Clinical Pharmacokinetics of Levetiracetam

Levetiracetam for seizures in children with brain tumors and other cancers

Children with brain tumors and other cancers can suffer from seizures. Unfortunately, most antiepileptic therapies are metabolized by the hepatic cytochrome P450 (CYP) system. Levetiracetam, a newer anticonvulsant, does not undergo CYP metabolism and does not alter the pharmacokinetics of chemotherapy, antiemetics, and corticosteroids, which are metabolized by the liver. We studied 23 patients with cancer and seizures treated with levetiracetam. Over 95% of patients had fewer seizures, with 65.2% becoming seizure free; only one patient experienced an adverse reaction. Levetiracetam is effective and well tolerated in children with brain tumors and other cancers, who are often on multiple enzyme-inducing drugs.

Safety and feasibility of switching from phenytoin to levetiracetam monotherapy for glioma-related seizure control following craniotomy: a randomized phase II pilot study

Seizures are common in patients with gliomas, and phenytoin (PHT) is frequently used to control tumor-related seizures. PHT, however, has many undesirable side effects (SEs) and drug interactions with glioma chemotherapy. Levetiracetam (LEV) is a newer antiepileptic drug (AED) with fewer SEs and essentially no drug interactions. We performed a pilot study testing the safety and feasibility of switching patients from PHT to LEV monotherapy for postoperative control of glioma-related seizures. Over a 13-month period, 29 patients were randomized in a 2:1 ratio to initiate LEV therapy within 24 h of surgery or to continue PHT therapy. 6 month follow-up data were available for 15 patients taking LEV and for 8 patients taking PHT. In the LEV group, 13 patients (87%) were seizure-free. In the PHT group, 6 patients (75%) were seizure-free. Reported SEs at 6 months was as follows (%LEV/%PHT group): dizziness (0/14), difficulty with coordination (0/29), depression (7/14) lack of energy or strength (20/43), insomnia (40/43), mood instability (7/0). The pilot data presented here suggest that it is safe to switch patients from PHT to LEV monotherapy following craniotomy for supratentorial glioma. A large-scale, double-blinded, randomized control trial of LEV versus PHT is required to determine seizure control equivalence and better assess differences in SEs.

Pharmacodynamic and pharmacokinetic interaction profiles of levetiracetam in combination with gabapentin, tiagabine and vigabatrin in the mouse pentylenetetrazole-induced seizure model: an isobolographic analysis

To characterize the interactions between levetiracetam and the antiepileptic drugs gabapentin, tiagabine, and vigabatrin in suppressing pentylenetetrazole-induced clonic seizures in mice, type II isobolographic analysis was used. Clonic seizures were evoked in Albino Swiss mice by subcutaneous injection of pentylenetetrazole at its CD(97)(98 mg/kg). Adverse-effect profiles with respect to motor performance, long-term memory and skeletal muscular strength were measured along with total brain antiepileptic drug concentrations. The combination of gabapentin with levetiracetam at the fixed-ratios of 2:1, 1:1, 1:2, and 1:4 were supra-additive (synergistic) in terms of seizure suppression whilst the combination at the fixed-ratio of 4:1 was additive. Tiagabine with levetiracetam and vigabatrin with levetiracetam at the fixed-ratios of 1:25, 1:50, 1:100, 1:200, and 1:400 and at 2:1, 3:1, 4:1, 6:1, 8:1, and 16:1 were additive, respectively. No acute adverse effects were observed. Measurement of total brain antiepileptic drug concentrations revealed that levetiracetam in combination with gabapentin at the fixed-ratio of 1:4 significantly elevated (21%) total brain gabapentin concentrations. In contrast, levetiracetam was without affect on tiagabine or vigabatrin concentrations and co-administration with gabapentin, tiagabine or vigabatrin had no effect on levetiracetam brain concentrations, indicating the pharmacodynamic nature of interaction between these antiepileptic drugs in the mouse pentylenetetrazole model. The combination of gabapentin with levetiracetam at the fixed-ratios of 2:1, 1:1, 1:2, and 1:4 appears to be particularly favorable combination exerting supra-additive interaction in suppressing pentylenetetrazole-induced seizures, although there is a pharmacokinetic contribution to the interaction between levetiracetam and gabapentin at the fixed-ratio of 1:4. Levetiracetam in combination with tiagabine and vigabatrin appear to be neutral combinations producing only additivity in the mouse pentylenetetrazole model.

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.

Levetiracetam for the treatment of co-occurring alcohol dependence and anxiety: case series and review

OBJECTIVES

Alcohol dependence is frequently associated with anxiety disorders. The exact nature of the relationship between alcohol dependence and anxiety disorders is unknown, but emerging evidence suggests that in a majority of cases, the anxiety disorder is independent of the alcohol use disorder. There is pre-clinical and clinical evidence that levetiracetam, a newer generation anticonvulsant medication, may be efficacious in the treatment of co-occurring alcohol use and anxiety disorders.

METHODS

In an open label clinical trial, three patients with alcohol dependence and a co-morbid anxiety disorder were treated with levetiracetam in doses up to 1500 mg twice daily for up to 8 weeks.

RESULTS

All three participants reported reductions in alcohol consumption and anxiety symptoms during the study period. Levetiracetam was generally well tolerated.

CONCLUSION

This study suggests that levetiracetam deserves further study in the treatment of alcohol dependence and co-occurring anxiety disorders.

Safety and pharmacokinetics of intravenous levetiracetam infusion as add-on in status epilepticus

PURPOSE

To evaluate the feasibility and safety of intravenous (iv) levetiracetam (LEV) added to the standard therapeutic regimen in adults with status epilepticus (SE), and as secondary objective to assess a population pharmacokinetic (PK) model for ivLEV in patients with SE.

METHODS

In 12 adults presenting with SE, 2,500 mg ivLEV was added as soon as possible to standardized protocol, consisting of iv clonazepam and/or rectal diazepam, as needed followed by phenytoin or valproic acid. ivLEV was administered over approximately 5 min, in general after administration of clonazepam, regardless the need for further treatment. During 24-h follow-up, patients were observed for any clinically relevant side-effects. Blood samples for PK analysis were available in 10 patients. A population PK model was developed by iterative two-stage Bayesian analysis and compared to PK data of healthy volunteers.

RESULTS

Eleven patients with a median age of 60 years were included in the per protocol analysis. Five were diagnosed as generalized-convulsive SE, five as partial-convulsive SE, and one as a nonconvulsive SE. The median time from hospital admission to ivLEV was 36 min. No serious side effects could be related directly to the administration of ivLEV. During PK analysis, four patients showed a clear distribution phase, lacking in the others. The PK of the population was best described by a two-compartment population model. Mean (standard deviation, SD) population parameters included volume of distribution of central compartment: 0.45 (0.084) L/kg; total body clearance: 0.0476 (0.0147) L/h/kg; distribution rate constants, central to peripheral compartment (k(12)): 0.24 (0.12)/h, and peripheral to central (k(21)): 0.70 (0.22)/h. Mean maximal plasma concentration was 85 (19) mg/L.

DISCUSSION

The addition of ivLEV to the standard regimen for controlling SE seems feasible and safe. PK data of ivLEV in patients with SE correspond to earlier values derived from healthy volunteers, confirming a two-compartment population model.

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.

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.

The effects of levetiracetam on alcohol consumption in alcohol-dependent subjects: an open label study

The aim of this open-label pilot study was to assess the efficacy and safety of the novel anticonvulsant agent, levetiracetam, for the treatment of alcohol dependence. A maximal dose of 2000 mg was administered daily for 10 weeks to alcohol dependent subjects (n = 20). Mean reported ethanol intake declined significantly from 5.3 to 1.7 standard drinks per day. Levetiracetam was well tolerated by most subjects.

