Use of new antiepileptic drugs in the treatment of childhood epilepsy

Pregabalin adjunctive therapy for focal onset seizures in children 1 month to <4 years of age: A double-blind, placebo-controlled, video-electroencephalographic trial

OBJECTIVE

To evaluate the efficacy and safety of pregabalin as adjunctive treatment for children (aged 1 month-<4 years) with focal onset seizures (FOS) using video-electroencephalography (V-EEG).

METHODS

This randomized, placebo-controlled, international study included V-EEG seizure monitoring (48-72 hours) at baseline and over the last 3 days of 14-day (5-day dose escalation; 9-day fixed dose) double-blind pregabalin treatment (7 or 14 mg/kg/d in three divided doses). This was followed by a double-blind 1-week taper. The primary efficacy endpoint was log-transformed seizure rate (log_e [24-hour seizure rate + 1]) for all FOS recorded during the double-blind V-EEG monitoring, evaluated in subjects who took ≥1 dose of study medication, experienced ≥1 baseline seizure(s), and had a treatment phase V-EEG. Safety and tolerability were assessed by adverse events (AEs), clinical laboratory data, physical/neurological examinations, vital signs, and electrocardiograms.

RESULTS

Overall, 175 patients were randomized (mean age = 28.2 months; 59% male, 69% white, 30% Asian) in a 2:1:2 ratio to pregabalin 7 or 14 mg/kg/d (n = 71 or n = 34, respectively), or placebo (n = 70). Pregabalin 14 mg/kg/d (n = 28) resulted in a statistically significant 35% reduction of log_e (24-hour seizure rate + 1) versus placebo (n = 53; P = .022), an effect that was not observed with pregabalin 7 mg/kg/d (n = 59; P = .461). The most frequently reported treatment-emergent AEs for pregabalin 7 mg/kg/d, 14 mg/kg/d, and placebo, respectively, were somnolence (11.3%, 17.6%, and 5.7%) and upper respiratory tract infection (7.0%, 11.8%, and 11.4%). All AEs were mild to moderate in severity.

SIGNIFICANCE

Pregabalin 14 mg/kg/d (but not 7 mg/kg/d) significantly reduced seizure rate in children with FOS, when assessed using V-EEG, compared with placebo. Both pregabalin dosages were generally safe and well tolerated in children 1 month to <4 years of age with FOS. Safety and tolerability were consistent with the known profile of pregabalin in older children with epilepsy.

Epilepsias na Infância

As crises epilépticas representam um dos mais freqüentes problemas neurológicos na infância. Entre 0,5% e 1% de crianças e adolescentes apresentam uma crise epiléptica associada com um distúrbio metabólico agudo ou um insulto neurológico, muitos dos quais ocorrem no período neonatal. Elevada incidência de epilepsia ocorre no primeiro ano de vida. A síndrome de West ocorre em cerca de 9% das epilepsias na infância, síndrome de Lennox-Gastaut por volta de 1% a 2%, epilepsia de ausência de 10% a 15%, epilepsias mioclônica juvenil ocorre em cerca de 5% e as epilepsia parciais benignas ocorrem em 10% de todas as epilepsias na infância, mas 20% a 25% das epilepsias são diagnosticadas entre 5 e 15 anos.

A long-term open-label extension study assessing cognition and behavior, tolerability, safety, and efficacy of adjunctive levetiracetam in children aged 4 to 16 years with partial-onset seizures

The objective of this study was to assess cognition and behavior in children (4-16 years; n = 103) with partial-onset seizures using the Leiter-R International Performance Scale and Achenbach Child Behavior Checklist. The study was a multicenter, open-label, noncomparative 48-week extension study (NCT00152516) of adjunctive levetiracetam (20-100 mg/kg/d, mean 50.2 mg/kg/d). Improvement from baseline in Leiter-R Memory Screen composite score at weeks 24 and 48 (mean [SD] change, +4.8 [12.6] and +4.5 [15.3]) was similar to changes observed with levetiracetam and placebo in a prior study. Child Behavior Checklist Syndrome scores improved from baseline at weeks 24 and 48 (total problems mean [SD] change, -9.3 [22.2] and -10.4 [23.4]). Adjunctive levetiracetam was well tolerated (most frequently reported central nervous system-related treatment-emergent adverse events: headache [24.3%], aggression [7.8%], irritability [7.8%]). Of the patients, 4.9% discontinued because of treatment-emergent adverse events. Levetiracetam provided good and sustained seizure control (median percentage reduction from baseline in partial-onset seizure frequency/wk during maintenance: 86.4%); 24.7% of patients had continuous seizure freedom from all seizure types for ≥40 weeks. In children, adjunctive levetiracetam was associated with long-term stability in cognitive functioning and improvement in emotional/behavioral functioning over time.

