Lamotrigine in absence and primary generalized epilepsies

mGlu3 Metabotropic Glutamate Receptors as a Target for the Treatment of Absence Epilepsy: Preclinical and Human Genetics Data

BACKGROUND

Previous studies suggest that different metabotropic glutamate (mGlu) receptor subtypes are potential drug targets for treating absence epilepsy. However, no information is available on mGlu3 receptors.

OBJECTIVE

To examine whether (i) changes of mGlu3 receptor expression/signaling are found in the somatosensory cortex and thalamus of WAG/Rij rats developing spontaneous absence seizures; (ii) selective activation of mGlu3 receptors with LY2794193 affects the number and duration of spikewave discharges (SWDs) in WAG/Rij rats; and (iii) a genetic variant of GRM3 (encoding the mGlu3 receptor) is associated with absence epilepsy.

METHODS

Animals: immunoblot analysis of mGlu3 receptors, GAT-1, GLAST, and GLT-1; realtime PCR analysis of mGlu3 mRNA levels; assessment of mGlu3 receptor signaling; EEG analysis of SWDs; assessment of depressive-like behavior. Humans: search for GRM3 and GRM5 missense variants in 196 patients with absence epilepsy or other Idiopathic Generalized Epilepsy (IGE)/ Genetic Generalized Epilepsy (GGE) and 125,748 controls.

RESULTS

mGlu3 protein levels and mGlu3-mediated inhibition of cAMP formation were reduced in the thalamus and somatosensory cortex of pre-symptomatic (25-27 days old) and symptomatic (6-7 months old) WAG/Rij rats compared to age-matched controls. Treatment with LY2794193 (1 or 10 mg/kg, i.p.) reduced absence seizures and depressive-like behavior in WAG/Rij rats. LY2794193 also enhanced GAT1, GLAST, and GLT-1 protein levels in the thalamus and somatosensory cortex. GRM3 and GRM5 gene variants did not differ between epileptic patients and controls.

CONCLUSION

We suggest that mGlu3 receptors modulate the activity of the cortico-thalamo-cortical circuit underlying SWDs and that selective mGlu3 receptor agonists are promising candidate drugs for absence epilepsy treatment.

Pharmacological activation of mGlu5 receptors with the positive allosteric modulator VU0360172, modulates thalamic GABAergic transmission

Previous studies have shown that injection of the mGlu5 receptor positive allosteric modulator (PAM) VU0360172 into either the thalamus or somatosensory cortex markedly reduces the frequency of spike-and-wave discharges (SWDs) in the WAG/Rij model of absence epilepsy. Here we have investigated the effects of VU0360172 on GABA transport in the thalamus and somatosensory cortex, as possible modes of action underlying the suppression of SWDs. Systemic VU0360172 injections increase GABA uptake in thalamic synaptosomes from epileptic WAG/Rij rats. Consistent with this observation, VU0360172 could also enhance thalamic GAT-1 protein expression, depending on the dosing regimen. This increase in GAT-1 expression was also observed in the thalamus from non-epileptic rats (presymptomatic WAG/Rij and Wistar) and appeared to occur selectively in neurons. The tonic GABA_A receptor current present in ventrobasal thalamocortical neurons was significantly reduced by VU0360172 consistent with changes in GAT-1 and GABA uptake. The in vivo effects of VU0360172 (reduction in tonic GABA current and increase in GAT-1 expression) could be reproduced in vitro by treating thalamic slices with VU0360172 for at least 1 h and appeared to be dependent on the activation of PLC. Thus, the effects of VU0360172 do not require an intact thalamocortical circuit. In the somatosensory cortex, VU0360172 reduced GABA uptake but did not cause significant changes in GAT-1 protein levels. These findings reveal a novel mechanism of regulation mediated by mGlu5 receptors, which could underlie the powerful anti-absence effect of mGlu5 receptor enhancers in animal models.

Mode of seizure inhibition by sodium channel blockers, an SV2A ligand, and an AMPA receptor antagonist in a rat amygdala kindling model

PURPOSE

A number of antiepileptic drugs (AEDs) with a variety of modes of action, are effective in treating focal seizures. Several AEDs, such as perampanel (PER), levetiracetam (LEV), lacosamide (LCM), lamotrigine (LTG), and carbamazepine (CBZ), have been shown to elevate the seizure threshold in kindling models. These AEDs are clinically effective, but differences exist in the anti-seizure profiles of drugs with similar modes of action. Therefore, we hypothesized that there are differences in how these AEDs affect seizures. Here, we evaluated the effects of AEDs on various seizure parameters in a rat amygdala kindling model upon stimulation at the after-discharge threshold (ADT) and at three-times the ADT (3xADT) to characterize the differences in the effects of these AEDs.

METHODS

PER, LEV, LCM, LTG, CBZ, or vehicle was administered intraperitoneally to fully kindled rats. Changes in Racine seizure score, after-discharge duration (ADD), and latency to Racine score 4 generalized seizure (S₄L) were measured to assess differences in the modes of seizure inhibition among the AEDs. Stimulation at 3xADT was used to eliminate the influence of any AED-induced elevation of the seizure threshold on these parameters.

