The new anticonvulsant drugs. Implications for avoidance of adverse effects

Neurological update: COVID-19

Coronavirus Disease 2019 is predominantly a disorder of the respiratory system, but neurological complications have been recognised since early in the pandemic. The major pathophysiological processes leading to neurological damage in COVID-19 are cerebrovascular disease, immunologically mediated neurological disorders and the detrimental effects of critical illness on the nervous system. It is still unclear whether direct invasion of the nervous system by the Severe Acute Respiratory Syndrome Coronavirus 2 occurs; given the vast numbers of people infected at this point, this uncertainty suggests that nervous system infection is unlikely to represent a significant issue if it occurs at all. In this review, we explore what has been learnt about the neurological complications of COVID-19 over the course of the pandemic, and by which mechanisms these complications most commonly occur.

A History of the Pharmacological Treatment of Bipolar Disorder

In this paper, the authors review the history of the pharmacological treatment of bipolar disorder, from the first nonspecific sedative agents introduced in the 19th and early 20th century, such as solanaceae alkaloids, bromides and barbiturates, to John Cade's experiments with lithium and the beginning of the so-called "Psychopharmacological Revolution" in the 1950s. We also describe the clinical studies and development processes, enabling the therapeutic introduction of pharmacological agents currently available for the treatment of bipolar disorder in its different phases and manifestations. Those drugs include lithium salts, valproic acid, carbamazepine, new antiepileptic drugs, basically lamotrigine and atypical antipsychotic agents (olanzapine, risperidone, quetiapine, ziprasidone, aripiprazole, asenapine, cariprazine and lurasidone). Finally, the socio-sanitary implications derived from the clinical introduction of these drugs are also discussed.

GWAS identifies two susceptibility loci for lamotrigine-induced skin rash in patients with epilepsy

PURPOSE

Lamotrigine (LTG)-induced maculopapular eruption (MPE) often causes treatment discontinuation and rising burdens on current healthcare systems. We conducted a genome-wide association study to identify novel susceptibility loci associated with LTG-induced MPE in patients with epilepsy.

MATERIALS AND METHODS

We enrolled patients with LTG-induced MPE (n=34) and utilized the Korea Association Resource project cohort as a control group (n=1214). We explored associations between LTG-induced MPE and single nucleotide polymorphisms (SNPs) through imputation and replicated these associations in samples from 59 LTG-induced MPE cases and 98 LTG tolerant-controls.

RESULTS

We found two novel SNPs associated with LTG-induced MPE: rs12668095 near CRAMP1L/TMEM204/IFT140/HN1L (P=4.89×10(-7)) and rs79007183 near TNS3 (P=3.15×10(-10)), both of which were replicated in an independent cohort.

CONCLUSION

These two validated SNPs may be good candidate markers for predicting LTG-induced MPE in epilepsy patients, although further experimental validation is needed.

Review of pharmacological treatment in mood disorders and future directions for drug development

After a series of serendipitous discoveries of pharmacological treatments for mania and depression several decades ago, relatively little progress has been made for novel hypothesis-driven drug development in mood disorders. Multifactorial etiologies of, and lack of a full understanding of, the core neurobiology of these conditions clearly have contributed to these development challenges. There are, however, relatively novel targets that have raised opportunities for progress in the field, such as glutamate and cholinergic receptor modulators, circadian regulators, and enzyme inhibitors, for alternative treatment. This review will discuss these promising new treatments in mood disorders, the underlying mechanisms of action, and critical issues of their clinical application. For these new treatments to be successful in clinical practice, it is also important to design innovative clinical trials that identify the specific actions of new drugs, and, ideally, to develop biomarkers for monitoring individualized treatment response. It is predicted that future drug development will identify new agents targeting the molecular mechanisms involved in the pathophysiology of mood disorders.

