Assessing risk to benefit ratio in antiepileptic drug therapy

The Use of Antiepileptic Drugs-Principles and Practice

Up to 70% of people developing epilepsy may expect to become seizure free with optimum antiepileptic drug (AED) therapy. The remaining 30% are the most difficult to treat. Most patients are controlled on a single AED, but a small proportion requires a combination of two agents. Add-on therapy with a second drug, rather than substitution, may be a viable and rational approach in some patients, particularly if the first drug is relatively well tolerated. Precise classification of the type of seizures, as well as the epilepsy syndrome, together with careful recording of both seizures and adverse effects, are essential if rational management decisions are to be made. The goal of therapy should be complete seizure freedom with a single drug taken once or twice a day and without adverse effects. If control is difficult to achieve, the maximum tolerated dose of each drug should be explored, but a balance needs to be struck between adverse effects and control of seizures. In patients in whom treatment appears to be ineffective, the diagnosis of epilepsy and adherence to therapy should be reviewed. Drugs used in combination must be carefully selected, as poor adherence, drug interactions, and toxicity are more likely if more than one drug is prescribed. Agents are usually chosen according to seizure type, patient characteristics, and often by clinician preference. Those that are better tolerated have a low potential for pharmacokinetic and pharmacodynamic interactions, and those that can be easily introduced without any complicated titration schedule have an advantage.

Medical risks in epilepsy: a review with focus on physical injuries, mortality, traffic accidents and their prevention

The present review aims at highlighting selective aspects of the medical risks in epilepsy and their prevention. Emphasis is put on accidents and physical injuries, including risk factors and effectiveness of prevention; mortality, its causes, risk factors and prevention of seizure-related deaths, as well as traffic accidents, their risk factors and the effectiveness of prevention. Accidents and injuries are slightly more frequent among people with epilepsy than in the general population. This increased risk is probably most prevalent in patients with symptomatic epilepsy and frequent seizures, most often in combination with associated handicaps. The majority of accidents are trivial and occur at home. The most frequent injuries among patients with epilepsy are contusions, wounds, fractures, abrasions and brain concussions. The standardised mortality ratio (SMR; the ratio of observed number of deaths in a population with epilepsy to that expected, based on age and sex-specific mortality rates in a reference population) in population-based studies of epilepsy is 2-3 compared to the general population. This increased mortality is largely related to the etiology of the epilepsy and is probably not influenced by the treatment of the epilepsy. On the other hand, most fatalities in patients with chronic, therapy resistant epilepsy seem to be seizure-related and often sudden unexpected deaths (SUDEP). The frequency of such seizure-related deaths is most likely to be reduced by intensified treatment aiming at early seizure control, although appropriate studies for definitive evidence are still lacking. Apparently, there is an increased rate of traffic accidents in drivers with epilepsy, even if population-based prospective data are lacking. Many of these accidents are seizure-related. Probably, the extent to which physicians report their patients with uncontrolled epilepsy to the authorities is too low, but this has not yet been explored. Moreover, the preventive measures in legislation may be ignored by many people with epilepsy.

Should antiepileptic drugs be withdrawn in seizure-free patients?

Discontinuation of antiepileptic drug (AED) treatment is a valuable option in patients with epilepsy who have been seizure free for 2 years or longer. However, the decision to withdraw AEDs must be based on a balanced view of the overall risk of seizure relapse, the factors most likely to affect that risk, and the medical, emotional and social implications of treatment continuation versus treatment withdrawal. In a critical review of 28 studies accounting for 4571 patients (2758 children, 1020 adults and a combined group of 793), most with at least 2 years of seizure remission, the proportion of patients with relapses during or after AED withdrawal ranged from 12 to 66%. Using life-table analysis, the cumulative probability of remaining seizure-free in children was 66-96% at 1 year and 61-91% at 2 years after withdrawal of AEDs. The corresponding values in adults were 39-74% and 35-57%, respectively. The relapse rate was highest in the first 12 months (especially in the first 6 months) after withdrawal and tended to decrease thereafter. Based on a previously published meta-analysis of data published up to 1992, the pooled relapse risk was 25% (95% CI 21, 30%) at 1 year and 29% (95% CI 24, 34%) at 2 years after AED withdrawal. The factors associated with a higher-than-average risk of seizure relapse included adolescent-onset epilepsy, partial seizures, the presence of an underlying neurological condition, and abnormal EEG findings at the time of AED withdrawal in children. Factors associated with a lower-than-average risk were childhood-onset epilepsy, idiopathic generalised epilepsy and - for children - a normal EEG. Selected epilepsy syndromes (e.g. benign epilepsy with centrotemporal spikes and juvenile myoclonic epilepsy) may be associated with significantly different outcomes after AED withdrawal. All these factors and their combinations may contribute to the development of guidelines for practising physicians to help them in making the best decision related to treatment discontinuation. The decision plan should also take into account social factors (driving license, job and leisure activities) as well as emotional and personal factors, and must be tailored to and discussed with the individual patient and his/her family.

Adjunctive therapy versus alternative monotherapy in patients with partial epilepsy failing on a single drug: a multicentre, randomised, pragmatic controlled trial

OBJECTIVE

To evaluate the value of alternative monotherapy versus adjunctive therapy in partial epilepsy refractory to single antiepileptic drug (AED) therapy.