RESULTS

PER, LEV, LCM, LTG, and CBZ significantly reduced the seizure score from Racine score 5 after stimulation at the ADT; this effect was lost with LEV and LTG after stimulation at 3xADT. PER and LEV significantly shortened the ADD when the seizure focus was stimulated at the ADT, whereas LCM, LTG, and CBZ did not. LEV, LCM, LTG, and CBZ failed to shorten the ADD upon stimulation at 3xADT. PER dose-dependently and significantly increased S₄L, even at doses that were ineffective for seizure score reduction, after stimulation at both the ADT and 3xADT. LEV and LTG significantly increased S₄L after stimulation at the ADT, whereas LCM and CBZ did not significantly increase S₄L at any of the doses tested.

CONCLUSIONS

The sodium channel blockers (LCM, LTG, and CBZ) appeared to act by elevation of the seizure threshold via reduction of neuronal excitability, whereas the AMPA receptor antagonist (PER) and the SV2A ligand (LEV), as well as LTG, exerted their effects through the weakening of synaptic transmission in neuronal networks at the seizure focus. Maintenance of the effect of PER even at 3xADT suggests direct and strong modulation of excitatory synaptic transmission by PER, both at the focus and along the seizure propagation route. These findings may provide further rationale for usage of AEDs beyond their respective modes of action.

Resveratrol suppressed seizures by attenuating IL-1β, IL1-Ra, IL-6, and TNF-α in the hippocampus and cortex of kindled mice

OBJECTIVE

There is an urge to identify new molecules which can modulate process of epileptogenesis, since currently available drugs act symptomatically and one-third of the patients remain refractory to the disease. Hence, the present study was conducted to evaluate the effects of Resveratrol (RESV) on epileptogenesis in pentylenetetrazole (PTZ)-induced kindling in mice.

METHOD

Swiss albino mice were administered RESV (10, 20 and 40 mg/kg,p.o) in acute study. On the seventh day animals were subjected to various neurological and neurobehavioral tests viz, Increasing Current Electroshock Test (ICES), PTZ-induced seizures, passive avoidance response, and elevated plus maze test. For the development of kindling PTZ was administered in a dose of 25 mg/kg, i.p. on every alternate day and RESV in all the three doses was administered daily. Seizure score was continuously monitored till the development of kindling and cognition tests were performed in the end of the study. The animals were sacrificed and levels of inflammatory biomarkers viz., IL-1β, interleukin-1 receptor antagonist (IL1-Ra), IL-6, and TNF-α were assessed in the hippocampus and cortex of the kindled animals.

RESULTS

RESV in all three doses increased the seizure threshold to hind limb extension in the ICES test. RESV in all the tested doses suppressed the development of kindling and reduced the levels of IL-1β, IL1-Ra, IL-6, and TNF-α in kindled mice.

CONCLUSION

RESV suppressed the development of kindling in mice and decreased the levels of inflammatory biomarkers in their hippocampus. RESV modified brain inflammation during epileptogenesis and found to possess nootropic activity in the kindled mice.

Lamotrigine and its applications in the treatment of epilepsy and other neurological and psychiatric disorders

Lamotrigine is a broad-spectrum antiepileptic drug, initially approved in 1994 for the adjunctive treatment of partial seizures in adults and for the generalized seizures of Lennox-Gastaut syndrome in pediatric (>2 years old) and adult populations. Its role in the treatment of bipolar disorder type I has also been well established. In addition, lamotrigine has been successfully used for the management of other neurological conditions such as migraines and neuropathic pain, and preliminary data show promising results. It has favorable pharmacokinetic properties and is generally well tolerated. The small risk of serious skin rash can be minimized with slow titration of the drug and dose adjustment with concomitant medications. Lamotrigine has demonstrated particular benefit in the treatment of women and elderly patients with epilepsy.

Lamotrigine in epilepsy, pregnancy and psychiatry--a drug for all seasons?

Lamotrigine has been demonstrated to be effective as both an antiepileptic drug and a mood stabiliser. For epilepsy it is less efficacious than valproate in primary generalised epilepsy, but it is comparable to some traditional drugs in partial epilepsy. In psychiatry it has significant advantages over other mood stabilisers for the treatment and prevention of depressive phases of bipolar illness, but not for the treatment of mania. It has a more benign adverse effect profile than older antiepileptic agents and is not a proven teratogen. Risk of adverse reactions is reduced by commencing treatment at a markedly reduced dose that is gradually increased.

Potentiation of mGlu5 receptors with the novel enhancer, VU0360172, reduces spontaneous absence seizures in WAG/Rij rats

Absence epilepsy is generated by the cortico-thalamo-cortical network, which undergoes a finely tuned regulation by metabotropic glutamate (mGlu) receptors. We have shown previously that potentiation of mGlu1 receptors reduces spontaneous occurring spike and wave discharges (SWDs) in the WAG/Rij rat model of absence epilepsy, whereas activation of mGlu2/3 and mGlu4 receptors produces the opposite effect. Here, we have extended the study to mGlu5 receptors, which are known to be highly expressed within the cortico-thalamo-cortical network. We used presymptomatic and symptomatic WAG/Rij rats and aged-matched ACI rats. WAG/Rij rats showed a reduction in the mGlu5 receptor protein levels and in the mGlu5-receptor mediated stimulation of polyphosphoinositide hydrolysis in the ventrobasal thalamus, whereas the expression of mGlu5 receptors was increased in the somatosensory cortex. Interestingly, these changes preceded the onset of the epileptic phenotype, being already visible in pre-symptomatic WAG/Rij rats. SWDs in symptomatic WAG/Rij rats were not influenced by pharmacological blockade of mGlu5 receptors with MTEP (10 or 30 mg/kg, i.p.), but were significantly decreased by mGlu5 receptor potentiation with the novel enhancer, VU0360172 (3 or 10 mg/kg, s.c.), without affecting motor behaviour. The effect of VU0360172 was prevented by co-treatment with MTEP. These findings suggest that changes in mGlu5 receptors might lie at the core of the absence-seizure prone phenotype of WAG/Rij rats, and that mGlu5 receptor enhancers are potential candidates to the treatment of absence epilepsy. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.

