In situ metabolism of levetiracetam in blood of patients with epilepsy

Final analysis of potential drug-drug interactions between highly purified cannabidiol and anti-seizure medications in an open-label expanded access program

OBJECTIVE

The aim of this study was to assess potential drug-drug interactions between highly purified cannabidiol (CBD) and anti-seizure medications (ASMs).

METHODS

Our group previously reported that in a sample of adults and children receiving CBD in an open-label expanded access program, there were several ASMs noted to increase in serum levels with increasing doses of CBD. We analyzed if an increased number of observations over time resulted in changes in potential interactions and if potential interactions were associated with time since enrollment, demographics, or the overall rating of adverse effects.

RESULTS

In 169 participants (80 adults), with increasing weight-based CBD dose, there were associated increases in serum levels of clobazam and N-desmethylclobazam, free valproate, felbamate, and topiramate in the adult and pediatric arms combined, levetiracetam in the pediatric arm only, and permapanel in the adult arm only. There were no associations noted in these level changes with time since enrollment, biological sex, and adverse events profile scores.

SIGNIFICANCE

This study confirms some previously identified interactions with CBD and identifies other potential pharmacokinetic interactions; however, the clinical significance of these observations is likely minor, and there is no effect of time on these findings.

Development and Validation of Physiologically Based Pharmacokinetic Model of Levetiracetam to Predict Exposure and Dose Optimization in Pediatrics

Levetiracetam (Lev) is an antiepileptic drug that has been increasingly used in the epilepsy pediatric population in recent years, but its pharmacokinetic behavior in pediatric population needs to be characterized clearly. Clinical trials for the pediatric drug remain difficult to conduct due to ethical and practical factors. The purpose of this study was to use the physiologically based pharmacokinetic (PBPK) model to predict changes in plasma exposure of Lev in pediatric patients and to provide recommendations for dose adjustment. A PBPK model of Lev in adults was developed using PK-Sim® software and extrapolated to the entire age range of the pediatric population. The model was evaluated using clinical pharmacokinetic data. The results showed the good fit between predictions and observations of the adult and pediatric models. The recommended doses for neonates, infants and children are 0.78, 1.67 and 1.22 times that of adults, respectively. Moreover, at the same dose, plasma exposure in adolescents was similar to that of adults. The PBPK models of Lev for adults and pediatrics were successfully developed and validated to provide a reference for the rational administration of drugs in the pediatric population.

Application of PBPK modeling in predicting maternal and fetal pharmacokinetics of levetiracetam during pregnancy

Levetiracetam is currently being used to treat epilepsy in pregnant women. The plasma concentration of levetiracetam drops sharply during pregnancy, and the inability of pregnant women to maintain therapeutic concentrations can lead to seizures. This study aimed to predict the changes in fetal and maternal plasma exposure to levetiracetam during pregnancy and provide advice on dose adjustment. The physiology-based pharmacokinetics (PBPK) model was developed using PK-Sim and Mobi software, and validated following comparison of the observed plasma concentration and pharmacokinetic parameters. The levetiracetam PBPK model for mother and the fetus at various stages of pregnancy was successfully established and verified. Predictions indicated that the area under the steady-state concentration-time curve for levetiracetam decreased to 83, 62, and 67% of baseline values in the first, second, and third trimesters, respectively. Based on PBPK predictions, the recommended dose of levetiracetam is 1.2, 1.6, and 1.5 times the baseline dose in the first, second, and third trimesters, respectively, not exceeding 4000 mg/day in the third trimester due to fetal safety. The levetiracetam PBPK model for pregnancy was successfully developed and validated, and could provide alternative levetiracetam dosing regimens across the stages of pregnancy.

Management of anti-seizure medications in lactating women with epilepsy

Epilepsy is a common neurological disease. At present, there are about 70 million epilepsy patients in the world, half of them are women, and 30–40% of women with epilepsy are of childbearing potential. Patients with epilepsy who are of childbearing potential face more challenges, such as seizures caused by hormonal fluctuations and the risk of adverse effects on the mother and baby from taking anti-seizure medications (ASMs). Breast milk is one of the best gifts that a mother can give her baby, and breastfeeding can bring more benefits to the baby. Compared with healthy people, people with epilepsy have more concerns about breastfeeding because they are worried that ASMs in their milk will affect the growth and development of the baby, and they are always faced with the dilemma of whether to breastfeed after childbirth. Regarding, whether women with epilepsy can breastfeed while taking ASMs, and whether breastfeeding will adversely affect the baby is still an important topic of concern for patients and doctors. This article reviews the existing research on breastfeeding-related issues in women with epilepsy to guide clinical practice, and improve the breastfeeding compliance of women with epilepsy.

