Vigabatrin Research Articles

Synthetic pharmaceutical grade cannabidiol for treatment of refractory infantile spasms: A multicenter phase-2 study

PurposeLimited data suggest that cannabidiol (CBD) may be effective for treatment of refractory infantile spasms (IS). This study was designed to more rigorously evaluate the efficacy and safety of synthetic CBD in the treatment of IS. MethodsChildren six to 36 months of age with IS that failed treatment with both adrenocorticotropic hormone (ACTH) and vigabatrin (VGB) were eligible for enrollment. Children receiving clobazam were excluded. After baseline overnight video-electroencephalography (vEEG) to confirm diagnosis and ascertain hypsarrhythmia, patients were treated with synthetic CBD oral solution (20 mg/kg/day). Overnight video-EEG was repeated after 14 days, and both baseline and repeat video-EEGs were completely de-identified and reviewed in a pairwise fashion by an independent, blinded pediatric electroencephalographer. The primary efficacy endpoint was freedom from spasms and hypsarrhythmia on day 14. ResultsNine patients were enrolled, comprising an older (median age = 23 months) cohort with long-standing IS (median duration = 13 months) and numerous prior treatment failures (median = 6). One patient responded to therapy and eight patients exhibited neither clinical nor electrographic response. ConclusionsThe immediate but temporary response in a single patient suggests that CBD oral solution is not particularly effective in highly refractory cases, but may, nevertheless, be effective in younger patients with shorter durations of IS. Further study, examining both short- and long-term outcomes, is warranted to further evaluate the efficacy and safety of CBD oral solution in the treatment of IS.

Metabolomic analyses of vigabatrin (VGB)-treated mice: GABA-transaminase inhibition significantly alters amino acid profiles in murine neural and non-neural tissues

The anticonvulsant vigabatrin (VGB; SabrilR) irreversibly inhibits GABA transaminase to increase neural GABA, yet its mechanism of retinal toxicity remains unclear. VGB is suggested to alter several amino acids, including homocarnosine, β-alanine, ornithine, glycine, taurine, and 2-aminoadipic acid (AADA), the latter a homologue of glutamic acid. Here, we evaluate the effect of VGB on amino acid concentrations in mice, employing a continuous VGB infusion (subcutaneously implanted osmotic minipumps), dose-escalation paradigm (35–140 mg/kg/d, 12 days), and amino acid quantitation in eye, visual and prefrontal cortex, total brain, liver and plasma. We hypothesized that continuous VGB dosing would reveal numerous hitherto undescribed amino acid disturbances. Consistent amino acid elevations across tissues included GABA, β-alanine, carnosine, ornithine and AADA, as well as neuroactive aspartic and glutamic acids, serine and glycine. Maximal increase of AADA in eye occurred at 35 mg/kg/d (41 ± 2 nmol/g (n = 21, vehicle) to 60 ± 8.5 (n = 8)), and at 70 mg/kg/d for brain (97 ± 6 (n = 21) to 145 ± 6 (n = 6)), visual cortex (128 ± 6 to 215 ± 19) and prefrontal cortex (124 ± 11 to 200 ± 13; mean ± SEM; p < 0.05), the first demonstration of tissue AADA accumulation with VGB in mammal. VGB effects on basic amino acids, including guanidino-species, suggested the capacity of VGB to alter urea cycle function and nitrogen disposal. The known toxicity of AADA in retinal glial cells highlights new avenues for assessing VGB retinal toxicity and other off-target effects.

