Advances in the medical treatment of epilepsy

Treatment options for epilepsy, especially using antiepileptic drugs, have increased substantially in the past five years. Since 1993, four novel antiepileptic drugs have been approved and marketed in the United States: felbamate, gabapentin, lamotrigine, and topiramate. Two others, tiagabine and vigabatrin, are likely to be approved in the near future. For many patients, these agents offer the realistic promise of improved seizure control, often with fewer adverse effects and less significant drug interactions compared with older agents. In addition, fosphenytoin, a water-soluble phenytoin prodrug with a number of advantages over intravenous phenytoin, has been released. There are new administration options for carbamazepine, diazepam, and valproic acid. For drug-resistant or -intolerant patients, there has been renewed interest in alternative therapies, especially the ketogenic diet. Taken together, these represent significant therapeutic advances that are benefiting patients with epilepsy. At the same time, improved understanding of the basic mechanisms of epileptogenesis, and of the cellular and molecular actions of available antiepileptic drugs, creates a framework for designing unique therapeutic strategies that are targeted at key sites of vulnerability involved in the development and maintenance of the epileptic state.

Vigabatrin-associated retinal cone system dysfunction: electroretinogram and ophthalmologic findings

OBJECTIVE

To determine the sources of vigabatrin-associated visual disturbances in patients treated for epilepsy.

BACKGROUND

Vigabatrin is an extremely effective antiepileptic drug that selectively increases brain gamma-aminobutyric acid (GABA). Several patients recently developed constricted visual fields during vigabatrin treatment in the United Kingdom, indicating the possibility of GABA-associated retinal dysfunction.

METHODS

Patients with visual symptoms treated chronically with vigabatrin at our center underwent visual evoked potentials (VEP), electroretinograms (ERG), and visual field and ophthalmologic examinations.

RESULTS

Four of 38 patients treated with vigabatrin developed visual symptoms 2 to 40 months after starting the drug. Two patients complained of constricted visual fields and two had blurred vision. ERG demonstrated evidence of bilateral retinal dysfunction consistent with reduced inner retinal cone response in all four patients. Oscillatory potential responses were lost, suggesting impairment of the highly GABAergic amacrine cells. Two of the patients had normal VEPs and minimal findings on clinical ophthalmology examinations despite abnormal ERGs. Abnormal examination findings were narrowed retinal arteries, surface wrinkling retinopathy, and abnormal macular reflexes. One patient also had reduced rod photoreceptor function in the more symptomatic left eye.

CONCLUSIONS

Visual field constriction and blurring during vigabatrin therapy is associated with retinal cone system dysfunction. Visual symptoms may represent selective vulnerability of retinas of affected patients to GABAergic effects of vigabatrin. The prevalence and course of retinal changes associated with vigabatrin therapy are important to determine in a larger group of patients.

Gabapentin add-on therapy with adaptable dosages in 610 patients with partial epilepsy: an open, observational study. The French Gabapentin Collaborative Group

The objectives were to evaluate gabapentin add-on therapy in a large population under conditions close to real practice and to determine the therapeutic doses as reached with adaptable dosages. A 6-month multicentre, open-label study, involved addition of gabapentin to pre-existing treatment at the initial dosage of 1200 mg and subsequent adjustment between 900 and 2400 mg/day according to efficacy and tolerability. A study group of 610 adult patients, with partial epilepsy, persistent seizures and a median seizure frequency with a baseline of 7.2 per month were recruited; one-third had less than four seizures per month. Polypharmacy was frequent, with a mean of 2.3 concomitant drugs. After 6 months, 368 patients (62%) continued on gabapentin, at a mean dosage of 1739 mg/day with 44% of responders. On an intention-to-treat basis, median reduction in frequency was 21.2%, and the responder rate was 33.9%. The responder rate increased to 40.7% in the less severe subgroup receiving only one concomitant drug. Seventy-nine patients (13.4%) remained without seizures during the last evaluation period, versus nine (1.5%) during the baseline. Most of them had initially less than four seizures per month. The most frequent adverse effects, somnolence (29.3%), asthenia (14.6%), nausea (7.9%), ataxia (7.7%) and vertigo (7.2%), occurred rapidly after initial titration to 1200 mg/day, and were usually transitory. Weight gain (8.8%) seemed to be related to gabapentin dose. The combination of two recent drugs, vigabatrin and gabapentin, in 190 patients led to similar efficacy levels, with a tendency for more frequent somnolence and asthenia.