Management of status epilepticus in patients with liver or kidney disease: a narrative review

Introduction: Status epilepticus (SE) is a neurologic and medical emergency with significant related morbidity and mortality. Hepatic or renal dysfunction can considerably affect the pharmacokinetics of drugs used for SE through a variety of direct or indirect mechanisms.Areas Covered: This review aims to focus on the therapeutic management of SE in patients with hepatic or renal impairment, highlighting drugs' selection and dose changes that may be necessary due to altered drug metabolism and excretion. The references for this review were identified by searches of PubMed and Google Scholar until May 2020.Expert opinion: According to literature evidence and clinical experience, in patients with renal disease, the authors suggest considering lorazepam as the drug of choice in pre-hospital and intra-hospital early-stage SE, phenytoin in definite SE, propofol in refractory or super-refractory SE. In patients with liver disease, the authors suggest the use of lorazepam as drug of choice in pre-hospital and intra-hospital early-stage SE, lacosamide in definite SE, propofol in refractory or super-refractory SE. A list of preferred drugs for all SE stages is provided.

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).

Levetiracetam

A comprehensive profile of levetiracetam is presented in this chapter which includes its description, formula, elemental analysis, appearance, uses and applications. Different earlier studies included for example methods of synthesis are described with its typical structural schemes. The profile also listed the drug's physical characteristics indicating its solubility, X-ray powder diffraction pattern, thermal methods of analysis as well as its spectroscopic characteristics. Different methods of analysis which includes compendial method of analysis, as well as reported method of analysis which include spectrophotometry, spectrofluorometry, electrochemical method, chromatographic method, and immunoassay method of analysis. The study was include drug stability, clinical pharmacology, e.g., mechanism of action, pharmacokinetic study. Around 70 references are recorded as a proof of this chapter.

Levetiracetam-Related Mania-Like Symptoms: An Adolescent Case

Levetiracetam is an antiepileptic agent that is used for partial and generalized epilepsy. Although it is well tolerated in most cases, behavioral and nonbehavioral adverse effects may be observed. Among behavioral symptoms, depression, hostility, and agitation have been frequently reported. However, mania or mania-like symptoms are relatively rare, especially in children and adolescents. Hereby, we report mania-like symptoms with levetiracetam use in a 15-year-old boy. Mania-like symptoms emerged 3 weeks after starting levetiracetam and disappeared after adding risperidone to ongoing levetiracetam treatment.

A simple and cost-effective HPLC-UV method for the detection of levetiracetam in plasma/serum of patients with epilepsy

A simple, fast and cost-effective method was developed and validated for the determination of levetiracetam (LEV) in plasma/serum of patients using high performance liquid chromatography (HPLC) with ultraviolet detection. The stability of LEV plasma/serum samples over time and in different blood collection tubes was evaluated. Serum/plasma samples were deproteinized by methanol spiked with the internal standard, gabapentin. HPLC was carried out on a Venusil XBP C₁₈ , 250 × 4.6 mm, 5 μm column, at a flow rate of 1.0 mL/min and with mobile phase consisting of 50 mm potassium dihydrogen phosphate-acetonitrile at a pH of 5.5. The UV detector was set at 205 nm and 10 μL was injected. Total runtime was 15 min. Calibration curves were linear (correlation coefficient = 0.999) over a concentration range of 1-60 μg/mL. Relative standard deviation values for both the inter-day and intra-day precision and accuracy were <5% for the concentration range. The influence of different collection tubes and the effect of time on the stability of LEV was investigated. These factors may cause inaccuracies owing to drug-protein binding and interference in the matrix. This method is simple, fast, cost-effective, reliable and accurate with minimal sample preparation for daily routine use in therapeutic drug monitoring.

Disposition of Extended Release Levetiracetam in Normal Healthy Dogs After Single Oral Dosing

Background

Levetiracetam is an anticonvulsant used for control of canine epilepsy. An extended release preparation should improve dosing convenience.

