Zonisamide

Drug-Induced Insomnia and Excessive Sleepiness

Undesirable side effects of insomnia and/or sleepiness may occur with many prescribed drugs, psychotropics as well as non-psychotropics. These central nervous system effects can be explained by the interactions of the drug with any of the numerous neurotransmitters and receptors that are involved in sleep and wakefulness. Also a close - sometimes bidirectional - relationship between disease and (disturbed) sleep/wakefulness is often present e.g. in chronic pain; drug effects may lead this vicious circle in both ways. Besides the importance for health and quality of life, effects on sleep or waking function can be a potential source of non-compliance.

Prospects for new drugs to treat binge-eating disorder: Insights from psychopathology and neuropharmacology

BACKGROUND

Binge-eating disorder (BED) is a common psychiatric condition with adverse psychological and metabolic consequences. Lisdexamfetamine (LDX) is the only approved BED drug treatment. New drugs to treat BED are urgently needed.

METHODS

A comprehensive review of published psychopathological, pharmacological and clinical findings.

RESULTS

The evidence supports the hypothesis that BED is an impulse control disorder with similarities to ADHD, including responsiveness to catecholaminergic drugs, for example LDX and dasotraline. The target product profile (TPP) of the ideal BED drug combines treating the psychopathological drivers of the disorder with an independent weight-loss effect. Drugs with proven efficacy in BED have a common pharmacology; they potentiate central noradrenergic and dopaminergic neurotransmission. Because of the overlap between pharmacotherapy in attention deficit hyperactivity disorder (ADHD) and BED, drug-candidates from diverse pharmacological classes, which have already failed in ADHD would also be predicted to fail if tested in BED. The failure in BED trials of drugs with diverse pharmacological mechanisms indicates many possible avenues for drug discovery can probably be discounted.

CONCLUSIONS

(1) The efficacy of drugs for BED is dependent on reducing its core psychopathologies of impulsivity, compulsivity and perseveration and by increasing cognitive control of eating. (2) The analysis revealed a large number of pharmacological mechanisms are unlikely to be productive in the search for effective new BED drugs. (3) The most promising areas for new treatments for BED are drugs, which augment noradrenergic and dopaminergic neurotransmission and/or those which are effective in ADHD.

What pharmacological interventions are effective in binge-eating disorder? Insights from a critical evaluation of the evidence from clinical trials

Binge-eating disorder (BED) is the commonest eating disorder and an important causal factor in obesity. Lisdexamfetamine is the only approved pharmacological treatment. Many drugs have been clinically evaluated and several were described as potentially promising treatments. A comprehensive reassessment of the evidence from these clinical trials has been performed. The questions to be answered were: (1) Does the evidence support claims of efficacy? (2) What pharmacological mechanisms show promise for developing new BED drugs? (3) What are the clinical implications for treating BED? PubMed and internal database searches identified every available published drug trial in BED. The trials and their results were summarised and reviewed to re-evaluate the evidence. Factors taken into consideration included psychiatric diagnosis, primary endpoint, secondary outcome measures, trial size, blinding and controls, drop-out rates, placebo response rates and weight-loss. Drugs were classified according to their pharmacology and therapeutic indication to determine which mechanisms were effective and to provide insights into the psychopathology of BED. For most drugs, robust evidence of efficacy in BED is insubstantial or absent. Some catecholaminergic drugs developed for ADHD are also effective in BED; other pharmacological mechanisms are weakly efficacious at best. Reducing BED severity has little impact on weight. Conversely, weight-loss from anti-obesity therapy is ineffective in ameliorating the psychopathological drivers of BED. (1) BED is a psychiatric not a metabolic disorder. (2) Weight-loss drugs are generally ineffective in BED. (3) Efficacy in BED is restricted to powerful catecholaminergic drugs. (4) Drugs acting via noradrenaline, 5-HT, GABA, carbonic anhydrase inhibition, opioid receptors and various ion channels are generally minimally effective at best. (5) Efficacy in BED is dependent on treating its core psychopathology; reducing impulsivity and compulsivity and increasing cognitive restraint over eating. (6) Obese subjects with BED may benefit from separate treatments for these two disorders.

Pharmacological management of dementia with Lewy bodies with a focus on zonisamide for treating parkinsonism

INTRODUCTION

Dementia with Lewy bodies (DLB) has no approved symptomatic or disease-modifying treatments in the US and Europe, despite being the second most common cause of neurodegenerative dementia.

AREAS COVERED

Herein, the authors briefly review the DLB drug development pipeline, providing a summary of the current pharmacological intervention studies. They then focus on the anticonvulsant zonisamide, a benzisoxazole derivative with a sulfonamide group and look at its value for treating parkinsonism in DLB.

EXPERT OPINION

Several new compounds are being tested in DLB, the most innovative being those aimed at decreasing brain accumulation of α-synuclein. Unfortunately, new drug testing is challenging in terms of consistent diagnostic criteria and lack of reliable biomarkers. Few randomized controlled trials (RCTs) are well-designed, with enough power to detect significant drug effects. Levodopa monotherapy can treat the parkinsonism in DLB, but it can cause agitation or visual hallucination worsening. Two Phase II/III RCTs of DLB patients recently reported a statistically significant improvement in motor function in those receiving zonisamide as an adjunctive treatment to levodopa. New biomarker strategies and validated outcome measures for DLB or prodromal DLB may enhance clinical trial design for the development of specific disease-modifying treatments.

