Topiramate use in pediatric patients

Double-blind, placebo-controlled trial of risperidone plus topiramate in children with autistic disorder

BACKGROUND

Autism is a complex neurodevelopmental disorder that forms part of a spectrum of related disorders referred to as Autism Spectrum Disorders. The present study assessed the effects of topiramate plus risperidone in the treatment of autistic disorder.

METHOD

Forty children between the ages of 4 and 12 years with a DSM IV clinical diagnosis of autism who were outpatients from a specialty clinic for children were recruited. The children presented with a chief complaint of severely disruptive symptoms related to autistic disorder. Patients were randomly allocated to topiramate+risperidone (Group A) or placebo+risperidone (Group B) for an 8-week, double-blind, placebo-controlled study. The dose of risperidone was titrated up to 2 mg/day for children between 10 and 40 kg and 3 mg/day for children weighting above 40 kg. The dose of topiramate was titrated up to 200 mg/day depending on weight (100 mg/day for <30 kg and 200 mg/day for >30 kg). Patients were assessed at baseline and after 2, 4, 6 and 8 weeks after starting medication. Measure of outcome was the Aberrant Behavior Checklist-Community (ABC-C) Rating Scale.

RESULTS

Difference between the two protocols was significant as the group that received topiramate had a greater reduction in ABC-C subscale scores for irritability, stereotypic behavior and hyperactivity/noncompliance.

CONCLUSION

The results suggest that the combination of topiramate with risperidone may be superior to risperidone monotherapy for children with autistic disorder. However the results need to be further confirmed by a larger randomized controlled trial.

Use of second-generation antiepileptic drugs in the pediatric population

Epilepsy is common in the pediatric population. Nine second-generation antiepileptic drugs have been approved in the US for use in epilepsy over the past 15 years: felbamate, gabapentin, lamotrigine, topiramate, tiagabine, levetiracetam, oxcarbazepine, zonisamide, and pregabalin. Their use in pediatric patients is fairly widespread, despite most of these agents not having US FDA indications for use. Felbamate and gabapentin were the first two second-generation antiepileptic drugs to be approved in the US. Felbamate use has been limited because of the occurrence of hepatotoxicity and aplastic anemia. Although gabapentin is a fairly well tolerated antiepileptic drug, its use has also been limited as a result of inconsistent efficacy and concern about seizure exacerbation. Lamotrigine and topiramate are broad-spectrum antiepileptic drugs with efficacy in a wide variety of seizure types. Both agents have some tolerability concerns: rash with lamotrigine and neuropsychiatric events with topiramate. There are very little data on tiagabine use in children, but this agent appears to be effective and to have a good tolerability profile. Levetiracetam is a second-generation antiepileptic agent that is available intravenously. Considering its good efficacy, fast onset of action, and low incidence of serious adverse effects, its use in the acute setting could potentially increase. Oxcarbazepine and zonisamide have been relatively well studied in pediatric seizure patients, including use as monotherapy. Both agents have demonstrated good efficacy and tolerability for patients as young as 1 month old. Vigabatrin and rufinamide are currently not available in the US, but have been shown to have some success in other countries. Pregabalin is the newest antiepileptic agent, but lacks pediatric data currently.

Age-dependent effects of topiramate on the acquisition and the retention of rapid kindling

PURPOSE

To examine antiepileptogenic, disease modifying, and anticonvulsant effects of topiramate under conditions of rapid kindling at different stages of development.

METHODS

Afterdischarge threshold (ADT) and duration (ADD) were examined in 2-, 3-, and 5-week-old Wistar rats before and after administration of topiramate (200 mg/kg). Animals underwent a rapid kindling protocol (sixty 10-s trains, bipolar 20 Hz square wave pulses delivered every 5 min). The progression of behavioral and electrographic seizures, and responses to test stimulations 24 h after the protocol were compared between topiramate and vehicle-treated control rats. In addition, rats that were previously given vehicle only prior to kindling, were then given topiramate to examine the effect on established kindled seizures.

RESULTS

In 2-week-old animals, topiramate affected neither the baseline afterdischarge, nor the progression of kindled seizures. In 3-week-old rats, topiramate did not modify the baseline afterdischarge, but significantly delayed the occurrence of full motor seizures in response to repeated stimulations. Topiramate treatment of 5-week-old rats increased baseline ADT, shortened ADD, and delayed the progression of kindled seizures. Twenty-four h after the last kindling stimulation, animals of all ages exhibited a decreased ADT, an increase ADD, and developed behavioral seizures in response to threshold stimulation. Vehicle-treated kindled rats that were then given topiramate displayed significantly attenuated behavioral seizures induced by the threshold stimulation.

CONCLUSIONS

Topiramate exhibited age-dependent disease-modifying effects under conditions of rapid kindling, but failed to block epileptogenesis. Topiramate also inhibited kindled seizures with equal efficacy across the three ages.