Isobolographic and behavioral characterizations of interactions between vigabatrin and gabapentin in two experimental models of epilepsy

The aim of this study was to characterize the pharmacodynamic, pharmacokinetic and adverse-effect profiles of vigabatrin and gabapentin. Isobolographic analysis was used in two mouse experimental models of epilepsy: the maximal electroshock seizure threshold test and pentylenetetrazole-induced seizures. In the maximal electroshock seizure threshold test, electroconvulsions were produced by a current with various intensities whilst in the pentylenetetrazole test a CD(97) dose (100 mg/kg) was used. Potential adverse-effect profiles of interactions of vigabatrin with gabapentin at three fixed-ratios of 1:3, 1:1 and 3:1 from both seizure tests were evaluated in the chimney (motor performance) and grip-strength (skeletal muscular strength) tests. Vigabatrin and gabapentin total brain concentrations were determined with high performance liquid chromatography. Vigabatrin and gabapentin administered singly increased the electroconvulsive threshold (TID(20) - 226.2 and 70.0 mg/kg, respectively). With isobolography, the combination of vigabatrin with gabapentin at the fixed-ratio of 1:3 exerted supra-additive (synergistic) interactions whilst at 1:1 and 3:1 additivity occurred. Similarly, vigabatrin and gabapentin administered singly suppressed the pentylenetetrazole-induced seizures (ED(50) values - 622.5 and 201.1 mg/kg, respectively). Isobolography revealed that vigabatrin with gabapentin in combination at the fixed-ratio of 1:1 produced supra-additive (synergistic) interaction whilst at 1:3 and 3:1 additivity occurred. In combination neither motor coordination nor skeletal muscular strength was affected. Total vigabatrin and gabapentin brain concentrations revealed that neither drug affected the pharmacokinetics of the other. Vigabatrin and gabapentin have a favorable pharmacodynamic interaction in animal seizure models in the absence of acute adverse effects or concurrent pharmacokinetic changes.

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.

Levetiracetam in the treatment of epilepsy

Epilepsy is a common chronic disorder that requires long-term antiepileptic drug therapy. Approximately one half of patients fail the initial antiepileptic drug and about 35% are refractory to medical therapy, highlighting the continued need for more effective and better tolerated drugs. Levetiracetam is an antiepileptic drug marketed since 2000. Its novel mechanism of action is modulation of synaptic neurotransmitter release through binding to the synaptic vesicle protein SV2A in the brain. Its pharmacokinetic advantages include rapid and almost complete absorption, minimal insignificant binding to plasma protein, absence of enzyme induction, absence of interactions with other drugs, and partial metabolism outside the liver. The availability of an intravenous preparation is yet another advantage. It has been demonstrated effective as adjunctive therapy for refractory partial-onset seizures, primary generalized tonic-clonic seizures, and myoclonic seizures of juvenile myoclonic epilepsy. In addition, it was found equivalent to controlled release carbamazepine as first-line therapy for partial-onset seizures, both in efficacy and tolerability. Its main adverse effects in randomized adjunctive trials in adults have been somnolence, asthenia, infection, and dizziness. In children, the behavioral adverse effects of hostility and nervousness were also noted. Levetiracetam is an important addition to the treatment of epilepsy.

Pharmaco-EEG-based assessment of interaction between ethanol and levetiracetam

Recent research suggests a potential role for a new generation of anticonvulsant drugs, including levetiracetam, in the treatment of alcohol dependence. Some elements of the central mechanism of action that levetiracetam has in common with ethanol, give rise to the question of whether there is an interaction between these two agents and whether there is any risk associated with the enhanced depressive effect of these agents on the central nervous system. In this study, we have used a pharmaco-electroencephalographic (EEG) method to examine the interaction of ethanol with levetiracetam. The influence of levetiracetam on the effect of ethanol on EEG of rabbits (midbrain reticular formation, hippocampus, frontal cortex) was determined. Levetiracetam was administered p.o. as a single dose (50mg/kg or 200mg/kg) or repeatedly at a dose of 100mg/kg/day for 14 days. Ethanol was injected i.v. at a dose of 0.8 g/kg 60 min after the administration of levetiracetam. Ethanol caused an increase in the low frequencies (0.5-4 Hz) in the recording, as well as a marked decrease in the higher frequencies (13-30 Hz and 30-45 Hz). Changes in the EEG recordings after levetiracetam alone were more significant when the drug was given in repeated doses. Combined administration of ethanol and levetiracetam (200mg/kg) resulted in a markedly synergistic effect in the frontal cortex and the midbrain reticular formation. The drug decreases the sensitivity of the hippocampus to ethanol, an observation that may be important in the treatment of alcohol addiction.

Intravenous levetiracetam in children with epilepsy

Intravenous levetiracetam recently became available for use in patients aged >16 years. There are few data about its safety and efficacy in children. We retrospectively analyzed data from children treated with intravenous levetiracetam. Ten patients (6 female, 4 male), aged 3 weeks to 19 years, were treated with intravenous levetiracetam at a mean dose of 50.5 mg/kg/day for a mean duration of 4.9 days. Four patients received intravenous levetiracetam for acute repetitive seizures/status epilepticus, and three as replacement for oral levetiracetam because administration of oral levetiracetam was temporarily infeasible. One patient each received intravenous levetiracetam for seizure prophylaxis during brain biopsy, as maintenance treatment after acute seizures, and as substitute for sodium valproate. Three of four patients with acute repetitive seizures/status epilepticus became seizure-free; the fourth patient had a partial reduction in seizure frequency. All three patients who received intravenous levetiracetam as substitute for oral levetiracetam tolerated the switch well. The other three patients were seizure-free on intravenous levetiracetam. No serious adverse effects were observed, and all patients completed treatment with intravenous levetiracetam for the intended period. Intravenous levetiracetam may be effective in various clinical situations requiring intravenous administration of an antiepileptic drug.

Serum concentration/dose ratio of levetiracetam before, during and after pregnancy

PURPOSE

To investigate changes in levetiracetam (LEV) serum concentration/dose ratio (C/D-ratio) in relation to pregnancy.

METHODS

Altogether 21 consecutive pregnancies in 20 women with epilepsy receiving LEV during gestation were studied retrospectively. The main target variable was the C/D-ratio before and during pregnancy, and in the post partum period. Secondary target variables were changes in LEV dose, concomitant use of other antiepileptic drugs and seizure frequency. Student's paired t-test and two-sample t-test for independent samples were used to test for statistically significant changes in C/D-ratio means.

RESULTS

Mean C/D-ratio in the third trimester was 50% of the mean C/D-ratio at baseline (p<0.001, n=11). Baseline levels were reached within the first weeks after pregnancy. The interindividual variability was pronounced.

CONCLUSIONS

Serum concentrations of LEV declined significantly in the third trimester of pregnancy and increased rapidly after delivery.

Therapeutic drug monitoring of levetiracetam by high-performance liquid chromatography with photodiode array ultraviolet detection: preliminary observations on correlation between plasma concentration and clinical response in patients with refractory epilepsy

Levetiracetam is a new antiepileptic drug prescribed for the treatment of patients with refractory partial seizures with or without secondary generalization as well as for the treatment of juvenile myoclonic epilepsy. A rapid and specific method by high-performance liquid chromatography diode array detection was developed to measure the concentration of levetiracetam in human plasma. The trough plasma concentrations measured in 69 epileptic patients treated with 500 to 3000 mg/d of levetiracetam ranged from 1.1 to 33.5 microg/mL. The mean (range) levetiracetam plasma concentrations in responders and nonresponders were 12.9 microg/mL (4.6-21 microg/mL) and 9.5 microg/mL (1.1-20.9 microg/mL), respectively. A wide variability in concentration-response relationships was observed in patients. Using a receiver operating characteristic curve, the threshold levetiracetam concentration for a therapeutic response was 11 microg/mL. The sensitivity and specificity for this threshold levetiracetam concentration were 73% and 71%, respectively. According to chi analysis, this finding was not significant probably because of the small number of patients and because of their refractory seizure type. Nevertheless, the levetiracetam plasma concentration could be used to help clinicians detect severe intoxication or to verify compliance by repeating the measurement in patients.

