Zonisamide reduces the increase in 8-hydroxy-2'-deoxyguanosine levels formed during iron-induced epileptogenesis in the brains of rats

Neuroprotective effects of zonisamide on cerebral ischemia injury via inhibition of neuronal apoptosis

It is known that neuronal apoptosis contributes to pathology of cerebral ischemia injury. Zonisamide (ZNS) has shown anti-apoptosis effects in recent studies. The present study investigated whether the anti-apoptotic effect can account for the neuroprotective action of ZNS on cerebral ischemia. Neuronal cells were maintained under oxygen-glucose deprivation conditions to simulate cerebral ischemia and treated with ZNS simultaneously. The apoptosis of the cells and expression of apoptosis-related proteins were investigated by flow cytometry and western blot analysis, respectively. A cerebral ischemia mouse model was created via middle cerebral artery occlusion, and the mice were treated with ZNS. Neurological deficit scores and infarct volumes of the cerebral ischemia mice were measured. The apoptosis status of the neuronal cells was evaluated by TUNEL staining. In vitro, the ZNS treatment inhibited both the apoptosis of the neuronal cells and apoptosis-related protein expression (caspase-3, caspase-8, and calpain-1) induced by the oxygen-glucose deprivation. The anti-apoptosis effect of ZNS could occur through the blocking of reactive oxygen species. Moreover, ZNS treatment significantly ameliorated neurological deficits and reduced infarct volumes in the cerebral ischemia mice model. In this study, ZNS exerted neuroprotective effects by inhibition of apoptosis in neuronal cells in cerebral ischemia. Therefore, ZNS might be a promising therapy for cerebral ischemia.

No prevention or cure of epilepsy as yet

Approximately 20% of all epilepsy is caused by acute acquired injury such as traumatic brain injury, stroke and CNS infection. The known onset of the injury which triggers the epileptogenic process, early presentation to medical care, and a latency between the injury and the development of clinical epilepsy present an opportunity to intervene with treatment to prevent epilepsy. No such treatment exists and yet there has been remarkably little clinical research during the last 20 years to try to develop such treatment. We review possible reasons for this, possible ways to rectify the situations and note some of the ways currently under way to do so. Resective surgical treatment can achieve "cure" in some patients but is sparsely utilized. In certain "self-limiting" syndromes of childhood and adolescence epilepsy remits spontaneously. In a proportion of patients who become seizure free on medications or with dietary treatment, seizure freedom persists when treatment is discontinued. We discuss these situations which can be considered "cures"; and note that at present we have little understanding of mechanism of such cures, and cannot therefore translate them into a treatment paradigm targeting a "cure" of epilepsy. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Zonisamide cotreatment delays striatal dopamine transporter reduction in Parkinson disease: A retrospective, observational cohort study

This study examined whether zonisamide (ZNS) cotreatment delays dopamine transporter (DAT) reduction on SPECT in Parkinson disease (PD) patients. The study participants met the following criteria: (i) age ≥ 40 years; (ii) HY stage = 2 or 3; (iii) average specific binding ratio (SBR) ≥2.00; (iv) levodopa administration without a prior history of ZNS use before the first DAT-SPECT (baseline). Attending physicians initially determined whether ZNS (25 mg/day) should be used or not. Levodopa and other anti-PD medications were not restricted. The second DAT-SPECT (endpoint) was conducted 1.2 ± 0.2 years after the first DAT-SPECT. Clinicoradiological changes of HY stage, UPDRS parts II to IV, dyskinesia subscore, and SBR were calculated. Statistical differences were analyzed by Student's t-test, ANOVA, or multilogistic analysis. ZNS cotreatment improved wearing off and prevented the development of dyskinesia without additional administration of selegiline, entacapone, and dopamine receptor agonists. The endpoint SBR reduced significantly in the non-ZNS group compared to the baseline (P < .01). The SBR decline rate reduced significantly in the ZNS group (P < .01). ZNS was an independent preventive factor for SBR reduction. These results suggested a beneficial potential that ZNS preserves striatal presynaptic DAT expression and slows disease progression in early-stage PD.

Prevention of epilepsy: Should we be avoiding clinical trials?