Efficacy and tolerability of the ketogenic diet versus high‐dose adrenocorticotropic hormone for infantile spasms: A single‐center parallel‐cohort randomized controlled trial

To compare the efficacy and safety of the ketogenic diet (KD) with standard adrenocorticotropic hormone (ACTH) treatment in infants with West syndrome. In this parallel-cohort (PC) randomized controlled trial (RCT), infants were randomly allocated to KD or high-dose ACTH. Those who could not be randomized were followed in a PC. Primary end point was electroclinical remission at day 28. Secondary end points were time to electroclinical remission, relapse after initial response, seizure freedom at last follow-up, adverse effects, and developmental progress. One hundred one infants were included: 32 in the RCT (16 KD; 16 ACTH) and 69 in the PC (37 KD; 32 ACTH). Electroclinical remission at day 28 was similar between KD and ACTH (RCT: 62% vs 69%; PC: 41% vs 38%; combined cohort: 47% vs 48%; KD vs ACTH, respectively). In the combined cohort, time to electroclinical remission was similar between both treatments (14 days for KD, 16 days for ACTH). However, relapse rates were 16% (KD) and 43% (ACTH, P = 0.09), and seizure freedom at last follow-up was 40% (KD) and 27% (ACTH, P = 0.18). Adverse effects needing acute medical intervention occurred more often with ACTH (30% with KD, 94% with ACTH, P < 0.001). Age-appropriate psychomotor development and adaptive behavior were similar. Without prior vigabatrin (VGB) treatment, remission at day 28 was 47% (KD) and 80% (ACTH, P = 0.02); relapse rates were 29% (KD) and 56% (ACTH, P = 0.13). Consequently, seizure freedom at last follow-up was similar. In infants with prior VGB, seizure freedom at last follow-up was 48% (KD) and 21% (ACTH, P = 0.05). The study is underpowered; therefore, its results should be interpreted with caution. KD is as effective as ACTH in the long term but is better tolerated. Without prior VGB treatment, ACTH remains the first choice to achieve short-term remission. However, with prior VGB, KD was at least as effective as ACTH in the short term and was associated with lower relapse rates in the long term; therefore, it represents an appropriate second-line treatment after VGB.

Analysis of the efficacy of antiepileptic drugs in the treatment of infantile spasms and focal epilepsy associated with tuberous sclerosis complex

Background. Adequate selection of the 1st antiepileptic drug (AED) is an obligatory condition for the successful treatment of epilepsy. It is well known that the first drug in the treatment of infantile spasms (IS) in tuberous sclerosis complex (TSC) is vigabatrin (VGB). With regard to focal seizures (FS) in TSC, there are certain differences: some authors insist on VGB (P. Curatolo, 2012), others as the first choice drugs are mentioning carbamazepine and valproate (A. Saxena, 2015). Data in general on the possible effectiveness of medical treatment of epilepsy in TSC, and the effectiveness of different AEDs are also contradictory.Objective: to make a comparative evaluation of the efficacy of various AEDs in the treatment of epilepsy in patients with TC.Materials and methods. Retrospective analysis of medical records of patients hospitalized with epilepsy and TSC in the Department of Epileptology and Psychoneurology, Research and Clinical Institute for Pediatrics named after Yu.E Vel’tishev of N.I. Pirogov Russian National Research Medical University, Ministry of Health of Russia, for the last 2 years was completed. Efficacy analysis was conducted in 134 patients (91 (67.9 %) with FS and 43 (32.1 %) with IS). Efficacy was estimated as the remission of epileptic seizures during 6 months. The percentage of patients with remission was also evaluated (seizures were stopped for 1 year or more) and percentage of patients with a decrease in the number of seizures. The results of the first monotherapy and the subsequent administration of two and three AEDs were analyzed.Results. Low efficiency of AEDs in starting monotherapy was noted – the remission of seizures within 6 months on any AED was only 27.5 % (25 from 91) with FS, with IS – 13.9 % (6 from 43). Remission on any 1st AED was observed only in 13.2 % (12 from 91) and 6.9 % (3 from 43), respectively. The effectiveness of individual AED is low, especially in achieving stable remission. So, valproate caused remission of FS in 14 (22.2 %) from 63, but in the future remission was stable only in 11 (17.5 %) from 63. VGB as the first monotherapy proved to be effective in 5 from 6 patients with FS and in 4 from 6 patients with IS. The introduction of the 2nd drug added another 13.3 % and 38.6 % of patients with remission of seizures, the 3rd AED – 7.3 % and 7.7 % in FS and IS, respectively. Most often, an effective drug in additional therapy was VGB. The efficiency of VGB was reduced if it was used not as the first, but as the second and third AED. The percentage of unsuccessful treatment (including combined therapy) is estimated as 51.5 % and 47.8 % of patients with FS and IS, respectively.Conclusion. Epilepsy associated with TSC is less sensitive to AEDs and gives a smaller percentage of remissions. Perhaps in our country this is due to the difficulties of prescription of VGB as a starting therapy for epilepsy in the patients with tuberous sclerosis complex.