Effectiveness of topiramate in medically complicated patients with status epilepticus or acute refractory seizures

Background and Purpose:

The conventional therapeutic regimen for status epilepticus (SE) may require artificial ventilation and hemodynamic support, and is associated with significant complications and increased mortality. We investigated the safety and effectiveness of topiramate (TPM) in patients with refractory SE, who had medical complications such as systemic infection, renal dysfunction, hepatic dysfunction, and bone marrow suppression.

Methods:

We analyzed the clinical features and therapeutic outcome in 16 patients with GCSE, NCSE or recurrent GTC in whom TPM was administered for its control.

Results:

The majority of our patients had GCSE (n=6) or NCSE (n=7). The common co-morbid diseases at the onset of seizures were hematological disorders (pancytopenia 8, anemia 2, anemia with thrombocytopenia 2) and sepsis (n=8). Twelve patients were under the renal and/or hepatic dysfunction. Within a few days, 13 patients could experience their seizure control (the mean duration, 3.7± 2.6 days), but the seizures of the other subjects did not be terminated in spite of all efforts. No patients experienced a worsening of their CBC or blood chemistry profiles with the TPM treatment.

Conclusions:

We could confirm that TPM was not only safe but very effective for the control of recurrent epileptic seizures or SE in patients with serious medical co-morbidities. TPM may be considered as another treatment option when conventional protocols are ineffective.

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.

Pharmacologic treatment of binge eating disorder

OBJECTIVE

To review the findings from pharmacologic trials of binge eating disorder (BED) and to provide guidelines for pharmacologic treatment.

METHODS

The literature was searched for studies of pharmacologic treatment of BED and related conditions, such as nonpurging bulimia nervosa.

RESULTS

Placebo-controlled studies of desipramine, fluvoxamine, fluoxetine, sertraline, citalopram, dexfenfluramine, sibutramine, and topiramate have demonstrated the efficacy of these agents in the treatment of BED. An open trial of venlafaxine has offered preliminary evidence for the efficacy of this medication. Guidelines for pharmacologic management of BED are provided.

CONCLUSIONS

The literature offers support for the use of agents from three categories of medication (antidepressants, appetite suppressants, and anticonvulsants) in the treatment of BED.

Mechanisms of idiosyncratic drug reactions: the case of felbamate

Idiosyncratic drug reactions (IDR) are a specific type of drug toxicity characterized by their delayed onset, low incidence and reactive metabolite formation with little, if any, correlation between pharmacokinetics or pharmacodynamics and the toxicological outcome. As the name implies, IDR are unpredictable and often result in the post marketing failure of otherwise useful therapies. Examples of drugs, which have failed as a result of IDR in recent years, include trovafloxacin, zileuton, troglitazone, tolcapone and felbamate. To date there exists no pre-clinical model to predict these adverse drug reactions and a mechanistic understanding of these toxicities remains limited. In an attempt to better understand this class of drug toxicities and gain mechanistic insight, we have studied the IDR associated with a model compound, felbamate. Our studies with felbamate are consistent with the theory that compounds which cause IDR undergo bioactivation to a highly reactive electrophilic metabolite that is capable of forming covalent protein adducts in vivo. In additon, our data suggest that under normal physiological conditions glutathione plays a protective role in preventing IDR during felbamate therapy, further emphasizing a correlation between reactive metabolite formation and a toxic outcome. Clinical studies with felbamate have been able to demonstrate an association between reactive metabolite formation and a clinically relevant toxicity; however, additional research is required to more fully understand the link between reactive metabolite formation and the events which elicit toxicity. Going forward, it seems reasonable that screening for reactive metabolite formation in early drug discovery may be an important tool in eliminating the post-marketing failure of otherwise useful therapies.

Population pharmacokinetics of gabapentin in infants and children

PURPOSE

To characterize gabapentin pharmacokinetics in infants and children using a population approach and to identify important demographic and/or physiologic determinants of gabapentin disposition.

METHODS

Gabapentin was administered in single doses of 10 mg/kg (N=48 healthy subjects, age 1 month-12 years) or in multiple doses of 10-65 mg/kg per day (N=205 patients with epilepsy, age 2 months-13 years) at 08:00, 14:00, and 20:00. Serial concentration-time data from the healthy subjects were combined with sparse data obtained in patients and were modeled using NONMEM.