Lack of Pharmacokinetic Interaction of Levetiracetam on Carbamazepine, Valproic Acid, Topiramate, and Lamotrigine in Children with Epilepsy

PURPOSE

To determine whether levetiracetam (LEV) affects plasma concentrations of carbamazepine, valproic acid, topiramate, and lamotrigine in children with epilepsy.

METHODS

The potential for interaction of LEV with other antiepileptic drugs (AEDs) was assessed using plasma drug levels obtained in a randomized placebo-controlled phase III trial of adjunctive LEV in children receiving one or two concomitant AEDs. Multiple plasma AED levels at baseline and during adjunctive treatment with LEV or placebo were compared by repeated measures analysis of covariance and mean concentration ratios (treatment/baseline) were estimated with their 90% confidence intervals (CI).

RESULTS

The study population included 187 children receiving any concomitant AED alone or in combination. The geometric mean concentrations at baseline and during LEV treatment were carbamazepine 8.4 microg/ml versus 8.1 microg/ml (coefficient of variation, CV = 30%; n = 35); valproic acid 83.8 versus 82.5 microg/ml (CV = 38%; n = 23); topiramate 7.3 versus 7.2 microg/ml (CV = 82%; n = 28); lamotrigine 8.2 versus 7.7 microg/ml (CV = 62%; n = 22). For each AED, the mean concentration ratios (LEV/baseline) and their 90% CIs showed that AED concentrations were unaffected by concomitant LEV administration. No differences were observed between LEV and placebo.

CONCLUSIONS

LEV does not affect plasma concentrations of carbamazepine, valproic acid, topiramate, or lamotrigine in children with epilepsy.

Modeling and simulation of intravenous levetiracetam pharmacokinetic profiles in children to evaluate dose adaptation rules

PURPOSE

To develop a pharmacokinetic model for intravenous levetiracetam in children, based on adult intravenous data and pediatric oral data.

METHODS

Data from two adult Phase-I studies in which levetiracetam was given intravenously were utilized to develop the adult population pharmacokinetic two-compartment intravenous model. After model qualification, combination with an existing pediatric one-compartment oral population pharmacokinetic model enabled simulation of twice-daily intravenous infusions of levetiracetam in children. Median and 90% confidence intervals for C(trough), C(max) (end of infusion) and AUC(tau) were simulated for 2000 children and compared to the values observed in adults.

RESULTS

The population pharmacokinetic two-compartment model successfully described intravenous levetiracetam pharmacokinetics in healthy adults. After combination with the oral pediatric population model, steady-state concentrations at the end of 15-, 30- and 60 min b.i.d. levetiracetam intravenous infusions in children were predicted to be 29-41, 17-24 and 6-13% higher than those observed after oral dosing of 30 mg/kg b.i.d. Concentrations returned to the range of oral exposures within 1h after the infusion peak. The combined model predicted that steady-state peak plasma concentrations and AUC(tau) in children receiving 30 mg/kg twice daily as 15 min intravenous infusions were within the range of predicted and observed C(max,ss) and AUC(tau )values of adults receiving 15 min intravenous infusions of 1500 mg levetiracetam.

CONCLUSIONS

The simulations suggest that levetiracetam may be administered intravenously in children as 15 min infusions.

The SKATE™ study: An open-label community-based study of levetiracetam as add-on therapy for adults with uncontrolled partial epilepsy

The Safety of Keppra as Adjunctive Therapy in Epilepsy (SKATE) study aimed to evaluate the safety and efficacy of levetiracetam (Keppra, LEV) as add-on therapy for refractory partial seizures in clinical practice. This Phase IV, 16-week, open-label study recruited patients > or =16-year old with treatment-resistant partial seizures. LEV (1000 mg/day) was added to a stable concomitant antiepileptic drug regimen. LEV dosage was adjusted based on seizure control and tolerability to a maximum of 3000 mg/day. 1541 patients (intent-to-treat population) were recruited including 1346 (87.3%) who completed the study and 77.0% who declared further continuing on LEV after the trial. Overall, 50.5% of patients reported at least one adverse event that was considered related to LEV treatment. The most frequently reported drug-related adverse events were mild-to-moderate somnolence, fatigue, dizziness and headache. Serious adverse events considered related to LEV occurred in 1.0% of patients. 7.5% of patients reported adverse events as the most important reason for study drug discontinuation. The median reduction from baseline in the frequency of all seizures was 50.2%; 15.8% of patients were seizure free; 50.1% had seizure frequency reduction of > or =50%. At the end of the study, 60.4% of patients were considered by the investigator to show marked or moderate improvement. There was a significant improvement in health-related quality of life as assessed with the QOLIE-10-P (total score increasing from 55.6 to 61.6; p<0.001). This community-based study suggests that LEV is well tolerated and effective as add-on therapy for refractory partial seizures in adults. These data provide supportive evidence for the safety and efficacy of LEV demonstrated in the pivotal Phase III placebo-controlled studies.

Levetiracetam: part II, the clinical profile of a novel anticonvulsant drug

The objective of this article was to review and summarize the available reports on the profile of the novel anticonvulsant drug levetiracetam (LEV) in a clinical setting. Therefore, a careful search was conducted in the MEDLINE database and combined with guidelines from regulatory agencies, proceedings of professional scientific meetings, and information provided by the manufacturers. This article is devoted to the clinical pharmacology and clinical trials of LEV investigating its efficacy and safety as add-on therapy or monotherapy for various seizure types. Finally, results from postmarketing surveillance of LEV are briefly discussed. In general, LEV is shown to be a safe, broad-spectrum anticonvulsant drug with highly beneficial pharmacokinetic properties, a favorable long-term retention rate, and a high responder rate, indicating that LEV is an efficient therapeutic option for the treatment of several types of epilepsy.

Influence of levetiracetam on the anticonvulsant efficacy of conventional antiepileptic drugs against audiogenic seizures in DBA/2 mice

Levetiracetam (LEV, [S]-alpha-ethyl-2-oxo-1-pyrrolidine acetamide) is a new antiepileptic that has been used as adjunctive therapy to treat patients with intractable epilepsy. Systemic administration of levetiracetam (2.5-30 mg/kg, intraperitoneally (i.p.)) was able to produce a dose-dependent decrease in DBA/2 audiogenic seizure severity score. In combination with conventional antiepileptic drugs, levetiracetam, 5mg/kg, i.p., which per se did not significantly affect the occurrence of audiogenic seizures in DBA/2 mice, potentiated the anticonvulsant activity of some antiepileptic drugs studied against sound-induced seizures in DBA/2 mice. The degree of potentiation induced by levetiracetam was greater, approximately twice, for carbamazepine, diazepam, felbamate, topiramate, gabapentin, and valproate, less for lamotrigine, phenobarbital and phenytoin. This increase was associated with a comparable impairment in motor activity; however, the therapeutic index of combined treatment of antiepileptic drugs with levetiracetam was more favourable than the combination with saline with the exception of lamotrigine, phenytoin and phenobarbital. Since levetiracetam did not significantly influence the total and free plasma and the brain levels of antiepileptics studied. In addition, levetiracetam did not significantly affect the hypothermic effects of the anticonvulsants tested. In conclusion, levetiracetam showed an additive anticonvulsant effect when administered in combination with some classical anticonvulsants, most notably carbamazepine, diazepam, felbamate, gabapentin, topiramate and valproate, implicating a possible therapeutic relevance of such drug combinations.

Effect of Age and Comedication on Levetiracetam Pharmacokinetics and Tolerability

PURPOSE

To compare pharmacokinetics and tolerability of levetiracetam (LEV) in older versus younger adults.