Pharmacokinetic Properties of New Antiepileptic Drugs

Eight new antiepileptic drugs (AEDs) have been approved for use within the United States within the past decade. They are felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, and zonisamide. These afford clinicians with more options to increase efficacy and tolerability in the treatment of patients with epilepsy. Pharmacokinetic properties and drug interactions with other AEDs and other medications taken for comorbidities are individually discussed for each of these new agents. Drug concentrations are not routinely monitored for these newer agents, and there have been few studies designed to investigate their concentration-effect relationships. For most of these medications, the concentrations observed in responders and nonresponders overlap considerably and levels associated with efficacy are often associated with adverse events, complicating the definition of target ranges. Also, epilepsy manifests itself sporadically causing difficulty in clinically monitoring efficacy of medications. Therapeutic drug monitoring provides for the individualization of treatment for these agents, which is important because they demonstrate significant variability in inter- and intraindividual pharmaco-kinetic properties. Therapeutic drug monitoring also allows for identification of noncompliance, drug interactions, and toxicity. Current knowledge of the relationships between efficacy, toxicity, and drug concentrations is discussed.

The T-type calcium channel as a new therapeutic target for Parkinson's disease

Parkinson's disease (PD) is one of the most prevalent movement disorder caused by degeneration of the dopaminergic neurons in substantia nigra pars compacta. Deep brain stimulation (DBS) at the subthalamic nucleus (STN) has been a new and effective treatment of PD. It is interesting how a neurological disorder caused by the deficiency of a specific chemical substance (i.e., dopamine) from one site could be so successfully treated by a pure physical maneuver (i.e., DBS) at another site. STN neurons could discharge in the single-spike or the burst modes. A significant increase in STN burst discharges has been unequivocally observed in dopamine-deprived conditions such as PD, and was recently shown to have a direct causal relation with parkinsonian symptoms. The occurrence of burst discharges in STN requires enough available T-type Ca(2+) currents, which could bring the relatively negative membrane potential to the threshold of firing Na(+) spikes. DBS, by injection of negative currents into the extracellular space, most likely would depolarize the STN neuron and then inactivate the T-type Ca(2+) channel. Burst discharges are thus decreased and parkinsonian locomotor deficits ameliorated. Conversely, injection of positive currents into STN itself could induce parkinsonian locomotor deficits in animals without dopaminergic lesions. Local application of T-type Ca(2+) channel blockers into STN would also dramatically decrease the burst discharges and improve parkinsonian locomotor symptoms. Notably, zonisamide, which could inhibit T-type Ca(2+) currents in STN, has been shown to benefit PD patients in a clinical trial. From the pathophysiological perspectives, PD can be viewed as a prototypical disorder of "brain arrhythmias". Modulation of relevant ion channels by physical or chemical maneuvers may be important therapeutic considerations for PD and other diseases related to deranged neural rhythms.

Review of therapeutic options for adjuvant treatment of focal seizures in epilepsy: focus on lacosamide

Epilepsy is one of the most common serious neurological conditions worldwide, with an age-adjusted incidence of approximately 50 per 100,000 persons per year in developed countries. Antiepileptic therapy can result in long-term remission in 60-70% of patients, but many patients will require combination treatment to achieve optimal seizure control, as monotherapy is ineffective at controlling seizures in 30-53% of patients. Despite the increase in available treatment options, patient outcomes have not improved significantly and there is still a need for more effective therapies. Drugs used in the treatment of focal-onset seizures are a diverse range of compounds, and in most cases their mechanism of action is unknown or poorly defined. This review discusses the efficacy and safety of the newer adjuvant antiepileptic therapies that may improve outcomes in patients unresponsive to monotherapy, including clobazam, vigabatrin, lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam, oxcarbazepine, pregabalin, zonisamide and eslicarbazepine, with focus on lacosamide. Lacosamide has been shown to exert its anticonvulsant effects predominantly by enhancement of the slow inactivation of voltage-gated sodium channels. Lacosamide is indicated for use as adjuvant treatment of focal-onset seizures in patients with epilepsy, and there is some evidence that it may also be of use in patients with status epilepticus and cancer patients with epilepsy. The efficacy of lacosamide has been assessed in three randomized, double-blind, placebo-controlled clinical trials, all of which have shown lacosamide to be effective at reducing seizure frequency and increasing 50% responder rates in patients with focal-onset seizures. Long-term lacosamide treatment is generally well tolerated and is not associated with significant drug interactions; the availability of an intravenous form of the drug also makes it particularly useful for a broad range of patients.

Myoclonic disorders: a practical approach for diagnosis and treatment

Myoclonus is a sudden, brief, involuntary muscle jerk. It is caused by abrupt muscle contraction, in the case of positive myoclonus, or by sudden cessation of ongoing muscular activity, in the case of negative myoclonus (NM). Myoclonus may be classified in a number of ways, although classification based on the underlying physiology is the most useful from the therapeutic viewpoint. Given the large number of possible causes of myoclonus, it is essential to take a good history, to clinically characterize myoclonus and to look for additional findings on examination in order to limit the list of possible investigations. With regards to the history, the age of onset, the character of myoclonus, precipitating or alleviating factors, family history and associated symptoms and signs are important. On examination, it is important to see whether the myoclonus appears at rest, on keeping posture or during action, to note the distribution of jerks and to look for the stimulus sensitivity. Electrophysiological tests are very helpful in determining whether myoclonus is cortical, subcortical or spinal. A single pharmacological agent rarely control myoclonus and therefore polytherapy with a combination of drugs, often in large dosages, is usually needed. Generally, antiepileptic drugs such as valproate, levetiracetam and piracetam are effective in cortical myoclonus, but less effective in other forms of myoclonus. Clonazepam may be helpful with all types of myoclonus. Focal and segmental myoclonus, irrespective of its origin, may be treated with botulinum toxin injections, with variable success.

