Effects of antiepileptic comedication on levetiracetam pharmacokinetics: a pooled analysis of data from randomized adjunctive therapy trials

Clinical Application of Pharmacokinetics to Appraise Adherence to Levetiracetam in Portuguese Epileptic Patients

Adherence to antiseizure drug treatment determines its effectiveness and safety, and consequently affects patients’ quality of life. Herein, we assessed adherence to levetiracetam in Portuguese patients with refractory epilepsy (n = 115), with resort to a pharmacokinetic drug monitoring approach. The pharmacokinetic parameters of levetiracetam in each patient were determined in steady-state while admitted to the hospital. Then, adherence was assessed by comparing the plasma concentration of the drug observed on the first day of hospitalization with the predicted plasma concentration, considering previously determined pharmacokinetic parameters. The rate of adherence was assessed according to gender, age, diagnosis, and antiseizure drug regimen. Among 115 enrolled patients, 49 (42.6%) were identified as non-adherent, 30 (26.1%) classified as under-consumers, and 19 (16.5%) as over-consumers. A relationship between adherence, daily dose and plasma concentrations was herein reported for the first time. Adherent patients received higher daily doses of levetiracetam [2500 (2000–3000) mg] than non-adherent over-consumers [1500 (1000–2000) mg] and non-adherent under-consumers [2000 (1500–3000) mg]. Higher average steady-state plasma concentrations of levetiracetam were found in non-adherent under-consumers [27.28 (15.33–36.36) mg/L], followed by adherent patients [22.05 (16.62–29.81) mg/L] and non-adherent over-consumers [17.50 (10.69–24.37) mg/L]. This study demonstrates that adherence (or lack thereof) influences the plasma concentrations of levetiracetam in steady-state and its pharmacological effects. Moreover, it emphasizes the importance of educating patients to encourage adherence to therapy. Otherwise, the risk of developing toxic and subtherapeutic concentrations is undeniable, compromising the therapeutic effect and safety of treatment.

Evaluating Therapeutic Equivalence of Generic and Original Levetiracetam in Patients with Epilepsy: A Retrospective Study

The brand interchangeability of antiepileptic drugs (AEDs) is a topic of debate, especially regarding their therapeutic equivalence. This study evaluates the efficacy and tolerability of generic levetiracetam compared to the brand-name equivalent in a routine clinical setting. We conducted a retrospective study, examining patients with stable seizure frequency who received generic levetiracetam after the brand-name drug. During the six-month substitution period, changes in seizure frequency, hospitalization due to seizure exacerbation, adverse events, composite outcomes related to adjusting the AED dosage, and switching back to original levetiracetam were analyzed. Seventy-five patients were enrolled; the majority (85.3%) had focal onset seizures, and almost half (49.3%) had refractory epilepsy. Six months after the substitution, the mean seizure frequency per month was not significantly different (3.15 ± 14.47 vs. 2.77 ± 11.41; p = 0.970). In patients with controlled seizures before the change, the seizure frequency increased significantly (0.56 ± 1.83 vs. 0.03 ± 0.16; p = 0.012). Adverse events occurred in six patients. We have observed recurrent seizures or adverse events from 14 days after the transition. The original drug return rates due to recurrent seizures and adverse events were 5.3% and 1.3%, respectively. Generic levetiracetam might not show therapeutic equivalence to the original molecule, especially in patients adequately controlled by the brand-name drug.

Relevant pharmacological interactions between alkylating agents and antiepileptic drugs: Preclinical and clinical data

Seizures are relatively common in cancer patients, and co-administration of chemotherapeutic and antiepileptic drugs (AEDs) is highly probable and necessary in many cases. Nonetheless, clinically relevant interactions between chemotherapeutic drugs and AEDs are rarely summarized and pharmacologically described. These interactions can cause insufficient tumor and seizure control or lead to unforeseen toxicity. This review focused on pharmacokinetic and pharmacodynamic interactions between alkylating agents and AEDs, helping readers to make a rational choice of treatment optimization, and thus improving patients' quality of life. As an example, phenobarbital, phenytoin, and carbamazepine, by increasing the hepatic metabolism of cyclophosphamide, ifosfamide and busulfan, yield smaller peak concentrations and a reduced area under the plasma concentration-time curve (AUC) of the prodrugs; alongside, the maximum concentration and AUC of their active products were increased with the possible onset of severe adverse drug reactions. On the other side, valproic acid, acting as histone deacetylase inhibitor, showed synergistic effects with temozolomide when tested in glioblastoma. The present review is aimed at providing evidence that may offer useful suggestions for rational pharmacological strategies in patients with seizures symptoms undertaking alkylating agents. Firstly, clinicians should avoid the use of enzyme-inducing AEDs in combination with alkylating agents and prefer the use of AEDs, such as levetiracetam, that have a low or no impact on hepatic metabolism. Secondly, a careful therapeutic drug monitoring of both alkylating agents and AEDs (and their active metabolites) is necessary to maintain therapeutic ranges and to avoid serious adverse reactions.