DESIGN AND METHODS

In a multicentre, parallel-group, open-label study, patients with cryptogenic or symptomatic partial epilepsy not controlled after single or sequential AED monotherapies were randomised to monotherapy with an alternative AED or to adjunctive therapy with a second AED. The AED to be added/substituted and dose adjustments were determined by the physician's best judgement. Patients were followed up until withdrawal from the allocated treatment or for 12 months, whichever first. Outcome measures included proportion of patients continuing on the assigned treatment strategy, proportion of patients seizure-free after achieving the target maintenance dose, and adverse effects rates. Data were analysed by actuarial life tables, Kaplan-Meier survival analysis and Cox proportional hazard regression model.

RESULTS

Of a total of 157 patients (including 94 previously exposed to only one AED), 76 were randomised to alternative monotherapy and 81 to adjunctive therapy. The two groups were balanced in clinical characteristics. The 12-month cumulative probability of remaining on the assigned treatment was 55% in patients randomised to alternative monotherapy and 65% in those randomised to adjunctive therapy (P=0.74). The 12-month probability of remaining seizure-free was 14 and 16%, respectively (P=0.74). Adverse effects were similar in the two groups. No significant differences in outcome within or between groups were identified based on etiology of epilepsy and previous AED exposure.

CONCLUSIONS

Although these findings should be interpreted with caution due to the low statistical power resulting from the relatively small sample size, alternative monotherapy and adjunctive therapy were associated with similar outcomes. Further work is required to determine whether outcome could be improved through identification of specific AED combinations with synergistic activity.

Benefit-risk analysis : a brief review and proposed quantitative approaches

Given the current status of benefit-risk analysis as a largely qualitative method, two techniques for a quantitative synthesis of a drug's benefit and risk are proposed to allow a more objective approach. The recommended methods, relative-value adjusted number-needed-to-treat (RV-NNT) and its extension, minimum clinical efficacy (MCE) analysis, rely upon efficacy or effectiveness data, adverse event data and utility data from patients, describing their preferences for an outcome given potential risks. These methods, using hypothetical data for rheumatoid arthritis drugs, demonstrate that quantitative distinctions can be made between drugs which would better inform clinicians, drug regulators and patients about a drug's benefit-risk profile. If the number of patients needed to treat is less than the relative-value adjusted number-needed-to-harm in an RV-NNT analysis, patients are willing to undergo treatment with the experimental drug to derive a certain benefit knowing that they may be at risk for any of a series of potential adverse events. Similarly, the results of an MCE analysis allow for determining the worth of a new treatment relative to an older one, given not only the potential risks of adverse events and benefits that may be gained, but also by taking into account the risk of disease without any treatment. Quantitative methods of benefit-risk analysis have a place in the evaluative armamentarium of pharmacovigilance, especially those that incorporate patients' perspectives.

Psychomotor development and general movements in offspring of women with epilepsy and anticonvulsant therapy

While the role of antiepileptic drug (AED) therapy in teratogenesis has widely been investigated, there are few prospective studies on later postnatal development in offspring of epileptic women in utero exposed. The aim of this study was a prospective investigation of the psychomotor development in a selected population of infant born to women with epilepsy on AED therapy during pregnancy.

PATIENTS AND METHODS

Children were assessed at various times until 30 months of age by general movement (GMs) observation (at 7 days and 4 and 13 weeks), traditional neurologic examination (at 7 days and 4 and 13 weeks, 6, 9 and 12 months) and Brunet-Lezine (B-L) administration (at 30 months). We present the preliminary results of our study conducted on 11 children.

RESULTS

Psychomotor delay in children was confirmed by traditional neurological examinations scores at 7 days, 4 weeks, 13 weeks and 6 months and by B-L score at 30 months. Between 9 and 12 months of age, traditional neurologic examination became "silent". GM assessment was found to be a better predictor of psychomotor development. In fact, GM analysis, particularly at 4 weeks, was strongly correlated with the Brunet-Lezine score at 30 months. In conclusion, on the basis of these data we suggest a psychomotor delay in the offspring of epileptic women and that GMs and neurologic evaluation provide complementary information concerning psychomotor development and later outcome of these children.

How accurate are witness descriptions of epileptic seizures?

PROBLEM

The diagnosis of epilepsy largely relies on the seizure description by a witness. Our aim was to assess the accuracy of seizure descriptions.

METHODS

Twenty volunteers (10 medical students, 4 junior doctors working on a neurological ward and 6 non-medical students) viewed a video of a partial then secondary, i.e. generalised seizure, and were then asked to provide a written account of the event. The seizure had eight key features. Volunteers scored one mark for each described key feature. One mark was deducted for each false observation.

RESULTS

The mean positive score was 3.5 (range 1 to 6). Unresponsiveness and lateralising features were often missed. The mean negative score was -0.8 (range 0 to -3). Erroneously described features included 'patient rolled over', 'agitated' or 'arms flopped about' as part of the tonic clonic seizure. Left and right were sometimes confused. The mean total score was 2.7 (range -2 to 6). A medical and a non-medical student achieved the highest scores, a doctor the lowest score.