Epilepsy prevention is one of the great unmet needs in epilepsy. Approximately 15% of all epilepsy is caused by an acute acquired CNS insult such as traumatic brain injury (TBI), stroke or encephalitis. There is a latent period between the insult and epilepsy onset that presents an opportunity to intervene with preventive treatment that is unique in neurology. Yet no phase 3 epilepsy prevention studies, and only 2 phase 2 studies have been initiated in the last 16years. Current prevailing opinion is that the research community is not ready for clinical preventive epilepsy studies, and that animal models should first be refined and biomarkers of epileptogenesis and of epilepsy discovered before clinical studies are embarked upon. We review data to suggest that there is basis to do epilepsy prevention studies now with the current knowledge and available drugs, and that those studies are feasible with currently available tools. We suggest that a different approach is needed from the past in order to maximize chances of success, minimize the cost, and set up platform for future preventive treatment development. That approach should include close coordination of preclinical and clinical development programs in a combined PTE prevention strategy, consideration of polytherapy, and simultaneous, combined clinical development of preventive treatment and of biomarker discovery. We argue that the currently favored approach of eschewing clinical studies until biomarkers are available will delay the discovery of epilepsy prevention treatment by at least 10 years and significantly increase the cost of such discovery.

Effect of Oxidative Stress on ABC Transporters: Contribution to Epilepsy Pharmacoresistance

Epilepsy is a neurological disorder affecting around 1%–2% of population worldwide and its treatment includes use of antiepileptic drugs to control seizures. Failure to respond to antiepileptic drug therapy is a major clinical problem and over expression of ATP-binding cassette transporters is considered one of the major reasons for pharmacoresistance. In this review, we have summarized the regulation of ABC transporters in response to oxidative stress due to disease and antiepileptic drugs. Further, ketogenic diet and antioxidants were examined for their role in pharmacoresistance. The understanding of signalling pathways and mechanism involved may help in identifying potential therapeutic targets and improving drug response.

Zonisamide Enhances Neurite Elongation of Primary Motor Neurons and Facilitates Peripheral Nerve Regeneration In Vitro and in a Mouse Model

No clinically applicable drug is currently available to enhance neurite elongation after nerve injury. To identify a clinically applicable drug, we screened pre-approved drugs for neurite elongation in the motor neuron-like NSC34 cells. We found that zonisamide, an anti-epileptic and anti-Parkinson’s disease drug, promoted neurite elongation in cultured primary motor neurons and NSC34 cells in a concentration-dependent manner. The neurite-scratch assay revealed that zonisamide enhanced neurite regeneration. Zonisamide was also protective against oxidative stress-induced cell death of primary motor neurons. Zonisamide induced mRNA expression of nerve growth factors (BDNF, NGF, and neurotrophin-4/5), and their receptors (tropomyosin receptor kinase A and B). In a mouse model of sciatic nerve autograft, intragastric administration of zonisamide for 1 week increased the size of axons distal to the transected site 3.9-fold. Zonisamide also improved the sciatic function index, a marker for motor function of hindlimbs after sciatic nerve autograft, from 6 weeks after surgery. At 8 weeks after surgery, zonisamide was protective against denervation-induced muscle degeneration in tibialis anterior, and increased gene expression of Chrne, Colq, and Rapsn, which are specifically expressed at the neuromuscular junction. We propose that zonisamide is a potential therapeutic agent for peripheral nerve injuries as well as for neuropathies due to other etiologies.

Protective effect of melatonin against zonisamide-induced reproductive disorders in male rats

INTRODUCTION

Zonisamide (ZNS) is a modern antiepileptic drug (AED) that is distinguished from other AEDs by its unique structure and broad mechanistic profile. The pineal hormone melatonin is involved in the regulation of reproductive function, including the timing of the luteinizing hormone (LH) surge. The aim of the present work was to study the protective effect of melatonin against the potential suppression impact of ZNS on reproductive activity.

MATERIAL AND METHODS

Ninety adult albino male rats were allocated to several groups treated with melatonin (10 mg/kg BW), ZNS (10, 20 and 50 mg/kg BW) and 10 mg/kg of melatonin plus ZNS (10, 20 or 50 mg/kg BW, respectively). Reproductive hormones (testosterone, LH and follicle-stimulating hormone (FSH)) levels were measured in animal serum. Sperm abnormalities and DNA fragmentation in testis tissues as well as expression alteration of several reproductive-related genes were analyzed.

RESULTS

The results revealed that ZNS decreased the levels of serum free testosterone, LH, and FSH and expression of their encoding genes in male rats. In addition, ZNS treatment increased the sperm abnormalities and DNA fragmentation and inducible nitric oxide synthase (iNOS) in testis tissues as well as GABA level in liver tissues. However, melatonin supplementation inhibited the negative symptoms of ZNS in which it increased the levels of reproductive hormones and expression of their encoding genes in the ZNS-treated rats. Moreover, melatonin decreased the sperm abnormalities, DNA fragmentation, iNOS activity and GABA level in ZNS-treated rats.