New approaches to the pharmacological treatment of obesity: can they break through the efficacy barrier?

In this review we assess the range of centrally active anorectics that are either in human clinical trials, or are likely to be so in the near future. We describe their weight loss efficacy, mode of action at both pharmacological and behavioural levels, where understood, together with the range of side effects that might be expected in clinical use. We have however evaluated these compounds against the considerably more rigorous criteria that are now being used by the Federal Drugs Agency and European Medicines Agency to decide approvals and market withdrawals. Several trends are evident. Recent advances in the understanding of energy balance control have resulted in the exploitation of a number of new targets, some of which have yielded promising data in clinical trials for weight loss. A second major trend is derived from the hypothesis that improved weight loss efficacy over current therapy is most likely to emerge from treatments targeting multiple mechanisms of energy balance control. This reasoning has led to the development of a number of new treatments for obesity where multiple mechanisms are targeted, either by a single molecule, such as tesofensine, or through drug combinations such as qnexa, contrave, empatic, and pramlintide+metreleptin. Many of these approaches also utilise advances in formulation technology to widen safety margins. Finally, the practicality of peptide therapies for obesity has become better validated in recent studies and this may allow more rapid exploitation of novel targets, rather than awaiting the development of orally available small molecules. We conclude that novel, more efficacious and better tolerated treatments for obesity may become available in the near future.

Urolithiasis on the ketogenic diet with concurrent topiramate or zonisamide therapy

Children with refractory epilepsy who are co-treated with the ketogenic diet (KD) and carbonic anhydrase inhibitor (CA-I) anti-epileptic medications including topiramate (TPM) and zonisamide (ZNS) are at risk for urolithiasis. Retrospective chart review of all children treated with ketogenic therapy at our institution was performed in order to estimate the minimal risk of developing signs or symptoms of stone disease. Children (N=93) were classified into groups according to KD+/-CA-I co-therapy. Fourteen patients had occult hematuria or worse, including 6 with radiologically confirmed stones. Three of 6 calculi developed in the KD+ZNS group of 17 patients who were co-treated for a cumulative total of 97 months (3.1 stones per 100 patient months). One confirmed stone was in the KD+TPM group of 22 children who were co-treated for a cumulative total of 263 months (0.4 stones per 100 patient months). All six patients had at least three of five biochemical risk factors including metabolic acidosis, concentrated urine, acid urine, hypercalciuria and hypocitraturia. Standard of care interventions to minimize hypercalciuria, crystalluria and stone formation used routinely by pediatric nephrologists should also be prescribed by neurologists treating patients with combination anti-epileptic therapy. Non-fasting KD initiation, fluid liberalization, potassium citrate prophylaxis as well as regular laboratory surveillance are indicated in this high risk population.

The safety and tolerability of newer antiepileptic drugs in children and adolescents

The newer antiepileptic drugs (AEDs) provide more therapeutic options and overall improved safety and tolerability for patients. To provide the best care, physicians must be familiar with the latest tolerability and safety data. This is particularly true in children, given there are relatively fewer studies examining the effects of AEDs in children compared with adults. Since we now have significant paediatric literature on each of these agents, we provide a comprehensive and current literature review of the newer AEDs, focusing on safety and tolerability data in children and adolescents. Because the safety profiles in children differ from those in adults, familiarity with this literature is important for child neurologists and other paediatric caregivers. We have organized the data by organ system for each AED for easier reference.

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.

Long-term cognitive and mood effects of zonisamide monotherapy in epilepsy patients

This study was a prospective, randomized, open-label investigation of the long-term effects of zonisamide (ZNS) monotherapy on cognition and mood of patients with epilepsy. Forty-three patients with epilepsy received ZNS, with final dose groups of 100, 200, 300, and 400mg/day. Cognitive and mood tests were done twice, at baseline and 1 year after starting medication. Nine patients were withdrawn prior to their follow-up tests. Three patients (33%) dropped out during the titration period because of cognitive and mood problems. Thirty-four patients completed follow-up neuropsychological tests. After 1 year of treatment, 16 patients (47%) complained of cognitive deficits. Only 5 patients (15%) experienced mood changes. Although ZNS decreased seizure frequency and EEG abnormalities and did not elicit significant mood changes, it had negative effects on several cognitive tests. Worse performance on delayed word recall, Trail Making Test Part B, and verbal fluency was related to dose. In conclusion, ZNS has adverse effects on cognition even after 1 year of treatment.

Long-term efficacy and safety of zonisamide monotherapy in epilepsy patients

BACKGROUND AND PURPOSE

Zonisamide (ZNS) is a useful antiepileptic drug with a broad therapeutic spectrum. However, there is limited information on the long-term use of ZNS as a monotherapy. This study investigated the long-term effects of ZNS as a monotherapy for the treatment of epilepsy.

METHODS

We retrospectively analyzed the records of epilepsy patients treated with ZNS monotherapy at our clinic. We identified outcomes for patients treated with ZNS monotherapy for a minimum of 6 months. Efficacy was quantified as the percentage change in seizure frequency, and safety was assessed by the frequency and types of adverse events.

RESULTS

Sixty patients who received ZNS for a minimum of 6 months were included. The mean duration of treatment was 19.8 months (range, 6-37 months), and the mean ZNS dosage was 255 mg/day (range, 100-500 mg/day). Twenty-seven patients (45%) were seizure-free, and an additional 20 patients (33%) had above 50% seizure frequency reduction at the last follow-up visit. Partial seizures with or without secondary generalization and generalized seizures were well controlled by ZNS, whereas complex partial seizures were not. Forty-eight patients (80%) reported mild-to-moderate adverse events, including memory loss (35%), attention deficit (27%), and weight loss (20%).