METHODS

As part of the Columbia Antiepileptic Drug Database, we retrospectively studied the pharmacokinetics and tolerability of LEV in patients who had been seen as an outpatient at our center during a 4-year period. We compared apparent clearance (CL) of LEV in the youngest (16-31 years; n=151) and oldest (55-88 years; n=157) quartile of 629 adult outpatients who had taken LEV. We also analyzed the frequency of adverse effects leading to dose change or discontinuation ("intolerability") and specific adverse effects in the younger versus older adults. One-year retention was determined for younger and older adults newly started on LEV at our center.

RESULTS

Mean LEV CL differed significantly between older (46.5 ml/h/kg) and younger adults (78.3 ml/h/kg). On average, older patients had a 40% lower LEV CL than younger patients. Comedication with an enzyme-inducing antiepileptic drug (EIAED; mostly carbamazepine) was associated with a 24% higher clearance of LEV compared to those who were not on EIAEDs. This difference was 37% in a subgroup of patients whose LEV CL was compared while they were on and off EIAEDs. Stepwise linear regression identified younger age and comedication with an EIAED as significant predictors of increased LEV CL. A total of 34.3% of the 629 patients (31.7% of younger vs. 40.7% of older patients; p=0.16) reported intolerability to LEV on at least one occasion. This difference in tolerability reached significance in the group of patients newly started on LEV (26.3% vs. 41.0%; p=0.017). Drowsiness and psychiatric/behavioral side effects were the most common adverse effects associated with LEV use in both age groups. One-year retention was 72% in the older group vs. 54% in the younger group (not significant).

CONCLUSION

Older adults have lower CL than younger adults and require a mean 40% lower dose of LEV to achieve the same serum level. Comedication with an EIAED increases LEV CL by 24-37%. Younger adults tolerate LEV better than older adults, but 1-year retention was (nonsignificantly) higher in the older group.

Pharmacokinetics of Levetiracetam in Infants and Young Children with Epilepsy

PURPOSE

To assess the single-dose pharmacokinetics of levetiracetam and its major metabolite ucb L057 in infants and young children with epilepsy.

METHODS

Eligible patients with a stable regimen of antiepileptic medications received a single oral dose of levetiracetam 20 mg/kg administered as a 10% oral solution followed by a 24-hour pharmacokinetic evaluation.

RESULTS

Thirteen subjects (age 2.3-46.2 months) enrolled and received levetiracetam; 12 provided evaluable pharmacokinetic data. Levetiracetam was rapidly absorbed and reached peak plasma concentration (t(max)) 1.4 +/- 0.9 hours after dosing. The mean half-life (t(1/2)) of levetiracetam was 5.3 +/- 1.3 hours, and the apparent clearance was 1.46 +/- 0.42 mL/min/kg. Graphical differences were observed among three age subgroups (1 to <6 months, 6 to <24 months, and 24 to <48 months); however, statistical analysis was limited due to each subgroup's small sample size. No significant gender differences were detected. Treatment-emergent adverse events were seen in three patients (23.1%) but were not considered to be related to levetiracetam.

CONCLUSIONS

The mean t(1/2) of levetiracetam was shorter and its apparent clearance was more rapid for infants and young children than that previously reported for adults. When determining dosage, age-dependent drug clearance should be considered; these findings suggest that a larger dose of levetiracetam (corrected for body weight) needs to be considered for infants and young children with epilepsy than that given to adults with epilepsy. A single dose of levetiracetam was well tolerated in this study population.

Pharmacokinetics of Levetiracetam during Pregnancy, Delivery, in the Neonatal Period, and Lactation

PURPOSE

To study pharmacokinetics of levetiracetam (LEV) during pregnancy, delivery, lactation, and in the neonatal period.

METHODS

Fourteen women with epilepsy receiving LEV treatment during pregnancy and lactation contributed with 15 pregnancies to this prospective study in which LEV concentrations in plasma and breast milk were determined. Trough maternal plasma samples were collected each trimester, and at baseline after delivery. Blood samples were obtained at delivery from mothers, from the umbilical cord, and from newborns during 2 days after delivery. LEV concentration was also determined in breast milk and in plasma collected from 11 of the mothers and their suckling infants after birth.

RESULTS

The umbilical cord/maternal plasma concentration ratios ranged from 0.56-2.0 (mean 1.15, n=13). LEV plasma concentrations in the neonates declined with an estimated half-life of 18 h (n=13). The mean milk/maternal plasma concentration ratio was 1.05 (range, 0.78-1.55, n=11). The infant dose of LEV was estimated to 2.4 mg/kg/day, equivalent to 7.9% of the weight-normalized maternal dose. Plasma concentrations in breastfed were approximately 13% of the mother's plasma levels. Maternal plasma concentrations during third trimester were only 40% of baseline concentrations outside pregnancy (p<0.001, n=7)

CONCLUSIONS

Our observations suggest considerable transplacental transport of LEV and fairly slow elimination in the neonate. Plasma concentrations of LEV in nursed infants are low despite an extensive transfer of LEV into breast milk. Pregnancy appears to enhance the elimination of LEV resulting in marked decline in plasma concentration, which suggests that therapeutic monitoring may be of value.

The safety of levetiracetam

Levetiracetam is an antiepileptic drug approved for use as an adjunct agent in partial-onset seizures in adults and children aged > or = 4 years. It was also approved as adjunctive therapy in the treatment of adults and adolescents aged > or = 12 years with juvenile myoclonic epilepsy. A parenteral intravenous formulation has recently become available allowing for its use when oral administration is temporarily not feasible. Available literature has demonstrated and supported that levetiracetam has an acceptable safety profile and this review discusses the safety profile of levetiracetam, with attention to special populations. The most common adverse effects are somnolence, asthenia and dizziness, which usually appear early after initiation of levetiracetam therapy and generally resolve without medication withdrawal. The most serious adverse effects are behavioral in nature and are more common in children and in patients with a prior history of behavioral problems.

Levetiracetam monotherapy in children with epilepsy

Although levetiracetam has shown efficacy in children with epilepsy, when used as adjunctive therapy, limited data are available regarding its use as monotherapy. The objective of this study is to evaluate the efficacy and tolerability of levetiracetam monotherapy in a cohort of pediatric patients with epilepsy. A retrospective analysis of pediatric epilepsy patients receiving levetiracetam at a single institution was performed over a 3-year period. Eighty-one patients were identified, 18 of whom received levetiracetam as monotherapy (mean age, 9.6 years). Epilepsy types were partial in 14 and generalized in 4. Conversion to levetiracetam monotherapy occurred in 16 patients due to lack of efficacy or adverse events, and 2 patients were initially started on monotherapy. Dose range of levetiracetam was 14-60 mg/kg, and duration of therapy ranged from 2-24 months. Eleven patients became seizure free on levetiracetam, one had at least 50% reduction in seizures, and six others had no change in seizure frequency. Adverse events included worsening of behavior, irritability, and possible cognitive changes, seen in 4 patients. Levetiracetam was discontinued in seven patients overall. Levetiracetam monotherapy appeared to be effective and well tolerated in this group of children with epilepsy and warrants further investigation in a well-controlled, prospective study.

Prospective assessment of levetiracetam pharmacokinetics during dose escalation in 4- to 12-year-old children with partial-onset seizures on concomitant carbamazepine or valproate

PURPOSE

To assess the multiple-dose pharmacokinetics of levetiracetam and its major metabolite ucb L057 in children with partial-onset seizures and determine whether it is affected by adjunctive carbamazepine or valproate. To correlate levetiracetam concentrations in plasma and saliva and to assess its safety and clinical response.