Levetiracetam Therapeutic Drug Monitoring in a Large Cohort of Korean Epileptic Patients

Levetiracetam is a new antiepileptic drug (AED) used for treating and preventing partial or generalized seizures. The usefulness of levetiracetam therapeutic drug monitoring (TDM) is related to inter- or intra-individual pharmacokinetic variability, drug interactions, and patient noncompliance. We aimed to investigate the levetiracetam TDM status in Korean epilepsy patients. Serum trough levetiracetam concentrations were measured using liquid chromatography–tandem mass spectrometry in 710 samples from 550 patients. The median (range) daily and weight-adjusted levetiracetam doses were 1500 (20–5000) mg and 25.5 (3.03–133.0) mg/kg, respectively. Patients on levetiracetam monotherapy constituted only 19.5% of the population, while 30.1% were on co-medication with valproate and 56.0% with enzyme-inducing AEDs (EIAEDs). Observed levetiracetam concentrations were widely distributed, ranging 0.8–95 mg/L, with a median of 17.3 mg/L. Levetiracetam concentrations were therapeutic, supra-therapeutic, and sub-therapeutic in 58.5% (n = 393), 11.6% (n = 78), and 29.9% (n = 201) of samples, respectively. There was a strong correlation between weight-adjusted levetiracetam dosage and concentrations (ρ = 0.6896, p < 0.0001). In this large-scale clinical study, a large inter-individual difference in levetiracetam pharmacokinetics was observed, and levetiracetam concentrations were influenced by EIAEDs. For individual dose adjustments and monitoring compliance, routine levetiracetam TDM is needed in epilepsy patients.

What Are the Predictors for Achieving Therapeutic Levetiracetam Serum Concentrations in Adult Neurological Patients?

BACKGROUND

Emerging studies suggest that levetiracetam pharmacokinetics can be difficult to predict in certain special patient populations, including the elderly, critically ill patients, and pregnant women.

OBJECTIVE

To determine clinical characteristics that predict the attainment of target serum concentrations in a heterogeneous group of patients prescribed levetiracetam.

METHODS

A retrospective observational study was conducted in adult neurological patients prescribed levetiracetam for the treatment or prophylaxis of seizures. Serum samples were collected after steady-state was reached, with a trough/steady-state serum concentration between 6 and 20 mg/L considered therapeutic. Logistic regression was used to identify significant predictors associated with the attainment of therapeutic concentrations.

RESULTS

One-hundred thirty patients (63 male) were included. The median (interquartile ranges) serum trough/steady-state concentration (Cmin/ss) was 16.2 (9.8-26.1) mg/L. The dose-normalized median (interquartile range) Cmin/ss was 11.5 (7.0-16.5) mg/L. The coefficient of variation of Cmin/ss and dose-normalized Cmin/ss were 69.4% and 64.2%, respectively. A weak correlation was observed between levetiracetam Cmin/ss and patient age (r = 0.21; P = 0.020), creatinine clearance (r = -0.26; P = 0.004), and daily dose (r = 0.42; P < 0.001). Logistic regression analysis identified age and daily levetiracetam dose as significant factors predicting target Cmin/ss attainment. The influence of concomitant antiepileptic therapy was not determined.

CONCLUSIONS

Age and daily dose were the most significant predictors of levetiracetam target-concentration attainment and should be considered in further investigations to develop a dosing algorithm for optimal levetiracetam therapy.

Comparison of levetiracetam versus phenytoin/fosphenytoin for busulfan seizure prophylaxis at a pediatric institution

INTRODUCTION

Busulfan is a chemotherapy agent used in hematopoietic stem cell transplant (HSCT) conditioning regimens. Busulfan is associated with tonic-clonic seizures in ~10% of patients if administered without seizure prophylaxis. Historically, phenytoin was the most commonly utilized seizure prophylaxis agent; however, phenytoin is associated with CYP450 drug interactions and potentially increases the clearance of busulfan. Levetiracetam is being used more recently for busulfan seizure prophylaxis and is not associated with drug-drug interactions; however, data supporting use in pediatric patients are limited. The primary objective is to determine whether there is any difference in seizure rates or safety profile between phenytoin and levetiracetam when used for seizure prophylaxis.

METHODS

We conducted a retrospective chart review including patients who received busulfan between 2010 and 2019 were identified. The data were evaluated to compare the incidence of busulfan-induced seizures in HSCT patients receiving either phenytoin or levetiracetam and to determine the impact of drug-drug interactions on treatment outcomes/adverse events.

RESULTS

A total of 342 patients were included with a median age of six years. Overall, five patients within the phenytoin group (n = 126) (4%) and zero patients in the levetiracetam group (n = 216) experienced a seizure (P = .007). There were no differences in liver enzyme elevations, recurrence rates of primary disease, and veno-occlusive disease.

CONCLUSION

Levetiracetam is effective at preventing seizures associated with busulfan administration with no clinically significant adverse effects when compared to phenytoin.