Vigabatrin in refractory childhood epilepsy. The Brazilian Multicenter Study

Children, 47, with various types of severe drug-resistant epilepsy were entered into a prospective, add-on, open trial with vigabatrin. Patients with West syndrome and idiopathic generalized epilepsies were excluded. Seven children had the drug withdrawn, five because of increase in seizure frequency and two because of adverse effects. Drug efficacy, measured according to seizure type, showed a 100% decrease in seizure frequency in 18.6% of partial seizures and 17.3% of the generalized seizures. There was a higher than 50% decrease in 39.5% of partial and 60.8% of generalized seizures, and less than 50% decrease or increase in seizure frequency in 41.8% and 21.8% of partial and generalized seizures, respectively. Vigabatrin mean dosage during phase 3 was 63.6 mg/kg per day (S.D. = 30.5), ranging from 19.3 to 110.5 mg/kg per day. Parametric statistical analysis (Student's t-test) of seizure frequency between phases 1 and 3 showed a significant decrease in seizure frequency for partial (P = 0.022), and generalized seizures (P < 0.0001). Drug-related adverse effects were observed in 18/47 cases (38.3%), consisting mainly of irritability, hyperactivity, dizziness, somnolence and gastrointestinal symptoms.

A survey of lamotrigine and vigabatrin treatment in children with severe epilepsy

A retrospective survey was carried out of add-on treatment with lamotrigine (LTG) and vigabatrin (GVG) in 109 children with severe epilepsy, treated between 1987 and 1994, identified from a total population of 300 patients seen annually, in a tertiary referral outpatient clinic in Cardiff, Wales. Of 79 patient treatments with LTG and 86 with GVG, 42 patients were treated with add-on LTG, 52 with add-on GVG and 20 with both drugs simultaneously. A Kaplan-Meier curve, applied to each of the two index drugs, indicated that 71 and 62% of patients would be expected to continue taking LTG or GVG, respectively after 40 months. Improved seizure control (> or = 50%) at the time of audit was seen in 65% of LTG and 58% of GVG patient treatments for all epilepsy syndromes, but there was a higher proportion of patients with generalized epilepsy improved by LTG (28/41, 68%) than that improved by GVG (8/20, 40%), and only those with generalized epilepsy treated with LTG became seizure free (8/38, 21%). Similar proportions of patients discontinued LTG (16%) and GVG (15%) due to an adverse experience, but a higher proportion discontinued GVG (18%) compared with LTG (6%) because of lack of efficacy. This study supports the relative clinical effectiveness of LTG and GVG in the real world, where children with severe epilepsy are treated in clinical practice and serves to generate hypotheses to enable design of prospectively controlled trials, which should enable more rational use of these two drugs in the paediatric population with epilepsy.

Evaluation of the efficacy of pivagabine on insomnia associated with mood disorders

The efficacy of a new drug, pivagabine (4-[(2,2-dimethyl-1-oxopropyl)amino]butanoic acid, CAS 69542-93-4, Tonerg), was studied on 100 patients affected by insomnia, associated with mood disorders. The pharmacological treatment with 900 mg/d pivagabine produced a significant improvement in the quality of both sleep and awakening. The results shown in the present study were positive and likely attributable to the inhibitory modulating activity of pivagabine on corticotropin releasing factor secretion, that is considered to be responsible for insomnia associated with anxiety or coexisting anxiety and depression, observed in patients with chronic stress. The recovery of sleep physiological structure provokes a significant reduction in the criteria reported in the Self-rating Anxiety Scale (SAS).

