanjing Medical University were retrospectively collected. Clinical data were obtained from the hospital information system.

RESULTS

76 pediatric patients (52 males) were finally enrolled. Mean age was 7.9 years (1.3-17.3 years) with a mean dose of LCM 6.3 mg/kg/day (2.0-11.3 mg/kg/day). The TDM data as a whole showed that the median plasma trough concentration (C ₀) was 3.42 μg/mL (1.25-8.31 μg/mL). A 6-month LCM add-on therapy produced 70% of patients achieving ≥50% seizure frequency reductions, and the number was 81% for the one-year follow-up findings. Interestingly, more patients who took LCM monotherapy achieved seizure freedom over the same periods of follow-up observations. Under maintenance dosages, approximately 92.1% of the C ₀ values were 2.0-7.0 μg/mL. The plasma-C ₀-to-daily dose (C ₀/Dose) ratio was significantly associated with age and body weight (BW). The C ₀/Dose ratio in patients aged 1- ≤ 6 and 6- ≤ 12 years was significantly higher by 81% and 29% than those aged 12- ≤ 18 years, respectively. The C ₀/Dose ratio in patients with a BW of ≥40 kg was 1.7-fold lower than in patients with a BW of ≤ 20 kg. In addition, complex LCM-ASMs interactions were observed. Oxcarbazepine significantly decreased the C ₀/Dose ratio of LCM by 28%.

CONCLUSION

This retrospective study confirmed the effectiveness and tolerability of the LCM treatment used alone or with other ASMs in children with focal epilepsy. Children with higher BW and older age have lower C ₀/Dose ratio. Complex drug interactions between LCM and other concomitant ASMs were revealed. Notably, based on the data in our hands, the reference range, i.e., 2.0-7.0 μg/mL, for routine LCM monitoring may be feasible. The real-world evidence of this study supports LCM as a promising option in children with focal epilepsy.

Clinical and Economic Outcomes of Intravenous Brivaracetam Compared With Levetiracetam for the Treatment of Seizures in United States Hospitals

Background: Seizures are common among hospitalized patients. Levetiracetam (LEV), a synaptic vesicle protein 2A (SV2A) ligand, is a common intravenous (IV) anti-seizure medication option in hospitals. Brivaracetam (BRV), a selective SV2A ligand for treatment of focal seizures in patients ≥16 years, has greater binding affinity, higher lipophilicity, and faster brain entry than IV LEV. Differences in clinical outcomes and associated costs between IV BRV and IV LEV in treating hospitalized patients with seizure remain unknown.

Objectives: To compare the clinical outcomes, costs, and healthcare resource utilization between patients with seizure treated with IV BRV and those with IV LEV within hospital setting.

Design/Methods: A retrospective cohort analysis was performed using chargemaster data from 210 United States hospitals in Premier Healthcare Database. Adult patients (age ≥18 years) treated intravenously with LEV or BRV (with or without BZD) and a seizure discharge diagnosis between July 1, 2016 and December 31, 2019 were included. The cohorts were propensity score-matched 4:1 on baseline characteristics. Outcomes included intubation rates, intensive care unit (ICU) admission, length of stay (LOS), all-cause and seizure-related readmission, total hospitalization cost, and in-hospital mortality. A multivariable regression analysis was performed to determine the association between treatment and main outcomes adjusting for unbalanced confounders.

Results: A total of 450 patients were analyzed (IV LEV, n = 360 vs. IV BRV, n = 90). Patients treated with IV BRV had lower crude prevalence of ICU admission (14.4 vs. 24.2%, P < 0.05), 30-day all-cause readmission (1.1 vs. 6.4%, P = 0.06), seizure-related 30-day readmission (0 vs. 4.2%, P < 0.05), similar mean total hospitalization costs ($13,715 vs. $13,419, P = 0.91), intubation (0 vs. 1.1%, P = 0.59), and in-hospital mortality (4.4 vs. 3.9%, P = 0.77). The adjusted odds for ICU admission (adjusted odds ratio [_aOR] = 0.6; 95% confidence interval [CI]:0.31, 1.16; P = 0.13), 30-day all-cause readmission (_aOR = 0.17; 95% CI:0.02, 1.24; P = 0.08), and in-hospital mortality (_aOR = 1.15; 95% CI:0.37, 3.58, P = 0.81) were statistically similar between comparison groups.