CONCLUSIONS

Long-term ZNS monotherapy is effective at treating a broad spectrum of seizure disorders, except complex partial seizures. However, a specific adverse event, such as cognitive impairment, is common and long-lasting.

A new look at the second-generation antiepileptic drugs: a decade of experience

OBJECTIVE

To review data from the literature regarding the efficacy and tolerability of the second-generation antiepileptic drugs which were approved by the Food and Drug Administration (FDA) since 1994.

METHODS

A MEDLINE search of the literature, as well as review of bibliographies, was performed to identify randomized controlled trials and other reports evaluating efficacy, pharmacokinetic profile, adverse effects, and drug interactions of the second-generation antiepileptic drugs. Key search terms included felbamate, gabapentin, lamotrigine, topiramate, tiagabine, levetiracetam, oxcarbazepine, zonisamide, and pregabalin.

RESULTS

Each of the second-generation antiepileptic drugs has demonstrated statistically significant reductions in seizure frequency over baseline compared with placebo or active control. Limited studies of efficacy of the new agents compared with the traditional antiepileptic drugs found no significant differences. Each of the second-generation antiepileptic drugs has a unique pharmacokinetic and side-effect profile. Compared with the traditional agents, the second-generation antiepileptic drugs have fewer serious adverse effects, as well as drug interactions.

CONCLUSION

Knowledge of the second-generation antiepileptic drugs has greatly expanded over the past decade. The newer agents offer many options in the treatment of epilepsy that are safe, efficacious, and well tolerated.

Erratum to “Safety of zonisamide therapy: Prospective follow-up survey”

Zonisamide safety was evaluated based on a postmarketing surveillance study of patients treated for 1-3 years. Nine hundred twenty-eight children and 584 adult (ages 1 month to 79 years), including 372 newly-diagnosed patients, received zonisamide for partial and generalized epilepsies. Of the intractable patients, 1088 received zonisamide in combination with other antiepileptic drugs (AED), and 52 successfully transitioned to zonisamide monotherapy. A total of 1089 adverse events occurred in 476 (31.5%) of 1512 patients. Incidence of adverse effects was significantly lower among patients receiving zonisamide monotherapy than in those receiving polytherapy: 21% (18.9% of children, 29.4% of adults) versus 35.6% (30.4% of children, 41.7% of adults), respectively. The total incidence of adverse effects was lower for children (26.2%) than for adults (39.9%). Most common adverse events included mental/psychiatric symptoms (19.4%), gastrointestinal symptoms (8.7%), and neurological symptoms (6.5%). Effects that seemed unique to zonisamide were impairment of mental function, motivation or volition, and hipohidrosis. Urinary calculi were detected in only two patients (0.13%). Teratogenicity was evaluated in six patients. Two patients on zonisamide monotherapy and three on polytherapy delivered normal children. One of four patients on polytherapy conceived a fetus with a skull defect with cerebral and cerebellar dysgenesis, namely anencephaly.

Zonisamide or levetiracetam for adults with cyclic vomiting syndrome: a case series

BACKGROUND & AIMS

Management of cyclic vomiting syndrome in adults is limited by the small number of effective medications for maintenance therapy. The clinical response to treatment with 2 newer antiepileptic drugs was evaluated retrospectively to see whether they might have a prophylactic role in this syndrome.

METHODS

Outpatient records from 20 adult patients with cyclic vomiting syndrome attending a university-based practice were reviewed. Each had received zonisamide (median dose, 400 mg/d) or levetiracetam (median dose, 1000 mg/d) because tricyclic antidepressants alone were unsatisfactory as maintenance medications. Outcome was graded from chart review and directed interview; characteristics of the vomiting episodes were compared before and after initiation of antiepileptic drug therapy.

RESULTS

At least moderate clinical response was described by 15 (75.0%) subjects, and 4 of these (20.0% of the total) reported symptomatic remission during 9.5 +/- 1.8 months of follow-up. Rate of vomiting episodes decreased from 1.3 +/- 0.3 to 0.5 +/- 0.2 per month (P = .01). Tricyclic antidepressants were discontinued in 11 (61.1%) of the 18 subjects who were still taking the medications when antiepileptic drug therapy was initiated. Moderate or severe side effects were reported by 45.0%, but by switching drugs, intolerance to antiepileptic drug therapy occurred in only 1 subject.

CONCLUSIONS

Newer antiepileptic drugs, specifically zonisamide and levetiracetam, appeared beneficial as maintenance medications for nearly three fourths of adults with cyclic vomiting syndrome in this uncontrolled clinical experience. Although side effects occur in a large proportion of subjects, newer antiepileptic drugs might offer an alternative for patients who fail conventional treatment.

Zonisamide - a review of experience and use in partial seizures

Zonisamide is a modern antiepileptic drug (AED) that is distinguished from other AEDs by its unique structure and broad mechanistic profile. Preclinical studies have reported a range of potential mechanisms of action for zonisamide, such as blocking voltage-gated sodium channels, reduction of T-type calcium channel currents, and enhancement of gamma-aminobutyric acid (GABA)-mediated inhibition, which are indicative of its broad antiseizure effects. Zonisamide has a favorable linear pharmacokinetic profile, a long half-life, and a low incidence of protein-binding interactions with other AEDs. Hepatically metabolized through the cytochrome P450 pathway, zonisamide does not induce its own metabolism or liver enzymes. For more than 2 decades, zonisamide has been extensively used as monotherapy and adjunctive therapy for the treatment of partial and generalized seizures in pediatric and adult patients in Japan. Zonisamide was approved in the USA in 2000 as adjunctive therapy for partial seizures in adults. With over 2 million patient-years of exposure internationally, zonisamide has demonstrated safety and efficacy against a multitude of epilepsy and seizure types, including both partial and generalized seizures. This review focuses on the experience and use of zonisamide in partial seizures, as well as possible new uses for zonisamide.