METHODS

Design was an open-label, multicenter study. Twenty-one children (4-12 years old) with epilepsy taking carbamazepine (13) or valproate (8) received adjunctive levetiracetam. Levetiracetam was initiated at 20 mg/(kg day) and titrated at 2-week intervals to 40 and then 60 mg/(kg day). Twelve-hour pharmacokinetics were determined at the end of each 2-week period. Efficacy was estimated from the partial seizure frequency per week and Global Evaluation Scale.

RESULTS

Levetiracetam was rapidly absorbed following oral dosing, with median t(max) of 0.5 h. Dose proportional increases were observed for C(max) and AUC((0-12)) over the dose range; t(1/2) was 4.9 h. Pharmacokinetics of levetiracetam and ucb L057 were not markedly different with concomitant carbamazepine or valproate; clearance was only 7-13% faster and AUC was decreased by only 15-24% in those on carbamazepine compared to valproate. Levetiracetam did not affect trough carbamazepine or valproate. Concentration in saliva and plasma were strongly correlated. Seizure frequency declined by 50% or more in 43% of subjects in the intent-to-treat population (n=21) and in 56% of those with seizures at baseline (n=16). Marked or moderate improvement occurred in 80% and 75% of patients based on Global Evaluation Scale ratings by investigators and parents/guardians, respectively. Levetiracetam was well tolerated.

CONCLUSION

Levetiracetam exhibits simple pharmacokinetics in children, with rapid absorption and dose-proportional kinetics. Small but not clinically relevant differences were observed between subjects receiving carbamazepine and valproate, suggesting significant dose adjustment is usually not necessary. This substantiates prior assessments that levetiracetam clearance is higher in children than adults, necessitating a higher dose in children on a mg/kg basis, and suggests it is useful add-on therapy for children with partial-onset seizures regardless of baseline therapy.

Levetiracetam Intravenous Infusion as an Alternative to Oral Dosing in Patients with Partial-Onset Seizures

PURPOSE

This multicenter, open-label study evaluated the short-term tolerability of intravenously (IV)-infused levetiracetam (LEV; 500-1,500 mg/100 ml, 15 min, b.i.d.) as a substitute for the same oral dose.

METHODS

The study consisted of screening, 4-day IV LEV and 1-7 days of follow-up, and was conducted in 25 adults with partial-onset seizures receiving adjunctive oral LEV.

RESULTS

During the 4-day IV LEV, 11 (44%) subjects experienced at least one treatment-emergent adverse event (TEAE), with headache and fatigue being the most frequently reported. Five (20%) subjects experienced TEAEs considered to be related to the study drug. The tolerability profile was consistent with that of oral LEV, with all events judged mild or moderate in severity, no discontinuations, and no serious AEs or deaths reported. No AE related to seizure worsening was reported during IV LEV or brief follow-up.

CONCLUSIONS

LEV IV appears to be a well-tolerated, practical alternative in patients with partial-onset seizures temporarily unable to take the drug orally.

Antiepileptic drug treatment in children

Epilepsy is one of the most common neurological disorders of childhood, and antiepileptic drugs represent the main component of its treatment. The current emphasis in epilepsy treatment is to improve quality of life, not only by suppressing seizure, but also by minimizing the side effects of medications. The last 15 years have been characterized by significant advances in the development of new agents that have helped us to get closer to this goal. Knowledge of the essential properties, key indications and interactions of each antiepileptic drug will help to optimize efficacy and reduce adverse reactions. Age is also a determining factor of the epilepsy phenotype and its treatment. This review addresses the principles of pediatric epilepsy treatment, summarizes the profile of each of the commonly used antiepileptic drugs, and provides a treatment paradigm for particular seizures and epilepsy syndromes of childhood.

Single-dose pharmacokinetics of levetiracetam in healthy Chinese male subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Levetiracetam has been evaluated for epilepsy since 1992. * Pharmacokinetic studies of levetiracetam have been conducted in healthy volunteers, in adults, children and elderly patients with epilepsy, and in patients with renal and hepatic impairment. * Although this antiepileptic has been well studied in Western countries, this paper describes the first such trial of the drug in a Chinese population.

WHAT THIS STUDY ADDS

* Information is given on the pharmacokinetics, dose proportionality, safety and tolerability profile of levetiracetam in healthy male Chinese volunteers, and the results are compared with published data obtained in White subjects. * The pharmacokinetics and the pattern of adverse events of levetiracetam in Chinese subjects are similar to the data reported in White subjects.

AIMS

The main aims of this study were to evaluate the pharmacokinetics of levetiracetam in healthy male Chinese volunteers and to assess the dose proportionality between the 500-mg and 1500-mg single doses.

METHODS

This was a randomized, single-centre, single-dose, two-way crossover study. Twenty-six healthy male Chinese subjects were enrolled. All subjects received a single dose of 500 mg or 1500 mg levetiracetam tablet(s) on the dosing day, and the wash-out period was 7 days. Blood was obtained for a 36-h pharmacokinetic evaluation.

RESULTS

Following single-dose administration of 500 mg and 1500 mg of levetiracetam, the median t(max) was 0.5 and 0.5 h; t(1/2) was 7.3 +/- 0.8 and 7.3 +/- 0.7 h; C(max) was 13.6 +/- 3.2 and 47.1 +/- 12.1 microg ml(-1); AUC(0-infinity) was 109.3 +/- 14.1 and 340.4 +/- 50.6 microg h(-1) ml(-1); and AUC(0-t) was 105.7 +/- 13.3 and 329.0 +/- 47.9 microg h(-1) ml(-1), respectively.

CONCLUSIONS

Both C(max) and AUCs were dose-proportional over the range of 500-1500 mg. The pharmacokinetic data obtained in these Chinese subjects were similar to the historical data from a matched group of White subjects.

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.

Combination therapy in epilepsy: when and what to use

After being regarded as a last resort for over two decades, the role of combination therapy as a treatment strategy for epilepsy is undergoing re-evaluation. This is a result of the growing appreciation that all seizures cannot be controlled by monotherapy in a substantial proportion of patients, and of the development of a range of modern antiepileptic drugs (AEDs), some of which are better tolerated and less prone to complex pharmacokinetic drug interactions than their older counterparts.Robust evidence to guide clinicians on when and how to combine AEDs is lacking, and current practice recommendations are largely empirical. Monotherapy should remain the treatment of choice for newly diagnosed epilepsy. A combination of two AEDs can be considered after failure, resulting from lack of efficacy, of one or two different monotherapy regimens. A few patients will become seizure-free with a combination of three AEDs, but treatment with a combination of four or more is unlikely to be successful. There is some evidence to support a pharmacomechanistic approach to AED combination. Care should be taken to avoid excessive drug load, which is associated with increased toxicity. Bigger and better randomised, controlled studies are needed to determine the optimal time and way to combine AEDs.

In situ metabolism of levetiracetam in blood of patients with epilepsy

PURPOSE

Although levetiracetam undergoes minimum metabolism, B-esterases have been identified in whole blood that are capable of metabolising levetiracetam. The present study was designed to ascertain any variability in levetiracetam blood concentrations that could be attributed to in situ metabolism and which could impact on the utility of such concentration measurements in guiding therapeutic management.

METHODS

Blood samples were collected from 40 patients that were prescribed levetiracetam. Sera (Groups 1 and 2) or whole blood (Groups 3 and 4) were compared. Paraoxan, an inhibitor of B-esterase activity, was added to samples assigned to Groups 2 and 4. Samples within each group were assigned to Time 0 (frozen within 30 min of sample collection), Time 2 days and Time 7 days (samples kept at ambient temperature for 2 and 7 days).

RESULTS

For serum samples, mean levetiracetam concentrations at Time 2 days and Time 7 days were indistinguishable from Time 0, regardless of whether B-esterase activity was inhibited on not. In contrast, for whole blood, in the absence of B-esterase inhibition, mean levetiracetam concentrations declined over time (11% and 29%; 2 and 7 days) compared to baseline values. In the presence of B-esterase inhibitor, mean levetiracetam concentrations at 2 days were indistinguishable from baseline values, although at 7 days values declined by 4%.