Animal models of infantile spasms

Infantile spasms(IS), an age-dependent epileptic encephalopathy seen in infancy, is characterized by unique electro-clinical features and pharmacological reactions.Most conventional antiepileptic drugs are ineffective for IS.Hormonal treatment(including adrenocorticotropic hormone ACTH, and oral steroids)and vigabatrin(VGB)now widely used as first-line treatments for IS, have certain effects on IS, but the effect of these two options on long-term outcomes has not been established.The etiology of IS is variable.It is unclear that how a wide variety of conditions result a common phenotype.Ideal animal models can help to understand pathogenesis of disease and explore new therapies to improve the ultimate outcome.This review summarizes the research status of animal models of IS. Key words: Infantile spasm; Animal model; Pathogenesis; New drug therapy

Clinical analysis of 51 children with seizure secondary to tuberous sclerosis

Objective To analyze the clinical characteristics and treatment of children with tuberous sclerosis (TSC) complicated with epilepsy, so as to improve the level of diagnosis and treatment and improve the prognosis of children with TSC. Methods The clinical data of TSC children complicated with epilepsy diagnosed and followed up in Xiangya Hospital of Central South University were collected and analyzed retrospectively. Results Of the 51 children, 49 (96.1%) had their first visit because of epileptic seizures. Their electroencephalogram (EEG) showed epileptiform discharges during the epileptic period. The therapeutic effect of vigabatrin on TSC patients with spastic seizures was significantly different from that of antiepileptic drugs alone or in combination. Conclusions Epileptic seizure is the most common reason for first visit and seizure control will affect the prognosis of children to a large extent. Vigabatrin had remarkable effect on TSC patients with spasm seizure, and rapamycin has broad prospects in the treatment of children with TSC. Key words: Tuberous sclerosis/CO; Epilepsy/CO; Child

S174. Use of vigabatrin in super refractory status epilepticus

Animal studies have shown very high glutamate levels in status epilepticus (SE). Vigabatrin (VGB) irreversibly inhibits γ-amino butyric acid-transaminase (GABA-T), increases GABA, and may indirectly lower glutamate levels. Theoretically, this effect could reduce excitatory states and help control SE. Our aims were to report the usefulness/efficacy of VGB in super refractory status epilepticus (SRSE) as an adjunct to general anesthesia and other anti-seizure medications (ASM). After IRB approval, we reviewed charts of patients admitted to the Neuro ICU for management of SRSE between the years of 2014 and 2017 at Ochsner Clinic Foundation. This is a single center, retrospective analysis of cases of SRSE in which VGB was used as an adjunct treatment. SRSE resolution was defined as successful stopping of anesthetic agents without return epileptic activity on electroencephalogram (EEG). We identified 54 patients (32 females, 22 males) diagnosed with SRSE treated with VGB. Ages ranged from 3 months to 89 yrs (mean 54.24 yrs). Etiologies included cerebrovascular accident (14), cerebral anoxia due to cardiac arrest (10), genetic/developmental (7), CNS/ Non-CNS infection (5), autoimmune disease (4), toxic (3), ASM non-compliance (2), tumor (1), metabolic (1) and unknown (7). VGB was used as the last ASM in 44/54 (82%) pts followed by Clobazam (6), perampanel (3) and valproic acid (1). ASM used prior to the starting VGB were levetiracetum (54), lacosamide (54), clobazam (19), valproic acid (23), lorazepam (19), topiramate (7), lamotrigine (3), perampanel (6), phenytoin (3), oxcarbazepine (2), clonazepam (2), and midazolam (10). Propofol and ketamine (Pro:Ket) were used alone in 18/54 and 3/54 patients, respectively and in combination in 33 pt. The time from diagnosis of NCSE to VGB initiation ranged from 0.3 to 47.3 days (average 7.96 days, median 5.65 days). Maximal dose of VGB ranged from 200 to 3000 mg per day. Ket:Pro controlled 29 pts but in 21 pts resolution was realized only after VGB was started. Control and resolution occurred in 25 pts after VGB was initiated. SRSE resolved with the addition of VGB in 38/54 (70%) pts. Mortality was in 19 pts primarily from withdrawal of care (n = 15) despite resolution of SRSE in 5. Our results suggest that vigabatrin has beneficial role in the management of patients with super-refractory status epilepticus. Resolution of SE was achieved in 70% of patients on VGB.