Conclusion: The use of IV BRV may provide an alternative to IV LEV for management of seizures in hospital setting due to lower or comparable prevalence of ICU admission, intubation, and 30-day seizure-related readmission. Additional studies with greater statistical power are needed to confirm these findings.

Therapeutic drug monitoring of newer generation antiseizure medications at the point of treatment failure

PURPOSE

The benefit of therapeutic drug monitoring (TDM) of newer generation antiseizure medications (ASM) has been little studied. A recent randomized study suggested that TDM at each medical visit did not bring a significant benefit, but the study did not investigate TDM in cases of treatment failure. Accordingly, we realized a post hoc analysis of this trial.

METHODS

We analyzed 282 TDMs in 136 patients. We compared TDM performed at visits after treatment failure versus without treatment failure, reporting the proportion of drug levels out of range and the prescriber's adherence to dosage recommendations according to measured drug levels.

RESULTS

There was no statistical difference in terms of proportion of out of range plasma drug levels (47% vs 50%, p = 0.7) or adherence of prescribers to the clinical pharmacologists' dosage recommendations (21% vs 30%, p = 0.6) between visits after treatment failure and visits without treatment failure, respectively. Knowledge of prior drug levels did not modify the results.

CONCLUSION

Systematic TDM at appointments following treatment failure showed similar results to TDM at visits without treatment failure. The prescribers' adherence with dosage recommendations was low in both cases. It is not clear whether better prescriber adherence would improve patient outcome. Furthermore, the ability to detect poor patient compliance is limited in a planned outpatient appointment. The study setting does not reflect on the general usefulness of TDM.

Seizure freedom and plasma levels of newer generation antiseizure medications

OBJECTIVES

Contrary to older antiseizure medications (ASM), correlation between plasma levels and seizure freedom is not well defined for newer generation ASM. We assessed correlations between efficacy and newer generation ASM plasma levels in patients with epilepsy.

MATERIALS AND METHODS

Plasma medication levels were measured over two years in consecutive patients taking lamotrigine, levetiracetam, oxcarbazepine, topiramate, zonisamide, lacosamide, perampanel or pregabalin. Seizure freedom was defined as three times the longest inter-seizure pre-treatment interval, or at least one year. Each medication level was stratified according to its position in relation to its proposed reference range (below or in lower half vs upper half or above).

RESULTS

168 patients on stable therapy were included. ASM plasma levels of seizure-free patients were lower than those with ongoing seizures; 45/48 (93.7%) were in the lower half or below the reference ranges, compared to 86/106 (81.1%; p = .004). Lamotrigine plasma levels were significantly lower in seizure-free patients (median 2.4 mg/L range 0.4-6.5 mg/L, none above 6.5 mg/L) compared with those with ongoing seizures (5 mg/L, 0.5-14.2 mg/L; p < .0001). Levetiracetam showed similar results (7.2 mg/L, 1.6-15.1 mg/L; none above 15.1 mg/L in seizure-free patients vs 16.4 mg/L, 0.6-47.7 mg/L; p = .005). Demographics, epilepsy type and polytherapy did not influence the results.

CONCLUSIONS

Efficacy of newer generation ASMs seems to be reached at the lower part or at times even below the reference ranges in drug responsive patients; this could inform regarding titrations of these treatments.

Redefining the age-specific therapeutic ranges of lamotrigine for patients with epilepsy: A step towards optimizing treatment and increasing cost-effectiveness

OBJECTIVE

The pharmacokinetics of lamotrigine exhibits age-related characteristics. Nevertheless, current evidence regarding the therapeutic range of lamotrigine has been derived almost exclusively from studies in adult patients, and the applicability of this therapeutic range to the pediatric population remains unclear. The purpose of this study was to establish the appropriate age-specific therapeutic ranges of lamotrigine corresponding to adequate clinical responses for patients with epilepsy.

METHODS

This prospective cohort study of therapeutic drug monitoring included 582 Chinese epilepsy patients receiving lamotrigine monotherapy. Patients were divided into three age-related subgroups: (1) toddler and school-age group (2-12 years old, n = 168), (2) adolescent group (12-18 years old, n = 171), and (3) adult group (>18 years old, n = 243). Patients with a reduction in seizure frequency of 50 % or greater than baseline were defined as responders, and the remaining patients were non-responders. The relationship between lamotrigine serum concentrations and clinical response was assessed using multivariate logistic regression analysis. A receiver operating characteristic curve was generated to determine the representative cut-off values of lamotrigine trough levels, to distinguish responders from non-responders. The upper margin of the therapeutic range of lamotrigine was determined by developing concentration-effect curves for the three age-related subgroups.