Objectives

To determine the disposition of extended release levetiracetam in normal dogs after single dosing.

Animals

Pharmacokinetic study: 16 healthy, adult dogs.

Methods

Using a partially randomized crossover study, levetiracetam (30 mg/kg) was administered intravenously (IV) and orally (PO) as extended release preparation with or without food. Blood was collected for 24 hours (IV) or 36 hours (PO). Serum levetiracetam was quantitated by immunoassay and data were subjected to noncompartmental analysis.

Results

Pharmacokinetic parameters for fasted versus fed animals, respectively, were (mean ± SEM): C_max = 26.6 ± 2.38 and 30.7 ± 2.88 μ/mL, T_max = 204.3 ± 18.9 and 393.8 ± 36.6 minutes, t_1/2 = 4.95 ± 0.55 and 4.48 ± 0.48 hours, MRT = 9.8 ± 0.72 and 10 ± 0.64 hours, MAT = 4.7 ± 0.38 and 5.6 ± 0.67 hours, and F = 1.04 ± 0.04 and 1.26 ± 0.07%. Significant differences were limited to T_max (longer) and F (greater) in fed compared to fasted animals. Serum levetiracetam concentration remained above 5 μ/mL for approximately 20 hours in both fasted and fed animals.

Conclusions and Clinical Importance

Extended release levetiracetam (30 mg/kg q12h), with or without food, should maintain concentrations above the recommended minimum human therapeutic concentration.

Stir bar-sorptive extraction, solid phase extraction and liquid-liquid extraction for levetiracetam determination in human plasma: comparing recovery rates

<p>Levetiracetam (LEV), an antiepileptic drug (AED) with favorable pharmacokinetic profile, is increasingly being used in clinical practice, although information on its metabolism and disposition are still being generated. Therefore a simple, robust and fast liquid-liquid extraction (LLE) followed by high-performance liquid chromatography method is described that could be used for both pharmacokinetic and therapeutic drug monitoring (TDM) purposes. Moreover, recovery rates of LEV in plasma were compared among LLE, stir bar-sorptive extraction (SBSE), and solid-phase extraction (SPE). Solvent extraction with dichloromethane yielded a plasma residue free from usual interferences such as commonly co-prescribed AEDs, and recoveries around 90% (LLE), 60% (SPE) and 10% (SBSE). Separation was obtained using reverse phase Select B column with ultraviolet detection (235 nm). Mobile phase consisted of methanol:sodium acetate buffer 0.125 M pH 4.4 (20:80, v/v). The method was linear over a range of 2.8-220.0 µg mL^-1. The intra- and inter-assay precision and accuracy were studied at three concentrations; relative standard deviation was less than 10%. The limit of quantification was 2.8 µg mL^-1. This robust method was successfully applied to analyze plasma samples from patients with epilepsy and therefore might be used for pharmacokinetic and TDM purposes.</p>

Rapid and simultaneous quantification of levetiracetam and its carboxylic metabolite in human plasma by liquid chromatography tandem mass spectrometry

A simple liquid chromatography tandem mass spectrometry method was developed and validated according to the guidelines of the US Food and Drug Administration and the European Medicines Agency for a simultaneous quantification of levetiracetam (LEV) and its metabolite, UCB L057 in the plasma of patients. A 0.050 mL plasma sample was prepared by a simple and direct protein precipitation with 0.450 mL acetonitrile (ACN) containing 1 µg/mL of internal standard (IS, diphenhydramine), then vortex mixed and centrifuged. A 0.100 mL of the clear supernatant was diluted with 0.400 mL water and well mixed. A 0.010 mL of the resultant solution was injected into an Agilent Zorbax SB-C18 (2.1 mm×100 mm, 3.5 µm) column with an isocratic elution at 0.5 mL/min using a mixture of 0.1% formic acid in water and ACN (40:60 v/v). Detection was performed using an AB Sciex API 3000 triple quadrupole mass spectrometer, equipped with a Turbo Ion Spray source, operating in a positive mode: LEV at transition 171.1>154.1, UCB L057 at 172.5>126.1, and IS at 256.3>167.3; with an assay run time of 2 minutes. The lower limit of quantification (LLOQ) for both LEV and UCB L057 was validated at 0.5 µg/mL, while their lower limit of detection (LOD) was 0.25 µg/mL. The calibration curves were linear between 0.5 and 100 µg/mL for both analytes. The inaccuracy and imprecision of both intra-assay and inter-assay were less than 10%. Matrix effects were consistent between sources of plasma and the recoveries of all compounds were between 100% and 110%. Stability was established under various storage and processing conditions. The carryovers from both LEV and UCB L057 were less than 6% of the LLOQ and 0.13% of the IS. This assay method has been successfully applied to a population pharmacokinetic study of LEV in patients with epilepsy.