Metabotropic glutamate receptors in the thalamocortical network: strategic targets for the treatment of absence epilepsy

Metabotropic glutamate (mGlu) receptors are positioned at synapses of the thalamocortical network that underlie the development of spike-and-wave discharges (SWDs) associated with absence epilepsy. The modulatory role of individual mGlu receptor subtypes on excitatory and inhibitory synaptic transmission in the cortico-thalamo-cortical circuitry makes subtype-selective mGlu receptor ligands potential candidates as novel antiabsence drugs. Some of these compounds are under clinical development for the treatment of numerous neurologic and psychiatric disorders, and might be soon available for clinical studies in patients with absence seizures refractory to conventional medications. Herein we review the growing evidence that links mGlu receptors to the pathophysiology of pathologic SWDs moving from the anatomic localization and function of distinct mGlu receptor subtypes in the cortico-thalamo-cortical network to in vivo studies in mouse and rat models of absence epilepsy.

Efficacy and safety of lamotrigine monotherapy in children and adolescents with epilepsy

Lamotrigine (LTG) has shown to confer broad-spectrum, well-tolerated control of epilepsy. Monotherapy is preferable over polytherapy because of better compliance, fewer adverse events, less interactions, lower teratogenicity and lower cost. The aim of this study is to evaluate the efficacy and safety of LTG monotherapy on seizure control in a cohort of children and adolescents with epilepsy. We retrospectively reviewed the records of children and adolescents treated with LTG monotherapy at our institution between 2001 and 2006. Data collected included demographics, seizure type, etiology of seizures, age at onset of seizures and at initiation of LTG treatment, number of antiepileptic drugs (AEDs) prior to LTG, dose of LTG, length of follow-up, treatment response, and adverse events. Seventy-two children and adolescents were identified (mean age 12.1 years); 37.5% had mental retardation. Age at onset of epilepsy was 5.7 years (0-16). Twenty three percent had symptomatic focal epilepsy, 15.5% idiopathic focal epilepsy, 19.4% symptomatic generalized epilepsy and 41.6% idiopathic generalized epilepsy. LTG was used as first-line monotherapy in 26.4% of patients and as a second-line monotherapy in 73.6%. Age at initiation of LTG therapy was 10 years (2.8-19). Mean number of AEDs tried prior to LTG was 1.3 (0-6). Mean dose of LTG was 5.5mg/kg/day (1.1-13.7). Mean follow-up period was 33 months (3 weeks to 11.5 years). The degree of seizure reduction was as follows: seizure free in 42%, 75-90% reduction in 17.4%, 50-74% in 11.6%, 25-49% in 10%. Sixteen percent had no change in seizure control and 3% became worse. The most common adverse event was rash (6.9%). Six (8.3%) patients discontinued LTG because of the adverse events. No patient had Stevens-Johnson syndrome. In conclusion, LTG was effective and well-tolerated as monotherapy in children and adolescents for both focal and generalized epilepsies.

Lamotrigine inhibits postsynaptic AMPA receptor and glutamate release in the dentate gyrus

PURPOSE

The dentate gyrus (DG) is a gateway that regulates seizure activity in the hippocampus. We investigated the site of action of lamotrigine (LTG), an effective anticonvulsant, in the regulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartic acid (NMDA) receptor-mediated excitatory synaptic transmission on DG.

METHODS

Evoked AMPA and NMDA receptor-mediated excitatory postsynaptic currents (eEPSCampa and eEPSCnmda) were recorded by whole-cell patch-clamp recording from the granule cells of DG in brain slice preparation of young Wistar rats (60-120 g). Exogenously applied AMPA and NMDA-induced currents and AMPA receptor-mediated miniature EPSC (mEPSCampa) were recorded in the presence of specific antagonists.

RESULTS

LTG inhibited both eEPSCampa and eEPSCnmda, and had no effect on exogenously applied NMDA-induced current indicating LTG inhibited glutamate release. Previous studies demonstrated that alteration in glutamate concentration in synaptic cleft causes parallel changes of eEPSCampa and eEPSCnmda. Our results showed that LTG inhibited eEPSCampa significantly more than eEPSCnmda (p < 0.05), suggesting that LTG may also have blocked the postsynaptic AMPA receptor. The hypothesis is further supported by the facts that; (1) LTG (30-100 microM) inhibited direct exogenously applied AMPA-induced currents (to 90%), (2) LTG significantly reduced the amplitude, but not the frequency of mEPSCampa and asynchronous (EPSC), and (3) LTG-induced reduction of eEPSCampa was not associated with a modification of the paired-pulse ratio. To sum up, LTG exerts a postsynaptic inhibitory mechanism on the AMPA receptor.