CONCLUSIONS

The data obtained in this study suggest that melatonin administration confers protection against toxicity inflicted by ZNS, and support the contention that melatonin protection is achieved by its ability as a scavenger for free radicals generated by ZNS.

Zonisamide attenuates hyperoxia-induced apoptosis in the developing rat brain

Oxygen therapy used in the treatment of perinatal hypoxia induces neurodegeneration in babies with immature antioxidant mechanisms. Zonisamide is a new antiepileptic drug used in childhood intractable seizures. Many studies demonstrated its neuroprotective effects. There is no study evaluating its effect on hyperoxic brain injury. The aim of this study was to investigate the neuroprotective effect of zonisamide on hyperoxia-induced neonatal brain injury. A total of 21 Wistar rat pups were used. The animals were divided into three groups: control group, hyperoxia group, and zonisamide-treated group. The zonisamide-treated group received an intraperitoneal injection of zonisamide. Zonisamide significantly preserved the number of neurons in CA1 and dentate gyrus parts of hippocampus, prefrontal, and parietal cortex. Zonisamide treatment also decreased the number of apoptotic neurons in all examined parts of hippocampus, prefrontal, and parietal cortex. We suggest that zonisamide treatment may be used as a neuroprotective agent in hyperoxic brain injury.

The role of reactive species in epileptogenesis and influence of antiepileptic drug therapy on oxidative stress

Epilepsy is considered one of the most common neurological disorders. The focus of this review is the acquired form of epilepsy, with the development process consisting of three major phases, the acute injury phase, the latency epileptogenesis phase, and the phase of spontaneous recurrent seizures. Nowadays, an increasing attention is paid to the possible interrelationship between oxidative stress resulting in disturbance of physiological signalling roles of calcium and free radicals in neuronal cells and mitochondrial dysfunction, cell damage, and epilepsy. The positive stimulation of mitochondrial calcium signals by reactive oxygen species and increased reactive oxygen species generation resulting from increased mitochondrial calcium can lead to a positive feedback loop. We propose that calcium can pose both, physiological and pathological effects of mitochondrial function, which can lead in neuronal cell death and consequent epileptic seizures. Various antiepileptic drugs may impair the endogenous antioxidative ability to prevent oxidative stress. Therefore, some antiepileptic drugs, especially from the older generation, may trigger oxygen-dependent tissue injury. The prooxidative effects of these antiepileptic drugs might lead to enhancement of seizure activity, resulting in loss of their efficacy or apparent functional tolerance and undesired adverse effects. Additionally, various reactive metabolites of antiepileptic drugs are capable of covalent binding to macromolecules which may lead to deterioration of the epileptic seizures and systemic toxicity. Since neuronal loss seems to be one of the major neurobiological abnormalities in the epileptic brain, the ability of antioxidants to attenuate seizure generation and the accompanying changes in oxidative burden, further support an important role of antioxidants as having a putative antiepileptic potential.

Zonisamide attenuates MPP+-induced oxidative toxicity through modulation of Ca2+ signaling and caspase-3 activity in neuronal PC12 cells

Parkinson's disease is an incurable progressive neurological condition caused by a degeneration of dopamine-producing cells characterized by motor and non-motor symptoms. The major mechanisms of the antiepileptic actions of ZNS are inhibition of voltage-gated Na(+) channel, T-type voltage-sensitive Ca(2+) channel, Ca(2+)-induced Ca(2+) releasing system, and neuronal depolarization-induced glutamate release; and enhancement of release of inhibitory neurotransmitters; however, the detailed mechanism of antiparkinsonian effects of ZNS remains to be clarified. We aimed to investigate to the effect of ZNS on the oxidative stress, cell viability, Ca(2+) signaling, and caspase activity that induced by the MPP(+) model of Parkinson's in neuronal PC12 cells. Neuronal PC12 cells were divided into four groups namely, control, ZNS, MPP(+), and ZNS+MPP(+) groups. The dose and duration of ZNS and MPP(+) were determined according to cell viability (MTT) analysis which used to assess the cell viability. The cells in ZNS, MPP(+), and ZNS+MPP(+) groups were incubated for 5 h with 100 μM ZNS, 10 h with 100 μM MPP(+), and 10 h with ZNS and MPP(+), respectively. Lipid peroxidation and cytosolic free Ca(2+) concentrations were higher in the MPP(+) group than in control although their levels were lower in ZNS and the ZNS+MPP(+) groups than in control. Reduced glutathione and glutathione peroxidase values were lower in the MPP(+) group although they were higher in the ZNS and the ZNS+MPP(+) groups than in control. Caspase-3 activity was lower in the ZNS group than in the MPP(+) group. In conclusion, ZNS induced modulator effects on the oxidative stress, intracellular Ca(2+), and the caspase-3 values in an experimental model of Parkinson disease.

