Efficacy and safety of adjunctive zonisamide therapy for refractory partial seizures

Interactions between antiepileptic drugs and direct oral anticoagulants for primary and secondary stroke prevention

INTRODUCTION

Direct oral anticoagulants (DOAC) are the guideline-recommended therapy for prevention of stroke in atrial fibrillation (AF) and venous thromboembolism. Since approximately 10% of patients using antiepileptic drugs (AED) also receive DOAC, aim of this review is to summarize data about drug-drug interactions (DDI) of DOAC with AED by using data from PubMed until December 2023.

AREAS COVERED

Of 49 AED, only 16 have been investigated regarding DDI with DOAC by case reports or observational studies. No increased risk for stroke was reported only for topiramate, zonisamide, pregabalin, and gabapentin, whereas for the remaining 12 AED conflicting results regarding the risk for stroke and bleeding were found. Further 16 AED have the potential for pharmacodynamic or pharmacokinetic DDI, but no data regarding DOAC are available. For the remaining 17 AED it is unknown if they have DDI with DOAC.

EXPERT OPINION

Knowledge about pharmacokinetic and pharmacodynamic DDI of AED and DOAC is limited and frequently restricted to in vitro and in vivo findings. Since no data about DDI with DOAC are available for 67% of AED and an increasing number of patients have a combined medication of DOAC and AED, there is an urgent need for research on this topic.

Zonisamide: A Comprehensive, Updated Review for the Clinician

Purpose of Review

Zonisamide (ZNS) was first approved in the United States in 2000 for the adjunctive treatment of patients aged 16 years or older with partial (focal) seizures. Although ZNS has been proven to treat multiple seizure types, it has been largely underutilized in US clinical practice.

Recent Findings

Published literature demonstrated that antiseizure medications (ASMs) acting on Na+ and Ca2+ channels may add beneficial effects in many seizure types by reducing seizure frequency and leading to overall improvements. In addition, effects of ZNS may lead to clinical improvements in Parkinson disease, alcohol and sleep disorders, pain, and migraine. ZNS is available in multiple formulations and is a safe and effective, broad spectrum ASM.

Summary

The purpose of this review was to provide an update to what is known about the efficacy of ZNS and where it shows benefits in the treatment of patients with epilepsy and other CNS disorders through its many unique mechanisms of action.

The Effect of Zonisamide and Ethanol on Various Types of Memory in Rats

Background: Antiepileptic drugs might be useful in the treatment of alcohol use disorder. One of these drugs is zonisamide, which has been found to decrease alcohol intake and cravings. An important structure in the pathophysiology of addiction is the hippocampus. Memory deficits, which frequently occur in alcoholics, are associated with ethanol-induced changes in hippocampal plasticity and neurogenesis. The aim of this study was to assess the potential protective effect of zonisamide on memory in rats receiving alcohol and after the discontinuation of its administration. Methods: Wistar rats (n = 43) were tested in four behavioral models, namely: Morris water maze (MWM), passive avoidance (PA), contextual fear conditioning (CFC), and cued fear conditioning (CuFC). Results: Zonisamide co-administered with ethanol impaired spatial memory in MWM, but the drug did not affect memory in PA. However, the beneficial effect of zonisamide was observed after the discontinuation of ethanol administration, which was associated with the improvement of associative memory in CFC and the alleviation of alcohol-induced locomotor disturbances in CuFC. Conclusion: Zonisamide has a differential influence on memory, which depends inter alia on type of the memory, length of ethanol administration, or its absence.

Effects of zonisamide monotherapy on bone health in drug-naive epileptic patients

OBJECTIVE

Alteration of bone strength is an adverse effect of antiepileptic drug treatment. We investigated the effects of zonisamide (ZNS) monotherapy on bone mineral density (BMD) and biomarkers of bone metabolism after 13 months of treatment in drug-naive epileptic patients.

METHODS

Fifty-nine patients with new onset drug-naive epilepsy were enrolled (29 women, 30 men; mean age = 31.5 ± 11.5 years). The BMD and T scores were measured at the lumbar spine and femoral neck by using dual-energy X-ray absorptiometry. Biomarkers specific for bone metabolism (bone-specific alkaline phosphatase, parathyroid hormone, osteocalcin, insulinlike growth factor-1, C-telopeptide, and vitamin D3 levels) were measured before and after long-term ZNS monotherapy. Analysis of covariance (ANCOVA) was used to estimate BMD and biomarkers of bone metabolism before and after ZNS therapy. Age, sex, treatment duration, and ZNS dosage were included as covariates for adjustment in the ANCOVA model. Furthermore, subgroup analyses were performed for each sex, and the effect size was calculated.