CONCLUSIONS

Our results demonstrate that LTG suppresses postsynaptic AMPA receptors and reduces glutamate release in granule cells of DG. The postsynaptic effect can be one of the underlying mechanisms of LTG's anticonvulsant action.

Choosing a First Drug Treatment for Epilepsy after SANAD: Randomized Controlled Trials, Systematic Reviews, Guidelines and Treating Patients

The ILAE treatment guidelines for initial monotherapy emphasise the poor quality of information available to inform everyday clinical practice. Industry sponsored studies comparing antiepileptic drugs answer restricted licensing questions, rather than those relevant to the clinical community (patients, health professionals and founders of health care). The SANAD study, a pragmatic randomized clinical trial, offers a methodology to address some of these questions. It identifies lamotrigine as a cost-effective alternative to carbamazepine for the treatment of focal epilepsies, but confirms valproate as the most effective drug for the treatment of generalized or unclassified epilepsy.

Lamotrigine adjunctive therapy among children and adolescents with primary generalized tonic-clonic seizures

CONTEXT AND OBJECTIVE

Primary generalized tonic-clonic seizures are relatively more common among children than among adults. Primary generalized tonic-clonic seizures are associated with increased risk of injury and death. Therefore, effective control of primary generalized tonic-clonic seizures is necessary to reduce epilepsy-related morbidity and mortality. Lamotrigine has demonstrated efficacy from published randomized clinical trials for childhood partial seizures, absence seizures, and for the generalized seizures associated with Lennox-Gastaut syndrome. A randomized, blinded, placebo-controlled study was conducted to assess the efficacy and tolerability of adjunctive therapy with lamotrigine in the treatment of primary generalized tonic-clonic seizures among patients > or = 2 years of age; we report the data from children and adolescents 2 to 20 years of age from this randomized clinical trial. This is the first published analysis of data from a randomized, double-blind, controlled clinical trial of primary generalized tonic-clonic seizures focusing on children and adolescents.

PATIENTS AND METHODS

We randomly assigned (1:1) 117 patients, aged 2 to 55 years, with primary generalized tonic-clonic seizures inadequately controlled on 1 to 2 current antiepileptic drugs and with evidence of primary generalized tonic-clonic seizures on electroencephalogram and no historical or electroencephalogram evidence of partial seizures to either lamotrigine or placebo in a double-blind parallel group clinical trial from 2001 through 2004. We analyzed the subgroup of children and adolescents, aged 2 to 20 years (n = 45), from this randomized clinical trial. Patients having > or = 3 primary generalized tonic-clonic seizures over an 8-week baseline were randomly assigned (1:1) to receive either lamotrigine or placebo. The treatment period consisted of an escalation phase (12 weeks for patients 2-12 years; 7 weeks for patients > 12 years) and a maintenance phase (12 weeks). The study had 4 phases: screening phase, baseline phase, escalation phase, and maintenance phase. During the screening phase, baseline medical examinations and seizure type and seizure frequency assessments were performed. During the 8-week baseline phase, the number and dosages of concomitant antiepileptic drugs were maintained while seizure frequency was assessed. The assessment of primary generalized tonic-clonic seizure frequency was determined during the 8-week baseline phase. Patients eligible for random assignment experienced > or =3 primary generalized tonic-clonic seizures during the baseline phase and > or = 1 primary generalized tonic-clonic seizure in the 8 weeks before the baseline phase. Lamotrigine was introduced and titrated using a schedule based on the patients' age and concurrent antiepileptic drug regimen. During the escalation phase, the number and doses of concomitant antiepileptic drugs were not changed. The escalation phase was followed by a 12-week maintenance phase during which time the lamotrigine dose was maintained at a specific dose defined by the patients' age and concomitant antiepileptic drugs, whereas the doses of concurrent antiepileptic drugs were maintained at a constant dose. Concurrent antiepileptic drugs could not be discontinued or added during the maintenance phase. The primary efficacy end point measure was the median reduction in the frequency of primary generalized tonic-clonic seizures from baseline; seizure counts were recorded prospectively in standardized daily seizure diaries. Other efficacy end point data for analysis were as follows: the median seizure counts, the median percentage change from the baseline phase in average monthly seizure frequency for other generalized seizure types, and the percentage of patients with a reduction of > or = 25%, > or = 50%, > or = 75%, or 100% in frequencies of primary generalized tonic-clonic seizures and all generalized seizures during the escalation phase and/or maintenance phase relative to the baseline phase. Accurate counts of absence seizure frequency require electroencephalogram-video monitoring; absence seizure frequency was not an outcome measure for this analysis.