CONCLUSIONS

If therapeutic monitoring of levetiracetam is to be undertaken, serum should be the matrix of choice and that whole blood should be separated as soon as possible after patient sampling so as to minimize in situ levetiracetam metabolism which could result in spuriously low concentrations and substantial intrapatient variability.

An open trial of levetiracetam for segmental and generalized dystonia

Local botulinum toxin injections represent the treatment of choice for most patients with focal dystonia. However, patients with segmental or generalized forms require additional pharmacologic treatment which is often ineffective or limited by intolerable side-effects. An animal study and three case reports suggested antidystonic effects of levetiracetam, a pyrrolidone derivate, whereas a recent open-label study found no improvement in 10 patients with primary idiopathic cervical dystonia. We studied the efficacy of levetiracetam in a daily dose of 3000 mg in 10 consecutive patients with otherwise therapy refractory segmental or generalized dystonia. At 4-week follow-up, none of the patients showed improvement of dystonia, mild side-effects were observed in 3 patients.

Predicting drug-resistant patients who respond to add-on therapy with levetiracetam

INTRODUCTION

Levetiracetam (LEV) is approved for use as add-on therapy in adult patients with partial epilepsy. It is apparent from clinical trials that up to 8% of previously drug-resistant patients may be rendered seizure-free by adding-on levetiracetam. As yet there is no way of predicting these unexpectedly responsive patients. We set out to identify our previously refractory patients who had demonstrated unexpected responsiveness to add-on therapy with levetiracetam, and compared these to patients who had not responded to the drug. We then attempted to characterise any clinical features that differentiated these groups of patients.

METHODS

We included all patients with a history of present or previous exposure to levetiracetam who had been unresponsive to at least two other prior anti-epileptic drugs (AEDs) and recorded their demographic and clinical data. We divided response into (a) 'seizure-free' (seizure-free for a minimum of 6 months after commencing LEV); (b) 'partial > 50%' (greater than 50% reduction in seizures for a minimum of 6 months after commencing LEV); (c) 'honeymoon' (seizure-free for less than 6 months after commencing LEV and then returned towards baseline frequency); and (d) 'no-response'. For the purpose of analysis we considered the 'seizure-free' and 'partial > 50%' groups as 'responders', and the 'no response' group as 'non responders'.

RESULTS

344 patients were included in the analysis. Fifty-six patients (16.3%) were rendered seizure-free on levetiracetam. Idiopathic generalised epilepsy and post-traumatic partial epilepsy were more common in the responder than the non-responder group (p = 0.005 and 0.05 respectively). Lamotrigine was used significantly more often in combination with levetiracetam in responders than non-responders (p = 0.003). The mean daily dose of levetiracetam was lower in responders than non-responders.

DISCUSSION

A higher than expected number of previously drug resistant patients was rendered seizure-free by add-on therapy with levetiracetam. Those who respond best appear to do so at relatively low doses and our data suggest the possibility of a beneficial pharmacodynamic interaction between levetiracetam and lamotrigine. We were unable to identify any clinical factors that clearly predicted which patients would become seizure-free and we hypothesise that response may be determined by genetic or molecular factors. All drug-resistant patients, including those being assessed for surgery, should be considered for a trial of levetiracetam, regardless of their epilepsy classification.

Single-dose bioavailability of levetiracetam intravenous infusion relative to oral tablets and multiple-dose pharmacokinetics and tolerability of levetiracetam intravenous infusion compared with placebo in healthy subjects

BACKGROUND

Antiepileptic drugs are usually administere dorally, but alternative routes of drug delivery may be required when oral administration is not feasible.

OBJECTIVE

The purpose of this study was to evaluate the single-dose bioavailability of an IV formulation of levetiracetam relative to oral tablets and the multiple-dose tolerability and pharmacokinetics of this formulation compared with placebo in healthy subjects.

METHODS

This study consisted of 2 phases. Subjects entered the first phase, which was a single-dose, randomized, open-label, 2-way crossover bioavailability comparison of a 15-minute IV infusion of levetiracetam 1,500 mg and three 500-mg oral tablets. Subjects then entered the second phase, a multiple-dose, randomized, double-blind, placebo-controlled (2:1), parallel-group tolerability and pharmacokinetic study, in which they received 9 successive doses of levetiracetam 1,500 mg IV or placebo at 12-hour intervals. Plasma levetiracetam concentrations were determined by gas chromatography with nitrogen-phosphorus detection. The comparison of bioavailability was based on the 90% CIs around the geometric mean ratios for AUC and C(max) (IV/oral).

RESULTS

Eighteen subjects (9 men, 9 women) participated in the study. All subjects were white. Their mean (SD) age was 35.0 (9.3) years, mean weight 73.3 (14.2) kg, and mean body mass index 23.9 (2.5) kg/m(2). After a single dose, the IV infusion and oral tablet were similar in terms of C(max) (50.5 and 47.7 microg/mL, respectively) and AUC (392.4 and 427.9 pg x h/mL). The geometric mean IV/oral ratios were 92.2 (90 % CI, 89.0-95.6) for AUC and 103.7 (90% CI, 91.6-117.4) for C(max) indicating that the IV and oral formulations were bioequivalent. After multiple twice-daily infusions, steady state was reached within 48 hours. Seventeen (94%) of 18 subjects had >or=1 treatment-emergent adverse event after single-dose administration. During the single-dose phase, the incidence of treatment-emergent adverse events was 89% (16/18) for the IV formulation and 72% (13/18) for the oral tablets; during the multiple-dose phase, the incidence of treatment-emergent adverse events was 67% (8/12) in the IV levetiracetam group and 33% (2/6) in the placebo group. The most common adverse events in the single-dose phase were somnolence (61% IV vs 28% oral) and postural dizziness (17% vs 39%, respectively). The most common adverse events with IV levetiracetam in the multiple-dose phase were also somnolence (33% vs 17% placebo) and postural dizziness (25% vs 0% placebo).

CONCLUSIONS

In these healthy subjects, single doses of levetiracetam 1,500 mg administered as a 15-minute IV infusion and as oral tablets were bioequivalent. General and local tolerability during multiple dosing were good. Steady state was reached within 48 hours. Despite the limitations of a study of short duration and small size conducted in healthy subjects, the findings suggest that use of a 15-minute IV infusion of levetiracetam should be further investigated.

Use of Antiepileptic Drugs in Patients with Kidney Disease

The number of medications used to treat different types of seizures has increased over the last 10-15 years. Most of the newer antiepileptic drugs (AEDs) are likely to be unfamiliar to many nephrologists. For both the older and newer AEDs, basic pharmacokinetic information, recommendations for drug dosing in patients with reduced kidney function or who are on dialysis, and adverse renal and fluid-electrolyte effects are reviewed. Newer AEDs are less likely to have significant drug-drug interactions than older agents, but are more likely to need dosage adjustment in patients with reduced kidney function. The most common renal toxicities of these drugs include metabolic acidosis, hyponatremia, and nephrolithiasis; interstitial nephritis and other adverse effects are less common. Little is known about the clearance of most of the newer AEDs with high-efficiency hemodialyzers or with peritoneal dialysis. Monitoring of drug levels when available, careful clinical assessment of patients taking AEDs, and close collaboration with neurologists is essential to the management of patients taking AEDs.