Anticonvulsant Therapy in Dogs and Cats

This article reviews anticonvulsant therapies in current use for dogs and cats and briefly describes new modes of anticonvulsant therapy that are being investigated or pending publication. Most of the information contained within the article is based on published information. Some of the information, however, is based on the author's clinical experience and is identified as such.

Zonisamide: a review of its use in the management of partial seizures in epilepsy

Zonisamide (Zonegran, Excegran) is a new-generation, broad-spectrum antiepileptic drug (AED) currently approved as adjunctive therapy for the treatment of medically refractory partial seizures in adults in the US and as adjunctive therapy or monotherapy in the control of partial and generalised seizures in adults and children in Japan and Korea. Either as adjunctive therapy or monotherapy, zonisamide effectively reduces the frequency of partial seizures, with or without secondary generalisation to tonic-clonic seizures, in adults and children with epilepsy. The drug is generally well tolerated and, additionally, has a favourable pharmacokinetic profile permitting once- or twice-daily administration. Direct head-to-head comparisons with other AEDs would be beneficial in fully defining the place of zonisamide in therapy. In the meantime, adjunctive therapy or monotherapy with zonisamide is a convenient, useful option for the management of partial seizures, including those refractory to other AEDs.

Myoclonus

Myoclonus is defined as sudden, brief, shock-like involuntary movements affecting one or more muscles. The term encompasses a wide range of different physiologic and pathologic processes. When evaluating a patient with myoclonus, the first step is to identify the underlying etiology. Initial treatment should be directed against any underlying toxic or metabolic conditions. Next, targeted pharmacotherapy should be chosen, principally on the basis of the probable anatomical localization. Although treatment is initiated with a single agent, polytherapy usually is necessary to achieve adequate symptomatic control. The prognosis of myoclonus is highly variable, and largely depends on the underlying cause.

Effect of zonisamide on the pharmacokinetics and pharmacodynamics of a combination ethinyl estradiol-norethindrone oral contraceptive in healthy women

BACKGROUND

Several antiepileptic drugs have clinically significant pharmacokinetic interactions with oral contraceptives (OCs) that may result in contraceptive failure.

OBJECTIVE

The aim of this study was to assess the effect of zonisamide on the pharmacokinetics of the individual components of a combination OC (ethinyl estradiol [EE] 0.035 mg and norethindrone [NOR] 1 mg) and on pharmacodynamic variables that may be increased in the event of reduced contraceptive efficacy (concentrations of serum luteinizing hormone [LH], follicle-stimulating hormone [FSH], and progesterone).

METHODS

This was a single-center, open-label, 1-sequence, crossover study. Healthy, premenopausal women received the combination OC for three 28-day cycles (combination OC for 21 days, followed by placebo for 7 days). Following stabilization on the OC during the first cycle, blood was collected during cycle 2 for the determination of serum EE and NOR profiles (day 14) and serum LH, FSH, and progesterone concentrations (days 13-15). Starting on day 15 of cycle 2, zonisamide was administered orally at 100 mg/d and titrated to a target dose of 400 mg/d. EE and NOR profiles and serum LH, FSH, and progesterone concentrations were obtained again in cycle 3 (in the presence of zonisamide) and compared with those from cycle 2 (in the absence of zonisamide).

RESULTS

Thirty-seven healthy premenopausal women (mean age, 26.1 years [range, 18-51 years]; mean body weight, 65.5 kg [range, 50.4-93.1 kg]; mean height, 165.8 cm [range, 152.4-182.9 cm]) received > or =1 dose of zonisamide. Of the 33 subjects (89.2%) who completed the study, 26 (78.8%) underwent titration to a stable zonisamide dose of 400 mg/d. For EE, the mean (SD) AUC over a 24-hour dosing interval (AUC(tau)) was 1139 (317) pg.h/mL in cycle 2 and 1143 (312) pg.h/mL in cycle 3; the mean C(max) in the respective cycles was 133 (39) and 141 (46) pg/mL. For NOR, the corresponding values were 140 (48) and 159 (46) ng.h/mL for AUC(tau) and 21 (5.4) and 23 (6.7) ng/mL for C(max). The 90% Cls for the geometric mean ratios (cycle 3:cycle 2) for AUC(tau) and C(max) fell within the accepted range for lack of interaction (0.80-1.25). There were no increases in LH, FSH, or progesterone concentrations between cycle 2 and cycle 3.

CONCLUSIONS

In these healthy volunteers, steady-state zonisamide dosing had no clinically significant effect on the pharmacokinetics of EE or NOR. There was no pharmacodynamic evidence that zonisamide is likely to reduce the contraceptive effectiveness of OCs containing EE and NOR.

Analysis of antiepileptic drugs in biological fluids by means of electrokinetic chromatography

An overview of the electrokinetic chromatographic methods for the analysis of antiepileptic drug levels in biological samples is presented. In particular, micellar electrokinetic capillary chromatography is a very suitable method for the determination of these drugs, because it allows a rapid, selective, and accurate analysis. In addition to the electrokinetic chromatographic studies on the determination of antiepileptic drugs, some information regarding sample pretreatment will also be reported: this is a critical step when the analysis of biological fluids is concerned. The electrokinetic chromatographic methods for the determination of recent antiepileptic drugs (e.g., lamotrigine, levetiracetam) and classical anticonvulsants (e.g., carbamazepine, phenytoin, ethosuximide, valproic acid) will be discussed in depth, and their pharmacological profiles will be briefly described as well.