Effects of vigabatrin, carbamazepine or its combination on the pituitarygonadal axis in male Wistar rats

Objectives: Epilepsy is the most common non-infectious neurologic disease in developing African countries following stroke and Alzheimer's disease. Most conventional antiepileptic drugs, due to their centrally acting potentials have been implicated in the deregulation of reproductive hormones. This study assessed the effect of the single and combined administration of vigabatrin (VIG) and carbamazepine (CBZ) on the pituitary-gonadal axis of male Wistar rats.Methods: Fifty male Wistar rats were randomly divided into 5 groups (n=10). The animals were administered with distilled water (0.1 ml/kg/day), VIG (200 mg/kg/day), CBZ (200 mg/kg/day), VIGCBZ combination (100 mg/kg/day each) and VIG-CBZ combination (200 mg/kg/day each) for 8 weeks. Twenty-four hours after the last dose, 5 rats from each group were sacrificed, while the remaining 5 eventually sacrificed after another 8 week of drug withdrawal. The level of luteinizing hormone, follicle stimulating hormone and testosterone were determined from the serum. The weight of the reproductive organs and sperm indices were assayed, while the testicular tissue were examined for signs of histological alteration.Results: The results showed significant decrease in the levels of luteinizing hormone, follicle stimulating hormone, testosterone and sperm physiological indices. Morphological alteration was noticed in the testes of all the treated rats. However, there was restoration of these parameters sequelae to 8 weeks cessation of treatment.Conclusion: Single and combined administration of VIG and CBZ resulted into pituitary-gonadal axis hormonal deregulation and alterations in the sperm profile which were however reversible upon cessation of treatment.Keywords: epilepsy, vigabatrin, carbamazepine, sperm, testosterone

West Syndrome: A Review and Guide for Paediatricians.

West syndrome (WS), also known as infantile spasms, occurs in infancy with a peak between 4 and 7months. Spasms, neurodevelopmental regression and hypsarrhythmia on electroencephalogram (EEG) basically define WS. The International League Against Epilepsy commission classifies the aetiologies of WS into genetic, structural, metabolic and unknown. Early diagnosis and a shorter lag time to treatment are essential for the overall outcome of WS patients. These goals are feasible with the addition of brain magnetic resonance imaging (MRI) and genetic and metabolic testing. The present work analysed the medical literature on WS and reports the principal therapeutic protocols of its management. Adrenocorticotropic hormone (ACTH), vigabatrin (VGB) and corticosteroids are the first-line treatments for WS. There is no unique therapeutic protocol for ACTH, but most of the evidence suggests that low doses are as effective as high doses for short-term treatment, which is generally 2weeks followed by dose tapering. VGB is generally administered at doses from 50 to 150mg/kg/day, but its related retinal toxicity, which occurs in 21-34% of infants, is most frequently observed when treatment periods last longer than 6months. Among corticosteroids, a treatment of 14days of oral prednisolone (40-60mg/day) has been considered effective and well tolerated. Considering that an early diagnosis and a shorter lag time to treatment are essential for successful outcomes in these patients, further studies on efficacy of the different therapeutic approaches with evaluation of final outcome after cessation of therapy are needed.