Population Pharmacokinetics of Levetiracetam: a Systematic Review

BACKGROUND

The use of levetiracetam (LEV) has been increasing given its favorable pharmacokinetic profile. Numerous population pharmacokinetic studies for LEV have been conducted. However, there are some discrepancies regarding factors affecting its pharmacokinetic variability. Therefore, this systematic review aimed to summarize significant predictors for LEV pharmacokinetics as well as the need for dosage adjustments.

METHODS

We performed a systematic search for population pharmacokinetic studies of LEV conducted using a nonlinear-mixed effect approach from PubMed, Scopus, CINAHL Complete, and Science Direct databases from their inception to March 2020. Information on study design, model methodologies, significant covariate-parameter relationships, and model evaluation was extracted. The quality of the reported studies was also assessed.

RESULTS

A total of 16 studies were included in this review. Only two studies were conducted with a two-compartment model, while the rest were performed with a one-compartment structure. Bodyweight and creatinine clearance were the two most frequently identified covariates on LEV clearance (CLLEV). Additionally, postmenstrual age (PMA) or postnatal age (PNA) were significant predictors for CLLEV in neonates. Only three studies externally validated the models. Two studies conducted pharmacodynamic models for LEV with relatively small sample size.

CONCLUSION

Significant predictors for LEV pharmacokinetics are highlighted in this review. For future research, a population pharmacokinetic-pharmacodynamic model using a larger sample size should be conducted. From a clinical perspective, the published models should be externally evaluated before clinical implementation.

Population Pharmacokinetics of Levetiracetam: A Systematic Review

BACKGROUND

Levetiracetam has been widely used as a treatment option for different types of epilepsy in both adults and children. Because of its large between-subject variability, several population pharmacokinetic studies have been performed to identify its pharmacokinetic covariates, and thus facilitate individualised therapy.

OBJECTIVE

The aim of this review was to provide a synopsis for population pharmacokinetic studies of levetiracetam and explore the identified influencing covariates.

METHODS

We systematically searched the PubMed and Embase databases from inception to 30 June 2020. The information on study designs, target population, model characteristics, and identified covariates was summarised. Moreover, the pharmacokinetic profiles were compared among neonates, children, and adults.

RESULTS

Fourteen studies were included, among which two involved neonates, four involved children, two involved both children and adults, and six involved adults only. The median value of apparent clearance for children (0.074 L/h/kg [range 0.038-0.079]) was higher than that for adults (0.054 L/h/kg [range 0.039-0.061]). Body weight was found to significantly influence the apparent clearance and volume of distribution, whereas renal function influenced the clearance. Likewise, coadministration with enzyme-inducing antiepileptic drugs (such as carbamazepine and phenytoin) increased the drug clearance by 9-22%, whereas coadministration with valproate acid decreased it by 18.8%.

CONCLUSION

Levetiracetam dose regimen is dependent on the body size and renal function of patients. Further studies are needed to evaluate levetiracetam pharmacokinetics in neonates and pregnant women.

Pharmacokinetic Monitoring of Levetiracetam in Portuguese Refractory Epileptic Patients: Effect of Gender, Weight and Concomitant Therapy

Levetiracetam is a second-generation antiepileptic drug, widely used in the treatment of focal and generalized epilepsy due to its pharmacokinetic and safety profiles. Its pharmacokinetic monitoring is ascribed as useful to personalize its dosing regimen. The aim of the present study was to describe, for the first time, the pharmacokinetics of levetiracetam in Portuguese refractory epileptic patients. Therefore, a retrospective study was carried out on 65 Portuguese refractory epileptic patients (pharmacokinetic study: 48; validation study: 17) admitted to the Refractory Epilepsy Centre of the Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal. The pharmacokinetic parameters of levetiracetam were estimated by applying a one-compartment model with first-order absorption and elimination analysis. Male patients showed higher distribution volume (Vd/F) and oral clearance (CL/F) than female patients (median Vd/F: 52.40 L in males and 38.60 L in females, p = 0.011; median CL/F: 4.71 L/h in males and 3.91 L/h in females, p = 0.028). Higher values of Vd/F (p = 0.026) and CL/F (p = 0.003) were also found in overweight patients relative to normal weight and obese patients. Carbamazepine was the co-administered antiepileptic drug that mostly affected the pharmacokinetics of levetiracetam, increasing both Vd/F (61.30 L with carbamazepine and 39.10 L without carbamazepine, p = 0.007) and CL/F (6.71 L/h with carbamazepine and 3.91 L/h without carbamazepine, p < 0.001). The pharmacokinetics of levetiracetam was affected by gender, body mass index, and co-administration of carbamazepine. This study highlights the impact of several factors on the CL/ and Vd/F of levetiracetam when administered to refractory epileptic patients. The importance of its pharmacokinetic monitoring in clinical pharmacy stands out, thereby enabling the optimization of antiepileptic drug therapy.

