Cognitive Adverse Effects of Antiepileptic Drugs : Incidence, Mechanisms and Therapeutic Implications

Treatment for the Benign Childhood Epilepsy With Centrotemporal Spikes: A Monocentric Study

Background and Purpose: To date, there is no specific treatment guideline for the benign childhood epilepsy with centrotemporal spikes (BECTS). Several countries recommend levetiracetam, carbamazepine, sodium valproate, oxcarbazepine, and lamotrigine as first-line drugs. Nevertheless, some of these drugs are associated with cognitive decline. Available studies that investigated the efficacy of levetiracetam and sodium valproate on BECTS involved small sample sizes. This study aimed to evaluate the efficacy of levetiracetam and sodium valproate on cognition, and to investigate the prognostic factors for BECTS as whole.

Methods: Clinical data and treatment status of all patients with BECTS at Xiangya Hospital, Central South University followed from 2008 to 2013 were analyzed retrospectively. Since electrical status epilepticus in sleep (ESES) has been confirmed to play a role in cognitive deterioration, in order to evaluate the response to drugs and their cognitive effects, we created two groups of patients according to the levels of spike wave index (SWI): group 1; 0–50% SWI and group 2; >50% SWI at the last follow up.

Results: A total of 195 cases were enrolled: 49.7% received monotherapies, 24.1% duotherapies and 27.2% polytherapies. Medications included; levetiracetam plus other drug (s) (75.9%), levetiracetam alone (32.8%), sodium valproate plus other drug (s) (31.3%), and sodium valproate alone (5.1%). After 2 years of treatment and follow up, 71% of the cases had a good seizure outcome, 15.9% had an improvement of SWI, and 91.7% had a normal DQ/IQ. Sodium valproate combined with levetiracetam, and sodium valproate alone correlated with good improvement of SWI, whereas, focal spikes were linked with poor improvement. For both groups (group 1 and group 2): monotherapy, levetiracetam alone, and a normal DQ/IQ at seizure onset correlated with good cognitive outcomes, in contrast, polytherapy, sodium valproate plus other drug (s), levetiracetam plus sodium valproate, an initial SWI of ≥85%, and multifocal spikes were linked to cognitive deterioration.

Conclusions: Monotherapy, particularly levetiracetam seems to be a good first-line therapy which can help in normalizing the electroencephalograph and preventing cognitive decline. Polytherapy, mostly the administration of sodium valproate seems to relate with poor cognition, therefore, it is recommended to avoid it.

Evaluation of sodium valproate loaded nanoparticles in acute and chronic pentylenetetrazole induced seizure models

BACKGROUND AND PURPOSE

Efficacy of sodium valproate in epilepsy is limited by its poor blood brain barrier penetration and side effects. Nanoparticles may offer a better drug delivery system to overcome these limitations. This study evaluated the efficacy of sodium valproate encapsulated in nanoparticles in pentylenetetrazole (PTZ) induced acute and kindling models of seizures in male Wistar rats.

METHODS

Poly lactic-co-glycolic acid (PLGA) based, polysorbate 80 stabilized sodium valproate loaded nanoparticles (nano sodium valproate) and rhodamine loaded nanoparticles (RLN) were formulated by double emulsion- solvent evaporation method and characterized for their size, shape, zeta potential and drug loading percentage. RLN was used to demonstrate blood brain barrier (BBB) permeability of nanoparticles. Serum drug levels were estimated using high performance liquid chromatography. The efficacy of standard sodium valproate (300 mg/kg) and nano sodium valproate (∼300, ∼150 and ∼75 mg/kg of sodium valproate) were evaluated in experimental animal models of seizures along with their effects on behavioral and oxidative stress parameters. Drugs were administered 60 min before PTZ in acute model. In the kindling model, drugs were administered every day while PTZ was administered on alternate days 60 min after drug administration. All the study drugs/compounds were administered intraperitoneally.