Determination of the R(-) and S(+)-enantiomers of vigabatrin in human plasma by ultra-high-performance liquid chromatography and tandem mass-spectrometry.

An analytical method was developed for the quantification in plasma of the R and S enantiomers of vigabatrin (VGB), a drug used for the treatment of some refractory pediatric epileptic syndromes. After adding 50μL of the internal standard, which consisted of a 15mg/L solution of deuterated racemic VGB, and 100μL of water to 100μL of plasma samples, a protein precipitation was performed by adding 600μL of methanol. The supernatant was evaporated to dryness under a stream of nitrogen and the dry residue was reconstituted with 500μL of water. Then, 100μL of 0.01M o-phthaldialdehyde and 0.01M N-acetyl-l-cysteine in borate buffer (0.1M, pH=9.5) were added for pre-column derivatization of the enantiomers as diastereomeric isoindoles. One microliter of the resulting mixture was injected in the chromatographic system. The chromatographic separation was performed in gradient elution mode at a flow rate of 400μL/min using a phenomenex EVO C-18 column with a mobile phase composed of 5mM ammonium acetate and a methanol:acetonitrile (63:37v/v) mixture. Detection was performed by mass spectrometry in selected reaction monitoring mode using heated electrospray ionization in positive mode as the ion source. Intra- and inter-day precision and accuracy were lower than 15% over the calibration range (0.2-50mg/L for each enantiomer) and the method was successfully used to assess plasma concentrations of VGB in epileptic children.

Efficacy and safety of antiepileptic drugs for refractory partial-onset epilepsy: a network meta-analysis.

The optimal combination of antiepileptic drugs (AEDs) for the treatment of refractory partial-onset epilepsy is a perpetual point of debate. While several network meta-analyses (NMAs) have been published, conclusions remain controversial, especially since newer AEDs have been introduced. In our review, we included the newer AEDs to evaluate the comparative efficacy and safety of AEDs for the treatment of refractory partial-onset epilepsy. We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials (Cochrane Library 2017, Issue 1) from their inception to February 18, 2017. The risk of bias in the included randomized controlled trials (RCTs) was evaluated according to the Cochrane Collaboration's risk of bias tool. An NMA was performed with a Bayesian random-effects model, and we used the surface under the cumulative ranking curve to detect the optimal AEDs. Seventy-six RCTs with 17 AEDs and 20,711 patients were included in the NMAs, which showed that Brivaracetam (BRV), Levetiracetam (LEV), Oxcarbazepine (OXC), Topiramate, Vigabatrin (VGB), and Valproate (VPA) had a greater likelihood of allowing patients to achieve seizure freedom. We also found that LEV was associated with a lower withdrawal rate due to adverse effects than Lacosamide, Eslicarbazepine acetate, OXC, Pregabalin, and Retigabine. LEV, VGB, VPA, and BRV emerged as the agents with the best combination of properties when considering the efficacy and safety outcomes based on the full double-blind treatment period. However, it is critical to perform RCTs and to obtain prospective data from representative cohort studies.

VIGABATRIN TOXICITY IN INFANCY IS ASSOCIATED WITH RETINAL DEFECT IN ADOLESCENCE: A Prospective Observational Study.

The purpose was to determine whether vigabatrin (VGB) (Sabril)-attributed retinal toxicity defined by electroretinogram in early childhood is associated with visual system defect in adolescents after discontinuation of VGB. This prospective cross-sectional study included 24 children previously treated with VGB and monitored in early childhood by electroretinogram for VGB-attributed retinal defects. Ten had been diagnosed with VGB-attributed retinal defect (Group I) and 14 had no VGB-attributed retinal defect (Group II). Outcome measures were extent of monocular visual fields using Goldmann kinetic perimetry and RNFL thickness at the optic nerve head, using optical coherence tomography. Of those able to complete testing (6 eyes Group I and 16 eyes Group II), Goldmann results revealed results of visual field loss in Group I and not in Group II. The optical coherence tomography results demonstrated attenuation of the RNFL in all 6 eyes of Group I participants and in only 1 eye of 10 Group II participants. Optical coherence tomography data were nonoverlapping between Group 1 and Group II eyes. The VGB-attributed retinal toxicity identified by means of electroretinogram in infancy was associated with visual field loss and RNFL attenuation of the retinal nerve when tested in adolescence.