CONCLUSIONS

The accuracy of seizure descriptions by witnesses was generally low and there were wide variations.

Current trends in antiepileptic drug therapy

Over the last two decades, drug therapy for epilepsy has improved substantially. This can be ascribed to a large extent to three factors, including the demonstration of the advantages of monotherapy; the realization of the need for dosage tailoring, coupled [for some antiepileptic drugs (AEDs)] with control of pharmacokinetic variability through therapeutic drug monitoring; and the introduction of newer agents with improved tolerability profiles. What further advances should we expect for the future? Current trends that are expected to increasingly affect our prescribing patterns include greater reliance on evidence-based medicine and treatment guidelines, a trend that will be facilitated by completion of therapeutically meaningful randomized trials (including cost-effectiveness studies) and high-quality observational studies (including multinational pregnancy registries), as well as initiatives from scientific societies and government organizations aimed at condensing the most relevant information into therapeutic guidelines. The explosion in communication technology will accelerate dissemination of this information and its application to clinical practice. Other factors include a more rational patient-tailored AED selection and dose individualization, aided by characterization of predictors of outcome as defined by clinical parameters (sex, age, epilepsy syndrome, and etiology), pathophysiological mechanisms, and newly discovered genetic markers of outcome; improved definition of the role of new AEDs, resulting in their increased use in newly diagnosed epilepsy; and reappraisal of the value of combination therapy in refractory epilepsies, based on evidence produced by experimental and clinical studies designed to identify favorable pharmacodynamic interactions. Additional important developments may come from the discovery of novel, more efficacious AEDs and from exploration of potential new targets, such as prevention of epileptogenesis.

The long-term effects of antiepileptic drugs on the visual system in rats: electrophysiological and histopathological studies

OBJECTIVE

We quantified the long-term effects of antiepileptic drugs (AEDs) on the visual system of rats using electroretinograms (ERGs) and visual evoked potentials (VEPs).

METHODS

Twenty adult Sprague-Dawley rats were divided into 4 groups (n=5). Each animal was treated by monotherapy of phenytoin (PHT), valproic acid (VPA), zonisamide (ZNS) or physiological saline as control. The AEDs were injected intraperitoneally daily for 180 days. ERGs and VEPs were recorded before the medication and on Days 30 and 180.

RESULTS

There were no significant changes in the 4 groups on Day 30. On Day 180, the amplitudes of a- and b-waves of dark-adapted (DA) ERGs were reduced in the PHT group compared with those of the control group. In the VPA group, the amplitudes of the DA ERG a- and b-waves, light-adapted ERG b-wave and the DA VEP were reduced. No significant changes were observed in the ZNS group. There were no histopathological changes of the retina and visual cortex in all groups.

CONCLUSIONS

Our results indicate that neurons along the visual pathways have different sensitivity to each AED. This may result from the differential pharmacological actions of each AED on visual neurons.

SIGNIFICANCE

Our findings suggest that epileptic patients on long-term use of AEDs might have subclinical influences to the visual systems.

Interactions between oxcarbazepine and conventional antiepileptic drugs in the maximal electroshock test in mice: an isobolographic analysis

PURPOSE

The aim of this study was to determine the types of interactions between oxcarbazepine (OCBZ) and conventional antiepileptic drugs (AEDs) against maximal electroshock-induced seizures (MES test) in mice, by using a method of isobolographic analysis.

METHODS

Adverse effects of combinations were evaluated in the chimney test (motor performance), also using the isobolographic method, which allowed determination of the median toxic dose (TD50) values for individual combinations; thus the protective indices could be determined.

RESULTS

OCBZ and phenytoin (PHT) at the fixed-ratio combination of 1:1 were significantly infraadditive (antagonistic) with respect to the antiseizure protection against MES and simultaneously additive in terms of side effects in the chimney test. Interestingly, combinations between OCBZ and clonazepam (CZP) in the MES test proved antagonistic or synergistic, depending on the proportion of both AEDs in the mixture. Low doses of OCBZ with high doses of CZP exerted antagonism. Conversely, high doses of OCBZ combined with low doses of CZP resulted in a synergistic interaction. Remaining combinations between OCBZ and phenobarbital, valproate, or carbamazepine were purely additive, either as regards the anticonvulsant activity against MES or in terms of motor impairment in the chimney test.

CONCLUSIONS

The results of this study indicate that interaction of OCBZ and CZP at fixed-ratio combination of 1:1 might be profitable from a clinical point of view. Conversely, combinations of OCBZ with PHT may not be clinically efficient.

Daytime vigilance and quality of life in epileptic patients treated with vagus nerve stimulation

OBJECTIVES

The goal of this study was to determine if vagus nerve stimulation (VNS) has any effect on daytime vigilance and perceived sense of well-being.

METHODS

Multiple Sleep Latency Tests (MSLTs) were performed and visual reaction times (VRTs) obtained in eight epileptic patients before and during treatment with VNS. Prior to VNS initiation patients' baseline MSLT and VRT scores were recorded. Six months after VNS was initiated, treatment MSLT and VRT scores were obtained. A group of 12 age-matched healthy subjects served as controls. In addition, there was a global evaluation of well-being at baseline and during a follow-up of 6 months.