Levetiracetam and brivaracetam: a review of evidence from clinical trials and clinical experience

Until the early 1990s, a limited number of antiepileptic drugs (AEDs) were available. Since then, a large variety of new AEDs have been developed and introduced, several of them offering new modes of action. One of these new AED families is described and reviewed in this article. Levetiracetam (LEV) and brivaracetam (BRV) are pyrrolidone derivate compounds binding at the presynaptic SV2A receptor site and are thus representative of AEDs with a unique mode of action. LEV was extensively investigated in randomized controlled trials and has a very promising efficacy both in focal and generalized epilepsies. Its pharmacokinetic profile is favorable and LEV does not undergo clinically relevant interactions. Adverse reactions comprise mainly asthenia, somnolence, and behavioral symptoms. It has now been established as a first-line antiepileptic drug. BRV has been recently introduced as an adjunct antiepileptic drug in focal epilepsy with a similarly promising pharmacokinetic profile and possibly increased tolerability concerning psychiatric adverse events. This review summarizes the essential preclinical and clinical data of LEV and BRV that is currently available and includes the experiences at a large tertiary referral epilepsy center.

Comparison of levetiracetam with phenytoin for the prevention of intravenous busulfan-induced seizures in hematopoietic cell transplantation recipients

Purpose

Busulfan is used as a conditioning regimen for hematopoietic stem cell transplantation and is known to cause seizures as a side effect. As various anticonvulsant drugs have been reported, we conducted a retrospective investigation regarding the preventive effects and adverse events associated with different anticonvulsants administered alongside intravenous busulfan (ivBu) in our institution.

Methods

We targeted 104 patients who received ivBu at our institution from May 1, 2010 to April 30, 2017. We investigated the seizure prevention rate and adverse events rate under anticonvulsant prophylaxis.

Results

There were 70 cases (67.3%) of phenytoin administration and 34 cases (32.7%) of levetiracetam administration for anticonvulsant therapy. The seizure prevention rate was 98.6% for phenytoin and 100% for levetiracetam; seizures occurred in one out of 104 patients. There were no significant differences in the seizure prevention rate depending on the type of anticonvulsant. Further, there were no differences in adverse events.

Conclusions

Anticonvulsant prophylaxis is considered necessary for safe conditioning with ivBu. Adverse events associated with the use of levetiracetam are within an acceptable range. Further, levetiracetam is considered useful as a preventive drug against seizures during ivBu administration because it is easy to administer and has ideal pharmacokinetics for supportive care.

Chromatographic Characterization and Method Development for Determination of Levetiracetam in Saliva: Application to Correlation with Plasma Levels

Levetiracetam (LVT) is a widely used antiepileptic drug (AED). A less invasive sampling method for therapeutic drug monitoring (TDM) would be very useful particularly for children. Saliva has been shown as an adequate sample for TDM of some AEDs. Due to the high hydrophilicity of LVT its separation on common stationary phases is quite a challenge so that previous methods for determination of LVT in saliva employed either gradient high performance liquid chromatographic (HPLC) system or mass spectrometer as a detector. In this study the retention behavior of LVT on some common stationary phases was examined, with C8 being the most retentive. A simple isocratic HPLC method that is based on simple protein precipitation was developed and validated for the determination of LVT in saliva. The method was applied to a sample group of epileptic children for the purpose of assessing potential correlation with plasma LVT levels and to investigate patient's compliance. The results confirmed a reasonable correlation between plasma and salivary levels of LVT (R = 0.9) which supports the use of saliva for TDM of LVT. The study also revealed a significant percentage of epileptic patients having LVT levels below the estimated therapeutic range.

Levetiracetam pharmacokinetics in Japanese subjects with renal impairment

BACKGROUND AND OBJECTIVE

The anti-epileptic drug levetiracetam is excreted renally. The objective of this trial was to evaluate the pharmacokinetics of levetiracetam in Japanese patients with renal impairment including end-stage renal disease (ESRD) to confirm that existing dosing instructions-based on data from European patients-are appropriate in a Japanese population.

METHODS

This was a nonrandomised, open-label trial. Six participants were allocated to each of five groups (normal renal function, mild, moderate and severe renal impairment and ESRD); 30 participants in total. Participants received a single dose of levetiracetam 500 mg (normal or mild), 250 mg (moderate or severe), or 500 mg followed by 250 mg post-haemodialysis (ESRD). Blood and urine samples were obtained serially for levetiracetam and metabolite determinations. Noncompartmental pharmacokinetic parameters were calculated and steady-state profiles were simulated using the superposition method.

RESULTS

In this trial, levetiracetam total clearance decreased proportionally with creatinine clearance: 52, 31, 25, 20 and 11 mL/min/1.73 m(2) in healthy controls and in patients with mild, moderate, severe renal impairment, and ESRD, respectively. Simulated levetiracetam plasma profiles using the recommended dose adjustments were within the range for normal renal function. Overall, results from this trial were consistent with historical European data.

CONCLUSION

These findings confirm that the dosing instructions are appropriate for Japanese patients with renal impairment including ESRD.

Retention rates of levetiraceram in Chinese children and adolescents with epilepsy

BACKGROUND

Levetiracetam (Lev) is a new antiepileptic drugs, proved to be effective and tolerance in regulatory trials, but these controlled trials do not always predict how useful a drug will be in day to day clinical practice, Retention rates can provide a better indication of efficacy and tolerability in everyday use.