RESULTS

After 13 months of ZNS treatment, the BMD and T scores at the lumbar spine (L1-L4 level) and femoral neck were not significantly different. Moreover, the biochemical markers showed no significant differences after ZNS monotherapy. Women showed significantly decreased baseline BMD at the femoral neck compared to men (P = .026), although the mean age and body mass index were not significantly different between the sexes. No significant changes in BMD or biomarkers of bone metabolism were seen in either sex after 13 months of ZNS treatment.

SIGNIFICANCE

The results suggest that long-term ZNS monotherapy does not affect bone health in drug-naive patients with epilepsy negatively.

Zonisamide add-on therapy for focal epilepsy

BACKGROUND

The majority of people with epilepsy have a good prognosis, and their seizures can be well controlled with the use of a single antiepileptic agent, but up to 30% develop dug-resistant epilepsy, especially those with focal seizures. In this review, we summarised the evidence from randomised controlled trials (RCT) of zonisamide, used as an add-on treatment for focal epilepsy uncontrolled by one or more concomitant antiepileptic drug. This is an updated version of the Cochrane review previously published in 2018.

OBJECTIVES

To evaluate the efficacy and tolerability of zonisamide, when used as an add-on treatment for people with focal epilepsy uncontrolled by one or more concomitant antiepileptic drugs.

SEARCH METHODS

For the latest update, we searched the Cochrane Register of Studies (CRS Web) and MEDLINE Ovid (September 2019). In addition, we contacted Eisai Limited (makers and licensees of zonisamide) and experts in the field, to seek any ongoing or unpublished studies.

SELECTION CRITERIA

Randomised controlled trials, in which add-on zonisamide was compared with placebo or another antiepileptic drug in people with focal epilepsy, uncontrolled by one or more concomitant antiepileptic drugs.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data, assessed for risk of bias using the Cochrane 'Risk of bias' tool, and assessed the certainty of the evidence, using the GRADE approach. The primary outcome was at least a 50% reduction in total seizure frequency; the secondary outcomes were (1) tolerability; and (2) adverse effects. We used an intention-to-treat approach for our primary analyses. We estimated summary risk ratios (RRs) for each outcome. We displayed a summary of the estimates of effects and certainty of the evidence for each outcome in a 'Summary of findings' table.

MAIN RESULTS

We did not find any new studies since the last version of this review. We included eight studies (1636 participants) from previous versions of this review. The overall RR with 95% confidence interval (CI) for at least a 50% reduction in seizure frequency for 300 mg to 500 mg/day of zonisamide compared to placebo was 1.90 (95% CI 1.63 to 2.22; 7 trials, 1371 participants; moderate-certainty evidence). The RR for 50% reduction in seizure frequency compared to placebo for any dose of zonisamide (100 mg to 500 mg/day) was 1.86 (95% CI 1.60 to 2.17; 7 trials, 1429 participants; moderate-certainty evidence). The number needed to treat for an additional beneficial outcome was six (95% CI 4.1 to 6.8). Two trials provided evidence of a dose-response relationship for this outcome. The RR for treatment withdrawal for 300 mg to 500 mg/day of zonisamide compared to placebo was 1.59 (95% CI 1.18 to 2.13; 6 trials, 1099 participants; moderate-certainty evidence), and for 100 mg to 500 mg/day was 1.44 (95% CI 1.08 to 1.93; 6 trials, 1156 participants; moderate-certainty evidence). The number needed to treat for an additional harmful outcome was 15 (95% CI 9.3 to 36.7). The following adverse effects were more likely to be associated with zonisamide than with placebo: ataxia (RR 3.85, 99% CI 1.36 to 10.93; 4 trials, 734 participants; low-certainty evidence); somnolence (RR 1.52, 99% CI 1.00 to 2.31; 8 trials, 1636 participants; moderate-certainty evidence); agitation (RR 2.35, 99% CI 1.05 to 5.27; 4 trials, 598 participants; low-certainty evidence); and anorexia (RR 2.74, 99% CI 1.64 to 4.60; 6 trials, 1181 participants; low-certainty evidence). Across the eight studies, we rated risk of bias domains at low or unclear risk of bias, apart from two studies, which we rated at high risk of attrition bias. Five of the eight studies were sponsored by the drug companies that produced zonisamide.

AUTHORS' CONCLUSIONS

When used as an add-on treatment in people with focal epilepsy, uncontrolled by one or more concomitant antiepileptic drugs, moderate-certainty evidence found that zonisamide was more successful than placebo at reducing the frequency of seizures by at least 50%. We were unable to identify minimum effective and maximum tolerated doses. The included trials evaluated a maximum stable-dose phase of 18 weeks, so results cannot be used to confirm longer periods of efficacy in seizure control. The results cannot be extrapolated to monotherapy, or to people with other seizure types or epilepsy syndromes.