Differences in absorption, distribution, metabolism and excretion of xenobiotics between the paediatric and adult populations

In children, the therapeutic benefits and potential risks associated with drug treatment may be different from those in adults and will depend on the exposure, receptor sensitivity and relationship between effect and exposure. In this paper, key factors undergoing maturational changes accounting for differences in drug metabolism and disposition in the paediatric population compared with adults are reviewed. Gastric and duodenal pH, gastric emptying time, intestinal transit time, secretion and activity of bile and pancreatic fluid, bacterial colonisation and transporters, such as P-glycoprotein (P-gp), are important factors for drug absorption, whereas key factors explaining differences in drug distribution between the paediatric population and adults are organ size, membrane permeability, plasma protein concentration and characteristics, endogenous substances in plasma, total body and extracellular water, fat content, regional blood flow and transporters such as P-gp, which is present not only in the gut, but also in liver, kidney, brain and other tissues. As far as drug metabolism is concerned, important differences have been found in the paediatric population compared with adults both for phase I enzymes (oxidative [e.g., cytochrome P450 (CYP)1A2, and CYP3A7 versus -3A4], reductive and hydrolytic enzymes) and phase II enzymes (e.g., N-methyltransferases and glucuronosyltransferases). Generally, the major enzyme differences observed in comparison with the adult age are in newborn infants, although for some enzymes (e.g., glucuronosyltransferases and other phase II enzymes) important differences still exist between infants and toddlers and adults. Finally, key factors undergoing maturational changes accounting for differences in renal excretion in the paediatric population compared with adults are glomerular filtration and tubular secretion. The ranking of the key factors varies according to the chemical structure and physicochemical properties of the drug examined, as well as to the characteristics of its formulation. It would be important to generate additional information on the developmental aspects of renal P-gp and of other renal transporters, as has been done and is still being done with the different -isozymes involved in drug metabolism.

Levetiracetam: past, present and future

Levetiracetam is an antiepileptic drug approved for use as an adjunctive agent in partial-onset seizures in adults. This approval was recently extended to children over 4 years of age. Among the currently approved antiepileptic drugs, levetiracetam is unique in its mechanism of action. Its CNS binding site, the synaptic vesicle protein SV2A, was discovered recently. Binding at this site may be important for the antiseizure activity of levetiracetam and the role of this binding site and its modulation by levetiracetam is an area of active research in epilepsy. Levetiracetam is generally safe, has near to ideal pharmacokinetics and does not interact with other medications. The most serious adverse events are behavioral in nature. Recent studies suggest that levetiracetam may be effective in generalized epilepsies, status epilepticus, pain and selected movement disorders. Intriguing studies using the kindling model of epilepsy suggest that levetiracetam may protect against the development of kindling and chronic epilepsy. A parenteral formulation of levetiracetam may soon become available and may lead to larger studies of levetiracetam in status epilepticus.

Levetiracetam Intravenous Infusion: A Randomized, Placebo-controlled Safety and Pharmacokinetic Study

PURPOSE

The primary objective of this placebo-controlled study was to evaluate the safety and tolerability of levetiracetam (LEV) administered intravenously (IV) at higher doses and/or at a faster infusion rate than proposed. The secondary objective was to assess LEV pharmacokinetics.

METHODS

Single ascending doses of LEV administered by IV infusion (2,000, 3,000, 4,000 mg over 15 min; 1,500, 2,000, 2,500 mg over 5 min) were evaluated in 48 healthy subjects in a randomized, single-blind, placebo-controlled study.

RESULTS

All randomized subjects completed the study. Adverse events reported after IV administration of LEV (<or=4,000 mg infused over 15 min and <or=2,500 mg infused over 5 min) were primarily related to the CNS (dizziness, 52.8%; somnolence, 33.3%; fatigue, 11.1%; headache, 8.3%) and were consistent with the established safety profile for the oral formulation. Safety profiles were similar for each dose level of LEV and for both IV infusion rates, with no clear relation noted between incidence of adverse events and IV dose level or infusion rate. The pharmacokinetics of LEV administered by IV infusion was comparable across all dose groups and infusion rates. Respective geometric means (coefficient of variation) for 4,000 mg administered over 15 min and 2,500 mg infused over 5 min were maximum plasma concentration, 145 (24.6%) and 94.3 (36.2%) mug/ml; area under the plasma concentration-time curve, 1,239 (19.2%) and 585 (9.6%) mug/h/ml; terminal half-life, 8.0 (14.5%) and 7.0 (12.7%) h.

CONCLUSIONS

LEV administered by IV infusion at dosages and/or infusion rates higher than those proposed was well tolerated in healthy subjects, and the pharmacokinetic profile was consistent with that for LEV administered orally.

Levetiracetam Pharmacokinetics in Neonates at Birth

Based on blood sampling in a formula-fed pair of twins, the estimated serum half-life of levetiracetam (LEV) at birth is 16-18 h.

Pharmacokinetic variability of new antiepileptic drugs at different ages

Newer generation antiepileptic drugs (AEDs) are increasingly used to treat epilepsies in infants, children, and the elderly. For rational prescribing in these populations, it is essential to understand the pharmacokinetic changes that occur during development and aging. Data obtained in recent years indicate that the apparent oral clearance (CL/F) of lamotrigine, topiramate, levetiracetam, oxcarbazepine, gabapentin, tiagabine, zonisamide, vigabatrin, and felbamate is considerably higher in children than in adults,the magnitude of the difference being on average in the order of 20%to 120%, depending on the drug and the age distribution of the assessed population. Information on the pharmacokinetics of these drugs in newborns is completely lacking or very sparse. Studies in the elderly have demonstrated that significant pharmacokinetic changes also occur at the other extreme of age. On average, CL/F values of newer generation AEDs have been found to be reduced by 10% to 50% compared with those found in young or middle-aged adults. These pharmacokinetic changes are clinically important and con-tribute to age-related differences in dosage requirements.

Levetiracetam therapy in patients with brain tumour and epilepsy

Epilepsy is a common clinical problem in patients with brain tumours, strongly affecting patients' quality of life. Tumour-related seizures are often difficult to control, and the clinical picture is complicated by frequent interactions between antiepileptic drugs (AEDs) and antineoplastic agents. We studied the safety and efficacy of levetiracetam (LEV), a new AED with a different pharmacological profile from traditional anticonvulsants, in 19 patients (6 females; age range 28-70 years, mean 48 years) with supratentorial gliomas and epilepsy. Seizure types were simple partial in four patients, complex partial in 4, complex partial with secondary generalization in 7, and generalized tonic-clonic in 4. LEV was added to the existing AED treatment on account of persisting seizures, and titrated at dosages of 1,000-3,000 mg/day. Patients were seen at the Outpatient's Centre every 1-3 months, and followed-up for 7-50 months (mean 25 months, median 20 months). At the end of the observation period, nine patients were seizure free (seizure free period ranging from 7 to 33 months, mean 16, median 12) and five patients reported an improvement in seizure-frequency from daily to weekly (n=1) or from weekly to monthly (n=3). Seizure frequency was unmodified in four patients and increased (from monthly to weekly) in one. No LEV-related adverse effects were observed. LEV plasma concentrations monitored in 12 subjects ranged from 11.9 to 82.1 microg/ml. Our preliminary open data indicate that add-on treatment with LEV in patients with brain tumours is safe and appears to be effective in reducing seizure frequency. Controlled studies on larger populations are warranted to confirm these open observations.

Onset of Action of Levetiracetam: A RCT Trial Using Therapeutic Intensive Seizure Analysis (TISA)

OBJECTIVES

To correlate the onset of clinical effects of add-on levetiracetam (LEV) therapy with daily serum LEV concentration, in pharmaco-resistant focal epilepsies, using the TISA method.

METHODS

25 adult patients (aged>6 years) with pharmaco-resistant focal epilepsies undergoing presurgical evaluation at the Epilepsy Center Erlangen were enrolled in the study. Eligible patients on a maximum of one other antiepileptic drug (AED) were recruited into the 48-hour baseline phase. Those who had at least two seizures during this phase were randomized into the seven-day treatment phase, when they received either LEV or placebo, under continuous day-and-night video-EEG monitoring. The starting daily dose of LEV was 500 mg bid, titrated from the second treatment day to 1,000 mg bid. The peak serum concentration of LEV was monitored daily at 8:00 am (one hour after drug administration) for every patient. The number and duration of seizures per 24h (N/24h and D/24h respectively) were investigated.