RESULTS

Forty-five (21 lamotrigine and 24 placebo) patients 2 to 19 years of age were randomly assigned and received study drug. Eight patients (3 lamotrigine and 5 placebo) had a combination of clinical (myoclonus and/or absence seizures) and electroencephalogram findings that were consistent with juvenile myoclonic epilepsy. Among the 45 children randomly assigned, 74% had generalized spike, polyspike, and/or generalized spike and wave discharges on routine electroencephalogram recordings; the remaining 26% of children had no electroencephalogram findings suggestive of partial epilepsy and a clear history consistent with primary generalized tonic-clonic seizures. Electroencephalogram findings were not significantly different between the lamotrigine and the placebo treatment groups. The median percentage decrease from baseline in primary generalized tonic-clonic seizures during the entire treatment period was 77% in the lamotrigine group and 40% in the placebo group (P = .044). The median primary generalized tonic-clonic seizure counts per month were 0.7 in the lamotrigine group and 3.6 in the placebo group during escalation (P = .008), 0.3 in the lamotrigine group and 2.0 in the placebo group during maintenance (P = .005), and 0.4 in the lamotrigine group and 2.5 in the placebo group during the entire treatment period (P = .007). Trends were noted during escalation and maintenance with a median percentage decrease in primary generalized tonic-clonic seizures during escalation of 72% in the lamotrigine group and 30% in the placebo group (P = .059), and 83% in the lamotrigine group and 42% in the placebo group during maintenance (P = .058). During the maintenance phase, 48% of lamotrigine patients were seizure free compared with 17% treated with placebo (P = .051). One patient from each treatment group discontinued from the study because of an adverse event; 1 patient who received lamotrigine experienced "disorientation"; and 1 patient who received placebo had a convulsion with apnea. No rashes occurred among patients taking lamotrigine or placebo. No patient experienced worsening of the intensity or frequency of myoclonus.

CONCLUSIONS

Adjunctive lamotrigine therapy seems effective in controlling primary generalized tonic-clonic seizures among patients 2 to 20 years of age.

The LAM-SAFE Study: Lamotrigine versus carbamazepine or valproic acid in newly diagnosed focal and generalised epilepsies in adolescents and adults

OBJECTIVE

To investigate efficacy and safety of lamotrigine (LTG) versus carbamazepine (CBZ) or valproic acid (VPA) in newly diagnosed focal (FE) and idiopathic generalised (GE) epilepsies in adolescents and adults.

METHODS

Open-label randomised comparative multicentre 24-week monotherapy trial in newly diagnosed epilepsy patients of >or=12 years of age. Patients with FE were treated with LTG or CBZ, those with GE received LTG or VPA. The primary efficacy variable was the number of seizure-free patients during study weeks 17 and 24.

RESULTS

Two hundred and thirty-nine patients were included. One hundred and seventy-six patients suffered from FE and 63 from GE. In the FE group, 88 patients each were treated with CBZ or LTG. Ninety-four percent of the CBZ patients and 89% of the LTG patients became seizure-free according to an intent-to-treat analysis (not statistically different). The rate of patients discontinuing treatment due to adverse events or a lack of efficacy was 19% with CBZ compared to 9% with LTG (not statistically different). In the GE group, 30 patients received VPA and 33 LTG. During study weeks 17 and 24, 61% of the LTG patients and 84% of the VPA patients had become seizure-free (not statistically significant). The drop-out rate due to lack of efficacy or adverse events was 12% with LTG and 3% with VPA (not statistically different).

CONCLUSIONS

This study indicates that the effectiveness of LTG in focal and generalised epilepsy syndromes as initial monotherapy in patients >or=12 years is in the range of standard first-line antiepileptic drugs.

Lamotrigine versus valproic acid as first-line monotherapy in newly diagnosed typical absence seizures: an open-label, randomized, parallel-group study

PURPOSE

To compare the efficacy of lamotrigine (LTG) and valproic acid (VPA) in newly diagnosed children and adolescents with typical absence seizures.

METHODS

A randomized, open-label parallel-group design was used. After undergoing an awake video-EEG recording, which included one to two trials of 3 min of hyperventilation and intermittent photic stimulation, eligible patients were randomized to receive LTG or VPA. LTG was initiated at a daily dose of 0.5 mg/kg for 2 weeks in two divided doses, followed by 1.0 mg/kg/day for an additional 2 weeks. Thereafter, doses were increased in 1-mg/kg/day increments every 5 days until seizures were controlled, intolerable adverse effects occurred, or a maximum dose of 12 mg/kg/day had been reached. VPA was equally uptitrated according to clinical response, starting at 10 mg/kg and increasing by 5 mg/kg/24 h every 3 days, if required, to a maximum of 30 mg/kg/day in three divided doses. Patients were seen in the clinic every month for < or = 12 months. The primary efficacy end point at each visit was seizure freedom, defined as lack of clinically observed seizures since the previous visit and lack of electroclinical seizures during ambulatory 24-h EEG testing and a video-EEG session with hyperventilation.

RESULTS

Thirty-eight children (17 boys, 21 girls), aged from 3 to 13 years (mean, 7.5 years), all newly diagnosed with childhood or juvenile typical absence seizures, were enrolled. After 1 month of treatment, 10 (52.6%) of 19 children taking VPA and one (5.3%) of 19 taking LTG were seizure free (p = 0.004). By the 3-month follow-up, 12 (63.1%) children taking VPA and seven (36.8%) taking LTG were controlled (p = 0.19). After 12 months, 13 children taking VPA (dose range, 20-30 mg/kg/day; mean serum level, 76.8 mg/L; range, 51.4-91 mg/L) and 10 taking LTG (dose range, 2-11 mg/kg/day; mean serum level, 8.1 mg/L; range, 1.1-18 mg/L) were seizure free (p = 0.51). Side effects were mostly mild and transient and were recorded in two (10.6%) children treated with VPA and in six (31.8%) treated with LTG.