[A retrospective analysis of using zonisamide and retention in monotherapy among patients with epilepsy in routine clinical practice]

INTRODUCTION

Zonisamide is one of the first antiepileptic drugs of new generation with a wide spectrum of action. It is successfully used in treatment of epilepsy for 30 years. The study aims at analyzing the results of the multicenter Russian trial on the efficacy and tolerability of zonisamide and retention in monotherapy.

MATERIAL AND METHODS

The analysis included 92 patients with focal epilepsy, aged 18-78 years, from 20 epileptology centers in different regions of Russia. The patients were treated with zonisamide in initial and subsequent treatment.

RESULTS AND CONCLUSION

The efficacy (the reduction of seizure frequency by >50%) was achieved in 81 (91%) out of 89 patients (95% CI 83.6-95.7%). Fifty-two patients received zonisamide for more than one year. The efficacy was achieved in 50 (96.2%) (95% CI 88.2-99.2%), including 39 (79.6%) patients with remission out of 49 patients with assessment of seizure free periods (95% CI was 66.8-89% for the frequency of remissions). The adverse effects were recorded in 27 (29.3%) patients. Seven (7.6%) patients were withdrawn due to these effects. The maximal duration of observation period was 50 month. Mean time of retention in treatment was 42.4 month (95% CI 38.7-46.2 month). The total frequency of retention in treatment was 82.1% (95% CI 73.1-91%) during the whole observation period.

Zonisamide add-on therapy for focal epilepsy

BACKGROUND

The majority of people with epilepsy have a good prognosis, and their seizures can be well controlled with the use of a single antiepileptic agent, but up to 30% develop refractory epilepsy, especially those with focal seizures. In this review, we summarised the evidence from randomised controlled trials (RCT) of zonisamide, used as an add-on treatment for focal epilepsy uncontrolled by one or more concomitant antiepileptic drug. This is an updated version of the Cochrane review previously published in 2013.

OBJECTIVES

To evaluate the efficacy and tolerability of zonisamide, when used as an add-on treatment for people with focal epilepsy uncontrolled by one or more concomitant antiepileptic drugs.

SEARCH METHODS

For this update, on 4 September 2017, we searched the Cochrane Epilepsy Group Specialised Register, Cochrane Register of Studies Online, MEDLINE Ovid, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform ICTRP. We searched SCOPUS on 13 February 2013, but this is no longer necessary, because RCTs and quasi-RCTs in Embase are now included in CENTRAL. In addition, we contacted Eisai Limited (makers and licensees of zonisamide) and experts in the field to seek any ongoing or unpublished studies.

SELECTION CRITERIA

Randomised controlled trials, in which add-on zonisamide was compared with placebo or another antiepileptic drug in people with focal epilepsy, uncontrolled by one or more concomitant antiepileptic drugs.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data, assessed for risk of bias using the Cochrane 'Risk of bias' tool, and assessed the quality of the evidence, using the GRADE approach. The primary outcome was at least a 50% reduction in total seizure frequency; the secondary outcomes were (1) tolerability; and (2) adverse effects. We used an intention-to-treat approach for our primary analyses. We estimated summary risk ratios (RRs) for each outcome. We displayed a summary of the estimates of effects and quality of the evidence for each outcome in a 'Summary of findings' table.

MAIN RESULTS

We included eight studies (1636 participants). The overall RR with 95% confidence interval (CI) for at least a 50% reduction in seizure frequency compared to placebo for 300 mg to 500 mg/day of zonisamide was 1.90 (95% CI 1.63 to 2.22; 7 trials, 1371 participants; moderate-quality evidence). The RR for 50% reduction in seizure frequency compared to placebo for any dose of zonisamide (100 mg to 500 mg/day) was 1.86 (95% CI 1.60 to 2.17; 7 trials, 1429 participants; moderate-quality evidence). The number needed to treat for an additional beneficial outcome was six (95% CI 4.1 to 6.8) for this outcome. Two trials provided evidence of a dose-response relationship for this outcome. The RR for treatment withdrawal for 300 mg to 500 mg/day of zonisamide compared to placebo was 1.59 (95% CI 1.18 to 2.13; 6 trials, 1099 participants; moderate-quality evidence), and for 100 mg to 500 mg/day was 1.44 (95% CI 1.08 to 1.93; 6 trials, 1156 participants; moderate-quality evidence). The number needed to treat for an additional harmful outcome was 15 (95% CI 9.3 to 36.7). The CIs of the following adverse effects indicated that they were significantly associated with zonisamide: ataxia RR 3.85 (99% CI 1.36 to 10.93; 4 trials, 734 participants; low-quality evidence); somnolence RR 1.52 (99% CI 1.00 to 2.31; 8 trials, 1636 participants; moderate-quality evidence); agitation RR 2.35 (99% CI 1.05 to 5.27; 4 trials, 598 participants; low-quality evidence); and anorexia RR 2.74 (99% CI 1.64 to 4.60; 6 trials, 1181 participants; low-quality evidence).Across the eight studies, we rated risk of bias domains at low or unclear risk of bias apart from two studies which we rated at high risk of attrition bias. Five of the eight studies were sponsored by the drug companies that produced zonisamide.