Epilepsy and epileptic syndrome

Epilepsy is one of the most common neurological disorders. In most patients with epilepsy, seizures respond to available medications. However, a significant number of patients, especially in the setting of medically-intractable epilepsies, may experience different degrees of memory or cognitive impairment, behavioral abnormalities or psychiatric symptoms, which may limit their daily functioning. As a result, in many patients, epilepsy may resemble a neurodegenerative disease. Epileptic seizures and their potential impact on brain development, the progressive nature of epileptogenesis that may functionally alter brain regions involved in cognitive processing, neurodegenerative processes that relate to the underlying etiology, comorbid conditions or epigenetic factors, such as stress, medications, social factors, may all contribute to the progressive nature of epilepsy. Clinical and experimental studies have addressed the pathogenetic mechanisms underlying epileptogenesis and neurodegeneration.We will primarily focus on the findings derived from studies on one of the most common causes of focal onset epilepsy, the temporal lobe epilepsy, which indicate that both processes are progressive and utilize common or interacting pathways. In this chapter we will discuss some of these studies, the potential candidate targets for neuroprotective therapies as well as the attempts to identify early biomarkers of progression and epileptogenesis, so as to implement therapies with early-onset disease-modifying effects.

Role of oxidative stress in epileptic seizures

Oxidative stress resulting from excessive free-radical release is likely implicated in the initiation and progression of epilepsy. Therefore, antioxidant therapies aimed at reducing oxidative stress have received considerable attention in epilepsy treatment. However, much evidence suggests that oxidative stress does not always have the same pattern in all seizures models. Thus, this review provides an overview aimed at achieving a better understanding of this issue. We summarize work regarding seizure models (i.e., genetic rat models, kainic acid, pilocarpine, pentylenetetrazol, and trimethyltin), oxidative stress as an etiologic factor in epileptic seizures (i.e., impairment of antioxidant systems, mitochondrial dysfunction, involvement of redox-active metals, arachidonic acid pathway activation, and aging), and antioxidant strategies for seizure treatment. Combined, this review highlights pharmacological mechanisms associated with oxidative stress in epileptic seizures and the potential for neuroprotection in epilepsy that targets oxidative stress and is supported by effective antioxidant treatment.

Zonisamide: aspects in neuroprotection

Zonisamide is widely used as an antiepileptic drug. Two studies published recently in Experimental Neurology focus on the drug's neuroprotective effect. In the present commentary, we discuss the significance of their findings and aspects of zonisamide in neuroprotection.

Zonisamide enhances delta receptor-associated neurotransmitter release in striato-pallidal pathway

A recent randomized control study demonstrated that zonisamide (ZNS), an antiepileptic drug, is effective in Parkinson's disease at the lower than the therapeutic doses against epilepsy (25-50 mg/day); however, the detailed mechanism of antiparkinsonian effects of ZNS remains to be clarified. To determine the mechanism of antiparkinsonian effect of ZNS, we investigated the effects of ZNS on extracellular levels of dopamine in the striatum (STR), glutamate in substantia nigra pars reticulata (SNr), GABA in globus pallidus (GP), subthalamic nucleus (STN) and SNr, using multiple microdialysis probes. Striatal perfusion of 1000 microM ZNS (within therapeutic-relevant concentration against epilepsy) increased extracellular levels of dopamine in STR, whereas 100 microM ZNS (lower than the therapeutic-relevant concentration against epilepsy but within the therapeutic rage against Parkinson's disease) did not affect it. Striatal perfusion of ZNS (100 and 1000 microM) decreased the extracellular levels of GABA in STN and glutamate in SNr, but decreased extracellular GABA level in GP without affecting GABA level in SNr. These concentration-dependent effects of ZNS on extracellular neurotransmitter levels were independent of dopamine and delta(2) receptors; however, blockade of delta(1) receptor inhibited the effects of ZNS. Furthermore, activation of delta(1) receptor enhanced the effects of ZNS on neurotransmitter level. These results suggest that ZNS does not affect the direct pathway but inhibits the indirect pathway, which is mediated by delta(1) receptor. Therefore, the antiparkinsonian effects of ZNS seem to be mediated through the interaction between lower than therapeutically-relevant concentration against epilepsy of ZNS (100 microM) and delta(1) receptor.