Case Report: Everolimus in a 10-Week-Old Patient with Tuberous Sclerosis and Refractory Epilepsy

Background/Purpose: The patient manifested with refractory focal, dyscognitive, and secondary generalized tonic clonic seizures at the age of 10 weeks, with a frequency of 20 to 30 seizures per day. Diagnosis of tuberous sclerosis (TSC) was confirmed by MRI. Initial therapy with first vigabatrin (VGB), then phenobarbitone (PHE), and levetiracetam (LEV) did not reduce the high seizure frequency. High-dosage steroid therapy was not effective. Ketogenic diet was tolerated well but did not influence seizure frequency after 4 weeks with adequate ketosis. Cessation of therapy with LEV did not influence the seizure frequency.

Increasing GABA reverses age-related alterations in excitatory receptive fields and intensity coding of auditory midbrain neurons in aged mice

A key feature of age-related hearing loss is a reduction in the expression of inhibitory neurotransmitters in the central auditory system. This loss is partially responsible for changes in central auditory processing, as inhibitory receptive fields play a critical role in shaping neural responses to sound stimuli. Vigabatrin (VGB), an antiepileptic agent that irreversibly inhibits γ-amino butyric acid (GABA) transaminase, leads to increased availability of GABA throughout the brain. This study used multi-channel electrophysiology measurements to assess the excitatory frequency response areas in old CBA mice to which VGB had been administered. We found a significant post-VGB reduction in the proportion of V-type shapes, and an increase in primary-like excitatory frequency response areas. There was also a significant increase in the mean maximum driven spike rates across the tonotopic frequency range of all treated animals, consistent with observations that GABA buildup within the central auditory system increases spike counts of neural receptive fields. This increased spiking is also seen in the rate-level functions and seems to explain the improved low-frequency thresholds.

Risk of vigabatrin-associated brain abnormalities on MRI in the treatment of infantile spasms is dose-dependent.

Although the link between vigabatrin (VGB) and retinotoxicity is well known, little attention has been focused on the risk of VGB-associated brain abnormalities on magnetic resonance imaging (MRI) (VABAM), namely reversible-and largely asymptomatic-signal changes in the thalami, basal ganglia, brainstem tegmentum, and cerebellar nuclei. Using a large infantile spasms cohort, we set out to identify predictors of these phenomena. Children with infantile spasms were retrospectively identified. Brain MRI reports were serially reviewed without knowledge of VGB exposure. Upon VABAM discovery, records were systematically reviewed to ascertain presence of symptoms attributable to VGB. Separately, progress notes were sequentially reviewed to identify and quantify VGB exposure. We identified 507 brain MRI studies among 257 patients with infantile spasms. VGB treatment was documented in 143 children, with detailed exposure data available for 104, of whom 45 had at least one MRI study during VGB treatment. Among the limited subset of asymptomatic children who underwent MRI (n = 40), 6 exhibited VABAM. Risk of asymptomatic VABAM was dose-dependent, as peak (but not cumulative) VGB dosage was strongly associated with asymptomatic VABAM (p = 0.0028). In an exploratory analysis, we encountered 4 children with symptomatic VABAM among 104 patients with detailed VGB exposure data. Risk of symptomatic VABAM was seemingly dose-independent, and potentially associated with concomitant hormonal therapy (i.e., prednisolone and adrenocorticotropic hormone [ACTH]) (p = 0.039). We have demonstrated dose-dependent risk of asymptomatic VABAM and uncovered a possible association between symptomatic VABAM and concomitant hormonal therapy. Caution should be exercised in the use of high VGB dosage (i.e., >175 mg/kg/day), and further study is warranted to confirm the potential impact of hormonal therapy.