AUTHORS' CONCLUSIONS

When used as an add-on treatment in people with focal epilepsy uncontrolled by one or more concomitant antiepileptic drugs, moderate-quality evidence found that zonisamide was more successful than placebo at reducing the frequency of seizures by at least 50%. We were unable to identify minimum effective and maximum tolerated doses. The included trials evaluated a maximum stable-dose phase of 18 weeks, so results cannot be used to confirm longer periods of efficacy in seizure control. The results cannot be extrapolated to monotherapy or to people with other seizure types or epilepsy syndromes.

New generation antiepileptic drugs: what do they offer in terms of improved tolerability and safety?

Over the last two decades a total of 11 antiepileptic drugs (AEDs) have been introduced to the US market. Randomized, placebo-controlled trials have yielded information about each drug's efficacy, tolerability, and safety profile; however, few studies have compared the newer generation AEDs directly with the older generation. Comparative studies are not always straightforward in their interpretation, as many characteristics of drugs, both favorable and unfavorable, may not be highlighted by such studies. In general, findings from the literature suggest that the newer generation AEDs (including vigabatrin, felbamate, gabapentin, lamotrigine, tiagabine, topiramate, levetiracetam, oxcarbazepine, zonisamide, pregabalin, rufinamide, and lacosamide) enjoy both improved tolerability and safety compared with older agents such as phenobarbital, phenytoin, carbamazepine, and valproate. This is partially supported by some of the findings of the QSS and the TTA Committee of the American Academy of Neurology (AAN), whose review of four AEDs (gabapentin, lamotrigine, topiramate, and tiagabine) is discussed. Briefly, when compared with carbamazepine, lamotrigine was better tolerated; topiramate adverse events (AEs) were fairly comparable to carbamazepine and valproate; and tiagabine compared with placebo was associated with a higher discontinuation rate due to AEs. The findings of the SANAD trial are also presented; when administered to patients with partial epilepsy, carbamazepine was most likely to fail due to AEs, and lamotrigine and gabapentin were least likely to fail due to AEs. When administered to patients with idiopathic generalized epilepsy, topiramate was most frequently associated with AE-related discontinuation, followed by valproate; and while valproate was the most efficacious drug in this arm of the study, lamotrigine was more tolerable. What makes the SANAD study valuable and somewhat unique is its head-to-head comparison of one drug with another. Such comparative trials are overall lacking for new AEDs, although some conclusions can be drawn from the available data. In the end, however, AED selection must be based on individual patient and drug characteristics.

Zonisamide as a treatment for partial epileptic seizures: a systematic review

Although the majority of people with epilepsy have a good prognosis and their seizures can be well controlled with pharmacotherapy, up to one-third of patients can develop drug-resistant epilepsy, especially those patients with partial seizures. This unmet need has driven considerable efforts over the last few decades aimed at developing and testing newer antiepileptic agents to improve seizure control. One of the most promising antiepileptic drugs of the new generation is zonisamide, a benzisoxazole derivative chemically unrelated to other anticonvulsant agents. In this article, the authors present the results of a systematic literature review summarizing the current evidence on the efficacy and tolerability of zonisamide for the treatment of partial seizures. Of particular interest within this updated review are the recent data on the use of zonisamide as monotherapy, as they might open new therapeutic avenues.

Zonisamide add-on for drug-resistant partial epilepsy

BACKGROUND

The majority of people with epilepsy have a good prognosis and their seizures can be well controlled with the use of a single antiepileptic agent, but up to 30% develop refractory epilepsy, especially those with partial seizures. In this review we summarise the current evidence regarding zonisamide, when used as an add-on treatment for drug-resistant partial epilepsy.