CONCLUSIONS

Both VPA and LTG can be efficacious against absence seizures, although VPA shows a much faster onset of action, at least in part because of its shorter titration schedule.

Lamotrigine as first-line drug in childhood absence epilepsy: a clinical and neurophysiological study

To investigate to which extent lamotrigine (LTG) may be effective and tolerated as a monotherapy for the treatment of newly diagnosed childhood absence seizures and, secondly, to evaluate the efficacy of this drug on the circadian interictal generalized epileptiform discharges, 20 consecutive newly diagnosed patients (five males, 15 females), aged 3-10 years (mean 6.9 years), affected by childhood absence epilepsy, were administered LTG as first-line drug at the initial dose of 0.5 mg/kg/day for 2 weeks, followed by 1.0 mg/kg/day for an additional 2 weeks. Thereafter, doses have been increased in 1-mg/kg/day increments up to 9-12 mg/kg/day in accordance with the clinical response. Each patient underwent an ambulatory (24 h) EEG monitoring before starting LTG therapy (time 0) and during the maintenance period at the end of LTG titration (time 1). After a mean follow-up period of 10.8 months (range 3-28 months), a 100% seizure control was obtained in 11 children (55.5%), a more than 75% seizure decrease was present in four (20%), and a >50% seizure decrease in five (25%), with a mean LTG dose of 6.2 mg/kg/day (range 1.2-11) in the controlled group. Adverse events were present in three patients (15%); they were generally mild and transient. Our series confirms that LTG monotherapy may control typical childhood absence seizures in about half the children as well as it may decrease interictal generalized spike and wave discharges both in seizure-free and uncontrolled patients. The slow titration phase of the drug due to the risk of the skin rash may eventually reduce compliance.

Valproic acid-associated weight gain in older children and teens with epilepsy

This research was undertaken to determine the incidence and predictors of weight gain in older children and teens treated with valproate for epilepsy. Subjects who were 10 to 17 years of age, who began valproate treatment between January 1, 1996, and December 31, 2000, and who had documented weight and height measurements at medication initiation and at least one follow-up visit were retrospectively identified. Exclusion criteria were follow-up <2 months, discontinuation of valproate within 2 months, concurrent therapy with medication known to affect weight, or gastrostomy feeding. Body mass index was calculated at initiation and either discontinuation of valproate or last follow-up and stratified into four categories: underweight, (<fifth percentile), appropriate (fifth to eighty-fifth percentile), potentially overweight (>/=eighty-fifth to ninety-fifth percentile) and overweight (ninety-fifth percentile or higher). Potential predictors of change in body mass index were examined. Mild-to-moderate weight gain was observed in 58% of the 43 subjects treated with valproate (median increase, 2; twenty-fifth to seventy-fifth percentile, 1-6.4). Seventy-nine percent remained in the same body mass index category, and 14% moved up to a potentially overweight or overweight category. The only predictor of an overweight category at follow-up was a potentially overweight or overweight category at initiation (P <0.0002). Two factors tended to predict an increase in body mass index: normal neurocognitive status (P = 0.06) and primary generalized seizure type (P = 0.07).

Efficacy, tolerability, and kinetics of lamotrigine in infants

OBJECTIVES

To investigate the efficacy, tolerability, and kinetics of lamotrigine during the first year of life.

STUDY DESIGN

We studied 13 infants with intractable seizures; 7 had partial seizures and 7 had infantile spasms (1 had both). Patients received open-label lamotrigine as add-on therapy for 3 months. Seizure frequency, response ratio, and side effects score were determined and compared with the baseline period.

RESULTS

The rate of partial seizures per day decreased from 8.57 +/- 2.29 to 4.00 +/- 2.15 (P =.027) and infantile spasms from 8.71 +/- 2.15 to 3.61 +/- 2.762 (P =.028). Apparent clearance increased during the first year of life, with a break point at 2 months of age (mean, 0.119 +/- 0.021, 0.217 +/- 0.094 L/h per kilogram for infants <2 months and those 2 to 12 months old, respectively,P <.001). Twenty-four-hour concentration to time plots of three 3- to 4-week-old neonates showed a half-life of 23.44 +/- 3.57 hours. Compared with a group of 17 older children, LTG had similar efficacy (response ratios, -0.68 +/- 0.12 and -0.74 +/- 0.11, P =.504), and similar adverse effects scores (0.67 +/- 0.67 and 0.23 +/- 0.166, P =.95).

CONCLUSIONS

Lamotrigine is a useful and well tolerated drug for partial seizures and infantile spasms in infants <1 year of age. However, lamotrigine has age-dependent kinetics that must be taken into consideration.