METHODS

Totally 124 patients with more than 3 months disease course were enrolled in the study from June 2007 to December 2007. The LEV dose ranged from 10 to 60 mg/kg per day. Follow up visit were performed at 6 months, 12 months, 24 months and 36 months, and treatment effects, adverse effects were recorded.

RESULTS

The LEV retention rates at 6, 12, 24, and 36 months were 93.5% (116/124), 84.7% (105/124), 65.3% (81/124), and 58.9% (73/124), respectively. The predominant causes of withdrawal were lack of efficacy (62.7%) and serious adverse effects (17.6%). In addition, 48.6% (51/105), 60.5% (49/81) and 72.6% (53/73) patients were seizure-free for 12 months, 24 months and 36 months, respectively. In this study, 75 (60.5%) patients experienced at least one side effect. The most common side effects observed were irritability 38.7% (29/75), somnolence 17.3% (13/75), learning disability 16.0% (12/75), anorexia 17.3% (13/75), somnipathy 13.3% (10/75), and abnormal behavior 13.3% (10/75).

CONCLUSIONS

Our study revealed the high retention rate of LEV in Chinese children and adolescents with epilepsy.

Effect of chronic administration of phenobarbital, or bromide, on pharmacokinetics of levetiracetam in dogs with epilepsy

BACKGROUND

Levetiracetam (LEV) is a common add-on antiepileptic drug (AED) in dogs with refractory seizures. Concurrent phenobarbital administration alters the disposition of LEV in healthy dogs.

HYPOTHESIS/OBJECTIVES

To evaluate the pharmacokinetics of LEV in dogs with epilepsy when administered concurrently with conventional AEDs.

ANIMALS

Eighteen client-owned dogs on maintenance treatment with LEV and phenobarbital (PB group, n = 6), LEV and bromide (BR group, n = 6) or LEV, phenobarbital and bromide (PB-BR group, n = 6).

METHODS

Prospective pharmacokinetic study. Blood samples were collected at 0, 1, 2, 4, and 6 hours after LEV administration. Plasma LEV concentrations were determined by high-pressure liquid chromatography. To account for dose differences among dogs, LEV concentrations were normalized to the mean study dose (26.4 mg/kg). Pharmacokinetic analysis was performed on adjusted concentrations, using a noncompartmental method, and area-under-the-curve (AUC) calculated to the last measured time point.

RESULTS

Compared to the PB and PB-BR groups, the BR group had significantly higher peak concentration (Cmax ) (73.4 ± 24.0 versus 37.5 ± 13.7 and 26.5 ± 8.96 μg/mL, respectively, P < .001) and AUC (329 ± 114 versus 140 ± 64.7 and 98.7 ± 42.2 h*μg/mL, respectively, P < .001), and significantly lower clearance (CL/F) (71.8 ± 22.1 versus 187 ± 81.9 and 269 ± 127 mL/h/kg, respectively, P = .028).

CONCLUSIONS AND CLINICAL IMPORTANCE

Concurrent administration of PB alone or in combination with bromide increases LEV clearance in epileptic dogs compared to concurrent administration of bromide alone. Dosage increases might be indicated when utilizing LEV as add-on treatment with phenobarbital in dogs.

Valproic Acid-induced Hyperammonemic Encephalopathy Promoted by Levetiracetam

Encephalopathy resulting from the administration of levetiracetam (LEV) is a rare occurrence. We experienced a patient receiving LEV treated with valproic acid (VPA) for partial seizures with secondary generalization, following which she developed hyperammonemic encephalopathy and showed complete recovery after the drug was withdrawan. LEV is able to promote hyperammonemic encephalopathy when added to VPA.

Pharmacokinetics of the antiepileptic drug levetiracetam in healthy Japanese and Caucasian volunteers following intravenous administration

The intravenous (iv) formulation of levetiracetam has been available in clinical practice worldwide for several years, but not in Japan. Two open-label studies were conducted: Study A evaluated the bioequivalence of iv and oral tablet formulations in healthy Japanese volunteers; and Study B subsequently compared the pharmacokinetics of iv levetiracetam in healthy Japanese and Caucasian volunteers. Study A had a randomised, two-way crossover design; a single 1,500 mg levetiracetam dose was administered as a 15-min iv infusion and as 3 × 500 mg oral tablets to Japanese volunteers. In Study B, 1,500 mg levetiracetam was administered as single and repeated 15-min iv infusions to Japanese and Caucasian volunteers. Overall, 26/27 volunteers completed Study A and 32/32 (16 Japanese; 16 Caucasian) completed Study B. In Study A, the point estimate and 90 % confidence interval (CI) for the geometric least squares mean (LSM) ratio (iv vs oral) were fully included within the acceptance range for bioequivalence (0.85-1.25) for the area under plasma concentration-time curve from 0 to last quantifiable observation (AUClast 0.97 [0.95, 0.99]), but not for the maximum plasma concentration (C max 1.64 [1.47, 1.83]). In Study B, after a single iv infusion, the point estimates (90 % CI) for the geometric LSM ratio (Japanese vs Caucasian) for body weight-normalised C max and AUClast were 1.21 (1.07, 1.36) and 0.97 (0.90, 1.04), respectively. Corresponding values after repeated iv infusions were C max,ss 1.01 (0.91, 1.12) and AUCτ,ss 0.89 (0.83, 0.96). Levetiracetam was well tolerated in both studies. Study A did not demonstrate the bioequivalence of single doses of levetiracetam 1,500 mg administered as an iv infusion and as oral tablets in healthy Japanese adults. Study B, however, showed that pharmacokinetic profiles were generally similar between Japanese and Caucasian adults after single and repeated iv infusions of levetiracetam 1,500 mg.