Neurobehavioral effects of vigabatrin and its ability to induce DNA damage in brain cells after acute treatment in rats.

Vigabatrin (VGB) is a drug indicated mostly for the treatment of spasms in childhood and West's syndrome patients. This drug inhibits irreversibly the enzyme GABA-transaminase (GABA-T), increasing GABA concentrations and enhancing GABAergic neurotransmission in the brain, which is known to induce behavioral changes. The aims of this study were to evaluate the effects of VGB in the short-term memory (STM), long-term memory (LTM), motivation, locomotion, and exploratory behavior tests and to detect deleterious or protective effects on DNA in target tissues of the drug. Male Wistar rats were treated with a single dose of VGB (100, 250, or 500mg/kg) or saline solution before the inhibitory avoidance and open-field tasks. DNA damage was evaluated using the alkaline comet assay in peripheral blood, cerebral cortex, and hippocampus after behavioral testing. There was no significant difference in the inhibitory avoidance task between the treated groups and the saline group. In all tested doses, VGB reduced the number of rearings in the open-field task. Besides, VGB 500mg/kg affected locomotion, though it was not able to induce any DNA damage. VGB did not affect STM and LTM, but the drug impaired the exploration and locomotion likely associated with its sedative effect. In addition, no DNA damage in cortex and hippocampus was detected after behavioral testing, when brain GABA levels are already increased.

Imbalance between Glutamate and GABA in Fmr1 Knockout Astrocytes Influences Neuronal Development.

Fragile X syndrome (FXS) is a form of inherited mental retardation that results from the absence of the fragile X mental retardation protein (FMRP), the product of the Fmr1 gene. Numerous studies have shown that FMRP expression in astrocytes is important in the development of FXS. Although astrocytes affect neuronal dendrite development in Fmr1 knockout (KO) mice, the factors released by astrocytes are still unclear. We cultured wild type (WT) cortical neurons in astrocyte-conditioned medium (ACM) from WT or Fmr1 KO mice. Immunocytochemistry and Western blotting were performed to detect the dendritic growth of both WT and KO neurons. We determined glutamate and γ-aminobutyric acid (GABA) levels using high-performance liquid chromatography (HPLC). The total neuronal dendritic length was reduced when cultured in the Fmr1 KO ACM. This neurotoxicity was triggered by an imbalanced release of glutamate and GABA from Fmr1 KO astrocytes. We found increased glutaminase and GABA transaminase (GABA-T) expression and decreased monoamine oxidase B expression in Fmr1 KO astrocytes. The elevated levels of glutamate contributed to oxidative stress in the cultured neurons. Vigabatrin (VGB), a GABA-T inhibitor, reversed the changes caused by glutamate and GABA release in Fmr1 KO astrocytes and the abnormal behaviors in Fmr1 KO mice. Our results indicate that the imbalance in the astrocytic glutamate and GABA release may be involved in the neuropathology and the underlying symptoms of FXS, and provides a therapeutic target for treatment.

The Impact of Anti-Epileptic Drugs on Growth and Bone Metabolism.

Epilepsy is a common neurological disorder worldwide and anti-epileptic drugs (AEDs) are always the first choice for treatment. However, more than 50% of patients with epilepsy who take AEDs have reported bone abnormalities. Cytochrome P450 (CYP450) isoenzymes are induced by AEDs, especially the classical AEDs, such as benzodiazepines (BZDs), carbamazepine (CBZ), phenytoin (PT), phenobarbital (PB), and valproic acid (VPA). The induction of CYP450 isoenzymes may cause vitamin D deficiency, hypocalcemia, increased fracture risks, and altered bone turnover, leading to impaired bone mineral density (BMD). Newer AEDs, such as levetiracetam (LEV), oxcarbazepine (OXC), lamotrigine (LTG), topiramate (TPM), gabapentin (GP), and vigabatrin (VB) have broader spectra, and are safer and better tolerated than the classical AEDs. The effects of AEDs on bone health are controversial. This review focuses on the impact of AEDs on growth and bone metabolism and emphasizes the need for caution and timely withdrawal of these medications to avoid serious disabilities.