Lamotrigine reduces spontaneous and evoked GABAA receptor-mediated synaptic transmission in the basolateral amygdala: implications for its effects in seizure and affective disorders

Lamotrigine (LTG) is an antiepileptic drug that is also effective in the treatment of certain psychiatric disorders. Its anticonvulsant action has been attributed to its ability to block voltage-gated Na(+) channels and reduce glutamate release. LTG also affects GABA-mediated synaptic transmission, but there are conflicting reports as to whether inhibitory transmission is enhanced or suppressed by LTG. We examined the effects of LTG on GABA(A) receptor-mediated synaptic transmission in slices from rat amygdala, a brain area that is particularly important in epileptogenesis and affective disorders. In intracellular recordings, LTG (100 microM) reduced GABA(A) receptor-mediated IPSPs evoked by electrical stimulation in neurons of the basolateral nucleus. In whole-cell recordings, LTG (10, 50 and 100 microM) decreased the frequency and amplitude of spontaneous IPSCs, as well as the amplitude of evoked IPSCs, but had no effect on the kinetics of these currents. LTG also had no effects on the frequency, amplitude or kinetics of miniature IPSCs recorded in the presence of TTX. These results suggest that in the basolateral amygdala, LTG suppresses GABA(A) receptor-mediated synaptic transmission by a direct and/or indirect effect on presynaptic Ca(++) influx. The modulation of inhibitory synaptic transmission may be an important mechanism underlying the psychotropic effects of LTG.

The management of refractory idiopathic epilepsies

Idiopathic epilepsies comprise a wide variety of partial and generalized syndromes that have in common a known or presumed genetic etiology and the lack of overt abnormalities other than the epilepsy itself. Most of these epilepsies have a benign natural history and/or show a favorable response to antiepileptic drug (AED) therapy, but pharmacoresistance does occur in some patients. In general, therapeutic algorithms in idiopathic partial epilepsies (IPEs) are similar to those used for symptomatic partial epilepsies, but aggressive pharmacologic therapy is rarely indicated in these patients. In self-limited conditions such as benign epilepsy of childhood with centrotemporal spikes or some forms of benign epilepsy with occipital paroxysms, AED treatment may not even be indicated unless seizures interfere significantly with quality of life. Valproate (VPA) is usually regarded as the drug of choice in idiopathic generalized epilepsies (IGEs). Most patients become rapidly seizure free, and poor compliance or prescription of an inappropriate AED because of misdiagnosis are the most common causes of treatment failure in IGEs. In those patients who did not respond well to VPA (or in whom VPA is considered contraindicated), the choice of alternative AEDs is guided by syndromic diagnosis and associated possible coexistence of multiple seizure types. Lamotrigine is establishing itself as a useful agent for many refractory IGEs, and might be considered for first-line use in selected patients. Topiramate (TPM) is another promising new agent in the management of refractory tonic-clonic seizures of nonfocal onset, but its potential efficacy against other primarily generalized seizure types has not been clearly established. Some of the older drugs, particularly ethosuximide (ESM), barbiturates, and benzodiazepines (BZDs), still have an important role in the management of refractory IGEs, especially in combination with VPA. Because carbamazepine (CBZ), phenytoin (PHT), tiagabine (TGB), vigabatrin (VGB), and gabapentin (GBP) may precipitate or aggravate absence and/or myoclonic jerks, their role in IGE syndromes associated with multiple seizure types is limited mostly to adjunctive use in patients unresponsive to first-line therapy.

The anticonvulsant, lamotrigine decreases spontaneous glutamate release but increases spontaneous GABA release in the rat entorhinal cortex in vitro

It has been suggested that the anticonvulsant effect of lamotrigine resides with it's ability to block voltage gated Na-channels at presynaptic sites, thus stabilizing the presynapse, and, consequently, reducing the release of synaptic transmitters. Neurochemical studies have shown that it can inhibit the veratrine-stimulated release of the excitatory transmitter, glutamate from cortical tissue, but that at slightly higher concentrations it also reduces the release of the inhibitory transmitter, GABA. In the present study we examined the effect of the drug on the release of these transmitters at synapses in the rat entorhinal cortex, using the whole-cell patch clamp technique to record spontaneous excitatory (EPSCs) and inhibitory postsynaptic currents (IPSCs). Lamotrigine reduced the frequency, but not the amplitude of spontaneous EPSCs. This clearly indicated a presynaptic effect to reduce the release of glutamate. However, the same effect was observed when we tested the drug on miniature EPSCs, recorded in the presence of TTX and Cd, showing that blockade of Na-channels or Ca-channels was not a prerequisite for inhibition of glutamate release. In contrast to it's effects on EPSCs, lamotrigine increased both the frequency and amplitude of spontaneous IPSCs, suggesting that the drug was acting presynaptically to enhance GABA release. Again, similar effects were seen with miniature IPSCs recorded in TTX. These opposite effects of lamotrigine on glutamate and GABA release are similar to those we have reported previously with phenytoin, and suggest that reciprocal modulation of the background release of the major excitatory and inhibitory transmitters may be a significant factor in dampening excitability in pathologically hyperexcitable cortical networks.