Advances in anti-epileptic drug testing

In the past twenty-one years, 17 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are clobazam, ezogabine (retigabine), eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. Therapeutic drug monitoring is often used in the clinical dosing of the newer anti-epileptic drugs. The drugs with the best justifications for drug monitoring are lamotrigine, levetiracetam, oxcarbazepine, stiripentol, and zonisamide. Perampanel, stiripentol and tiagabine are strongly bound to serum proteins and are candidates for monitoring of the free drug fractions. Alternative specimens for therapeutic drug monitoring are saliva and dried blood spots. Therapeutic drug monitoring of the new antiepileptic drugs is discussed here for managing patients with epilepsy.

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.

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.

Population pharmacokinetics modeling of levetiracetam in Chinese children with epilepsy

AIM

To establish a population pharmacokinetics (PPK) model of levetiracetam in Chinese children with epilepsy.

METHODS

A total of 418 samples from 361 epileptic children in Peking University First Hospital were analyzed. These patients were divided into two groups: the PPK model group (n=311) and the PPK validation group (n=50). Levetiracetam concentrations were determined by HPLC. The PPK model of levetiracetam was established using NONMEM, according to a one-compartment model with first-order absorption and elimination. To validate the model, the mean prediction error (MPE), mean squared prediction error (MSPE), root mean-squared prediction error (RMSPE), weight residues (WRES), and the 95% confidence intervals (95% CI) were calculated.

RESULTS

A regression equation of the basic model of levetiracetam was obtained, with clearance (CL/F)=0.988 L/h, volume of distribution (V/F)=12.3 L, and K(a)=1.95 h(-1). The final model was as follows: K(a)=1.56 h(-1), V/F=12.1 (L), CL/F=1.04×(WEIG/25)(0.583) (L/h). For the basic model, the MPE, MSPE, RMSPE, WRES, and the 95%CI were 9.834 (-0.587-197.720), 50.919 (0.012-1286.429), 1.680 (0.021-34.184), and 0.0621 (-1.100-1.980). For the final model, the MPE, MSPE, RMSPE, WRES, and the 95% CI were 0.199 (-0.369-0.563), 0.002082 (0.00001-0.01054), 0.0293 (0.001-0.110), and 0.153 (-0.030-1.950).

CONCLUSION

A one-compartment model with first-order absorption adequately described the levetiracetam concentrations. Body weight was identified as a significant covariate for levetiracetam clearance in this study. This model will be valuable to facilitate individualized dosage regimens.

Levetiracetam compared to valproic acid: plasma concentration levels, adverse effects and interactions in aneurysmal subarachnoid hemorrhage

OBJECTIVE

Both valproic acid and levetiracetam are anti-epileptic drugs, often used either alone or in combination. The present study compares valproate (VPA) with levetiracetam (LEV) as an intravenous (i.v.) anticonvulsant treatment in intensive care patients suffering from aneurysmal subarachnoid hemorrhage (aSAH) with a high risk of seizures.

PATIENTS AND METHODS

A prospective, single-center patient registry of 35 intensive care unit (ICU) patients with onset seizure and/or high risk of seizures underwent an anticonvulsive, first-line single treatment regimen either with VPA or LEV. Plasma concentrations (pc), interactions between drugs in the ICU context, adverse effects and seizure occurrences were observed and recorded.

RESULTS

A significant decrease in the pc in patients treated with LEV was observed after changing from intravenous (160±51μmol/l) to enteral liquid application (113±58μmol/l), corresponding to a 70.3% bioavailability for enteral liquid applications. The pc in VPA patients decreased significantly, from (491±138μmol/l) to (141±50μmol/l), after adding meropenem to the therapy (p<0.05). Three epileptic seizures occurred during anticonvulsive therapy in the LEV group, and two in the VPA group, including one non-convulsive status epilepticus (NCSE).