The aspects and mechanisms of cognitive alterations in epilepsy: the role of antiepileptic medications

Epilepsy is a major health problem. Several studies suggest a significant influence of epilepsy and its treatment on dynamic and functional properties of brain activity. Epilepsy can adversely affect mental development, cognition, and behavior. Epileptic patients may experience reduced intelligence, attention, and problems in memory, language, and frontal executive functions. Neuropsychological, functional, and quantitative neuroimaging studies revealed that epilepsy affect the brain as a whole. Mechanisms of epilepsy-related cognitive dysfunction are poorly delineated. Cognitive deficits with epilepsy may be transient, persistent, or progressive. Transient disruption of cognitive encoding processes may occur with paroxysmal focal or generalized epileptic discharges, whereas epileptogenesis-related neuronal plasticity, reorganization, sprouting, and impairment of cellular metabolism are fundamental determinants for progressive cognitive deterioration. Also antiepileptic drugs (AEDs) have differential, reversible, and sometimes cumulative cognitive adverse consequences. AEDs not only reduce neuronal irritability but also may impair neuronal excitability, neurotransmitter release, enzymes, and factors critical for information processing and memory. The present article serves as an overview of recent studies in adult and childhood epilepsy literatures present in PubMed that highlighted cognitive evaluation in epilepsy field (publications till 2008 were checked). We also checked the reference lists of the retrieved studies for additional reports of relevant studies, in addition to our experience in this field. Our search revealed that although the aspects of cognitive dysfunction, risk factors, and consequences have been explored in many studies; however, the mechanisms of contribution of epilepsy-related variables, including AEDs, to patients' cognition are largely unexplored. In this review, we discussed the differential effect of AEDs in mature and immature brains and the known mechanisms underlying epilepsy and AEDs adverse effects on cognition. The nature, timing, course, and mechanisms of cognitive alteration with epilepsy and its medications are of considerable clinical and research implications.

Curcumin protects against electrobehavioral progression of seizures in the iron-induced experimental model of epileptogenesis

The purpose of the study was to investigate whether dietary intake of curcumin can inhibit the onset and progression of seizures and their associated pathophysiology in experimental FeCl(3)-induced epileptogenesis. Curcumin was considered for this study because it can cross the blood-brain barrier and bind redox-active metal ions. It is also well known for its antioxidative, anticancer, and anti-inflammatory properties. In the present study, seizures were induced by intracortical injection of FeCl(3) into young rats. Synchronized video/EEG recordings were obtained to diagnose the progression of seizures. Short-term treatment with a curcumin-supplemented diet (1500 pp mw/w) significantly inhibited the onset of grade III and IV seizures in rats with iron-induced epilepsy. The lower dose of curcumin (500 ppm) was not effective in inhibiting grade III seizures, but retarded the onset and progression of generalized seizures. The seizure-suppressing potential of curcumin is explained by the observed biochemical, behavioral, and ultrastructural results. Our results indicate that curcumin significantly prevents generalization of electroclinical seizure activity as well as the pathogenesis associated with iron-induced epileptogenesis.

Long-term safety and effectiveness of zonisamide in the treatment of epilepsy: a review of the literature

Zonisamide (ZNS) efficacy and safety in epilepsy have been demonstrated in four double-blind, placebo-controlled studies. In the present article, we examined all long-term studies performed with this drug. Nine open-label studies, in which ZNS had been administered as an add-on or as monotherapy to epileptic patients for at least 6 months, were selected for our analysis. Four outcome measures were searched. Retention of this drug after 1 year varied between 45% and 65%. The percentages of patients achieving a >/=50% seizure reduction, with respect to baseline, ranged between 37% and 65%. In patients with drug-resistant forms of epilepsy, the percentage of patients reaching a 6-month seizure freedom period was 9%. The percentages of patients who discontinued the experimental drug due to adverse effects ranged between 4% and 24%. Somnolence and dizziness were the most frequently reported adverse effects. Long-term studies demonstrate that ZNS has a good efficacy and tolerability profile, and support its use as adjunctive therapy for epileptic patients.

Posttraumatic epilepsy: hemorrhage, free radicals and the molecular regulation of glutamate

Traumatic brain injury causes development of posttraumatic epilepsy. Bleeding within neuropil is followed by hemolysis and deposition of hemoglobin in neocortex. Iron from hemoglobin and transferring is deposited in brains of patients with posttraumatic epilepsy. Iron compounds form reactive free radical oxidants. Microinjection of ferric ions into rodent brain results in chronic recurrent seizures and liberation of glutamate into the neuropil, as is observed in humans with epilepsy. Termination of synaptic effects of glutamate is by removal via transporter proteins. EAAC-1 is within neurons while GLT-1 and GLAST are confined to glia. Persistent down regulation of GLAST production is present in hippocampal regions in chronic seizure models. Down regulation of GLAST may be fundamental to a sequence of free radical reactions initiated by brain injury with hemorrhage. Administration of antioxidants to animals causes interruption of the sequence of brain injury responses induced by hemorrhage, suggesting that such a strategy needs to be evaluated in patients with traumatic brain injury.