Differential effect of carbamazepine and oxcarbazepine on excitatory synaptic transmission in rat hippocampus

In this study, we have compared the effects of two structurally related compounds carbamazepine (CBZ) and oxcarbazepine (OXC), both in current use for the treatment of epilepsy and bipolar disorder, on fast excitatory transmission in rat hippocampal slices. Using electrophysiological recordings, we have investigated the effects of CBZ and OXC on repetitive action potential discharge of CA1 pyramidal neurons demonstrating that both compounds produced firing inhibition with similar IC(50) values. Moreover, we show that bath applied CBZ (0.01-1 mM) exerted a concentration-dependent decrease in the amplitude of the field excitatory postsynaptic potentials with an IC(50) of approximately 194.3 microM. When OXC was used at the same concentrations, the concentration-response curve was shifted to the right (IC(50) of approximately 711.07 microM). In addition, we demonstrated that CBZ and OXC reduced, to a different extent, both evoked excitatory postsynaptic currents and NMDA-, AMPA-, and KA-mediated inward currents, CBZ being more potent than OXC. These data highlight distinct presynaptic and postsynaptic sites of action for both compounds and suggest that CBZ, by markedly depressing postsynaptic ionotropic glutamate receptors-mediated responses, may produce more severe cognitive and memory impairment. Thus, we assume that relatively high doses of OXC could be better tolerated than therapeutically equivalent doses of CBZ, justifying the preferential use of OXC as first-line treatment in the therapy of neurological and psychiatric disorders, particularly when compared with CBZ.

Behavioural abnormalities and retention rates of anti-epilepsy drugs during long-term treatment of epilepsy: a clinical perspective

Vigabatrin is among the most promising of the new anti-epilepsy drugs, but two unrelated complications have been noted in patients receiving vigabatrin for chronic refractory epilepsy. These are, transient behavioural abnormalities and falling numbers of patients continuing to take vigabatrin (decreasing retention rate) during long-term treatment. Psychotic reactions have been carefully documented both in patients receiving standard and new anti-epilepsy drugs, and in up to 6% of patients after epilepsy surgery. As many psychotic episodes are associated with a dramatic cessation of seizures (i.e. high efficacy of treatment), it is not surprising that behavioural abnormalities are more often seen in patients receiving higher, more effective doses of vigabatrin, particularly those taking more than 3 g/day. A gradual dose increase and slow withdrawal is recommended for possible prevention of behavioural abnormalities, at least in some patients. During treatment with standard anti-epilepsy drugs, approximately 50% of patients remain on randomized treatment with the same drug for several years. For oxcarbazepine, a new drug, the figure is 60%, and for vigabatrin it is about 50%. Although comparative trials are not available, the retention rate for vigabatrin does not appear to be strikingly different to that reported for conventional anti-epilepsy drugs. In summary, behavioural abnormalities and falling retention rates appear to be general features of chronic epilepsy, and are certainly not exclusively associated with the use of vigabatrin. Controlled trials are required to establish the specific contribution, if any, of vigabatrin in development of these complications of intractable epilepsy.

Lamotrigine-induced seizures in a child: Case report and literature review

INTRODUCTION

Lamotrigine is an antiepileptic agent. There is only one previous report of a seizure associated with lamotrigine overdose with laboratory confirmation (a 2-year-old girl, lamotrigine level of 3.8 mg/L).

CASE REPORT

A healthy 19-month-old boy ingested an unknown amount of his sister's lamotrigine tablets. Twenty minutes later, the child experienced generalized seizure activity lasting 10 seconds, followed by another brief self-limited seizure. Vitals signs: heart rate 152-207 bpm crying, respiratory rate 26 /min, temperature 95.7 degrees F, and pupils 3mm. The one-hour lamotrigine level = 20.3 mg/L. The child was discharged 24 hours later.

LITERATURE REVIEW

Six previous case reports of lamotrigine poisoning with serum levels, as well as a retrospective review of lamotrigine exposures, are discussed.

CONCLUSION

A case of lamotrigine-induced seizures in a pediatric patient is reported, with a level approximately five times the upper limit of the therapeutic range. The pediatric population may be at increased risk of seizures following lamotrigine poisoning, and serum levels may not be clinically useful for predicting outcome after overdose.

Enaminones: Exploring Additional Therapeutic Activities

Enaminones, enamines of beta-dicarbonyl compounds, have been known for many years. Their early use has been relegated to serving as synthetic intermediates in organic synthesis and of late, in pharmaceutical development. Recently, the therapeutic potential of these entities has been realized. This review provides the background and current research in this area with emphasis of these agents as potential anticonvulsants, their proposed mechanisms of action, and as potential modulators of multidrug resistance (MDR).