RESULTS

RLN were observed to be clustered in cortex which implied that the nanoparticles crossed BBB. Both standard sodium valproate and nano sodium valproate reached therapeutic serum level at 15 min and 1 h, but were undetectable in serum at 24 h. In acute PTZ (60 mg/kg) model, nano sodium valproate (∼300 mg/kg of sodium valproate) and standard sodium valproate showed protection against seizures till 6 h and 4 h, respectively. There were significant behavioral impairment and oxidative stress with standard sodium valproate in acute model as compared to nano sodium valproate at 6 h. In kindling model, induced with PTZ (30 mg/kg, every alternate day for 42 days), complete protection from seizures was observed with nano sodium valproate (∼150 mg/kg and ∼75 mg/kg of sodium valproate) and standard sodium valproate (300 mg/kg). Similarly, significant protection from behavioral impairment and oxidative stress was observed with standard sodium valproate and nano sodium valproate as compared to PTZ.

CONCLUSION

When compared to conventional therapy, nano sodium valproate showed protection from seizures at reduced doses and for a longer duration in animal models of epilepsy. This study suggests the potential of nano sodium valproate in the treatment of epilepsy.

Antiepileptic drug treatment of generalized tonic-clonic seizures: An evaluation of regulatory data and five criteria for drug selection

BACKGROUND

A generalized tonic-clonic seizure (GTCS) is the most severe form of common epileptic seizure and carries the greatest risk of harm. The aim of this review is to provide an evidence-based guide for the selection of antiepileptic drugs (AEDs) for patients with GTCSs. Eight AEDs are approved in Europe and the USA for the treatment of both primarily GTCSs (PGTCSs) and secondarily GTCSs (SGTCSs) and are considered in this paper.

METHODS

Each AED is evaluated using five criteria: (1) efficacy, by seizure type (a: PGTCSs and b: SGTCSs); (2) adverse effects; (3) interactions; (4) adherence and dosing; and (5) mechanism of action (MOA). To ensure the inclusions of robust data, only efficacy data accepted by regulatory authorities were considered, and data related to adverse effects, interactions, adherence, and MOA were all extracted from UK Summaries of Product Characteristics (SPCs).

RESULTS

(1a) There is class 1 evidence of the efficacy of only four AEDs in controlling PGTCSs (lamotrigine, levetiracetam, perampanel, and topiramate). (1b) There is no class 1 evidence of the efficacy of any AED in SGTCSs although some evidence from pooled/subgroup analyses or meta-analyses supports the use of the four AEDs (levetiracetam, perampanel, topiramate, and with less robust data for lamotrigine). (2) AEDs are associated with different, but to some extent overlapping, common adverse effect profiles but have differing idiosyncratic adverse effects. (3) Pharmacokinetic interactions are seen with most, but not all, AEDs and are most common with carbamazepine and phenytoin. (4) Good adherence is important for seizure control and is influenced by frequency of dosing, among other factors. (5) Mechanism of action is also a consideration in rationalising AED selection when switching or combining AEDs.

CONCLUSION

Ultimately, the choice of AED depends on all these factors but particularly on efficacy and adverse effects. Different patients will weigh the various factors differently, and the role of the treating physician is to provide accurate information to allow patients to make informed choices.

Assessing cognitive functioning in females with Rett syndrome by eye-tracking methodology

BACKGROUND

While many individuals with severe developmental impairments learn to communicate with augmentative and alternative communication (AAC) devices, a significant number of individuals show major difficulties in the effective use of AAC. Recent technological innovations, i.e., eye-tracking technology (ETT), aim to improve the transparency of communication and may also enable a more valid cognitive assessment.

OBJECTIVES

To investigate whether ETT in forced-choice tasks can enable children with very severe motor and speech impairments to respond consistently, allowing a more reliable evaluation of their language comprehension.

METHODS

Participants were 17 girls with Rett syndrome (M = 6:06 years). Their ability to respond by eye gaze was first practiced with computer games using ETT. Afterwards, their receptive vocabulary was assessed using the Peabody Picture Vocabulary Test-4 (PPVT-4). Target words were orally presented and participants responded by focusing their eyes on the preferred picture.