Genotoxic and mutagenic effects of vigabatrin, a γ-aminobutyric acid transaminase inhibitor, in Wistar rats submitted to rotarod task.

Vigabatrin (VGB) is an antiepileptic drug thatincreases brain γ-aminobutyric acid (GABA) levels through irreversible inhibition of GABA transaminase. The aim of this study was to evaluate neurotoxicological effects of VGB measuring motor activity and genotoxic and mutagenic effects after a single and repeated administration. Male Wistar rats received saline, VGB 50, 100, or 250 mg/kg by gavage for acute and subchronic (14 days) treatments and evaluated in the rotarod task. Genotoxicity was evaluated using the alkaline version of the comet assay in samples of blood, liver, hippocampus, and brain cortex after both treatments. Mutagenicity was evaluated using the micronucleus test in bone marrow of the same animals that received subchronic treatment. The groups treated with VGB showed similar performance in rotarod compared with the saline group. Regarding the acute treatment, it was observed that only higher VGB doses induced DNA damage in blood and hippocampus. After the subchronic treatment, VGB did not show genotoxic or mutagenic effects. In brief, VGB did not impair motor activities in rats after acute and subchronic treatments. It showed a repairable genotoxic potential in the central nervous system since genotoxicity was observed in the acute treatment group.

A lack of clinically apparent vision loss among patients treated with vigabatrin with infantile spasms: The UCLA experience.

Vigabatrin (VGB) is one of two FDA-approved medications for treatment of infantile spasms. Despite demonstrated efficacy, its use has been curtailed by reports indicating a substantial risk of VGB-associated visual field loss (VAVFL). As these reports have conflicted with our clinical observations in routine practice, we systematically reviewed the experiences of patients treated with VGB at UCLA to estimate the prevalence of clinically apparent VAVFL. Patients with video-EEG-confirmed infantile spasms evaluated at our center between February 2007 and February 2014 were retrospectively identified. Among patients with VGB exposure, we documented relevant clinical factors and determined the duration of therapy, peak dosage, and cumulative dosage. Based on a review of serial neurologic and ophthalmologic reports and aided by electroretinography (ERG) assessments when available, we ascertained whether each patient had evidence of clinically apparent vision impairment (i.e., recognized by a neurologist or ophthalmologist during any follow-up visit) and whether or not the vision loss was attributed to VGB exposure (i.e., evidence of bilateral, symmetric, and peripheral visual field loss), either by the treating physician or on retrospective review by the study team. During the study period, 257 patients with video-EEG-confirmed infantile spasms were identified. One hundred and forty-three (56%) patients received VGB. Although visual loss of any cause was common among patients with (31%) and without (32%) VGB exposure, there were no cases in which visual field defects were plausibly linked to VGB. We estimate that the risk of clinically significant VAVFL does not exceed 3.2% (95% CI upper bound). Vision loss was never characterized as exclusively peripheral and was always better explained by other causes (e.g., hemianopsia following hemispherectomy and cortical vision impairment after hypoxic ischemic encephalopathy). Precise quantitative exposure data were available for 104 (73%) patients treated with VGB, among whom the median duration of treatment was 8.6 (IQR: 3.7-16.2) months, the median peak dosage was 141.5 (IQR: 104.8-166.0) mg/kg/day, and the median cumulative dosage was 314 (IQR: 140.8-645.7) grams. We found that the risk of clinically apparent vision loss is quite low among young children treated for infantile spasms. Our estimate of risk contrasts with prior studies and likely reflects our ascertainment of vision loss without the aid of perimetry or serial ERG, the short treatment duration, and the relatively young age of our patients. In the treatment of infantile spasms, risk-benefit assessment should consider both the low prevalence of ERG-identified VAVFL among patients with brief (<6-9months) exposure and the very low prevalence of clinically apparent VAVFL in this population.