Zonisamide: review of pharmacology, clinical efficacy, tolerability, and safety

BACKGROUND

Zonisamide (ZNS), a sulphonamide derivative, is a new-generation anticonvulsant with multiple potential mechanisms that contribute to its antiepileptic efficacy and may also explain its as yet incompletely assessed utility for non-seizure disorders such as headaches, neuropathic pain, and weight loss.

OBJECTIVE

A review of the pharmacokinetics, pharmacodynamics, evidence for efficacy in different seizure types and non-seizure conditions, adverse effects, and tolerability of ZNS is presented.

METHODS

A review of all manuscripts published in the English literature on ZNS was performed in preparing this manuscript.

RESULTS/CONCLUSIONS

ZNS has a broad label for use in Japan, while the regulatory bodies in the USA and Europe have approved it for use only as an adjunctive therapy for partial seizures in adults. It has favorable pharmacokinetic characteristics, proven efficacy in seizure disorders, and is well tolerated in long-term use.

Preventing effects of a novel anti-parkinsonian agent zonisamide on dopamine quinone formation

The neurotoxicity of dopamine (DA) quinones as dopaminergic neuron-specific oxidative stress is considered to play a role in the pathogenesis and/or progression of Parkinson's disease (PD), since DA quinones conjugate with several key PD pathogenic molecules (e.g., tyrosine hydroxylase, alpha-synuclein and parkin) to form protein-bound quinone (quinoprotein) and consequently inhibit their functions. Zonisamide (ZNS) is used as an anti-epileptic agent but also improved the cardinal symptoms of PD in recent clinical trials in Japan. To evaluate the effects of ZNS on excess cytosolic free DA-induced quinone toxicity, we examined changes in DA quinone-related indices after ZNS treatment both in in vitro cell-free system and in cultured cells. Co-incubation of DA and ZNS in a cell-free system caused conversion of DA to stable melanin via formation of DA-semiquinone radicals and DA chrome. Long-term (5 days) treatment with ZNS decreased quinoprotein and increased DA/DOPA chromes in dopaminergic CATH.a cells. ZNS significantly inhibited quinoprotein formation induced by treatment with tetrahydrobiopterin and ketanserin that elevate cytosolic free DA in the cells. Our results suggest that the novel anti-parkinsonian agent ZNS possesses preventing effects against DA quinone formation induced by excess amount of cytosolic DA outside the synaptic vesicles.

Clinical pharmacology and mechanism of action of zonisamide

Antiepileptic drugs (AEDs) suppress seizures by selectively modifying the excitability of neurons and blocking seizure firing with minimal disturbance of nonepileptic activity. All AEDs have been shown to work by at least one of 3 main mechanisms of action: through modulation of voltage-gated ion channels, enhancement of synaptic inhibition, and inhibition of synaptic excitation. Zonisamide is a novel AED that has a broad combination of complementary mechanisms of action, which may offer a clinical advantage over other antiepileptic agents. By altering the fast inactivation threshold of voltage-dependent sodium channels, zonisamide reduces sustained high-frequency repetitive firing of action potentials. Zonisamide also inhibits low-threshold T-type calcium channels in neurons, which may prevent the spread of seizure discharge across cells. In addition, zonisamide is a weak inhibitor of carbonic anhydrase. However, this mechanism is not believed to contribute to the antiepileptic activity of zonisamide. Although zonisamide also seems to alter dopamine, serotonin, and acetylcholine metabolism, it is not clear to what extent these effects on neurotransmitters are involved in the clinical actions of the drug. In addition to these actions, recent evidence suggests that zonisamide may exert neuroprotective actions, independent of its antiepileptic activity. These potential effects may be important in preventing neuronal damage caused by recurrent seizures. Therefore, it seems that the multiple pharmacological actions of zonisamide may contribute to the seizure reductions observed in a wide range of epilepsies and may help to preserve efficacy in individual patients despite possible changes in electrophysiological status.