RESULTS

Gabapentin oral clearance (l/h) was directly related to creatinine clearance (ml/min) with a slope of 0.116. The slope of the relationship was 36% greater in blacks than in subjects of other races. When oral clearance was normalized for body weight, young children (<5 years) had higher and more variable values than older children. Volume of distribution was related to body weight and appeared to differ between subjects and patients. Intersubject variability was approximately 30% for oral clearance and volume of distribution and was larger for the absorption rate constant and lag time. Residual variability, a measure of intrasubject variability and measurement error, was smaller in subjects than in patients.

CONCLUSIONS

On a weight basis, 33% larger doses would be required in younger children (<5 years) to achieve the same exposure as older children.

Zonisamide in West syndrome

Zonisamide (ZNS), a new antiepileptic drug developed in Japan, is being used as the initial treatment of West syndrome in some Japanese institutes. The reported response rate varied from 20 to 38%. The cryptogenic patients showed a better response than the symptomatic patients. A striking finding was that the response to ZNS is rapid; most of the children who responded did so within 1-2 weeks of starting ZNS at a dose of 4-8 mg/kg/day. No serious side effects have been reported so far. ZNS may be both effective and well tolerated for the initial treatment of selected patients with West syndrome.

Effective and safe but forgotten: methsuximide in intractable epilepsies in childhood

The efficacy and safety of methsuximide (MSM) was evaluated in children with intractable epilepsies in a prospective uncontrolled study. MSM was added to the therapeutic regimen of 112 children with intractable epilepsy under inpatient conditions, all of whom were therapeutically refractory to various first-line antiepileptic drugs (AED) or combinations of other AED. Titration of MSM was performed following a uniform protocol. Administration of MSM resulted in a 50% or greater reduction in seizure frequency in 40 patients after a short-term observation period (mean 9.1 weeks). After a mean of 3.7 years, the rate of seizures and side effects were re-evaluated in 39 patients who were still receiving MSM as part of their antiepileptic regimen. Twenty two of these patients derived long-term benefit from MSM. In patients with good seizure control, fasting plasma levels of N-desmethylmethsuximide, the principal active metabolite of MSM, were 25.3-44.7 mg l(-1)(mean 36.0 mg l(-1)). Thus effective plasma levels of N-desmethylmethsuximide in children were found to be higher than previously described. Forty one of 112 patients (28.9%) developed side effects during MSM treatment. No serious or irreversible side effects were seen. Our study demonstrates the value of MSM as an 'add-on' drug in intractable epilepsies.

The role of tiagabine in the treatment of intractable epilepsy of childhood with multifocal independent spikes: a case report

Multifocal independent spike syndrome (MISS) is an identifiable electroclinical syndrome, which combines intractable motor seizures, mental retardation and multifocal independent spike discharges. Similarities to the Lennox Gastaut syndrome cause frequent misdiagnosis; however, MISS is a distinct electroclinical syndrome in children with a better prognosis and a different EEG pattern. We report an 8-year-old boy with MISS, whose intractable seizures were completely controlled for the first time with tiagabine as add-on therapy. Tiagabine should be studied further in the treatment of intractable multiple seizures of childhood.

Gabapentin in the management of convulsive disorders

Gabapentin, in clinical use since 1993, is indicated as an adjunctive antiepileptic drug (AED) for treatment of complex partial seizures, with or without secondary generalization, in patients over 12 years of age. Although several cellular actions have been described in the literature, the molecular mechanism(s) of action responsible for the anticonvulsant effect of gabapentin has not been conclusively determined. It is likely that gabapentin has multiple concentration-dependent actions that combine in a unique manner to produce antiepileptic efficacy. The pharmacokinetic properties of this water-soluble, amino-acid AED are generally favorable. Absorption appears to be dependent on transport by the L-system amino acid transporter. Elimination of unmetabolized drug occurs by the renal route. Although its therapeutic range is not well characterized, gabapentin has a broad therapeutic index. This implies that a wide range of doses can be used, based on individual patient needs, without significant limitation due to dose-dependent side effects. Gabapentin has few drug-drug interactions, none of which is clinically limiting. Several studies have demonstrated the long-term efficacy of gabapentin with no systematic evidence of tachyphylaxis. In addition, there is increasing evidence to support the use of gabapentin as monotherapy. Gabapentin is safe and is generally well tolerated. To date, nearly 3 million patients have been treated in studies and in open use without causal relationship to a specific life-threatening organ toxicity. Seizure control superior to that observed in well-controlled trials has been reported at higher doses used in clinical practice and in studies. Therefore, gabapentin dosing must be optimized on an individual basis to achieve an adequate trial of the drug and obtain the best seizure control.