Topiramate monotherapy for childhood absence seizures: an open label pilot study

This open-label, single-site, pilot study evaluated the therapeutic usefulness of topiramate in five children with typical absence seizures defined as loss of awareness associated with 3 Hz spike-wave activity on 24 hour ambulatory electroencephalogram (EEG). The children were previously untreated or treated unsuccessfully using other antiepileptic medication. Topiramate was initiated at a dose of 1 mg x kg (-1)day (-1), titrated twice weekly in 1 mg x kg (-1)day (-1)increments to 12 mg x kg (-1)day (-1)or individual maximally tolerated dose. Response was assessed after 6 weeks with ambulatory EEG monitoring and patient/parent record of seizure counts. All children completed the study. One previously untreated child became seizure-free on 5 mg x kg (-1)day(-1) topiramate, with no residual spike-wave activity at the final visit. In two patients, the frequency of seizures decreased in the early phases of titration, but rose to baseline levels as the topiramate dose was increased. With a reduction in dose to 6 mg x kg (-1)day (-1), seizure control improved, with substantial reductions in spike-wave activity. Seizure counts were not improved in the two remaining patients. Transient mood changes were noted in two patients. No child was withdrawn secondary to adverse effects. The results suggest that topiramate may be effective in childhood absence epilepsy. Controlled studies are now required to identify the clinically optimal dose.

Topiramate in refractory partial-onset seizures in children, adolescents and young adults: a multicentric open trial

PURPOSE

This study was to evaluate the efficacy and safety of topiramate (TPM) in refractory partial epilepsy in children, adolescents and young adults.

METHODS

We performed a prospective open label add-on study in 55 patients (age 2-30 years, mean 15 years) with refractory partial seizures. Topiramate was added to one or two other baseline drugs and the efficacy was rated according to seizure type and frequency.

RESULTS

TPM was initiated at a daily dose of 0.5-1 mg/kg, followed by a 2-week titration at increments of 1-3 mg/kg/24h, up to a maximum daily dose of 12 mg/kg. After 9 months of treatment, 11 patients (20%) had 100% fewer seizures and 25 patients (45%) had a more than 50% seizure reduction. TPM appeared to be effective both in cryptogenic (76.2%) and symptomatic (58.8%) partial epilepsies. Mild to moderate adverse events were present in 25 patients (45.4%), mostly represented by drowsiness, nervousness and hyporexia with or without weight loss.

CONCLUSION

TPM was an overall effective and safe add-on drug both in cryptogenic and symptomatic childhood refractory partial seizures, the adverse reactions being generally mild or moderate.

Efficacy and tolerability of topiramate in childhood and adolescent epilepsy: a clinical experience

A 3-year retrospective review was undertaken of the use of topiramate in 51 children aged 3-16 years with partial and generalized epilepsies who attended a tertiary referral epilepsy centre in a large children's hospital. The mean follow-up period was 19 months (range 6-33 months). Twenty-six children (51%) were still receiving topiramate at the time of their last review. Fifteen children (29%) showed a greater than 50% reduction in their seizure frequency and four children (8%) became seizure free, three on topiramate monotherapy. The drug appeared to be most effective in children with moderate learning difficulties with 75% showing an improvement in seizure control compared with 25% of children with normal educational functioning. Topiramate was withdrawn in 25 patients. The reasons for withdrawal included adverse effects in 20, lack of effect in three and worsening of seizures in two patients. Adverse side effects were reported in 57% of the 51 patients. The majority of the side effects were related to behavioural and cognitive difficulties, with less-common side effects including anorexia, weight loss and headaches.

Topiramate in intractable childhood onset epilepsy--a cautionary note

OBJECTIVES

To study the effectiveness and safety of topiramate in clinical practice, for a group of patients with childhood onset epilepsy.

METHODS

All patients treated with topiramate at the three study centers between November 1995 and December 31, 1997 were analyzed retrospectively, using a standardized study protocol. Data were gathered on demographic features, seizures response and medication related adverse events.

RESULTS

Eighty-seven patients were treated with topiramate. Over 90% seizure reduction was achieved in 8 (9%) patients, 50%-90% in 21 (24%), < 50% in 54 (62%) patients. Four patients (5%) had a deterioration in seizure control. Adverse events required topiramate discontinuation in 36 (41%). Of these 27 (31%) complained of unacceptable cognitive dulling. The rate of dose escalation and final dose in mg/kg were similar in those who remained on topiramate and those who were intolerant because of cognitive side effects.

CONCLUSIONS

Although topiramate resulted in > 50% seizure reduction in 29 (33%) of this group of patients with difficult epilepsy, its usefulness was limited by a high incidence of adverse effects. Adverse events prevented ongoing therapy for 36 (41%) and cognitive dulling resulted in topiramate discontinuation by 27 (31%) of the group.

Topiramate

Six studies are cited to demonstrate that topiramate is effective as adjunctive therapy for refractory partial-onset seizures in adults. Subsequent studies indicate that topiramate is also effective as monotherapy in adults and as adjunctive therapy for partial-onset seizures in children, tonic-clonic seizures of nonfocal origin in children and adults, and drop attacks in Lennox-Gastaut syndrome. Adverse effects for adults and children included dizziness, fatigue, ataxia, confusion, somnolence, nephrolithiasis, paresthesia, and weight loss. More adverse effects were observed at higher doses. Topiramate exhibits rapid absorption, long duration of action, and minimal interaction with other antiepileptic drugs.