RESULTS

As expected, patients evaluated both at baseline and during VNS showed more sleepiness than controls. In this group, baseline sleep latencies on the MSLT were significantly shorter, while VRT latencies were significantly longer than those of controls. After 6 months of VNS, MSLT scores in the eight patients did not change significantly with respect to baseline. However, if the single patient treated with relatively high stimulus intensities (1.75 mA) was excluded from the group and only the seven patients treated with low stimulus intensities (<or=1.5 mA) were considered, a significant effect of chronic VNS on MSLT scores could be observed. In fact, the mean sleep latency (MSL) average of the seven subjects significantly improved from 9.9+/-2.5 minutes during baseline to 10.9+/-2.3 minutes after 6 months of VNS (P<0.05). Conversely, the only patient treated with high stimulus intensities showed increased sleepiness, with MSL decreasing from 14.4 to 9.8 minutes. On the other hand, VRT latencies did not significantly change during VNS. Patients considered as a whole had significant improvements on global evaluation scores of quality of life.

CONCLUSION

VNS at low stimulus intensities promotes daytime vigilance in adult epileptic patients and has a positive effect on quality of life.

Topiramate: efficacy and tolerability in children according to epilepsy syndromes

To evaluate the efficacy and tolerability of topiramate (TPM) as add-on therapy in children less than 12 years of age with refractory epilepsy, according to epilepsy syndromes, we conducted an open, prospective, pragmatic and multicenter study in France. Efficacy was assessed, especially according to epilepsy syndromes, as well as tolerability. We included 207 children (41 of whom were less than 4 years of age). TPM was effective (responders with >50% decrease in seizure frequency) in 50% of 128 patients with partial epilepsy, and in 44% of 79 patients with generalized epilepsy. In case of generalized epilepsy, responders more frequently had generalized symptomatic epilepsy, severe myoclonic epilepsy and myoclono-astatic epilepsy, whereas response rate was mild in both infantile spasms and Lennox-Gastaut syndrome (LGS). Improvement was well maintained in all patients during the treatment period (median 5.6 months). Seizure frequency/severity increased (worsening) in 13% of patients with partial epilepsy and 17% with generalized epilepsy (particularly in those with infantile spasms), and resulted in withdrawal of TPM for 8%. The most frequently reported adverse events were moderate neurobehavioral and gastrointestinal disorders. Adverse events led to withdrawal of TPM from 13.5% of patients. Children less than 4 years of age had particularly good tolerability. Results confirm that TPM is effective and well tolerated in children under 12 years of age in a broad range of epilepsy syndromes, including refractory partial epilepsy, and symptomatic and myoclonic generalized epilepsy. Use of TPM should be considered in children under 4 years of age, and slow and progressive titration is important.

Pharmacological and therapeutic properties of valproate: a summary after 35 years of clinical experience

Thirty-five years since its introduction into clinical use, valproate (valproic acid) has become the most widely prescribed antiepileptic drug (AED) worldwide. Its pharmacological effects involve a variety of mechanisms, including increased gamma-aminobutyric acid (GABA)-ergic transmission, reduced release and/or effects of excitatory amino acids, blockade of voltage-gated sodium channels and modulation of dopaminergic and serotoninergic transmission. Valproate is available in different dosage forms for parenteral and oral use. All available oral formulations are almost completely bioavailable, but they differ in dissolution characteristics and absorption rates. In particular, sustained-release formulations are available that minimise fluctuations in serum drug concentrations during a dosing interval and can therefore be given once or twice daily. Valproic acid is about 90% bound to plasma proteins, and the degree of binding decreases with increasing drug concentration within the clinically occurring range. Valproic acid is extensively metabolised by microsomal glucuronide conjugation, mitochondrial beta-oxidation and cytochrome P450-dependent omega-, (omega-1)- and (omega-2)-oxidation. The elimination half-life is in the order of 9 to 18 hours, but shorter values (5 to 12 hours) are observed in patients comedicated with enzyme-inducing agents such as phenytoin, carbamazepine and barbiturates. Valproate itself is devoid of enzyme-inducing properties, but it has the potential of inhibiting drug metabolism and can increase by this mechanism the plasma concentrations of certain coadministered drugs, including phenobarbital (phenobarbitone), lamotrigine and zidovudine. Valproate is a broad spectrum AED, being effective against all seizure types. In patients with newly diagnosed partial seizures (with or without secondary generalisation) and/or primarily generalised tonic-clonic seizures, the efficacy of valproate is comparable to that of phenytoin, carbamazepine and phenobarbital, although in most comparative trials the tolerability of phenobarbital was inferior to that of the other drugs. Valproate is generally regarded as a first-choice agent for most forms of idiopathic and symptomatic generalised epilepsies. Many of these syndromes are associated with multiple seizure types, including tonic-clonic, myoclonic and absence seizures, and prescription of a broad-spectrum drug such as valproate has clear advantages in this situation. A number of reports have also suggested that intravenous valproate could be of value in the treatment of convulsive and nonconvulsive status epilepticus, but further studies are required to establish in more detail the role of the drug in this indication. The most commonly reported adverse effects of valproate include gastrointestinal disturbances, tremor and bodyweight gain. Other notable adverse effects include encephalopathy symptoms (at times associated with hyperammonaemia), platelet disorders, pancreatitis, liver toxicity (with an overall incidence of 1 in 20,000, but a frequency as high as 1 in 600 or 1 in 800 in high-risk groups such as infants below 2 years of age receiving anticonvulsant polytherapy) and teratogenicity, including a 1 to 3% risk of neural tube defects. Some studies have also suggested that menstrual disorders and certain clinical, ultrasound or endocrine manifestations of reproductive system disorders, including polycystic ovary syndrome, may be more common in women treated with valproate than in those treated with other AEDs. However, the precise relevance of the latter findings remains to be evaluated in large, prospective, randomised studies.