Presynaptic modulation controlling neuronal excitability and epileptogenesis: role of kainate, adenosine and neuropeptide Y receptors

Based on the idea that seizures may arise from an overshoot of excitation over inhibition, all substances that may decrease glutamatergic function while having no effect or even increasing GABAergic neurotransmission are likely to be effective anticonvulsants. We now review the possible role of three such neuromodulators, kainate, adenosine, and neuropeptide Y receptors in controlling hyperexcitability and epileptogenesis. Particular emphasis is given on the robust neuromodulatory role of these three groups of receptors on the release of glutamate in the hippocampus, a main focus of epilepsy. Moreover, we also give special attention to the mechanisms of receptor activation and coupled signaling events that can be explored as attractive targets for the treatment of epilepsy and excitotoxicity. The present paper is a tribute to Arsélio Pato de Carvalho who has been the main driving force for the development of Neuroscience in Portugal, notably with a particular emphasis on the presynaptic mechanisms of modulation of neurotransmitter release.

Effects of carbamazepine and novel 10,11-dihydro-5H-dibenz[b,f]azepine-5-carboxamide derivatives on synaptic transmission in rat hippocampal slices

The effects of carbamazepine on synaptic transmission in rat hippocampal slices were compared with those of two novel analogues (BIA2-093 and BIA2-024) with equivalent anticonvulsant efficacy but with fewer side effects. Carbamazepine (10-1000 microM) inhibited in a concentration-dependent manner the field excitatory postsynaptic potential (fPSP) response, with an EC50 of 263 microM, and also attenuated the presynaptic volley with a similar EC50 value. Carbamazepine was more potent to inhibit the NMDA receptor component of the fPSP (fPSPNMDA), with an EC50 of 160 microM. BIA2-093 and BIA2-024 were nearly equipotent with carbamazepine to inhibit synaptic transmission, and displayed similar potency to inhibit the fPSP (EC50 of 145 microM and 205 microM) and fPSPNMDA responses (EC50 of 198 microM and 206 microM). As with carbamazepine, BIA2-093 and BIA2-024 also attenuated the presynaptic volley with EC50 values ranging from 142 to 322 microM. These results indicate that carbamazepine and its analogues mostly inhibit synaptic transmission through inhibition of conduction, although carbamazepine, but not BIA2-093 and BIA2-024, may also depress NMDA receptor-mediated responses.

Strategies for optimizing antiepileptic drug therapy in elderly people

The elderly take more antiepileptic drugs (AEDs) than all other adults. This extensive use directly correlates with an increased prevalence of epilepsy in a growing population of older people, as well as other neuropsychiatric conditions such as neuropathic pain and behavioral disorders associated with dementia and for which AEDs are administered. The agents account for nearly 10% of all adverse drug reactions in the elderly and are the fourth leading cause of adverse drug reactions in nursing home residents. Numerous factors associated with advanced age contribute to the high frequency of untoward drug effects in this population; however, strategies are available to ensure optimal outcomes.