Randomised, double-blind, placebo-controlled study of pivagabine in neurasthenia

One hundred and eighteen patients with neurasthenia, as defined by ICD 10 (International Classification of Diseases), participated in a randomised, double-blind, placebo-controlled trial of pivagabine (4-[(2,2-dimethyl-1-oxopropyl)amino]butanoic acid, CAS 69542-93-4, Tonerg). Pivagabine 1800 mg/d was administered orally for four weeks. At the end of the trial, active medication was significantly superior to placebo on the Clinical Global Impression (CGI) improvement of illness scale. In addition, pivagabine treatment reduced the physical and mental fatigability of patients, and increased their sense of well-being.

Role of pivagabine in the treatment of climacteric syndrome

A multicenter, double-blind, controlled study of pivagabine (4-[(2,2-dimethyl-1-oxopropyl)amino]butanoic acid, CAS 69542-93-4, Tonerg) was conducted in 186 female patients (age: 33-79 years) suffering from climacteric syndrome. In these patients, climacteric syndrome was mainly constituted by symptoms of anxiety, often with mild symptoms of depression and sometimes with mild symptoms of cardiac somatization. The enrolled patients were randomized to two treatment groups: the first group was administered pivagabine, 900 mg/d, for 90 days in succession; the second group was administered placebo for the same period. The efficacy of the treatments was assessed by the Hamilton Depression Rating Scale (HDRS) and the Zung's Self-rating Anxiety Scale (SAS) before the start of treatment, after one month and at the end of treatment. At the end of the study, the physicians and the patients were also requested to evaluate the efficacy of the two treatments. Tolerability was evaluated by recording side effects and by assessing the course of arterial blood pressure, of heart rate and of selected laboratory parameters. The study showed that pivagabine was able to reduce symptoms of anxiety and depression. As a consequence, when asked to evaluate the efficacy, the physicians and the patients consistently stated that pivagabine was effective in controlling the symptoms of anxiety, often associated with mild symptoms of depression, that may arise during the climacterium. Furthermore, these results were obtained with a high safety margin, since the few side effects recorded were mild and transient and the laboratory results were normal as well as the physical examination findings.

Use of pivagabine in the management of hospitalization distress in children

A double-blind, placebo-controlled study was performed in order to evaluate the efficacy of pivagabine (4-[(2,2-dimethyl-1-oxopropyl)amino]butanoic acid, CAS 69542-93-4, Tonerg) on "distress" in children hospitalized for acute disorders. Ninety children (43 boys and 47 girls) aged between 2 and 13 years were randomly distributed into two groups of equal size. The first group was treated with 450-900 mg/d of pivagabine by oral route, whereas the second group was given identical quantities of placebo. Treatment was continued for 21 days, with a medical examination after 7 days and another at its termination. Diurnal behaviour, motor activity, attention, sleep disturbances (insomnia) and sleep characteristics and behaviour upon awakening were assessed during treatment by means of a semiquantitative rating scale. Pivagabine induced significantly greater improvement in all the items listed above as compared to the control group. In many cases complete remission of the symptoms of "distress" was recorded. The results obtained therefore confirm the hypothesis that pivagabine acts by intervening on the biochemical mechanisms that regulate the CNS adjustment response to stress. It is likely that the intervention consists in the inhibition of the release of hypothalamic corticotropin releasing factor.

Vigabatrin as add-on therapy in children and adolescents with refractory epilepsy: an open trial

Seventy-seven children and adolescents with drug-resistant epilepsies received vigabatrin as add-on therapy for a median of 18 months (range 4-36 months) at a dose of 50 mg/kg/day divided in two doses; patients with spasms were given a maximum dose of 100 mg/kg/day. In 23 patients (29.9%), seizure frequency decreased by 50-100% and in 12 patients (15.6%) by 25-50%. The number of seizures remained unchanged in 34 patients (44.1%) and increased in seven (9.1%). Vigabatrin was most effective in cryptogenic and symptomatic partial seizures (39% and 43%, respectively), and in infantile spasms (25%). Adverse events occurred in 20 patients (26%), though they were generally mild and transient, suggesting that vigabatrin is well tolerated.