RESULTS

The median trough levels of lamotrigine were significantly higher in responders than in non-responders from all three age-related groups (P < 0.0001). Results of logistic regression analysis revealed that higher serum concentrations of lamotrigine predicted a higher probability that seizure frequency would be reduced by more than 50 % compared to baseline (adjusted odds ratio: 1.228, 95 % CI: 1.137-1.327; P < 0.0001), and younger children were less likely to be responders (adjusted odds ratio: 1.027, 95 % CI: 1.012-1.043; P = 0.001). Based on a trade-off between sensitivity and specificity, the optimal cut-off values for lamotrigine trough concentrations corresponding to clinical response were 3.29 mg/L, 2.06 mg/L, and 1.61 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. By reducing interpatient variability, the results of the concentration-effect curves suggested no additional clinical benefit from a continued increase of doses for lamotrigine concentrations exceeding 9.08 mg/L, 8.43 mg/L, and 10.38 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. In conclusion, the therapeutic ranges of lamotrigine trough concentrations corresponding to adequate clinical response were 3.29-9.08 mg/L in the toddler and school-age group, 2.06-8.43 mg/L in the adolescent group, and 1.61-10.38 mg/L in the adult group.

CONCLUSIONS

The study determined age-specific therapeutic ranges corresponding to optimal clinical efficacy for lamotrigine. Our findings lay the foundation for catalyzing novel opportunities to optimize treatment and reduce therapeutic costs. Based on the age-specific therapeutic ranges identified in this study, individualized and cost-effective algorithms for lamotrigine treatment of epilepsy patients may be developed and validated in larger cohort studies of therapeutic drug monitoring.

Brivaracetam prevents astroglial l-glutamate release associated with hemichannel through modulation of synaptic vesicle protein

The antiepileptic/anticonvulsive action of brivaracetam is considered to occur via modulation of synaptic vesicle protein 2A (SV2A); however, the pharmacological mechanisms of action have not been fully characterised. To explore the antiepileptic/anticonvulsive mechanism of brivaracetam associated with SV2A modulation, this study determined concentration-dependent effects of brivaracetam on astroglial L-glutamate release associated with connexin43 (Cx43), tumour-necrosis factor-α (TNFα) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/glutamate receptor of rat primary cultured astrocytes using ultra-high-performance liquid chromatography. Furthermore, interaction among TNFα, elevated extracellular K⁺ and brivaracetam on expression of SV2A and Cx43 was determined using capillary immunoblotting. TNFα and elevated extracellular K⁺ predominantly enhanced astroglial L-glutamate release associated with respective AMPA/glutamate receptor and hemichannel. These effects were enhanced by a synergistic effect of TNFα and elevated extracellular K⁺ in combination. The activation of astroglial L-glutamate release, and expression of SV2A and Cx43 in the plasma membrane was suppressed by subchronic brivaracetam administration but were unaffected by acute administration. These results suggest that migration of SV2A to the astroglial plasma membrane by hyperexcitability activates astroglial glutamatergic transmission, perhaps via hemichannel activation. Subchronic brivaracetam administration suppressed TNFα-induced activation of AMPA/glutamate receptor and hemichannel via inhibition of ectopic SV2A. These findings suggest that combined inhibition of vesicular and ectopic SV2A functions contribute to the antiepileptic/anticonvulsive mechanism of brivaracetam action.

Carbamate group as structural motif in drugs: a review of carbamate derivatives used as therapeutic agents

Due to their very good chemical and proteolytic stability, ability to penetrate cell membranes, and resemblance to a peptide bond, carbamate derivatives have received much attention in recent years and got an important role in modern drug discovery and medicinal chemistry. Today, carbamates make structural and/or functional part of many drugs and prodrugs approved and marketed for the treatment of various diseases such as cancer, epilepsy, hepatitis C, HIV infection, and Alzheimer's disease. In drugs they can play a role in drug-target interaction or improve the biological activity of parent molecules. In prodrugs they are mainly used to delay first-pass metabolism and enhance the bioavailability and effectiveness of compounds. This brief review takes a look at the properties and use of carbamates in various fields of medicine and provides quick insights into the mechanisms of action for some of them.