Oxcarbazepine, topiramate, zonisamide, and levetiracetam: potential use in neuropathic pain

BACKGROUND

Oxcarbazepine, topiramate, zonisamide, and levetiracetam are the antiepileptic drugs (AEDs) most recently approved by the US Food and Drug Administration. Based on the experience with carbamazepine, gabapentin, and lamotrigine, these newer AEDs are being investigated for the management of neuropathic pain.

OBJECTIVE

This article reviews preclinical and clinical data on the efficacy and tolerability of these 4 AEDs in the management of neuropathic pain, as well as the pharmacokinetics, drug-interaction potential, adverse effects, and dosing of these agents, with an emphasis on their use in older individuals.

METHODS

Relevant studies were identified through a MEDLINE search of the Englidh-language literature published between 1986 and May 2003, a review of the reference lists of identified articles, and abstracts from the annual meetings of the American Academy of Neurology (1986-2002) and the 2003 Annual Meeting of the American Pain Society. Search terms were oxcarbazepine, topiramate, zonisamide, and levetiracetam.

RESULTS

Oxcarbazepine and topiramate have been effective in animal models of neuropathic pain. Thirty-four publications on the efficacy and tolerability of the 4 agents were identified (25 case reports/case series, 6 randomized parallel-group studies, and 3 randomized crossover studies). The 9 randomized studies were restricted to oxcarbazepine and topiramate, and 23 (68%) publications were available in abstract form only. These preliminary data suggest that the 4 newer AEDs may be useful in a wide variety of neuropathic pain syndromes; however, additional data, including full-length peer-reviewed reports, are necessary before their true analgesic potential in neuropathic pain can be determined. All 4 agents have pharmacodynamic interactions with other psychotherapeutic drugs, potentiating adverse central nervous system events such as sedation. With the exception of levetiracetam, these drugs also have pharmacokinetic interactions with other drugs, although to a somewhat lesser extent than carbamazepine. These agents have some unique adverse effects not frequently monitored by clinicians, such as hyponatremia, nephrolithiasis, acute myopia with secondary angle-closure glaucoma, and weight loss.

CONCLUSIONS

Based on preliminary data, oxcarbazepine, topiramate, zonisamide, and levetiracetam may be useful in the treatment of a wide variety of neuropathic pain syndromes, although full publication of the results of controlled trials is awaited. These agents are associated with specific adverse effects not commonly monitored by clinicians. Of the 4, levetiracetam appears to be easiest to use (ie, no need for dose adjustment in organ dysfunction, no need for laboratory monitoring) and best tolerated, and has not been associated with the unique toxicities seen with oxcarbazepine, topiramate, and zonisamide. The ultimate role of these agents in the therapeutic armamentarium against pain requires further research and experience. In the interim, these 4 agents should be used to treat neuropathic pain in the elderly only when carbamazepine, gabapentin, or lamotrigine cannot be used or when the response to the aforementioned agents is suboptimal.

Safety of zonisamide therapy: prospective follow-up survey

Zonisamide safety was evaluated based on a postmarketing surveillance study of patients treated for 1-3 years. Nine hundred twenty-eight children and 584 adults (ages 1 month to 79 years), including 372 newly-diagnosed patients, received zonisamide for partial and generalized epilepsies. Of the intractable patients, 1008 received zonisamide in combination with other antiepileptic drugs (AED), and 52 successfully transitioned to zonisamide monotherapy. A total of 1089 adverse events occurred in 476 (31.5%) of 1512 patients. Incidence of adverse effects was significantly lower among patients receiving zonisamide monotherapy than in those receiving polytherapy: 21% (18.9% of children, 29.4% of adults) versus 35.6% (30.4% of children, 41.7% of adults), respectively. The total incidence of adverse effects was lower for children (26.2%) than for adults (39.9%). Most common adverse events included mental/psychiatric symptoms (19.4%), gastrointestinal symptoms (8.7%), and neurological symptoms (5.8%). Effects that seemed unique to zonisamide were impairment of mental function, motivation or volition, and hypohidrosis. Urinary calculi were detected in only two patients (0.13%). Teratogenicity was evaluated in six patients. Two patients on zonisamide monotherapy and three on polytherapy delivered normal children. One of four patients on polytherapy conceived a fetus with a skull defect with cerebral and cerebellar dysgenesis.

Zonisamide Therapy for Refractory Idiopathic Epilepsy in Dogs

Twelve dogs with poorly controlled idiopathic epilepsy were entered into a prospective, open-label, noncomparative study. Oral zonisamide was administered as an additional therapy at a dosage adequate to achieve serum drug concentrations of 10 to 40 microg/mL. Seizure frequency before and after initiation of zonisamide therapy was recorded. A dosing interval of q 12 hours was sufficient to maintain serum zonisamide concentrations within the therapeutic range. The mean dosage of zonisamide required was 8.9 mg/kg q 12 hours. Seven (58%) dogs responded favorably, experiencing a mean reduction in seizures of 81.3%. Five dogs had an increase in seizure frequency. Mild side effects (e.g., transient sedation, ataxia, vomiting) occurred in six dogs.