RESULTS

Remarkable differences between the participants in receptive vocabulary were demonstrated using ETT. The verbal comprehension abilities of 32% of the participants ranged from low-average to mild cognitive impairment, and the other 68% of the participants showed moderate to severe impairment. Young age at the time of assessment was positively correlated with higher receptive vocabulary.

CONCLUSIONS

The use of ETT seems to make the communicational signals of children with severe motor and communication impairments more easily understood. Early practice of ETT may improve the quality of communication and enable more reliable conclusions in learning and assessment sessions.

Effect of carbamazepine and lamotrigine on cognitive function and oxidative stress in brain during chemical epileptogenesis in rats

The present study assessed the effect of carbamazepine and lamotrigine on cognitive function and oxidative stress in brain during chemically induced epileptogenesis in rats. Epileptogenesis was induced by administration of pentylenetetrazole (30 mg/kg, s.c.) on alternate days (three times/week) for 9-11 weeks or until stage 4 of seizure score was achieved. The neurobehavioural parameters used for cognitive assessment were step-down latency in continuous avoidance apparatus and transfer latency in elevated plus maze test paradigm. Carbamazepine and lamotrigine were administered intraperitoneally in doses of 60 mg/kg and 25 mg/kg, respectively, according to the groups, once a day for 11 weeks. Oxidative stress was assessed in isolated homogenized whole brain samples and estimated for the levels of malondialdehyde, reduced glutathione, catalase and superoxide dismutase. The results showed that lamotrigine did not produce any change in cognitive function, while carbamazepine produced cognitive dysfunction. Cognitive decline seen in the carbamazepine-treated pentylenetetrazole-kindled group was also associated with increased oxidative stress. Lamotrigine treatment had no effect on oxidative stress parameters alone, while it significantly decreased oxidative stress in the pentylenetetrazole-kindled group as compared to the pentylenetetrazole-kindled carbamazepine-treated group.

CNS adverse events associated with antiepileptic drugs

A variety of newer antiepileptic drugs (AEDs) are now available for treating patients with epilepsy in addition to the 'conventional' drugs that have been available throughout a large part of the last century. Since these drugs act to suppress the pathological neuronal hyperexcitability that constitutes the final substrate in many seizure disorders, it is not surprising that they are prone to causing adverse reactions that affect the CNS.Information on adverse effects of the older AEDs has been mainly observational. Equally, whilst the newer drugs have been more systematically studied, their long-term adverse effects are not clearly known. This is illustrated by the relatively late emergence of the knowledge of visual field constriction in the case of vigabatrin, which only became known after several hundred thousand patient-years of use. However, older drugs continue to be studied and there has been more recent comment on the possible effect of valproate (valproic acid) on cognition following exposure to this drug in utero.With most AEDs, there are mainly dose-related adverse effects that could be considered generic, such as sedation, drowsiness, incoordination, nausea and fatigue. Careful dose titration with small initial doses can reduce the likelihood of these adverse effects occurring. Adverse effects such as paraesthesiae are more commonly reported with drugs such as topiramate and zonisamide that have carbonic anhydrase activity. Weight loss and anorexia can also be peculiar to these drugs. Neuropsychiatric adverse effects are reported with a variety of AEDs and may not be dose related. Some drugs, such as carbamazepine when used to treat primary generalized epilepsy, can exacerbate certain seizure types. Rare adverse effects such as hyperammonaemia with valproate are drug specific. There are relatively very few head-to-head comparisons of AEDs and limited information is available in this regard.In this review, we discuss the available literature and provide a comprehensive summary of adverse drug reactions of AEDs affecting the CNS.

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.

The tolerability of lamotrigine in elderly patients with epilepsy

OBJECTIVE

To determine the tolerability of lamotrigine in elderly patients with epilepsy.

DESIGN

Pooled data from 13 lamotrigine clinical trials.

SETTING

Multicentre clinical trials conducted in primary care and neurology practices.

PARTICIPANTS

208 elderly patients (aged > or = 65 years) were identified: 146 lamotrigine-treated patients, 53 carbamazepine-treated patients and 9 phenytoin-treated patients.