Seizures and epilepsy in cats

Seizures are a common presenting complaint in cats, although causes and options for the treatment of seizures in this species have been historically poorly described in the veterinary literature. Seizure manifestation in cats may be different than what is typically seen in dogs, but the underlying causes of seizure activity are the same. These include primary epilepsies, structural epilepsies, and reactive seizures. Although primary epilepsy was once believed to be rare in cats, we now commonly appreciate this syndrome, albeit at a lower frequency than in dogs. Because of this, a complete diagnostic work-up is recommended for all cats presenting for initial evaluation of seizures. Symptomatic treatment of seizures in cats is similar to dogs, with only a few limitations related to species-specific antiepileptic drug toxicities. The goal of this review is to summarize the recent veterinary literature related to feline seizures, with a focus on seizure classification, clinical manifestation, diagnostic evaluation, and treatment options.

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.

Antiepileptic drug interactions - principles and clinical implications

Antiepileptic drugs (AEDs) are widely used as long-term adjunctive therapy or as monotherapy in epilepsy and other indications and consist of a group of drugs that are highly susceptible to drug interactions. The purpose of the present review is to focus upon clinically relevant interactions where AEDs are involved and especially on pharmacokinetic interactions. The older AEDs are susceptible to cause induction (carbamazepine, phenobarbital, phenytoin, primidone) or inhibition (valproic acid), resulting in a decrease or increase, respectively, in the serum concentration of other AEDs, as well as other drug classes (anticoagulants, oral contraceptives, antidepressants, antipsychotics, antimicrobal drugs, antineoplastic drugs, and immunosupressants). Conversely, the serum concentrations of AEDs may be increased by enzyme inhibitors among antidepressants and antipsychotics, antimicrobal drugs (as macrolides or isoniazid) and decreased by other mechanisms as induction, reduced absorption or excretion (as oral contraceptives, cimetidine, probenicid and antacides). Pharmacokinetic interactions involving newer AEDs include the enzyme inhibitors felbamate, rufinamide, and stiripentol and the inducers oxcarbazepine and topiramate. Lamotrigine is affected by these drugs, older AEDs and other drug classes as oral contraceptives. Individual AED interactions may be divided into three levels depending on the clinical consequences of alterations in serum concentrations. This approach may point to interactions of specific importance, although it should be implemented with caution, as it is not meant to oversimplify fact matters. Level 1 involves serious clinical consequences, and the combination should be avoided. Level 2 usually implies cautiousness and possible dosage adjustments, as the combination may not be possible to avoid. Level 3 refers to interactions where dosage adjustments are usually not necessary. Updated knowledge regarding drug interactions is important to predict the potential for harmful or lacking effects involving AEDs.

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.

Efficacy and tolerability of levetiracetam in children with epilepsy

OBJECTIVE

To assess the efficacy and tolerability of levetiracetam (Lev) in children with epilepsy.

METHODS

Open-label observational, prospective, single arm, non-interventional study examining patients (≤14 years) with epilepsy, receiving mono- or combination therapy with levetiracetam. Levetiracetam was started at a dose of approximately 10mg/kg/day. The dose was titrated up with 10mg/kg increments if seizures were poorly controlled but the maximum daily dose could not be more than 60 mg/kg/day. Documented were seizure type and frequency, levetiracetam dose and side effects.

RESULTS

120 patients (39.3% females, mean age 4.5 ± 3.9 years) were enrolled. Average duration of follow-up was 10.3 ± 3.5 months. At study endpoint, 64.8% of patients got seizure free and 83.0% got a seizure reduction of ≥50%. Observed side effects were somnolence, dysphoria, nervousness, dystrophy, somnipathy, asitia, debilitation, etc. and the incidence rate in the study was 47.5%. Four (3.3%) of 120 patients withdrew because of intolerance of side effects. The estimated one year retention rate of levetiracetam was 73.3%. Poor effect was the most common reason for withdrawal.

CONCLUSIONS

In our study, it seemed that levetiracetam was safe and effective for a wide range of epileptic seizures in children with epilepsy.