Zonisamide for the treatment of Parkinson's disease

Zonisamide is an antiepileptic drug widely used to treat seizures worldwide. In addition to epilepsy, zonisamide may have beneficial efficacy in various neurological or psychiatric diseases. This article reviews the structure, mechanism of action, pharmacokinetics and possible antiparkinsonian action of zonisamide. A multicentered, randomized, double-blind, placebo-controlled study conducted in Japan provided data suggesting that zonisamide, as an add-on treatment, has efficacy in treating motor symptoms in patients with Parkinson's disease (PD). Zonisamide may be effective in reducing the duration of 'off' time in patients with PD treated with L-DOPA. The therapeutic doses of zonisamide for the treatment of PD are 50-100 mg/day, considerably lower than those for the treatment of epilepsy (200-400 mg/day). It is expected that zonisamide will be safe and tolerated in patients with PD, as it has been used as an antiepileptic for more than 15 years; however, further studies are required to evaluate its safety and tolerability in the treatment of PD. The pharmacological mechanisms of the beneficial actions of zonisamide in PD remain unclear. Various hypotheses have been proposed, but the supporting data are not yet sufficient to draw any conclusions. Further basic research is required to advance our understanding of the antiparkinsonian mechanism of zonisamide.

Acute encephalopathy with refractory status epilepticus: bilateral mesial temporal and claustral lesions, associated with a peripheral marker of oxidative DNA damage

We describe a 12-year-old girl, who had been medicated with theophylline for bronchial asthma and developed acute encephalopathy with refractory status epilepticus, showing bilateral mesial temporal and claustral lesions, which were evident on fluid-attenuated inversion recovery images, obtained with 1.5 T magnetic resonance imaging. To date, oxidative stress has been implicated in aging or various disorders, including inflammatory or degenerative neurological disorders. One of the oxidative stress markers, 8-hydroxydeoxyguanosine, was increased in our patient's cerebro-spinal fluid, plasma and urine. We speculate that augmented oxidative stress was associated with refractory status epilepticus in our patient, accompanying bilateral mesial temporal, claustral lesions and severe neuronal damage. Serial measurements of oxidative stress markers in acute encephalitis, encephalopathy, or status epilepticus could clarify the relationships between acute brain damage and free radicals.

Antiepileptic drugs and neuroprotection: current status and future roles

There has been a growing interest in the use of antiepileptic drugs (AEDs) for neuroprotection, and in the possible role of AEDs in disease modification (i.e., antiepileptogenesis). Increased understanding of the mechanisms underlying brain injury has led to advances in the study of neuroprotection. However, defining the clinical paradigm and selecting appropriate outcomes to detect neuroprotective effects present challenges to clinicians studying the neuroprotective properties of drugs. Established AEDs, such as phenytoin, phenobarbital, and carbamazepine, have shown neuroprotective activity in an ischemic/hypoxic model of neuronal injury. Animal model studies also have suggested that newer AEDs, such as levetiracetam, topiramate, and zonisamide, may have neuroprotective or antiepileptogenic properties. However, the prevention of epileptogenesis by an AED has yet to be demonstrated in clinical trials. The future of neuroprotection may involve established and newer AEDs, as well as other compounds, such as immunophilins, caspase inhibitors, endocannabinoids, and antioxidants.

Postoperative seizures: epidemiology, pathology, and prophylaxis

The risk of epileptic seizures after craniotomy is extremely important but the incidence of postoperative epilepsy varies greatly, depending on the patient's conditions such as primary diseases, severity of surgical insult, and pre-existing epilepsy. Animal studies suggest that neurosurgical insults lead to seizures by two different mechanisms: One mechanism is mediated by free radical generation and the other by impaired ion balance across the cell membrane caused by ischemia or hypoxia. Conventional antiepileptic agents such as phenytoin, phenobarbital, carbamazepine, and valproic acid are promising for the prevention of early seizures, but the effect in preventing postoperative epilepsy is still controversial. Studies on the prophylactic effect of newer antiepileptic agents in craniotomized patients were very limited. Zonisamide, an antiepileptic agent with antiepileptogenic, free radical scavenging and neuroprotective actions in experimental animals, showed promising effects against postoperative epilepsy in a randomized double blind controlled trial. Prophylactic treatment for craniotomized patients significantly prevented the development of partial seizures during the follow-up period. Most recent studies have not supported the prophylactic use of antiepileptic agents in craniotomized patients, but further studies are required.