INTERVENTIONS

Extent of exposure, incidence of drug-related adverse events, serious adverse events and study withdrawals were examined.

RESULTS

The median duration of exposure for lamotrigine monotherapy and add-on therapy was 24.1 and 47.4 weeks, respectively. The median daily dosage of lamotrigine was 100 mg for monotherapy (range 75 to 500 mg) and 300 mg for add-on therapy (range 25 to 700 mg). Overall, the incidence of drug-related adverse events was lower for lamotrigine than comparator drugs: 49% (72/146) for lamotrigine compared with 72% (38/53) for carbamazepine (p = 0.006), and 89% (8/9) for phenytoin (p = 0.035) although patient numbers in each treatment group were not comparable. Patients receiving lamotrigine reported incidences of somnolence (p = 0.012), rash (p = 0.034), and headache (nonsignificant) that were one-half the incidence reported with carbamazepine monotherapy. Rash was the most common reason for study withdrawal: 4% (6/146) lamotrigine, 17% (9/53) carbamazepine and 0% phenytoin. Seven (5%, 7/146) lamotrigine-treated patients, 4 (8%, 4/53) carbamazepine-treated patients and 1 (11%, 1/9) phenytoin-treated patient experienced drug-related serious adverse events.

CONCLUSION

Lamotrigine, used in the currently prescribed adult dosage regimen, was well tolerated in elderly patients with epilepsy.

Spatial working memory performance in patients with schizoaffective psychosis versus schizophrenia: a tale of two disorders?

We explored the relationship between schizophrenia and schizoaffective disorder by comparing the two patient groups in terms of their performance on measures of executive functioning (spatial working memory and Wisconsin Card Sorting Test). Patients with schizophrenia (N=34) and those with schizoaffective disorder (N=23) performed significantly poorer than community controls (N=30). However, the schizoaffective and schizophrenia groups did not differ from each other in terms of working memory accuracy or mean response latencies. Similarly, the two patient groups did not differ in terms of the number of categories achieved or number of perseverative errors on the Wisconsin Card Sorting Test. Among the patients, working memory accuracy was associated with number of WCST perseverative errors and number of categories achieved, though working memory performance was not associated with number of WCST nonperseverative errors. These findings indicate that both schizophrenia and schizoaffective disorder are associated with executive functioning deficits. The findings are discussed in the context of the ongoing debate regarding the conceptualization of schizoaffective disorder.

Peripheral and gasserian ganglion-level procedures for the treatment of trigeminal neuralgia

This review discusses the various peripheral and ganglion-level procedures available for treating trigeminal neuralgia and summarizes specific success and complication rates for each technique.

METHOD

A review of the available literature.

RESULTS

It appears that expertly performed ganglion-level procedures (radiofrequency thermocoagulation, balloon compression, and glycerolysis) are more effective than peripheral procedures but neither approach can be relied on to produce long-term pain relief. All of these procedures are neurodestructive and can cause sensory loss and dysesthesia. Effective drug therapy may not be acceptable to some patients as adverse cognitive side effects are increasingly recognized.

CONCLUSIONS

Each patient should receive an informed and impartial account of the available surgical options. There is a need for prospective randomized controlled studies in procedure-naïve subjects to determine the optimal surgical management of trigeminal neuralgia.