Strategies to prevent overtreatment with antiepileptic drugs in patients with epilepsy

Overtreatment is defined here as an unnecessary and excessive drug load in the management of epilepsy leading to a suboptimal risk-to-benefit balance. Pharmacological overtreatment can often be prevented by deciding and counselling carefully about the need for antiepileptic drugs (AEDs) given the limitations of current AEDs. Although AEDs will reduce the incidence of seizures, they have no demonstrated ability to prevent epilepsy in patients at risk or to modify the course of epilepsy in patients following the first seizure. In addition, starting AEDs may not be necessary for control of epileptic seizures induced by precipitation or predisposing factors or for benign epilepsies with rare or mild seizures. Start monotherapy with the chosen first-line AED, initially at low doses titrating up to the low maintenance dose. Avoid drug loading (except for emergency treatment). If seizures continue, titrate to the limit of tolerability which will however, achieve additional seizure control in approximately 20% of patients. If, as in many patients, dosing to the limit of tolerability is not beneficial, the dose should be reduced. Switching to an average dose of another first line AED is another option to prevent overtreatment. Avoid drug overload during add-on therapy by slowly reducing the dose of the first drug in patients having adverse effects, ideally by an amount that the patient does not experience any further adverse effects, if possible, before adding another drug. If the patient does not benefit unequivocally from two-drug therapy within 3 months (and approximately 75% will not benefit), slowly transfer to monotherapy of the second drug and start with a newly chosen AED for add-on. To counteract the propensity to overmedication in chronic epilepsy is not easy. Great benefits, without loss of seizure control, are often gained by slowly reducing the overall drug load.

Overtreatment in epilepsy: adverse consequences and mechanisms

The most important determinant of quality of life in patients with epilepsy is complete seizure control, and therefore this should be the ultimate goal of pharmacological therapy. Seizure freedom, or a reduction in seizure frequency, however, should not be sought at all costs, and the situation should never arise where a person with epilepsy is made to suffer more from the side effects of treatment than from the consequences of the underlying disease. Overtreatment is not uncommon in patients taking antiepileptic drugs, and it may occur in many forms and with a variety of mechanisms. Long-term use (or continuation) of anticonvulsant therapy in situations where it is not indicated (e.g. in children with simple febrile seizures, or in non-epileptic seizure-free patients who underwent brain surgery) constitutes a blatant case of overtreatment. Other forms of overtreatment include the use of unnecessarily fast dose escalation rates, which may expose the patient to potentially serious or severe side effects, or the prescription of unnecessarily high maintenance dosages. The latter occurrence may result from inadequate understanding of dose-response relationships, from misinterpretation of serum drug concentrations (e.g. targeting concentrations within the 'range' in patients who are well controlled at lower concentrations) or, at times, from failure to recognize a paradoxical increase in seizure frequency as a manifestation of drug toxicity. The most common form of overtreatment, however, involves the unnecessary use of combination therapy (polypharmacy) in patients who could be treated optimally with a single drug. Adverse effects associated with polypharmacy often result from undesirable drug-drug interactions. While pharmacokinetic interactions are somewhat predictable and can be minimized or controlled by monitoring serum drug concentrations and/or dose adjustment, pharmacodynamic interactions leading to enhanced neurotoxicity (as seen, for example, in some patients given a combination of lamotrigine and carbamazepine) can only be identified by careful clinical observation. There is evidence that not all antiepileptic drug combinations are equally adverse, and that the combined use of specific drugs (e.g. lamotrigine and valproic acid) may even exhibit an improved therapeutic index compared with either agent given alone, provided appropriate dose adjustments are made. Although the suggestion has been made that adverse effects are more likely to result from combining anticonvulsants having a similar mode of action, our knowledge of the pharmacology of individual agents is insufficient to allow a reliable prediction of the clinical effects of specific drug combinations.

Pharmacological overtreatment in epilepsy: mechanisms and management

Despite considerable advances in the drug treatment of epilepsy in the last decade, pharmacoresistant epilepsy continues to occur today in as many as one in three patients with newly diagnosed epilepsy. These limitations of current drug treatment may result in the inadvertent overtreatment of patients with epilepsy. Overtreatment is defined here as unnecessary and excessive drug load in the management of epilepsy leading to a suboptimal risk-to-benefit balance. Pharmacological overtreatment is relatively common and may occur at all stages of epilepsy therapy. Scenarios for overtreatment include the unnecessary use of AEDs for prevention of epilepsy in patients at risk where current medications have not been shown to be effective or in patients with benign epilepsy syndromes with mild and rare partial seizures. Unnecessary rapid titration leading to overtreatment is a common occurrence in many patients. In addition, dose titration to the limit of tolerability and polytherapy are of limited utility and thus may cause overtreatment in many patients. As no markers currently exist for prediction of individual drug effect, trial and error still prevail in the pharmacotherapy of epilepsy. The increased drug load needs to be reversed once the risk-to-benefit balance worsens in the eye of the patient and in the assessment of the physician. Informing the patient about the benefit and the limitation of the planned change in medication is important. Because of emerging concern that drug overload may cause significant and even serious adverse effects without adequate benefit in seizure control, more data from rigorous scientific studies and new concepts for early recognition, reduction and prevention of overtreatment are needed.