RESULTS

23 patients completed the study (LEV group n=11 and placebo group n=12). Seven patients in the LEV group and two patients in the placebo group achieved seizure-freedom during the treatment phase. The intergroup comparison of the decrease in N/24h and D/24h from the baseline phase to the treatment phase was in favor of the LEV group (p<0.05). A significant effect of LEV on D/24h was seen as early as the second treatment day (p=0.013), becoming more apparent on the third treatment day (p=0.009).

CONCLUSION

The present study objectively quantified the correlation between the anticonvulsant effects of LEV in focal epilepsies and the peak serum concentration of the drug. For the first time, direct measurement was used to demonstrate the onset of action of LEV to be two days after drug initiation.

Clinical Pharmacokinetics of New-Generation Antiepileptic Drugs at the Extremes of Age

In recent years, several new-generation antiepileptic drugs (AEDs) have been introduced in clinical practice. These agents, which include felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, tiagabine, topiramate, vigabatrin and zonisamide, are being increasingly used in the treatment of epilepsy at the extremes of age. For a rational prescribing of these drugs in specific age groups, major pharmacokinetic changes that occur during development and aging need to be taken into consideration. A review of available evidence indicates that the apparent oral clearance (CL/F) of new-generation AEDs in children is increased by 20-170% (depending on the type of drug and characteristics of the patients studied) compared with adults, with the highest CL/F values usually being observed in the youngest age groups. These findings do not necessarily apply to the first weeks of life, when drug eliminating capacity is still undergoing maturation, as in the case of lamotrigine for which preliminary data suggest that CL/F in neonates aged <2 months can be much lower than in infants aged 2-12 months. At the other extreme of age, in the elderly, CL/F is almost invariably reduced (on average by 10-50%) compared with values found in non-elderly adults. Age-related CL/F changes, together with the large interindividual pharmacokinetic variability, contribute to the need for individualised dosage requirements in these patients. Measurement of serum drug concentrations can be useful as an aid to dosage individualization in these age groups but interpretation of therapeutic drug monitoring data should also take into account the possibility of age-related changes in pharmacodynamic sensitivity and, for neonates and the elderly, alterations in drug binding to serum proteins.

Pharmacodynamic and Pharmacokinetic Characterization of Interactions between Levetiracetam and Numerous Antiepileptic Drugs in the Mouse Maximal Electroshock Seizure Model: An Isobolographic Analysis

PURPOSE

Approximately 30% of patients with epilepsy do not experience satisfactory seizure control with antiepileptic drug (AED) monotherapy and often require polytherapy. The potential usefulness of AED combinations, in terms of efficacy and adverse effects, is therefore of major importance. The present study sought to identify potentially useful AED combinations with levetiracetam (LEV) METHODS: With isobolographic analysis, the mouse maximal electroshock (MES)-induced seizure model was investigated with regard to the anticonvulsant effects of carbamazepine (CBZ), phenytoin, phenobarbital (PB), valproate, lamotrigine, topiramate (TPM), and oxcarbazepine (OXC), administered singly and in combination with LEV. Acute adverse effects were ascertained by use of the chimney test evaluating motor performance and the step-through passive-avoidance task assessing long-term memory. Brain AED concentrations were determined to ascertain any pharmacokinetic contribution to the observed antiseizure effect.

RESULTS

LEV in combination with TPM, at the fixed ratios of 1:2, 1:1, 2:1, and 4:1, was supraadditive (synergistic) in the MES test. Likewise, the combination of LEV with CBZ (at the fixed ratio of 16:1) and LEV with OXC (8:1 and 16:1) were supraadditive. In contrast, all other LEV/AED combinations displayed additivity. Furthermore, none of the investigated LEV/AED combinations altered motor performance and long-term memory. LEV brain concentrations were unaffected by concomitant AED administration, and LEV had no significant effect on brain concentrations of concomitant AEDs.

CONCLUSIONS

These preclinical data would suggest that LEV in combination with TPM is associated with beneficial anticonvulsant pharmacodynamic interactions. Similar, but less profound effects were seen with OXC and CBZ.

Pharmacological and clinical aspects of antiepileptic drug use in the elderly

In this article, epidemiological and clinical aspects related to the use of antiepileptic drugs (AEDs) in the elderly are highlighted. Studies have shown that people with epilepsy receiving AED treatment show important deficits in physical and social functioning compared with age-matched people without epilepsy. To what extent these deficits can be ascribed to epilepsy per se or to the consequences of AED treatment remains to be clarified. The importance of characterizing the effects of AEDs in an elderly population is highlighted by epidemiological surveys indicating that the prevalence of AED use is increased in elderly people, particularly in those living in nursing homes. Both the pharmacokinetics and the pharmacodynamics of AEDs may be altered in old age, which may contribute to the observation that AEDs are among the drug classes most commonly implicated as causing adverse drug reactions in an aged population. Age alone is one of several contributors to alterations in AED response in the elderly; other factors include physical frailty, co-morbidities, dietary influences, and drug interactions. Individualization of dosage, avoidance of unnecessary polypharmacy, and careful observation of clinical response are essential for an effective and safe utilization of AEDs in an elderly population.

Properties of antiepileptic drugs in the treatment of idiopathic generalized epilepsies

Although valproate is considered to be the drug of first choice for the treatment of idiopathic generalized epilepsies (IGEs), other antiepileptic drugs (AEDs), both old (ethosuximide, clobazam, and clonazepam) and new (lamotrigine, levetiracetam, topiramate, and zonisamide) are also available. These AEDs do not appear to have a common mechanism of action in that both inhibitory gamma-aminobutyric acid (GABA; e.g., clobazam, clonazepam, and valproate) and excitatory glutamate (e.g., lamotrigine and topiramate) mechanisms are involved. Ethosuximide primarily acts by blocking T-type voltage-gated calcium channels in thalamic neurones while topiramate and zonisamide have multiple mechanisms of action. In contrast, levetiracetam is unique in that it may act via a specific binding site in the brain. In terms of their pharmacokinetic characteristics, all eight AEDs are rapidly absorbed after oral ingestion with peak blood concentration being achieved within 1-4 hours. Bioavailability is 100% with the exception clonazepam (90%) and topiramate (81-95%). Plasma protein binding is variable with valproate (90%), clobazam (85%) and clonazepam (86%) showing substantial binding, lamotrigine (55%) and zonisamide (50%) intermediate binding, and levetiracetam (0%), ethosuximide (0%) and topiramate (10%) being minimally bound. However, the binding by zonisamide is complicated by its binding to erythrocytes as well as albumin. All AEDs, with the exception of lamotrigine and levetiracetam, undergo elimination as a result of extensive metabolism by hepatic cytochrome P450 enzymes, which are highly amenable to induction and inhibition by other drugs and therefore susceptible to pharmacokinetic interactions. Lamotrigine metabolism is via hepatic glucuronidation, a process that is also susceptible to induction and inhibition by concurrent drugs. Levetiracetam is minimally metabolized (by hydrolysis in blood), is excreted predominantly unchanged in urine, and to date has not been associated with any clinically significant pharmacokinetic interactions. Using a semiquantitative pharmacokinetic rating system, based on 16 pharmacokinetic characteristics, a direct comparison between AEDs is possible. Thus valproic acid, regarded as the drug of first choice in the treatment of IGEs, rates lowest with respect to favorable pharmacokinetic characteristics, mostly because of its nonlinear pharmacokinetics, extensive hepatic metabolism, and its high propensity to interact both with other AEDs and non-AEDs. Levetiracetam rates highest with topiramate in second place.