Postmarketing experience with topiramate and cognition

Ideal antiepileptic drugs (AEDs) are designed to stop seizures with limited central nervous system (CNS) side effects. However, CNS-related treatment-emergent adverse events (TEAEs) often occur in patients receiving AEDs. Topiramate (TPM) is an AED proven to be safe and effective as adjunctive treatment for epilepsy patients with partial seizures. Double-blind, placebo-controlled, multicenter trials demonstrated potential effects on cognition. The P.A.D.S. (post-marketing antiepileptic drug survey) group, a cooperative group of 14 epilepsy centers that collaborate on obtaining data about new AEDs and devices, prospectively collected standardized data forms before and during treatment with TPM for epilepsy, and analyzed the postmarketing experience of CNS TEAEs with TPM. Our results from 701 treated patients show that cognitive complaints were the most common reason to discontinue TPM. The presence of complaints did have predictive value if the patient would discontinue TPM, although was not specific as to when discontinuation would occur. The spectrum of complaints in our open-label prospective multicenter postmarketing study was similar to those observed in controlled clinical trials. We were unable to demonstrate a specific population, dose titration, or concomitant AED that was at risk to discontinue treatment. We conclude that most patients treated with TPM will continue therapy beyond 6 months. Cognitive complaints and not efficacy reflect the primary reason for discontinuing therapy. Psychomotor slowing was the most common complaint, yet most patients elect to continue treatment, with "better" or "much better" ratings of both seizure and global improvement during treatment.

Neuropsychological effects of epilepsy and antiepileptic drugs

Epilepsy and its treatment can have deleterious cognitive and behavioural consequences. Affected individuals have a higher prevalence of neuropsychological dysfunction than the general population because of complex interactions among several multifaceted and overlapping influences--for example, underlying neuropathologies, ictal and interictal neuronal discharges, a plethora of antiepileptic drugs, and numerous psychosocial issues. Research into the clinical relevance of these factors has been dogged by a range of methodological pitfalls including lack of standardisation of neuropsychological tests, small numbers and multiple testing, and statistical failure to appreciate differential effects of interactive elements in individual patients. Although antiepileptic drugs can impair neuropsychological functioning, their positive effect on seizure control might improve cognition and behaviour. Each person should be assessed individually with respect to factors unique to his or her seizure disorder and its treatment.

Current discoveries on the cognitive effects of antiepileptic drugs

The cognitive effects of antiepileptic drugs (AEDs) are of particular concern to clinicians because these drugs are the primary therapeutic modality for managing epilepsy. In general, the cognitive effects of most AEDs are modest and offset by their benefit in reducing seizures. Nonetheless, the cognitive effects of a particular AED may be clinically significant when treating specific patient populations, such as children and the elderly.

Anticonvulsants and breast feeding: a critical review

Progress in the diagnosis and management of seizure disorders and the availability of effective anticonvulsive medications has enabled increasing numbers of epileptic women of child-bearing age to raise families. Breast feeding, which these women may wish to choose, provides health, nutritional, immunological, developmental, social, economic and environmental benefits. The traditional anticonvulsants, such as phenytoin, carbamazepine and valproic acid (valproate sodium), are generally considered safe for use during breast feeding; however, observation for adverse effects is recommended. The use of phenobarbital while breast feeding is controversial because of its slow elimination by the nursing infant. The newer anticonvulsants, such as clobazam, felbamate, gabapentin, lamotrigine, oxcarbazepine, tiagabine, topiramate, and vigabatrin, are used mainly as adjunctive therapy. Data on the use of these drugs in pregnancy and lactation, and regarding long term effects on cognition and behaviour, are sparse. Weighing the benefits of breast feeding against the potential risk to the nursing infant, breast feeding is considered to be safe when the mother is taking carbamazepine, valproic acid or phenytoin. Infant monitoring for potential adverse effects is advisable when the mother is taking phenobarbital, clobazam, gabapentin, lamotrigine, oxcarbazepine or vigabatrin. Monitoring of infant serum drug concentrations is advisable but not compulsory. The use of felbamate, tiagabine and topiramate during breast feeding should await further study.