Effect on epileptogenesis of carbamazepine treatment during the silent period of the pilocarpine model of epilepsy

PURPOSE

This study addresses the question of epileptogenesis by investigating the effects of carbamazepine (CBZ) on the silent period of the pilocarpine model of epilepsy.

METHODS

Adult Wistar rats were subjected to status epilepticus (SE) induced by pilocarpine and treated with CBZ or saline, i.p, during 56 days. Latency for the first spontaneous seizure, incidence, frequency, and duration of seizures were monitored for < or =56 days after treatment. Hippocampal histologic analysis was performed.

RESULTS

CBZ reduced the frequency and duration of the seizures and the hippocampal damage.

CONCLUSIONS

CBZ did not abort the epileptogenesis but minimized the expression of seizures and hippocampal damage.

Lamotrigine monotherapy improves health-related quality of life in epilepsy: a double-blind comparison with valproate

The effects of monotherapy with lamotrigine on health-related quality of life were compared with those of valproate monotherapy in a randomized, double-blind trial designed to evaluate treatment-emergent weight changes in patients with epilepsy. At the end of 8 months of treatment, significantly more patients using lamotrigine compared with valproate experienced quality-of-life improvements on the Health Perceptions (42% vs 15%), Energy/Fatigue (47% vs 28%), and Social Isolation (35% vs 16%) subscales of the Quality of Life in Epilepsy-89 (QOLIE-89) questionnaire (P<0.05). Compared with valproate-treated patients, lamotrigine-treated patients were four times more likely to experience improvement in Health Perceptions, 2.3 times more likely to experience improvement in Energy/Fatigue, and 2.8 times more likely to experience improvement in Social Isolation (P<0.05). These quality-of-life improvements are consistent with the improvements in mood measured with the Beck Depression Inventory, the Cornell Dysthymia Rating Scale, and the Profile of Mood States among patients receiving lamotrigine. These data show that lamotrigine monotherapy provides benefits over valproate monotherapy in improving several aspects of health-related quality of life in patients with epilepsy. The observation that quality-of-life improvements during lamotrigine monotherapy occurred concurrently with improvements in mood suggests that the quality-of-life and mood changes may be causally related.

The clinical impact of new antiepileptic drugs after a decade of use in epilepsy

The introduction of numerous effective, well tolerated and safe new antiepileptic drugs (AEDs) in the last decade of the 20th century has widened the choice of treatment options in epilepsy and improved the tolerability and the ease of use of treating patients with epilepsy. Nevertheless, significant safety and efficacy deficits continue to exist. Severe idiosyncratic reactions and organ toxicity have hampered the wide use of some of the newer AEDs. As a decade before, about one third of patients with chronic epilepsy is resistant to current pharmacotherapy. Even in patients in whom pharmacotherapy is efficacious, current AED do not seem to affect the progression or the underlying natural history of epilepsy. In addition, there is currently no drug available which prevents the development of epilepsy, e.g. after head trauma. Thus, there is an unmet need for safer and more effective drugs, especially for chronic, drug-resistant epilepsy. To stimulate the development of even better compounds, the demonstrated benefits and risks of current new AEDs are reviewed.

What can we learn from clinical trials of anticonvulsant drugs in epilepsy?

Any physician who intends to utilize the available antiepileptic drugs (AEDs) judiciously, cannot do so without being well versed on their pharmacological properties and the large body of evidence that is continuously accumulating on their relative efficacy and tolerability in different types of epilepsy. While informal observations such as retrospective surveys and case reports can be useful under special circumstances, prospective randomized clinical studies represent by far the most important tool by which objective information can be obtained about the clinical value of existing drugs. Even randomized trials, however, can produce misleading conclusions because of inherent weaknesses or bias in study design, analysis, and interpretation. Common deficiencies identified in some of the most recent drug trials in epilepsy include 1) inclusion of inappropriately heterogeneous patient groups (for example, patients with partial and primarily generalized seizures); 2) low statistical power due to insufficient sample size (for trials designed to show therapeutic equivalence); 3) inappropriate titration rates or suboptimal dosages or dosing schedules (often favouring the sponsor's product over the comparator); 4) insufficient duration of treatment; and 5) utilization of endpoints of questionable clinical significance. In part, some of the above shortcomings can be ascribed to the fact that most clinical drug trials are designed to address regulatory needs rather than to provide the type of information required for rational prescribing. Physicians need to be alerted about the importance of these issues, and they should make every possible effort to interpret critically the medical literature on which they rely to guide and support their therapeutic decisions.

Refractory epilepsy: a progressive, intractable but preventable condition?