Age and comedications influence levetiracetam pharmacokinetics in children

The pharmacokinetics of many antiepileptic drugs differs between adults and children. The influence of age and concomitant medications on the dose/concentration ratio of levetiracetam was examined in 103 children with epilepsy. Dosing and plasma levels of levetiracetam and concomitant antiepileptic drugs were reviewed retrospectively. The dose/concentration ratio was calculated as the weight-normalized dose (mg/kg/day) divided by the steady-state trough plasma drug level, which was used as a measure of apparent oral clearance of levetiracetam. Children were classified into age groups and treatment groups: levetiracetam given with enzyme inducers (n = 24) or nonenzyme inducers (n = 69), or as monotherapy (n = 10). Levetiracetam clearance differed significantly between age groups (0-4, 5-11, and 12-17 years), i.e., the younger the child, the higher the clearance. The increase was 1.7-fold between the youngest and oldest age groups. Children on enzyme inducers exhibited significantly higher clearance (1.3-fold), compared with those on nonenzyme inducers and monotherapy. Levetiracetam did not influence the clearance of lamotrigine, valproate, topiramate, or clonazepam. In conclusion, younger age and comedication with an enzyme inducer increased levetiracetam clearance. This finding should be taken into account when treating individual patients.

Intravenous Levetiracetam as first-line treatment of status epilepticus in the elderly

BACKGROUND

Status epilepticus is a condition of prolonged/repetitive seizures that often occurs in the elderly. Treatment in the elderly can be complicated by serious side effects associated with traditional drugs.

OBJECTIVE

The aim of this pilot study was to evaluate the short-term efficacy/safety of intravenously administered LEV (IVLEV) as the treatment of choice for SE in the elderly.

METHODS

We enrolled nine elderly patients (five female/four male; median age 78 years) with SE. Two patients had a previous diagnosis of epilepsy; in the remaining seven, SE was symptomatic. SE was convulsive in five and non-convulsive in four. All the patients presented concomitant medical conditions (arrhythmias/respiratory distress/hepatic diseases). As the traditional therapy for SE was considered unsafe, IVLEV was used as first-line therapy (loading dose of 1500 mg/100 ml/15 min, mean maintenance daily dose of 2500 mg/24 h) administered during video-EEG monitoring.

RESULTS/CONCLUSIONS

In all the patients but one, IVLEV was effective in the treatment of SE and determined either the disappearance of (7/8), or significant reduction in (1/8), epileptic activity; no patient relapsed in the subsequent 24 h. No adverse events or changes in the ECG/laboratory parameters were observed. These data suggest that IVLEV may be an effective/safe treatment for SE in the elderly.

Adjunctive levetiracetam in infants and young children with refractory partial-onset seizures

PURPOSE

To evaluate the efficacy and tolerability of adjunctive levetiracetam in very young children (aged 1 month to <4 years) with partial-onset seizures inadequately controlled with one or two antiepileptic drugs.

METHODS

This multicenter, double-blind, randomized, placebo-controlled study consisted of a 48-h inpatient baseline video-EEG (electroencephalography) and a 5-day inpatient treatment period (1-day up-titration; 48-h evaluation video-EEG in the last 2 days). Children who experienced at least two partial-onset seizures during the 48-h baseline video-EEG were randomized to either levetiracetam [40 mg/kg/day (age 1 to <6 months); 50 mg/kg/day (age >or=6 months to <4 years] or placebo.

RESULTS

Of 175 patients screened, 116 patients were randomized [60 levetiracetam; 56 placebo; intent-to-treat (ITT) population], and 111 completed the study. The responder rate in average daily partial-onset seizures frequency (48-h video-EEG monitoring; primary efficacy variable) was 43.1% for levetiracetam [modified ITT (mITT) = 58] versus 19.6% for placebo (mITT = 51; p=0.013), with odds ratio for response 3.11 [95% confidence interval (CI), 1.22-8.26]. The median percent reduction from baseline in average daily partial-onset seizure frequency was 43.6% for levetiracetam and 7.1% for placebo with a median difference between treatment groups of 39.2% (95% CI, 17.5-62.2; p < 0.001). In general, levetiracetam was well tolerated. Treatment-emergent adverse events were reported by 55.0% levetiracetam- and 44.6% placebo-treated patients (ITT population). The most frequently reported adverse events were somnolence (13.3% levetiracetam, 1.8% placebo) and irritability (11.7% levetiracetam, 0% placebo).

DISCUSSION

Adjunctive levetiracetam is an efficacious and well-tolerated treatment for partial-onset seizures in infants and young children.