Review of controlled trials of gabitril (tiagabine): a clinician's viewpoint

A recent problem for doctors has been the choice of which new antiepileptic drug (AED) to select for treatment of pharmacoresistant epilepsy. This article summarizes the clinical experience to date regarding the efficacy and safety of tiagabine (TGB; Gabitril) as adjunctive therapy in patients with partial-onset seizures. In its early Phase II development, TGB was evaluated in two multicenter pilot studies. Each had an open-label enrichment phase followed by a treatment phase with randomized, double-blind, two-period, cross-over phases. Between 24 and 50% of patients experienced reductions in seizure rates of > or =50%, depending on the type of partial seizure. In Phase III, three double-blind, parallel group, placebo-controlled adjunctive studies determined the efficacy of TGB in patients with refractory partial seizures. The first was a dose-response study employing doses of TGB-HCl of 16, 32 or 56 mg/day. Significant reductions in seizure rates were found with 32 and 56 mg/day. The second and third studies evaluated the efficacy of dosing TGB twice, three times, and four times daily, all of which showed similar efficacy. TGB efficacy in partial seizures was supported in several open trials, and no tolerance to efficacy was noted in long-term continuation studies. Tolerability was documented in all trials. Most adverse events were mild or moderate and transient, occurring during dose titration. They were clearly dose-related. No relevant changes in hematologic and biochemical tests, vital signs, or body weight were attributable to TGB. TGB appears to be an effective new drug for partial seizures with an acceptable safety profile.

Treatment of epilepsy in the elderly

Management of epilepsy in the elderly involves many challenges, including the presence of concomitant diseases, polypharmacy and changes in body physiology. Age-related changes in pharmacokinetics and pharmacodynamics have to be taken into account in order to avoid potentially severe adverse drug reactions in elderly people. The present study reviews the most commonly used antiepileptic drugs (AEDs) in the elderly. Because some AEDs may induce the metabolism of other agents and reduce the effectiveness of several drugs, the physicians have to carefully evaluate concomitant drugs being administered. Moreover, the main problems appear to be when beginning therapy, the first choice drug, the appropriate dosage and pharmacologic compliance. Elderly patients must be screened for hepatic and renal functions before beginning a treatment with an AED, carefully interviewed to reduce complaints for drug side-effects which may negatively influence compliance and monitored for total and free blood levels. Besides the 'classic' AEDs, such as phenytoin, phenobarbital, carbamazepine, valproic acid, primidone and benzodiazepines, the review shows the possible advantages of new AEDs, such as felbamate, gabapentin, lamotrigine, oxcarbazepine and gamma-vinyl-GABA, which may be used in the elderly too for their good tolerability. A careful control of drug assumption is requested in the elderly, especially when it is difficult to achieve seizure control.

Cognitive effects of anticonvulsant monotherapy in elderly patients: a placebo-controlled study

Old age is recognized to be the commonest time in life to develop epilepsy. There is a perception that older patients are more sensitive to the deleterious cognitive effects of antiepileptic drugs (AEDs). Elderly patients (median age 70 years, range 60-88 years) taking anticonvulsant monotherapy (10 carbamazepine [CBZ], 8 sodium valproate [VPA], 5 phenytoin [PHT]) took an extra dose of their usual medication (200mg CBZ, 500mg VPA, 100mg PHT) and matched placebo each for a month in random order. The concentrations of AEDs were higher after 7 and 28 days of active treatment compared with placebo (7 days: CBZ 9.5 vs. 7.8 mg L(-1), p < 0.05; VPA 97 vs. 64 mg L(-1), p < 0.05; PHT 13 vs. 11 mg L(-1), p < 0.05; 28 days: CBZ 9.4 vs. 7.7 mg L(-1); p < 0.01, VPA 85 vs. 60 mg L(-1), p < 0.05; PHT 16 vs. 13 mg L(-1), p < 0.05). Despite these increases in concentration, there were no significant changes in attention, reaction time, finger tapping, memory, side-effect scale or sedation scoring during the active phases compared with placebo phases for the three drugs analysed together and separately. Elderly patients taking standard AEDs as monotherapy did not develop cognitive impairment when the dose was modestly increased within the target range for each drug.