Intractable seizures are just one manifestation of 'refractory epilepsy', which can be recognized as a distinct condition with multifaceted dimensions, including neurobiochemical plastic changes, cognitive decline and psychosocial dysfunction, leading to dependent behaviour and a restricted lifestyle. The biological basis of 'refractoriness' is likely to be multifactorial, and may include the severity of the syndrome and/or underlying neuropathology, abnormal reorganization of neuronal circuitry, alteration in neurotransmitter receptors, ion channelopathies, reactive autoimmunity, and impaired antiepileptic drug (AED) penetration to the seizure focus. Some of these deleterious changes may be a consequence of recurrent seizures. We hypothesize that 'refractory epilepsy' may be prevented by interrupting this self-perpetuating progression. There is increasing evidence that these patients can be identified early in the clinical course and, thus, be targeted early for effective therapeutic intervention. Failure of two first-line AEDs due to lack of efficacy or poor tolerability should prompt consideration of epilepsy surgery in a patient with a resectable brain abnormality. For the majority not suitable for 'curative' surgery, AEDs should be combined with the aim of achieving 'synergism'. This strategy has the potential to improve outcome by preventing the insidious progression to intractable 'refractoriness' and a downward spiraling quality of life.

Marketed new antiepileptic drugs: are they better than old-generation agents?

Until a decade ago, the pharmacologic armamentarium for the management of epilepsy was restricted to a little more than a handful of drugs that had been introduced 20 to 70 years earlier. This situation has changed dramatically, with as many as nine new-generation drugs (oxcarbazepine, gabapentin, lamotrigine, levetiracetam, tiagabine, topiramate, zonisamide, vigabatrin, and felbamate, in addition to the water-soluble phenytoin prodrug fosphenytoin) having been introduced in Europe, the United States, or other parts of the world. These drugs represent a welcome addition because they produce an appreciable reduction in seizure frequency in up to 40% to 50% of patients who had been refractory to older-generation drugs. However, only a few patients with truly refractory disease can be made seizure-free by these new drugs, and the search for more effective anticonvulsants should continue. Although in patients with newly diagnosed epilepsy the efficacy of new-generation drugs is not superior to that of older agents, some of the newer drugs offer advantages in terms of improved tolerability, ease of use, and reduced interaction potential. However, the increased availability of treatment options implies that drug choice in patients with epilepsy is more complicated than in the past, and there is a concern that inadequate knowledge of indications, contraindications, and mode of use of the newer drugs could result in some patients receiving suboptimal treatment or being exposed to undue risks from side effects and drug interactions. Although measurement of plasma drug concentrations is often used to adjust the dosage of classic antiepileptic drugs, therapeutic drug monitoring has been claimed to be of little or no value with newer-generation drugs. This view has been challenged in light of the evidence that pharmacokinetic variability contributes to an important extent to differences in dosage requirements for most of these drugs.

Clinical pharmacology and therapeutic use of the new antiepileptic drugs

Although older generation antiepileptic drugs (AEDs) such as carbamazepine, phenytoin and valproic acid continue to be widely used in the treatment of epilepsy, these drugs have important shortcomings such as a highly variable and nonlinear pharmacokinetics, a narrow therapeutic index, suboptimal response rates, and a propensity to cause significant adverse effects and drug interactions. In an attempt to overcome these problems, a new generation of AEDs has been introduced in the last decade. Compared with older agents, some of these drugs offer appreciable advantages in terms of less variable kinetics and, particularly in the case of gabapentin, levetiracetam and vigabatrin, a lower interaction potential. Lamotrigine, topiramate, zonisamide and felbamate protect against partial seizures and a variety of generalized seizure types, vigabatrin is effective against partial seizures (with or without secondary generalization) and infantile spasms, while the use of oxcarbazepine, tiagabine and gabapentin is mainly restricted to patients with partial epilepsy (and, in the case of oxcarbazepine, also primarily generalized tonic-clonic seizures). Levetiracetam, the latest AED to be introduced, has been found to be effective in partial seizures, but its potentially broader efficacy spectrum remains to be determined in clinical studies. Currently, the main use of new generation AEDs is in the adjunctive therapy of patients refractory to older agents. However, due to advantages in terms of tolerability and ease of use, some of these drugs are increasingly used for first-line management in certain subgroups of patients. Due to serious toxicity risks, felbamate and vigabatrin should be prescribed only in patients refractory to other drugs. In the case of vigabatrin, however, first line use may be justified in infants with spasms.

A systematic review of the safety profile of levetiracetam: a new antiepileptic drug

PURPOSE

This report provides detailed review of safety information on levetiracetam (LEV) (Keppra), a new antiepileptic drug.

METHODS

The integrated summary of safety report submitted for regulatory review was examined to collate information about abnormal laboratory tests values and adverse event reports collected during the overall LEV development program. Analyses included 3347 patients exposed to LEV in clinical trials for epilepsy, cognition, and anxiety disorders.