Treatment Strategies for Myoclonic Seizures and Epilepsy Syndromes with Myoclonic Seizures

Despite the availability of numerous treatment options, the diagnosis and treatment of myoclonic seizures continue to be challenging. Based on clinical experience, valproate and benzodiazepines have historically been used to treat myoclonic seizures. However, many more treatment options exist today, and the clinician must match the appropriate treatment with the patient's epilepsy syndrome and its underlying etiology. Comorbidities and other medications must also be considered when making decisions regarding treatment. Rarely, some antiepileptic drugs may exacerbate myoclonic seizures. Most epileptic myoclonus can be treated pharmacologically, but some cases respond better to surgery, the ketogenic diet, or vagus nerve stimulation. Because myoclonic seizures can be difficult to treat, clinicians should be flexible in their approach and tailor therapy to each patient.

Myoclonus

PURPOSE OF REVIEW

Myoclonus, one of the most common involuntary movement disorders, poses particular challenges for the treating physician. The evaluation of a patient with myoclonus depends completely on the clinical history and examination, supported when necessary by electrophysiology, neuroimaging and selected genetic and laboratory testing. The sudden, shock-like jerks which define myoclonus may be highly disabling, and when they persist, often require treatment.

RECENT FINDINGS

In a paper published in this journal, we reviewed the published trials of antimyoclonic agents, and formulated a treatment algorithm based on the available evidence. In the current paper, we present our approach for evaluating patients with myoclonus, and suggest practical guidelines for treating patients based on the pre-2000 literature and on studies published in the last 2 years. The newer medications which are being used in management of myoclonus are levetiracetam and gamma-hydroxybutyric acid. Levetiracetam is especially useful for posthypoxic myoclonus and gamma-hydroxybutyric acid for alcohol-sensitive myoclonus. A combination of medications is often needed to obtain adequate control of symptoms. Botulinum toxin is also being introduced for focal myoclonus with encouraging results.

SUMMARY

There are no approved medications for myoclonus, and most therapies are borrowed from the antiepileptic and psychiatric armamentarium. Nonetheless, there is a logic to the choice and dosing of antimyoclonic drugs, and we hope that by applying a few simple principles, neurologists will approach the care of these patients with confidence.

Antiepileptic drugs as a possible neuroprotective strategy in brain ischemia

Several new antiepileptic drugs (AEDs) have been introduced for clinical use recently. These new AEDs, as did the classic AEDs, target multiple cellular sites both pre- and postsynaptically. The major common goal of the pharmacological treatment using AEDs is to counteract abnormal brain excitability by either decreasing excitatory transmission or enhancing neuronal inhibition. Interestingly, an excessive release of excitatory amino acids and a reduced neuronal inhibition also occur in brain ischemia. Thus, recently, the use of AEDs as a possible neuroprotective strategy in brain ischemia is receiving increasing attention, and many AEDs have been tested in animal models of stroke, providing encouraging results. Experimental studies utilizing global or focal ischemia in rodents have provided insights into the possible neuroprotective action of the various AEDs. However, the implication of these studies in the treatment of acute stroke in humans is not always direct. In fact, various clinical studies with drugs targeting the same voltage- and ligand-gated channels modulated by most of the AEDs failed to show neuroprotection. The differential mechanisms that underlie the development of focal ischemic injury in experimental animal models versus human stroke require further investigation to open a new therapeutic perspective for neuroprotection that might be applicable in the future.

Oligohydrosis and hyperthermia: pilot study of a novel topiramate adverse effect

A 6-year-old boy with partial complex seizures developed recurrent episodes of hyperthermia 2 months after topiramate was introduced into his antiepilepsy drug regimen. Further investigation revealed that the febrile episodes were related to environmental temperature and physical activity. A pilocarpine iontophoresis sweat test showed that the amount of sweat produced by the child was 5% that of age-matched controls. Topiramate discontinuation resulted in the disappearance of febrile episodes and normalization of sweat quantity in repeat sweat testing. Based on this observation and the previous data on zonisamide and isolated case reports on topiramate-related hyperthermia and the effect on sweat production, topiramate was suspected of causing oligohydrosis. A pilot study was carried out involving 13 additional children and young adults (age range 1-37 years) receiving topiramate. All patients were directly questioned regarding symptoms of decreased sweating and heat intolerance, went through a pilocarpine iontophoresis sweat test, and were compared with 14 age-matched controls who went through the sweat test for unrelated reasons. Nine of the patients were found to have reduced sweat quantity on the pilocarpine iontophoresis sweat test (including index case) (mean 0.089 g/30 minutes, SD 0.082; age-matched control: mean 0.21 g/30 minutes, SD 0.06). Eight of them were children (below 16 years). However, only three patients revealed symptoms related to heat intolerance. Topiramate is most likely responsible for decreased sweat production as detected by a pilocarpine iontophoresis sweat test. The effect seems to be more significant in children than in adults. There is a discrepancy between test results and clinical symptoms. Interestingly, oligohydrosis was found to be a relatively common side effect of zonisamide. Both zonisamide and topiramate share a carbonic anhydrase inhibitor activity. The significance of oligohydrosis in hot climates should not be underestimated. Its extent, the role of sweat test prediction, and clinical significance during topiramate treatment should be further estimated.

Visual hallucinations associated with zonisamide

Zonisamide is a broad-spectrum antiepileptic drug used to treat various types of seizures. Although visual hallucinations have not been reported as an adverse effect of this agent, we describe three patients who experienced complex visual hallucinations and altered mental status after zonisamide treatment was begun or its dosage increased. All three had been diagnosed earlier with epilepsy, and their electroencephalogram (EEG) findings were abnormal. During monitoring, visual hallucinations did not correlate with EEG readings, nor did video recording capture any of the described events. None of the patients had experienced visual hallucinations before this event. The only recent change in their treatment was the introduction or increased dosage of zonisamide. With either discontinuation or decreased dosage of the drug the symptoms disappeared and did not recur. Further observations and reports will help clarify this adverse effect. Until then, clinicians need to be aware of this possible complication associated with zonisamide.