Review of levetiracetam, with a focus on the extended release formulation, as adjuvant therapy in controlling partial-onset seizures

Levetiracetam is a second-generation antiepileptic drug (AED) with a unique chemical structure and mechanism of action. The extended release formulation of levetiracetam (Keppra XR(); UCB Pharma) was recently approved by the Food and Drug Administration for adjunctive therapy in the treatment of partial-onset seizures in patients 16 years of age and older with epilepsy. This approval is based on a double-blind, randomized, placebo-controlled, multicenter, multinational trial. Levetiracetam XR allows for once-daily dosing, which may increase compliance and, given the relatively constant plasma concentrations, may minimize concentration-related adverse effects. Levetiracetam's mode of action is not fully elucidated, but it has been found to target high-voltage, N-type calcium channels as well as the synaptic vesicle protein 2A (SV2A). Levetiracetam has nearly ideal pharmacokinetics. It is rapidly and almost completely absorbed after oral ingestion, is <10% protein-bound, demonstrates linear kinetics, is minimally metabolized through a pathway independent of the cytochrome P450 system, has no significant drug-drug interactions, and has a wide therapeutic index. The most common reported adverse events with levetiracetam XR were somnolence, irritability, dizziness, nausea, influenza, and nasopharyngitis. Levetiracetam XR provides an efficacious and well-tolerated treatment option for adjunctive therapy in the treatment of partial-onset seizures.

Effects of levetiracetam on generalized discharges monitored with ambulatory EEG in epileptic patients

PURPOSE

Quantitative analysis of epileptiform discharges (EDs) before and after the initiation of an antiepileptic treatment is a useful tool to objectively documentate the efficacy of an antiepileptic drug (AED). Aim of this study was to evaluate the effect of levetiracetam (LEV) on EDs, monitored with ambulatory EEG (A/EEG), in a limited series of patients with generalized epilepsy.

METHODS

We performed 24h A/EEG recording in basal condition and at follow-up after LEV therapy in 21 adult epileptic patients. Eleven received LEV as monotherapy and 10 as add-on. For each patient we quantified total epileptic activity considering the following parameters: total number, total duration, maximal duration and median duration of EDs. Self-reported information on the effect of LEV on clinical seizures was also collected, to determine the electro-clinical correlation.

RESULTS

A high variability of the response to LEV was observed in the monotherapy group, without statistical differences for all the parameters investigated. A significant reduction of the total number of seizures (113.6 vs. 41.2; p=.01) was observed in patients in add-on therapy. The modifications of epileptiform EEG abnormalities did not necessarily correlate with the self-reported clinical impressions.

DISCUSSION

The quantification of EDs monitored by A/EEG provides a useful objective support for evaluating the neurophysiologic profile and the real efficacy of an antiepileptic treatment. In our patients LEV was able to significantly reduce the EDs only in add-on therapy. Further larger studies are necessary to clarify the effects of LEV on electro-clinical features of generalized epilepsy.

Impending status epilepticus and anxiety in a pregnant woman treated with levetiracetam

Levetiracetam (LEV) has been considered to undergo no significant change in bioavailability during pregnancy; however, it was recently demonstrated to display modifications leading to a drop in its serum level. We describe a patient who displayed impending status epilepticus following a fall in her LEV level during the first trimester. The oral LEV dosage was increased, and phenytoin and benzodiazepines were transiently prescribed. She experienced severe anxiety and an unbearable fear over the deleterious consequences for her baby despite repeated, reassuring explanations. Her anxiety was so strong that she aborted electively shortly after leaving the hospital. This observation emphasizes the need for LEV level monitoring during pregnancy to prevent unexpected seizure relapses. The rapid increase in levetiracetam dosage in parallel with the loss of seizure control is suspected of facilitating the induction of significant psychiatric changes.

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.

Multicenter double-blind, randomized, placebo-controlled trial of levetiracetam as add-on therapy in Chinese patients with refractory partial-onset seizures

PURPOSE

To evaluate efficacy and tolerability of levetiracetam (LEV; Keppra) as add-on therapy in Chinese patients with refractory partial-onset seizures.

METHODS

In this multicenter, double-blind, randomized, placebo-controlled trial, 206 patients aged 16-70 years with uncontrolled partial-onset seizures were randomized to receive LEV (n =103) or placebo (n =103); 202 patients (LEV, n =102; placebo, n = 100) comprised the intent-to-treat population. An 8-week historical baseline period confirmed eligibility according to seizure count. The 16-week treatment period consisted of a 4-week up-titration period (LEV, 1,000-3,000 mg/day in two equal divided doses) followed by a 12-week maintenance period. Efficacy assessments were based on weekly frequency of partial-onset seizures during the 16-week treatment period.

RESULTS

LEV significantly decreased weekly partial-onset seizure frequency over placebo by 26.8% (p < 0.001). Median percentage reductions in weekly partial-onset seizure frequency from historical baseline were 55.9% for LEV and 13.7% for placebo (p < 0.001). The >or=50% responder rates were 55.9% for LEV, compared with 26.0% for placebo (p < 0.001). Freedom from partial-onset seizures during treatment period was achieved by 11 LEV patients (10.8%) and 2 placebo patients (2.0%) (p = 0.012). Adverse events were reported by 65 LEV-treated patients (63.1%) and 62 placebo-treated patients (60.2%); most were of mild-to-moderate intensity. The most common adverse events were somnolence (LEV, 17.5%; placebo, 17.5%), decreased platelet count (LEV, 9.7%; placebo, 9.7%), and dizziness (LEV, 7.8%; placebo, 13.6%).

DISCUSSION

Add-on LEV was effective and well-tolerated in Chinese patients with refractory partial-onset seizures.