[Carbamazepine and vigabatrin in epileptic pregnant woman and side effects in the newborn infant]

BACKGROUND

Carbamazepine (Tegretol) is frequently prescribed to pregnant epileptic women. Various congenital malformations constitute the most described side-effects in their newborns.

CASE REPORTS

Case 1. Esteban was born by caesarean section at 39 weeks of gestation, weighing 3,860 g. His Apgar score was 8, 9, 10 at 1, 3 and 5 minutes. His mother was given phenobarbital until 1.5 months of pregnancy then carbamazepine 400 mg LP x 2/day, raised to 600 mg LP x 2/day at the 25th week of gestation because of epileptic crisis. The newborn was transferred at day 4 for drowsiness, mild jaundice, persistent vomiting and bouts of hypotonia/hypertonia, tremors and hyperexcitability. His plasma Tegretol level was 5.9 micrograms/mL and severe hypocalcemia (1.35 mmol/L) was noted. Hypocalcemia disappeared within 48 hours and gastric and neurologic troubles by day 6. The patient left the hospital at day 14. Case 2. Matheo, Esteban's brother, was born by caesarean section after 39 weeks of gestation, weighing 3,210 g. His Apgar score was 9, 10, 10 at first, third and fifth minutes. The mother's anti-epieptic treatment associated carbamazepine LP 400 mg x 3/day and vigabatrin four tablets of 500 mg/d until the 6th month of pregnancy and five tablets by day thereafter. The newborn presented vomiting from the first feeding; tremors were noted on day 2. His plasma Tegretol level was 5.7 micrograms/mL (N = 4-8 micrograms/mL) and the baby was transferred. Upon arrival, persistent vomiting and succession of hypotonia/hypertonia with intermittent opisthotonos were noted. Blood and urine tests showed: low calcemia (2.19 mmol/L), negative Brand reaction and DNPH test, normal urinary and blood amino acid chromatography. The course was spontaneously favourable and the child went home at day 11.

CONCLUSION

Newborns of epileptic mothers treated with carbamazepine and/or vigabatrin during pregnancy should be placed under clinical observation during their first postnatal week. Calcemia monitoring is suggested for infants whose mothers were not supplemented with vitamin D during pregnancy. With a follow up of respectively 26 and 7 months, both brothers have normal milestones, confirming the transitory and benign character of reported side-effects.

Lack of association between vigabatrin and impaired cognition

Of 14 patients with a history of partial epilepsy who received vigabatrin 2 g daily for 6 months, eight were newly diagnosed and received vigabatrin as monotherapy, while the remaining six received vigabatrin in addition to pre-existing treatment with phenobarbitone. Neurophysiological and neuropsychological evaluations, done before and after the therapeutic period, included the Luria-Nebraska neuropsychological battery (LNNB), electroencephalograms (EEGs) and evoked potentials. The results for each item of the test battery at baseline were compared with those after 6 months' treatment. There were no statistically significant differences on the functional scales of the LNNB, the EEG or the evoked potentials. There was a significant improvement (P = 0.01) in the LNNB topographic scales for the right frontal lobe and the motor-sensory area following treatment. These results indicate that vigabatrin has no detrimental effects on cognitive function and may improve function.

The effects of clonazepam and vigabatrin in hyperekplexia

Hyperekplexia is an autosomal dominant disorder caused by a point mutation in the alpha1 subunit of the glycine receptor, characterized by excessive startle responses followed by temporary generalized stiffness. Clonazepam, effective in open case studies, potentiates, through unknown mechanisms, the neurotransmitter gamma-aminobutyric acid (GABA). Vigabatrin increases GABA by inhibition of the GABA catabolic enzyme GABA-transaminase. Effects of clonazepam (1 mg for 1 day) and vigabatrin (1000 mg per day for 5 days) were investigated in a double-blind placebo-controlled cross-over study in 4 patients with hyperekplexia. The pharmacodynamic parameters were startle reflexes, studied 3 times during the day. At each time, 2 trains of 10 auditive stimuli (113 dB) were given at intervals of 10 and 60 s. Startle movements were quantified with summed areas of EMG-bursts of the orbicularis oculi, sternocleidomastoid, biceps and thenar muscles. The degrees of stiffness and drowsiness were quantified with visual analogue scores (VAS) 10 times during the day, by both the patient and the observer. Clonazepam, but not vigabatrin, reduced startle activity significantly in both paradigms. The degree of stiffness and drowsiness was not significantly influenced by either drug.