Adverse reactions to new anticonvulsant drugs

A lack of systematic pharmacoepidemiological studies investigating adverse drug reactions (ADRs) to anticonvulsants makes it difficult to assess accurately the incidence of anticonvulsant-related ADRs. Most of the available information in this regard stems from clinical trial experience, case reports and postmarketing surveillance, sources that are not, by any means, structured to provide precise data on adverse event epidemiology. For various ethical, statistical and logistical reasons, the organisation of structured clinical trials that are likely to provide substantial data on ADRs is extremely difficult. This review concentrates on current literature concerning serious and life-threatening ADRs. As with the older anticonvulsants, the majority of ADRs to newer anticonvulsants are CNS-related, although there are several that are apparently unique to some of these new drugs. Gabapentin has been reported to cause aggravation of seizures, movement disorders and psychiatric disturbances. Felbamate should only be prescribed under close medical supervision because of aplastic anaemia and hepatotoxicity. Lamotrigine causes hypersensitivity reactions that range from simple morbilliform rashes to multi-organ failure. Psychiatric ADRs and deterioration of seizure control have also been reported with lamotrigine treatment. Oxcarbazepine has a safety profile similar to that of carbamazepine. Hyponatraemia associated with oxcarbazepine is also a problem; however, it is less likely to cause rash than carbamazepine. Nonconvulsive status epilepticus has been reported frequently with tiagabine, although there are insufficient data at present to identify risk factors for this ADR. Topiramate frequently causes cognitive ADRs and, in addition, also appears to cause word-finding difficulties, renal calculi and bodyweight loss. Vigabatrin has been reported to cause seizure aggravation, especially in myoclonic seizures. There have been rare reports of other neurological ADRs to vigabatrin, such as encephalopathy, aphasia and motor disturbances. Vigabatrin-induced visual field constriction is the latest and most worrying ADR. Many questions regarding the nature of this potentially serious ADR remain unanswered, as no prospective controlled study examining the phenomenon has been published. Rare cases of behavioural ADRs and IgA and IgG2 deficiency associated with the use of zonisamide have been reported. However, relatively few patients so far have been exposed to this drug, and therefore more postmarketing information is required. The relatively late establishment of aplastic anaemia and hepatic failure as potentially fatal ADRs of felbamate, and of visual field constriction with vigabatrin, should serve as ample reminders that ADRs can appear at any time.

Anticonvulsant use during lactation

The issue of prescribing anticonvulsant drugs during lactation is clinically important, but also complex. Data for some drugs are completely lacking and for other drugs information is only available from single dose or short term studies or case reports. Moreover, limited knowledge exists about the practical impact of the drug concentrations found in breast milk and there are great methodological problems in the assessment of possible adverse drug reactions in infants. Nevertheless, based on current knowledge, some recommendations can be suggested. Treatment with carbamazepine, valproic acid (sodium valproate) and phenytoin is considered compatible with breastfeeding. Treatment with ethosuximide or phenobarbital (phenobarbitone)/primidone should most probably be regarded as potentially unsafe and close clinical monitoring of the infant is recommended if it is decided to continue breastfeeding. Occasional or short term treatment with benzodiazepines could be considered as compatible with breastfeeding, although maternal diazepam treatment has caused sedation in suckling infants after short term use. During long term use of benzodiazepines, infants should be observed for signs of sedation and poor suckling. Only very limited clinical data are available for the new generation anticonvulsant drugs and no clearcut recommendations can be made until further data are present. If it is decided to continue breast feeding during treatment with these drugs, the infant should be monitored for possible adverse effects. In general, the drug should be given in the lowest effective dose, guided by maternal serum or plasma drug concentration monitoring. If breast feeding is avoided at times of peak drug levels in milk, the exposure of the infant can be reduced to some extent. As breast milk has considerable advantages over formula milk, the benefits of continuing breast feeding should always be taken into consideration in the risk-benefit analysis.

Factors influencing the incidence of lamotrigine-related skin rash

OBJECTIVE

To determine the incidences of serious and nonserious lamotrigine-related rash, determine the risk factors for lamotrigine-related rash, and evaluate the impact on the incidence of rash of the manufacturer's recommendation to reduce the starting dose of lamotrigine.

METHODS

This was a retrospective case record survey at five tertiary referral epilepsy centers in the UK. The risk factors for lamotrigine-related rash were identified by logistic regression. The independent factors tested were gender, age, epilepsy type, concurrent medication, and starting dose of lamotrigine. The incidences of rash before and after the recommendation of reduction in starting dose were compared by chi2 analysis.

RESULTS

A total of 1050 patients were included. The incidences of serious and nonserious rash were 1.1% (95% CI 0.5% to 1.8%) and 7% (95% CI 5.5% to 8.6%), respectively. Females were at higher risk of developing rash than were males, with a relative risk of 1.8 (95% CI 1.2 to 2.8). The starting dose of lamotrigine was reduced in response to the manufacturer's recommendation, and there was a significant reduction (p = 0.045) in the incidence of serious rash, from 1.5% (12/805) to 0% (0/245). However, there was no reduction in the overall incidence of lamotrigine-related rash, with 63/805 (8%) before and 23/245 (9%) after the recommendation.