The Impact of COVID-19 on Epilepsy Care: A Survey of the American Epilepsy Society Membership

The COVID-19 pandemic has impacted the delivery of care to people with epilepsy (PWE) in multiple ways including limitations on in-person contact and restrictions on neurophysiological procedures. To better study the effect of the pandemic on PWE, members of the American Epilepsy Society were surveyed between April 30 and June 14, 2020. There were 366 initial responses (9% response rate) and 337 respondents remained for analysis after screening out noncompleters and those not directly involved with clinical care; the majority were physicians from the United States. About a third (30%) of respondents stated that they had patients with COVID-19 and reported no significant change in seizure frequency. Conversely, one-third of respondents reported new onset seizures in patients with COVID-19 who had no prior history of seizures. The majority of respondents felt that there were at least some barriers for PWE in receiving appropriate clinical care, neurophysiologic procedures, and elective surgery. Medication shortages were noted by approximately 30% of respondents, with no clear pattern in types of medication involved. Telehealth was overwhelmingly found to have value. Among the limitation of the survey was that it was administered at a single point in time in a rapidly changing pandemic. The survey showed that almost all respondents were affected by the pandemic in a variety of ways.

Measure for Measure: Measuring the Usefulness of Measuring Antiseizure Medication Levels

Therapeutic Drug Monitoring of Newer Antiepileptic Drugs: A Randomized Trial for Dosage Adjustment

Aícua-Rapún I, André P, Rossetti AO, et al. Ann Neurol. 2020;87(1):22-29. doi:10.1002/ana.25641.

Objective:

Therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) is widely established for older generation AEDs, whereas there is limited evidence about newer AEDs. Our aim is to assess the benefit of TDM of newer generation AEDs in epilepsy. Methods: We performed a randomized, controlled trial comparing systematic with rescue TDM of lamotrigine, levetiracetam, oxcarbazepine, topiramate, brivaracetam, zonisamide, or pregabalin. Participants were adults with epilepsy, in whom treatment with newer generation AEDs was initiated or needed adjustment. In the systematic TDM arm, AED plasma levels were available at each appointment, whereas in the rescue TDM arm, levels were known only if a study end point was reached (inefficacy or adverse events). The primary outcome was the proportion of participants who followed 1 year without reaching one of the predefined end points. Results: A total of 151 participants were enrolled; global retention in the study was similar in both arms (56% overall, 58% in the systematic, and 53% in the rescue TDM arm, P = .6, Cox regression). There was no difference in terms of outcome regarding treatment efficacy or tolerability. Partial adherence of clinicians to TDM (adjusting or not AED dosage based on blood levels) did not explain this lack of benefit. Interpretation: This study provides class A evidence that systematic drug-level monitoring of newer generation AEDs does not bring tangible benefits in the management of patients with epilepsy. Poor correlation between clinical effects and drug levels likely accounts for this finding. However, TDM is useful in several situations, such as pregnancy, as well as when there are compliance issues.

Serum Levels of Valproic Acid and Carbamazepine Do Not Correlate Well with End-Organ Dysfunction

BACKGROUND

Serum levels of anticonvulsants are commonly ordered; however, the clinical utility of these laboratory tests is unclear. Clarifying the significance of anticonvulsant drug levels is essential to allow physicians to make appropriate management decisions. We aimed to determine to what extent elevated serum levels of valproic acid (VPA) and carbamazepine (CBZ) correlate with laboratory indications of end-organ dysfunction.

METHODS

We reviewed a consecutive sample of patients 0-18 years of age who, over a 2-year period, had at least one blood collection in which (1) serum [VPA] or [CBZ] was tested; and (2) at least one of the following tests was performed: alanine aminotransferase (ALT), aspartate aminotransferase (AST), platelets, white blood cells (WBC), ammonia, sodium.

RESULTS

913 and 300 blood collections met criteria for VPA and CBZ, respectively. A slight increased frequency of having any abnormal laboratory value for elevated [VPA] compared to low/normal [VPA] was observed (p = 0.02; relative risk 1.27), while there was no difference in frequency of having any abnormal lab value for CBZ, nor were there significant differences for the individual lab values. When ALT and AST were plotted against [VPA] and [CBZ], no significant correlation was observed.

CONCLUSION

Serum [VPA] and [CBZ] are poor indicators of risk for drug-induced end-organ dysfunction. There are likely other, individualized risk factors that explain why certain patients develop adverse effects from these medications.