Topiramate. A review of its pharmacodynamic and pharmacokinetic properties and clinical efficacy in the management of epilepsy

Topiramate is a sulphamate-substituted monosaccharide derived from D-fructose and is structurally unrelated to other antiepileptic drugs. It acts by multiple mechanisms that suggest it may be effective in several types of epilepsy. In double-blind placebo-controlled trials, add-on therapy with topiramate 400 to 1000 mg/day reduces the seizure rate by > or = 50% in 35 to 52% of adult patients with resistant partial epilepsy (with or without secondarily generalised seizures) compared with 0 to 19% of placebo recipients; a 200 mg/day dosage was less effective. Topiramate has also been shown to be superior in efficacy to placebo in well controlled trials in patients with generalised tonic-clonic seizures, Lennox-Gastaut syndrome and in paediatric patients with partial epilepsy. Efficacy has been maintained for 7 years and some patients may also be satisfactorily treated with topiramate monotherapy. Further study is needed to follow up on the promising results of topiramate use in other paediatric epilepsies. Adverse CNS events are the most common untoward effects during topiramate therapy and are most likely to lead to withdrawal of the drug. However, most adverse events are mild to moderate in severity and lessen with continued drug therapy. In clinical trials, most adverse events which were dose limiting or led to discontinuation of treatment occurred during the titration phase. The overall incidence of adverse events may be reduced by slower upward dosage titration. In summary, topiramate appears to be a suitable agent for add-on therapy in adult patients with partial epilepsy. Preliminary reports support the use of add-on topiramate in adults with generalised epilepsy, in childhood epilepsies and in patients with Lennox-Gastaut syndrome, as well as the use of topiramate monotherapy in patients with partial epilepsy. Thus, topiramate can be considered an important new drug for the management of patients with refractory epilepsy.

Established antiepileptic drugs

Despite the recent entry into the market-place of a range of new pharmacological treatments for epilepsy, most patients still receive the standard antiepileptic drugs. This review considers the clinical place and practical use of these agents. Detailed consideration is given to carbamazepine, phenytoin, sodium valproate, phenobarbital and ethosuximide, with lesser emphasis on primidone, clobazam and clonazepam. Individualization of therapy, polypharmacy, refractory epilepsy, therapeutic drug monitoring, pregnancy, withdrawing treatment, epilepsy prophylaxis and referral to an epilepsy centre are also discussed. The paper concludes with a statement of 12 basic rules in prescribing established antiepileptic drugs.

Gabapentin and cognition: a double blind, dose ranging, placebo controlled study in refractory epilepsy

OBJECTIVE

To assess the effect of different doses of gabapentin (GBP) on cognitive function in treated epileptic patients.

METHODS

Twenty seven patients with refractory partial seizures commenced a double blind, dose ranging, placebo controlled, crossover study of adjuvant GBP. Each treatment phase lasted three months, during which the dose of GBP or matched placebo was increased stepwise at intervals of four weeks (1200 mg/day, 1800 mg/day, and 2400 mg/day in three daily doses). Psychomotor and memory testing was carried out at the end of each four week period, at which time the patient also completed subjective measures of cognition, fatigue, worry, temper, and dysphoria. A visual analogue scale was used to assess drowsiness and a questionnaire was employed to gauge the severity of side effects.

RESULTS

In the 21 patients completing the study, GBP produced a significant reduction in median monthly seizure frequency from 7 to 4.3 (P = 0.02), the decrease being most pronounced for secondarily generalised seizures (from 1.0 to 0.3, P = 0.01). Forty three per cent of patients reported a reduction in seizure frequency of at least 50% throughout all GBP doses. Mean (SD) plasma concentrations of GBP at 1200, 1800, and 2400 mg/day were 4.7 (2.6), 6.8 (3.8), and 8.6 (3.3) mg/l respectively. The drug had no effect on composite psychomotor and memory scores; nor was there alteration in any self assessment subscore. The mean drowsiness (P = 0.03) score was higher during treatment with 2400 mg GBP daily compared with matched placebo. Composite psychomotor (r = -0.47, P < 0.01), tiredness (r = 0.42, P < 0.01), and side effect (r = 0.61, P < 0.001) scores correlated significantly with seizure frequency but not with GBP dose.

CONCLUSION

GBP is a well tolerated and effective antiepileptic drug which had no measurable effect on cognition but did produce sedation at the highest dose. This study also supports the suggestion that seizures can cause cognitive impairment.