CONCLUSIONS

Failure to detect a reduction in the incidence of lamotrigine-related rash since the new (reduced) recommended starting dose of lamotrigine may arise from failure to reduce the starting dose below a critical threshold level, incomplete compliance with current recommendations, or insufficient sample size. The results of this and other studies show that the starting dose of lamotrigine is a significant factor affecting the incidence of rash; furthermore, this study also shows that significant reduction in the incidence of serious rash can be achieved by reducing the starting dose. Therefore, clinicians should not deviate from the recommendations.

An update on GABAA receptors

Recent advances in molecular biology and complementary information derived from neuropharmacology, biochemistry and behavior have dramatically increased our understanding of various aspects of GABAA receptors. These studies have revealed that the GABAA receptor is derived from various subunits such as alpha1-alpha6, beta1-beta3, gamma1-gamma3, delta, epsilon, pi, and rho1-3. Furthermore, two additional subunits (beta4, gamma4) of GABAA receptors in chick brain, and five isoforms of the rho-subunit in the retina of white perch (Roccus americana) have been identified. Various techniques such as mutation, gene knockout and inhibition of GABAA receptor subunits by antisense oligodeoxynucleotides have been used to establish the physiological/pharmacological significance of the GABAA receptor subunits and their native receptor assemblies in vivo. Radioligand binding to the immunoprecipitated receptors, co-localization studies using immunoaffinity chromatography and immunocytochemistry techniques have been utilized to establish the composition and pharmacology of native GABAA receptor assemblies. Partial agonists of GABAA receptors are being developed as anxiolytics which have fewer and less severe side effects as compared to conventional benzodiazepines because of their lower efficacy and better selectivity for the GABAA receptor subtypes. The subunit requirement of various drugs such as anxiolytics, anticonvulsants, general anesthetics, barbiturates, ethanol and neurosteroids, which are known to elicit at least some of their pharmacological effects via the GABAA receptors, have been investigated during the last few years so as to understand their exact mechanism of action. Furthermore, the molecular determinants of clinically important drug-targets have been investigated. These aspects of GABAA receptors have been discussed in detail in this review article.

Lamotrigine serum concentration-to-dose ratio: influence of age and concomitant antiepileptic drugs and dosage implications

Using bivariate and multivariate methods, we retrospectively analyzed the influence of patient age and the use of concomitant antiepileptic drugs (AEDs) on the lamotrigine (LTG) concentration-to-dose (C/D) ratio in samples from 164 patients (68 children, 96 adults) with epilepsy receiving LTG alone (n = 28) or in combination with various antiepileptic drugs (n = 136). The LTG C/D ratio increased with age in children receiving LTG alone (r = 0.60, p < 0.01), but decreased with age in adults receiving LTG and inducers (r = -0.42, p < 0.001). In patients receiving LTG and inducers, the ratio was statistically lower in those younger than 9 years of age (0.23 +/- 0.08) and older than 30 years of age (0.32 +/- 0.15) than it was in those between 9 and 30 years of age (0.44 +/- 0.15). The mean LTG C/D ratio was 0.37 +/- 0.15 in patients receiving LTG and inducers (n = 92), 0.84 +/- 0.41 in patients receiving LTG alone (n = 28), 1.09 +/- 0.44 in those receiving LTG with VPA plus inducers (n = 17), and 3.41 +/- 1.18 in those receiving LTG and VPA (n = 27). Differences in the LTG C/D ratio between treatment groups were similar in children and in adults. We reached the following conclusions: The LTG C/D ratio increased with age in children but may decrease with age in adults receiving concomitant enzyme-inducing AEDs; the LTG C/D ratio was 10 times lower in patients receiving LTG and inducers than in those receiving LTG and VPA (in both children and adults), and this difference was higher than the four-fold difference described for LTG half-life and the two-fold differences currently used in LTG dosage.

Lamotrigine toxicity secondary to sertraline

Blood level monitoring helps to determine the therapeutic and toxic ranges for anticonvulsants and antidepressants. We investigated initial drug-drug interactions between lamotrigine and sertraline. We report on case histories of two epileptic patients who were initially on lamotrigine and to whom sertraline was added to control psychiatric features. In case 1, a total daily dose of 25 mg sertraline, with nondetectable sertraline and desmethylsertraline blood levels, resulted in a doubling of the lamotrigine blood level with symptoms of toxicity. In case 2, a 25 mg reduction in the total daily dose of sertraline resulted in halving of the lamotrigine blood level even though the lamotrigine dosage was increased by 33%. This shows that sertraline has potent interactions with lamotrigine metabolism. The authors hypothesize that inhibition of glucuronidation is responsible. Clinicians are advised to observe for symptoms of toxicity and to do serial blood levels to monitor this interaction.