CONCLUSION

Though this finding needs further verification, the enteral liquid application of levetiracetam seems to be associated with lower bioavailability than the common oral application of levetiracetam. The use of the antibiotic drug meropenem together with valproic acid leads to lower pc levels in patients treated with of valproic acid. For clinical practice, this indicates the need to monitor the levels of valproic acid in combination with meropenem.

Modern methods for analysis of antiepileptic drugs in the biological fluids for pharmacokinetics, bioequivalence and therapeutic drug monitoring

Epilepsy is a chronic disease occurring in approximately 1.0% of the world's population. About 30% of the epileptic patients treated with availably antiepileptic drugs (AEDs) continue to have seizures and are considered therapy-resistant or refractory patients. The ultimate goal for the use of AEDs is complete cessation of seizures without side effects. Because of a narrow therapeutic index of AEDs, a complete understanding of its clinical pharmacokinetics is essential for understanding of the pharmacodynamics of these drugs. These drug concentrations in biological fluids serve as surrogate markers and can be used to guide or target drug dosing. Because early studies demonstrated clinical and/or electroencephalographic correlations with serum concentrations of several AEDs, It has been almost 50 years since clinicians started using plasma concentrations of AEDs to optimize pharmacotherapy in patients with epilepsy. Therefore, validated analytical method for concentrations of AEDs in biological fluids is a necessity in order to explore pharmacokinetics, bioequivalence and TDM in various clinical situations. There are hundreds of published articles on the analysis of specific AEDs by a wide variety of analytical methods in biological samples have appears over the past decade. This review intends to provide an updated, concise overview on the modern method development for monitoring AEDs for pharmacokinetic studies, bioequivalence and therapeutic drug monitoring.

Therapeutic Drug Monitoring of the Newer Anti-Epilepsy Medications

In the past twenty years, 14 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. In general, the clinical utility of therapeutic drug monitoring has not been established in clinical trials for these new anticonvulsants, and clear guidelines for drug monitoring have yet to be defined. The antiepileptic drugs with the strongest justifications for drug monitoring are lamotrigine, oxcarbazepine, stiripentol, and zonisamide. Stiripentol and tiagabine are strongly protein bound and are candidates for free drug monitoring. Therapeutic drug monitoring has lower utility for gabapentin, pregabalin, and vigabatrin. Measurement of salivary drug concentrations has potential utility for therapeutic drug monitoring of lamotrigine, levetiracetam, and topiramate. Therapeutic drug monitoring of the new antiepileptic drugs will be discussed in managing patients with epilepsy.

Therapeutic Drug Monitoring of the Newer Anti-Epilepsy Medications

In the past twenty years, 14 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. In general, the clinical utility of therapeutic drug monitoring has not been established in clinical trials for these new anticonvulsants, and clear guidelines for drug monitoring have yet to be defined. The antiepileptic drugs with the strongest justifications for drug monitoring are lamotrigine, oxcarbazepine, stiripentol, and zonisamide. Stiripentol and tiagabine are strongly protein bound and are candidates for free drug monitoring. Therapeutic drug monitoring has lower utility for gabapentin, pregabalin, and vigabatrin. Measurement of salivary drug concentrations has potential utility for therapeutic drug monitoring of lamotrigine, levetiracetam, and topiramate. Therapeutic drug monitoring of the new antiepileptic drugs will be discussed in managing patients with epilepsy.

New treatment options in status epilepticus: a critical review on intravenous levetiracetam

The effectiveness of Levetiracetam (LEV) in the treatment of focal and generalised epilepsies is well established. LEV has a wide spectrum of action, good tolerability and a favourable pharmacokinetic profile. An injectable formulation has been released as an intravenous (IV) infusion in 2006 for patients with epilepsy when oral administration is temporarily not feasible. Bioequivalence to the oral preparation has been demonstrated with good tolerability and safety enabling a smooth transition from oral to parenteral formulation and vice versa. Although IV LEV is not licensed for treatment of status epilepticus (SE), open-label experience in retrospective case series is accumulating. Until now (August 2008) 156 patients who were treated with IV LEV for various forms of SE have been reported with an overall success rate of 65.4%. The most often used initial dose was 2000-3000 mg over 15 minutes. Adverse events were reported in 7.1%, and were mild and transient. Although IV LEV is an interesting alternative for the treatment of SE due to the lack of centrally depressive effects and low potential of drug interactions, one has to be aware of the nonrandomised retrospective study design, the heterogenous patient population and treatment protocols, and the publication bias inherent in these type of studies. Only a large randomised controlled trial with an adequate comparator will reveal the efficacy and effectiveness of this promising new IV formulation.