Tolerance to the anticonvulsant effects of lamotrigine on amygdala kindled seizures: cross-tolerance to carbamazepine but not valproate or diazepam

Using an amygdala-kindled seizure paradigm, we evaluated the acute and chronic anticonvulsant effects of lamotrigine (LTG). Lamotrigine produced dose-dependent inhibitory effects on seizure stage, afterdischarge (AD), and seizure duration. Lamotrigine (15 mg/kg) also increased the afterdischarge and seizure thresholds. Following repeated LTG administration and stimulation at 48-h intervals, tolerance developed to LTG's (15 mg/kg) anticonvulsant effects, and cross-tolerance was observed to the anticonvulsant effects of carbamazepine (CBZ, 15 mg/kg). In a separate group of kindled rats, CBZ (15 mg/kg) was repeatedly administered to induce tolerance. This led to a partial cross-tolerance to LTG, manifesting as an increased rate of tolerance development to LTG, and seizures following the first injection in some animals, which were not observed in CBZ-nontolerant controls. When these rats were made fully tolerant to LTG and then exposed to higher doses of LTG (30 and 50 mg/kg), no anticonvulsant effects were observed. In contrast, higher doses of CBZ (30 mg/kg) did restore efficacy in CBZ-tolerant animals. Cross-tolerance from LTG to valproate and diazepam was not observed, although cross-tolerance from CBZ to valproate has been reported previously. These data suggest that LTG has both shared and distinct anticonvulsant mechanisms from those of CBZ on amygdala-kindled seizures. The implications of these results for clinical therapeutics remain to be evaluated.

[Lamotrigine therapy in children. Retrospective study of 32 children]

BACKGROUND

Lamotrigine is one of the new anti-epileptic drugs, which is a phenyltriazine derivative. It is considered to act via an inhibitory effect on voltage-sensitive sodium channels and to have no GABAergic action.

PATIENTS AND METHOD

We studied its efficiency in 32 children with refractory epilepsy after a treatment of at least one year with other anti-epileptic drugs. We then compared our results with other publications.

RESULTS

Good efficiency (at least 50% reduction of crises) has been demonstrated for lamotrigine in children with generalized epilepsy (62.5% good results), particularly with absence epilepsy and Lennox-Gastaut syndrome. Results are encouraging for our few patients with epilepsy with continuous spike waves during slow-wave sleep. On the other hand, more precise indications are needed in partial epilepsy.

CONCLUSION

Seizure control was generally maintained during one year of lamotrigine treatment. Association to sodium valproate is relevant for most of the authors. Adverse effects are uncommon, and we did not observe any skin rash. Lastly, improvement of behaviour and cognitive functions represents another important benefit of lamotrigine.

Potential hepatotoxicity of lamotrigine

Lamotrigine is a new antiepileptic drug that is effective for a broad range of seizures in adults and children. Three children with seizures of different causes who were treated with lamotrigine and developed reversible hepatotoxicity are reported. In one child, this therapy led to relatively severe hepatic failure that required and responded to aggressive therapy. Unlike most of the previously reported six patients with similar severe hepatic involvement, this patient's liver function and blood hepatic enzymes became normal. All three patients were on multiple drugs, and two were in epilepsia partialis continua secondary to encephalitis. Two of the patients had relatively rapid medication titration schedules. The close time relationship between the initiation of the lamotrigine therapy and the reversal of the liver abnormalities with lamotrigine discontinuation argues against a cause other than the lamotrigine; however, because of the complexity of the reported cases, the causality remains an assumption. Review of the literature revealed six other previously reported patients (five adults and one child) who had hepatotoxicity during lamotrigine therapy, with or without associated multisystem failure, and similar patient profiles. Lamotrigine is generally a safe and effective medication; however, it should be used with caution in patients on polytherapy and in those with complicated acute systemic and central nervous system conditions, such as fever, status epilepticus, epilepsia partialis, and encephalitis.

Double-blind, placebo-controlled, crossover study of lamotrigine in treatment-resistant generalised epilepsy

PURPOSE

Lamotrigine (LTG) is recognised as effective add-on therapy for focal epilepsies, but this is the first double-blind, placebo-controlled, crossover study in treatment-resistant generalised epilepsy.

METHODS

The study consisted of 2 x 8-week treatment periods followed by a 4-week washout period. Patients received doses of either 75 or 150 mg daily, depending on their concomitant antiepileptic drugs (AEDs). Long-term continuation was offered at the end of the study with open-label LTG.

RESULTS

Five centres in Australia recruited 26 patients who were having absence, myoclonic, or generalized tonic-clonic seizures or a combination of these. Twenty-two patients completed the study. There was a significant reduction in frequency of both tonic-clonic and absence seizure types with LTG. A 350% decrease in seizures was observed for tonic-clonic seizures in 50% of cases and for absence seizures in 33% of evaluable cases. Rash was the only adverse effect causing discontinuation. Twenty-three of 26 opted for open-label LTG, with 20 still receiving LTG for a mean of 26 months. In these 20, 80% had > or =50% seizure reduction and five (25%) were seizure free.

CONCLUSIONS

This study shows that LTG is effective add-on therapy in patients with refractory generalised epilepsies. Statistically significant reduction in seizures in both absence and tonic-clonic seizure types was seen even with low doses of LTG.

Diagnosis and management of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal-dominant neurocutaneous disorder with a high spontaneous mutation rate. Understanding of this disorder has greatly increased in recent years. Two chromosomal loci can produce the TSC phenotype: 9q34 and 16p13. These appear to code for proteins that have a tumor suppressor function. TSC results in hamartomas that affect various organ systems, most commonly brain, skin, heart, and kidney. Previously thought to consist of intractable seizures, facial angiofibromas, and dementia, increasing numbers of persons with less severe involvement have been identified. Diagnostic criteria, various types of lesions, and medical management are reviewed.