New visions in the pharmacology of anticonvulsion

Seizures are resistant to treatment with currently available anticonvulsant drugs in about 1 out of 3 patients with epilepsy. Thus, there is a need for new, more effective anticonvulsant drugs for intractable epilepsy. Furthermore, because of the inadequacy of the currently available anticonvulsant armamentarium with respect to safety, newly developed drugs should be less toxic than existing drugs. Previous and current strategies for development of novel anticonvulsants with improved efficacy or safety are critically discussed in this review. 'Old drugs' (or 'first generation' drugs), which were developed and introduced between 1910 and 1970, are compared with new anticonvulsants both in terms of clinical efficacy and safety and in terms of mechanisms of action. The new drugs are referred to as 'second generation' drugs, i.e. anticonvulsants which have been introduced into clinical practice in recent years, or 'third generation' drugs, i.e. compounds in the pipeline of development. In spite of some 30 years of 'modern' neuroscientific epilepsy research, most novel, clinically effective second generation anticonvulsants have been found by screening (i.e. serendipity) or structural variation of known drugs and not by rational strategies based on knowledge of processes involved in generation of seizures or in development of epilepsy. An exception are only the GABA (gamma-aminobutyrate)-mimetic drugs vigabatrin and tiagabine and, to some extent, gabapentin, which have been developed by a rational strategy, i.e. the 'GABA hypothesis' of epilepsy. The fact that preclinical seizure models used for identification and development of novel drugs have been originally validated by old drugs, i.e. conventional anticonvulsants, may explain that several of the new drugs possess mechanisms which do not differ from those of the standard drugs. This may also explain that none of the new drugs seems to offer any marked advantage towards the old, first generation drugs with respect to the ultimate goal of drug treatment of epilepsy, i.e. complete control of seizures, although some of the second generation drugs may have benefits in terms of side effects and tolerability. It is to be hoped that the various novel currently used or planned strategies for drug development produce more effective and safe anticonvulsants than previous strategies. This goal can only be achieved by strengthening our understanding of the fundamental pathophysiology of seizure expression and epileptogenesis as theoretical substrates for new pharmacological strategies, and by devising and refining laboratory models for studying new agents obtained by such strategies.

Animal models of intractable epilepsy

Twenty to 30% of patients with epilepsy develop chronic or intractable epilepsy, i.e. the seizures persist despite accurate diagnosis and carefully monitored treatment with antiepileptic drugs. It is still not known why and how epilepsy becomes an intractable disorder in such patients, while other patients with seemingly identical seizure types can achieve control of seizures with medication. Experimental epilepsy research has generated new neurophysiological, neurochemical and neuropharmacological approaches but is still hampered by a lack of adequate experimental models of chronic intractable epilepsy. An animal model of epilepsy allowing selection of pharmacoresistant and pharmacosensitive subgroups of animals would be a valuable tool to study mechanisms of intractability and to develop more effective treatment strategies. This review concentrates on identifying animal models that mimic patterns of pharmacological resistance in humans with epilepsy. Two models seem to be interesting in this regard, epileptic dogs with different types of spontaneous recurrent seizures and amygdala-kindled rats. In both models, animals which do not respond to repeated or chronic administration of antiepileptic drugs (non-responders) can be separated from animals in whom antiepileptics are effective (responders). Unfortunately, the dog model has several inherent logistical problems, whereas pharmacoresistant subgroups of kindled rats offer a unique tool to study why seizures become intractable, particularly because pathophysiologically processes in these resistant rats can be compared directly with those of kindled rats which respond to treatment. Furthermore, the new rat model can be used to identify predictors of intractability during onset of treatment with an antiepileptic drug and is a valuable addendum to the battery of animal models used in preclinical evaluation of novel drugs. In addition to pharmacoresistant epileptic dogs and kindled rats, several other potential models of intractable epilepsy are described to stimulate and outline areas for future research.