RESULTS

Safety data from all studies depict a similar pattern of adverse effects, predominantly somnolence, asthenia, and dizziness that occurred most frequently during the first month of LEV treatment. Changes in laboratory test values from placebo-controlled trials that were statistically significant remained in the normal range (red blood cells, hematocrit, hemoglobin, white blood cells, and neutrophils). Reports of the coding term 'infection' (common cold, upper respiratory infection) were not preceded by low neutrophil counts that might suggest impaired immunological status. Selection of adverse event coding terms probably contributed to the high rate of adverse effects termed 'infection.' Higher incidences of adverse effects, particularly behavioral effects, were found among epilepsy patients than in elderly patients with cognitive disorders or patients with anxiety disorders given lower doses.

CONCLUSIONS

This review of patients evaluated during the clinical development program suggests that LEV was well tolerated and safe for patients with seizure, cognitive and anxiety disorders. Overall incidence of adverse effects in the LEV groups was little higher than reports from the placebo groups. Of course, this data was derived from clinical trials that are of relatively short duration, and provide data on only several thousand patients. Therefore, long-term side effects, and/or rare side effects cannot be ruled out on the basis of this analysis.

Harnessing the clinical potential of antiepileptic drug therapy: dosage optimisation

For patients with epilepsy, effective seizure control is the most important determinant of good quality of life. To achieve this, antiepileptic drug (AED) dosages should be individualised to maximise therapeutic benefit and to avoid most--if not all--adverse effects. Several studies suggest that, in routine clinical practice, dosage individualisation is often suboptimal. This may lead to patients receiving unnecessarily large dosages. Conversely, it may lead to patients switching to an alternative therapy (when clinical response is deemed insufficient), without exploration of the full dosage range. Indeed, dosage optimisation--which should involve consideration of the treatment setting and individual patient characteristics--can be a complicated process requiring skill and patience. In general neurological practice, most AEDs should be started at a low dosage and gradually titrated upwards. Starting dosages are similar in most types of epilepsy; however, if a rapid onset of therapeutic action is required, phenytoin, phenobarbital (phenobarbitone), levetiracetam and gabapentin are probably the best tolerated AEDs for starting at full dosage. The initial target maintenance dosage of an AED should be based on the dose-response profile of the drug, and on specific patient characteristics. Usually, the lowest effective daily dose expected to provide seizure control should be used, although various factors (e.g. stage and severity of epilepsy, pharmacokinetic and pharmacodynamic considerations, attitude of the patient) will markedly influence dosage selection. If seizures are not controlled on the initial target dose, the dosage should be increased gradually until complete seizure control is achieved or intolerable adverse effects occur. In most patients who fail to respond to the initially prescribed drug, switching to another AED (monotherapy) is the best option. Combination therapy may be appropriate for patients unresponsive to 2 or more sequential monotherapies. Therapeutic drug monitoring (measurement of serum drug concentrations) is useful in various settings, such as when drug interactions are expected, toxicity is suspected, or when AEDs with nonlinear pharmacokinetics (e.g. phenytoin, carbamazepine) are used. No indications currently exist for routine therapeutic drug monitoring of the newer AEDs. In summary, dosage regimens of AEDs should be assessed regularly, and adjusted if necessary, so that patients can derive optimal therapeutic benefit. For patients considered 'difficult to treat' (i.e. those in whom seizures remain incompletely controlled after several attempts at treatment), referral to a specialist is recommended.

Health outcomes in persons with epilepsy

Epilepsy is a common disorder that effects millions of persons worldwide and costs billions of dollars for direct medical care. Despite the importance of epilepsy from a public health perspective, the physiological and psychosocial outcomes from epilepsy are incompletely understood and are in some ways controversial. The paroxysmal nature and the immense social stigma of the disorder have contributed to misunderstanding of its associated health outcomes. This article reviews the issues surrounding the assessment of health outcomes from the epilepsies and the interventions used to treat recurrent seizures.

Trial duration and follow-up

The chronic nature of most seizure disorders requires that antiepileptic drugs (AEDs) be administered for many years. Therefore, new drugs should be evaluated over a period sufficient to assess potential development of tolerance as well as long-term safety. While patients and prescribers desire extensive long-term data prior to registration, too stringent requirements would discourage industry's investment into new treatments, and a compromise between these stakes should be sought. In add-on studies, it is recommended that patients completing double-blind assessment be offered indefinite open-label treatment, and that safety data be collected prospectively. Monotherapy trials in refractory patients include presurgical and conversion to monotherapy studies. Duration of assessment in these studies rarely exceeds few weeks, and endpoints relate to seizure deterioration rather than improvement; this surrogate measure of efficacy is not necessarily predictive of clinical usefulness and, in view of ethical concerns, the rationale for these studies should be questioned. There may be scope, however, for alternative study designs whereby refractory patients are converted to monotherapy and followed up for several months. Active-control long-term monotherapy trials in newly diagnosed patients represent the mainstay for evaluating efficacy and safety. In patients with partial or generalized tonic-clonic seizures, most trials conducted to date had a duration of 6-12 months, but this period may be insufficient to assess seizure freedom rates at optimized dosages, and at least one 2-year trial would be desirable. With respect to open-label follow-up, many protocols require that the randomization code not be broken until the database has been sealed. Patients completing blind assessment are often forced through unblinding procedures which involve tapering of trial medication and institution of an open-label therapy which may differ, in dosage or type of medication, from that taken previously. In view of ethical concerns, the rationale for this practice should also be questioned.