Multicentre clinical evaluation of vigabatrin (Sabril) in mild to moderate partial epilepsies. French Neurologists Sabril Study Group

Vigabatrin (VGB) has been shown through several studies to be safe and effective as add-on therapy, particularly for the treatment of partial seizures in patients with severe epilepsies followed for years in hospital-based clinics. We now report additional clinical experience with VGB arising from an open trial of add-on VGB therapy in patients with relatively few seizures followed by qualified neurologists in private practice (the French Neurologists Sabril Study Group). VGB was administered to 397 patients aged 12-74 years (mean age = 37.5 +/- 13.8 years) who presented with no more than seven partial seizures of any type per month during a 3-month baseline period (mean number of seizures = 3.7 +/- 1.9/month). Simple partial seizures were reported in 121 (30.5%) patients, complex partial seizures in 282 (71.0%) and seizures with secondary generalization were reported in 111 (28.0%). The mean number of associated antiepileptic drugs (AEDs) was 1.9 +/- 0.9 and the mean dose of VGB was 2.21 +/- 0.64 g/day. Following introduction of VGB, 53 (13.4%) became seizure-free and remained so during the whole trial. During the fourth month of treatment, 158 patients (39.8%) had no seizures at all and a further 69 (17.4%) had their seizure frequency reduced by more than 50%. Secondary generalization was controlled during the whole period of treatment in 55 out of 97 patients (56.7%), 17 of which remained free of all types of partial seizures. VGB showed a good tolerability profile; adverse experiences more frequently reported were drowsiness and sleep disturbances. No action was necessary in the great majority of cases; the dose was reduced in 26 (6.5%) and VGB was discontinued in 32 (8%) patients. These data provide additional evidence that VGB can be used safely early on to treat patients with mild to moderate partial epilepsies. Secondary generalization was controlled in the majority of patients. Factors associated with the everyday clinical use of VGB, that resulted from a series of organized meetings with the investigators, are discussed.

Obstructive sleep apnoea following rapid weight gain secondary to treatment with vigabatrin (Sabril)

A case of a patient with medically intractable epilepsy, who developed obstructive sleep apnoea (OSA), and an increase in seizure frequency, as a consequence of weight gain following treatment with vigabatrin is described. The relationship between exacerbation of epilepsy and sleep disruption secondary to OSA is discussed. Recommendations regarding the choice of anticonvulsants in patients at risk of developing OSA are made.

A quantitative study of daytime sleepiness induced by carbamazepine and add-on vigabatrin in epileptic patients

INTRODUCTION

The clinical relevance of daytime sleepiness associated with carbamazepine (CBZ) and vigabatrin (VGB) was objectively assessed by the multiple sleep latency test (MSLT) and nocturnal sleep recordings.

MATERIAL AND METHODS

Twenty-six patients with partial epilepsy and mean monthly seizure frequency of 4, aged 18 to 48 years, receiving chronic monotherapy with CBZ and subsequent VGB addition for 2 months (14 patients), were compared with a group of healthy subjects. Subjective daytime sleepiness was complained by 13 patients on CBZ monotherapy and 9 patients during VGB add-on treatment.

RESULTS

No differences in nocturnal sleep parameters, but significantly shorter daytime sleep latencies at the MSLT, were detected in CBZ-treated patients as compared with healthy controls. Addition of VGB therapy did not further enhance objective daytime sleepiness.

CONCLUSION

Some sleepiness occurs in chronically CBZ-treated epileptic patients, which can be objectively measured by the MSLT, but it is not aggravated by add-on VGB.