New antiepileptic drug therapies

The introduction of these new antiepileptic drugs, from felbamate to levetiracetam, raised hope of control of epilepsy with fewer adverse effects and improved quality of life. Unfortunately, many patients continue to experience refractory epilepsy despite the use of these new agents, and dose-related adverse effects and idiosyncratic reactions continue to be problematic. A recent report describes six new compounds in preclinical development, and five in clinical trials [131]. As the number of available, effective, but imperfect antiepileptic drugs increases, many challenges remain. These include: choosing the drug appropriate for the epileptic syndrome, assessing accurately the range of a drug's adverse effects in an individual patient, and considering carefully the drug's interactions in combination drug therapy. In considering drug combinations, differing mechanisms of drug action and favorable pharmacodynamic interactions (an area requiring additional studies) are of importance. Clinicians caring for children who have epilepsy anticipate further advances in the pharmacogenetics and molecular pathophysiology of epilepsy, leading to individually tailored, effective, and safe therapy.

Frontiers in Neuropharmacotherapy Part I: Alzheimer’s Disease and Epilepsy

Cholinesterase inhibitors, and particularly donepezil, are the standard of care in the management of Alzheimer’s disease. Newer agents, such as rivastigmine, galantamine, and metrifonate, provide therapeutic alternatives but have advantages and disadvantages compared with donepezil. Clinical studies and continued research of the pathophysiology of Alzheimer’s disease help define the role of both the newer agents and the original cholinesterase inhibitor, tacrine. Therapies with other mechanisms of action, such as estrogen and nonsteroidal anti-inflammatory drugs (NSAIDs), are also being actively investigated for their effects on cognition. Since 1993, 8 new antiepileptic drugs have been approved by the FDA, including felbamate, gabapentin, lamotrigine, topiramate, tiagabine, and 3 recently introduced agents, oxcarbazepine, levetiracetam, and zonisamide. These second-generation agents are generally more tolerable and have fewer drug interactions than traditional antiepileptics, and some provide alternative mechanisms that may be beneficial in the management of refractory epileptic disorders. However, until clinical experience with the newer antiepileptics accumulates and well-designed comparative trials are conducted, a review of individual studies of the safety and efficacy of the newer agents helps provide the basis for treatment decisions. New information regarding traditional therapies, including new formulations and updated treatment guidelines, also assist clinicians in optimizing antiepileptic therapy.

Myoclonic status epilepticus: video presentation

A young woman with juvenile myoclonic epilepsy had recurrent attacks of myoclonic status epilepticus related to a long history of limited compliance and irregular sleep. The diagnosis of this clinical pattern is based mainly on clinical description. A home video captured an attack.

Progressive Myoclonic Epilepsies

The treatment of progressive myoclonus epilepsy (PME) remains a major therapeutic challenge in neurology. Generalized convulsive seizures are often well controlled through classic antiepileptic drugs (AEDs) like valproate and clonazepam, whereas myoclonus, the main symptom that is affecting patients most in their daily life, is usually refractory to standard AEDs. Alternative therapy concepts have been and still are investigated. Among the new drugs, zonisamide and piracetam have shown the most promising results as add-on treatments. Other therapeutic approaches, like the use of antioxidants, 5-hydroxytryptophan (5-HTP), and baclofen should also be taken into consideration for the treatment of intractable cases of PME. Nonpharmacologic treatment options such as diet and physical therapy should always be considered, because they may save costs and side effects. In some instances, the occasional use of alcohol has shown beneficial effects.

Contrasting effects of zonisamide and acetazolamide on amygdaloid kindling in rats

PURPOSE

Zonisamide (ZNS) and acetazolamide (AZM) are two antiepileptic drugs (AEDs) that differ in clinical efficacy. To elucidate the mechanisms of action of these compounds, we investigated their therapeutic and prophylactic effects in rats by using a kindling model of partial epilepsy.

METHODS

Electrodes were implanted into the left amygdala of adult male Wistar rats. The animals were stimulated at the afterdischarge threshold until five stage 5 seizures were induced. The generalized seizure threshold was then determined. Therapeutic effects were examined in rats manifesting successive convulsions with near-threshold stimulation. To test prophylactic effects, drugs were administered intraperitoneally before daily kindling stimulation until the animal had a stage 5 seizure or reached day 18.

RESULTS

ZNS (10-40 mg/kg; n=6) suppressed kindled seizures in a dose-dependent manner. Repeated administration for 7 days produced tolerance to anticonvulsive effects. AZM (25-200 mg/kg; n=7) showed limited therapeutic effect, alleviating only the clonic convulsion in stage 5 seizures and reducing afterdischarge duration. Secondary generalization was not significantly suppressed during repeated treatment (50-200 mg/kg; n=6). ZNS, 25 or 40 mg/kg (n=8), significantly retarded seizure development; 15.0 or 17.0 daily stimulations were required to produce a stage 5 seizure. AZM, 50-200 mg/kg (n=6), also retarded seizure development, with 14.0-14.8 stimulations required.

CONCLUSIONS

ZNS exhibited modest therapeutic and prophylactic effects, whereas AZM showed mainly prophylactic effects. Hypotheses are presented that may explain the mechanisms of action of these drugs.