Safety of long-term lamotrigine in epilepsy

PURPOSE

To examine the safety of lamotrigine (LTG) used in general practice to treat epilepsy.

METHODS

Information was collected on 11,316 patients who were included in a noninterventional observational cohort study conducted by means of Prescription-Event Monitoring (PEM). A follow-up study provided information on the first 3,994 patients who had taken LTG for > or = 6 months. Incidence density (ID) measurements were used to rank the frequency of the reported events.

RESULTS

Rash was the most frequently reported nonepileptiform event (ID, 19.7/1,000 patient-months) in the first month of treatment and resulted in LTG being stopped in 2% of the 11,316 patients. Rash was reported more frequently among children aged 2-12 years (ID, 29.4/1,000 patient-months) than adults. Other events associated with the use of LTG included headache, drowsiness, nausea, vomiting, malaise, and lassitude. Rare serious events possibly associated with LTG included 12 cases reported as Stevens-Johnson syndrome, four cases of neutropenia, three cases of thrombocytopenia, and two cases of disseminated intravascular coagulation. There were also individual cases of leucopenia, a meningitic reaction, acute renal failure, hepatotoxicity, and a "lupus-like" reaction possibly associated with the drug. No foetal abnormalities were specifically associated with the use of the drug in pregnancy. No death was attributed to LTG.

CONCLUSIONS

Patients had severe epilepsy, inadequately controlled by other antiepileptic agents. The results of these two studies suggest that LTG is acceptably safe when used for the treatment of refractory epilepsy.

Serum concentrations of lamotrigine in epileptic patients: the influence of dose and comedication

Lamotrigine (LTG) is a new antiepileptic drug (AED), chemically unrelated to the drugs in current use. Previous studies have shown that LTG has only a limited effect on other AEDs, but its own metabolism can be strongly induced or inhibited by the comedication. We investigated the influences of carbamazepine (CBZ), phenytoin (PHT), phenobarbital (PB), valproic acid (VPA), and combinations of these drugs on the serum concentration of LTG. A total of 588 blood samples from 302 patients were analyzed. The mean duration of LTG therapy was 141 +/- 137 days (mean +/- SD). A patient was only considered twice in this study if his or her comedication had been changed. The LTG serum concentration in relation to LTG dose/body weight (level-to-dose ratio, LDR, microgram/ml/mg/kg) was calculated and compared for different drug combinations. The results showed that comedication had a highly significant (p < 0.001) influence on the LTG serum concentrations. The mean LDR for LTG was 0.32 (LTG + PHT) < 0.52 (LTG + PB) approximately equal to 0.57 (LTG + CBZ) < 0.98 (LTG mono) approximately equal to 0.99 (LTG + VPA + PHT) < 1.67 (LTG + VPA + CBZ) approximately equal to 1.80 (LTG + VPA + PB) < 3.57 (LTG + VPA (<, p < 0.05; approximately equal to, p > 0.05, multiple comparisons). The mean LTG concentrations in patients on comedication with VPA were about two times higher than on patients on LTG monotherapy or on comedication without VPA (5.0 vs. 2.6 micrograms/ml), despite the LTG doses being half as high (3.0 vs. 5.9 mg/kg). The correlations of the serum concentrations and doses of CBZ, PB, PHT, and VPA with the LDR of LTG were only weak or not significant. Furthermore, the distribution of LTG serum concentrations and dosages was compared with the tentative therapeutic range for the LTG concentration (1-4 micrograms/ml), proposed by some investigators, and the recommendations for the LTG dosage. Remarkable discrepancies were observed. The comedication has an important influence on the LTG concentration and should be considered in LTG dosage.

Retrospective study of vigabatrin and psychiatric behavioural disturbances

Vigabatrin (VGB) is an effective add-on anti-epileptic drug. The major serious adverse drug reactions (ADRs) are behavioural and psychiatric disturbances. This study does not support the view that a previous history of behavioural and psychiatric features increases the risk of behavioural/psychiatric ADRs (relative risk 1.23, 95% CI 0.57-2.66, P = 0.61). The results suggest that a low starting does of vigabatrin does not reduce the risk of psychiatric and behavioural ADRs (P = 0.31) or prevent a more overt psychotic reaction from occurring.