Treatment of Chronic Pain with Zonisamide

Mechanistic similarities underlying neuropathic pain and epilepsy suggest that anticonvulsants can be used for treating neuropathic pain. This open-label prospective study assesses the use of zonisamide in patients with chronic neuropathic pain. Fifty-five patients were initiated on zonisamide, given 100 mg every fourth night and titrated to a stable maintenance dosage (mean=285 mg/d, range=100 to 700 mg/d). Patients rated their pain on a 0 to 10 scale in pain diaries. After > or =3 months on a stable maintenance zonisamide dosage, pain ratings were compared with baseline. Adverse events (AEs) were monitored. Forty-two patients had efficacy data available. Fifteen patients (35.7%) had a >50% improvement in daily pain scores; 10 patients (23.8%) had a 25% to 50% improvement. Zonisamide was well tolerated; only 5 patients discontinued for AEs (drowsiness, nausea, and itching). These results suggest that zonisamide may be useful for treating neuropathic pain. Further investigation in double-blind, placebo-controlled trials is warranted.

New antiepileptic drugs

BACKGROUND

Eight novel anticonvulsant drugs have been introduced in the United States in the past 10 years, as well as two new intravenous preparations of anticonvulsant drugs. The role of each in the treatment of patients with epilepsy is being refined as experience and research data accumulate.

REVIEW SUMMARY

Gabapentin, tiagabine, and oxcarbazepine are effective for partial seizures, whereas felbamate, lamotrigine, topiramate, levetiracetam, and zonisamide treat both partial and generalized seizure types. In general, these newer agents differ from older agents by relative lack of drug-drug interactions, and many show improved tolerability compared with phenytoin and carbamazepine. Each has distinguishing features that can prove useful in specific clinical situations. Despite limited Food and Drug Administration indications, all are useful in monotherapy under certain circumstances. Fosphenytoin avoids the adverse effects of intravenous phenytoin vehicle, and intravenous valproate represents a much needed option in patients who require rapid loading of this medication.

CONCLUSIONS

The greater number of antiseizure drugs available today makes it possible to tailor treatment to individual patient needs, allowing more patients to be free of debilitating adverse effects. Additionally, some patients can achieve complete seizure freedom even after failing one or more other antiepileptic drugs.

Advancing the medical management of epilepsy: disease modification and pharmacogenetics

Despite the recent development of new antiepilepsy drugs, a significant number of children are still unable to achieve seizure freedom without side effects. Understanding the factors behind individual variability in antiepilepsy drug tolerability and dose response and incorporating these factors into a treatment plan would represent an important advance in epilepsy pharmacotherapy. A more thorough understanding of the epileptogenic process may allow clinicians to select antiepilepsy drugs that interrupt or modify various steps in the epileptogenic progression (ie, disease modification). Additionally, advances in the understanding of human genetics may allow for selection of antiepilepsy drugs and dosage regimens based on a patient's clinical characteristics and genotype (ie, pharmacogenetics). This article focuses on these two areas of potential improvement in the medical treatment of patients with epilepsy. Such methods of tailoring antiepilepsy drug therapy would be preferable to the trial-and-error system that is currently used.

New antiepileptic drugs

Finding a niche for each antiepileptic drug has become challenging as more new agents are approved. In this article, the most recent information regarding these drugs is reported, with emphasis on the agents approved in the past 10 years. The evidence clearly shows that, despite limited Food and Drug Administration indications, all drugs are useful in monotherapy, and many have broader spectrums of action. Adverse effects can also help distinguish between agents. Familiarity with this latest information will help clinicians make the best choice for each of their patients with epilepsy.

The efficacy of an antioxidant cocktail on lipid peroxide level and superoxide dismutase activity in aged rat brain and DNA damage in iron-induced epileptogenic foci

Mixed natural antioxidants can be combined in a prophylactic food against age related disease involving reactive oxygen species. beta-Catechin is an antioxidant drink, having free radical scavenging activities. It contains green tea extract as a main component as well as ascorbic acid, sunflower seed extract, dunaliella carotene and natural vitamin E. In the present study, we examined the effect of beta-catechin on lipid peroxide formation and superoxide dismutase (SOD) activity in aged rat brain and the effect on 8-hydroxy-2'-deoxyguanosine (8-OHdG) in ipsilateral cortex, 30 min after ferric chloride solution was injected into the left cortex of rats. beta-Catechin solution was orally administered to aged rats and normal rats for 1 month. One-month administration of beta-catechin solution increased SOD activity in the mitochondria fraction of striatum and midbrain and decreased thiobarbiturate reactive substance formation in the cortex and cerebellum of aged rats. It also inhibited 8-OHdG formation in the ipsilateral cortex 30 min after injection of ferric chloride solution. These results suggest that beta-catechin is a suitable prophylactic beverage against age-related neurological diseases associated with reactive oxygen species.