Levetiracetam in patients with epilepsy and chronic liver disease: observations in a case series

OBJECTIVES

To evaluate levetiracetam (LEV) tolerability in patients with epilepsy and liver disease.

METHODS

Fourteen patients with epilepsy and concomitant liver disease were treated with LEV in an open prospective investigation mimicking the daily clinical practice. All patients were stabilized (ie, for at least 1 year) on traditional antiepileptic drugs with complete or partial control of seizures. In the 6-month pre-LEV baseline period, seizure frequency ranged from 3 to 300. Levetiracetam was added on to the basal treatment at a starting daily dose of 250 mg, and the dose was adjusted according to the tolerability and the therapeutic response. Four patients discontinued the drug within the first 3 months because of intolerable side effects. The remaining 10 continued LEV treatment, and the present follow-up is 12 to 38 months.

RESULTS

In the last 6 months of observation, none of the patients showed worsening of liver function on the basis of blood chemistry, and in 4 patients, a complete normalization or a trend toward physiological values of transaminase and/or gamma-glutamyltransferase activity was observed. A greater than 50% reduction in seizure frequency occurred in all uncontrolled patients, 2 of whom achieved seizure freedom during LEV treatment.

CONCLUSIONS

Based on these observations, LEV seems to be an attractive therapeutic option in epileptic patients with chronic liver diseases.

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.

Levetiracetam has no acute effects on brain gamma-aminobutyric acid levels

OBJECTIVE

The mechanism of action of levetiracetam (LEV), an antiepileptic drug, is related to a novel binding site, SV2, but LEV acts on GABA-A receptors. The objective of the study described here was to determine if LEV modulates brain GABA in vivo.

METHODS

Concentrations of cerebral GABA and serum LEV were obtained in seven healthy individuals using 1H magnetic resonance spectroscopy at baseline and 3 and 6 hours following oral administration of 1 g of LEV.

RESULTS

Brain cerebral GABA acutely concentrations did not change from baseline.

CONCLUSION

The results indicate that LEV does not increase human cerebral GABA concentrations acutely in healthy individuals.

Levetiracetam and felbamate interact both pharmacodynamically and pharmacokinetically: an isobolographic analysis in the mouse maximal electroshock model

PURPOSE

Polytherapy with two or more antiepileptic drugs (AEDs) is generally required for approximately 30% of patients with epilepsy, who do not respond satisfactorily to monotherapy. The potential usefulness of AED combinations, producing synergistic anticonvulsant efficacy and minimal adverse effects, is therefore of significant importance. The present study sought to ascertain the potential usefulness of levetiracetam (LEV) and felbamate (FBM) in combination in the mouse maximal electroshock (MES)-induced seizure model.

METHODS

The anticonvulsant interaction profile between LEV and FBM in the mouse MES-induced seizure model was determined using type II isobolographic analysis. Acute adverse effects (motor performance) were ascertained by use of the chimney test. LEV and FBM brain concentrations were measured by HPLC in order to determine any pharmacokinetic contribution to the observed antiseizure effect.

RESULTS

LEV in combination with FBM, at the fixed ratios of 1:2, 1:1, 2:1, and 4:1, were supraadditive, whereas at the fixed ratio of 1:4, additivity was observed in the mouse MES model. Furthermore, none of the investigated combinations altered motor performance in the chimney test. Brain FBM concentrations were unaffected by concomitant LEV administration. In contrast, FBM significantly increased LEV brain concentrations.

CONCLUSIONS

LEV in combination with FBM was associated with pharmacodynamic supraadditivity in the MES test. However, this anticonvulsant supraadditivity was associated with a concurrent increase in brain LEV concentrations indicating a pharmacokinetic contribution to the observed pharmacodynamic interaction between LEV and FBM.