OBJECTIVES

To evaluate the efficacy and tolerability of zonisamide when used as an add-on treatment for people with drug-resistant partial epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (12 February 2013), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2013, Issue 1) (January 2013), MEDLINE (Ovid, 1946 to 12 February 2013), SCOPUS (13 February 2013), ClinicalTrials.gov (12 February 2013) and the WHO International Clinical Trials Registry Platform ICTRP (13 February 2013). In addition, we contacted Eisai Limited (makers and licensees of zonisamide) and experts in the field to seek any ongoing/unpublished studies.

SELECTION CRITERIA

Randomised, placebo-controlled, add-on trials of zonisamide in people with drug-resistant partial epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and extracted data. Outcomes were: (1) 50% or greater reduction in total seizure frequency; (2) treatment withdrawal; (3) adverse effects. Primary analyses were intention-to-treat. We estimated summary risk ratios (RRs) for each outcome. All studies were assessed for risk of bias using the Cochrane risk of bias tool and the quality of evidence was assessed using the GRADE approach and presented in a summary of findings table.

MAIN RESULTS

Five trials (949 participants) were included. The overall RR with 95% confidence interval (CI) for 50% reduction in seizure frequency compared to placebo for 300 to 500 mg/day of zonisamide was 2.00 (95% CI 1.58 to 2.54). The RR for 50% reduction in seizure frequency compared to placebo for any dose of zonisamide (100 to 500 mg per day) was 1.92 (95% CI 1.52 to 2.42). The number needed to treat (NNT) was 6 for this outcome. Two trials provide evidence of a dose response relationship for this outcome. The RR for treatment withdrawal for 300 to 500 mg/day of zonisamide compared to placebo was 1.64 (95% CI 1.20 to 2.25) and for 100 to 500 mg per day was 1.47 (95% CI 1.07 to 2.01). NNT for this outcome was 21. The CIs of the following adverse effects indicate that they are significantly associated with zonisamide: ataxia 3.77 (99% CI 1.28 to 11.11); somnolence 1.83 (99% CI 1.08 to 3.11); agitation 2.35 (99% CI 1.05 to 5.27) and anorexia 2.71 (99% CI 1.29 to 5.69). Across the 5 studies, risk of bias domains were rated as low is bias or unclear. None of the evidence for outcomes was downgraded for quality.

AUTHORS' CONCLUSIONS

Zonisamide has efficacy as an add-on treatment in people with drug-resistant partial epilepsy. In this review minimum effective and maximum tolerated doses cannot be identified. The trials reviewed were of a maximum stable-dose phase of 18 weeks in duration and results cannot be used to confirm longer periods of effectiveness in seizure control. The results cannot be extrapolated to monotherapy or to people with other seizure types or epilepsy syndromes.

Effect of second-generation antiepileptic drugs on diplopia: a meta-analysis of placebo-controlled studies

Different antiepileptic drugs (AEDs) may cause similar adverse effects, one of which is diplopia. However, the AEDs causing diplopia and the dose-response effect of each drug remains uncertain. In this study, we compared several second-generation AEDs to find out whether they would contribute to the risk of diplopia and their effect-causing dose. A meta-analysis was performed on 19 studies in agreement with our inclusion criteria. The results showed that eight commonly used second-generation AEDs (gabapentin, levetiracetam, oxcarbazepine, lamotrigine, pregabalin, topiramate, vigabatrin and zonisamide) could cause diplopia. The reported odds ratios (ORs) ranged from 1.406 to 7.996. Ranking risks from the highest to the lowest ORs of the eight AEDs of any dose resulted in the following order: use of oxcarbazepine (7.996), levetiracetam (7.472), lamotrigine (5.258), vigabatrin (3.562), pregabalin (3.048), topiramate (2.660), gabapentin (1.966), zonisamide (1.406). Taking into account the ORs above, we can conclude that second-generation AEDs of any dose may cause diplopia. However, the levetiracetam-caused diplopia needs to be further studied according to the data (OR, 7.472; 95% confidence interval, 0.375-148.772). These findings ask for better concerns about patients' quality of life when giving antiepileptic treatments.

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

Childhood epilepsy continues to be intractable in more than 25% of patients diagnosed with epilepsy. The introduction of new anti-epileptic drugs (AEDs) provides more options for treatment of children with epilepsy. We review the safety and tolerability of seven new AEDs (levetiracetam, lamotrigine, oxcarbazepine, rufinamide, topiramate, vigabatrin and zonisamide) focusing on their side effect profiles and safety in children and adolescents. Many considerations that are specific for children such as the impact of AEDs on the developing brain are not addressed during the development of new AEDs. They are usually approved as adjunctive therapies based upon clinical trials involving adult patients with partial epilepsy. However, 2 of the AEDs reviewed here (rufinamide and vigabatrin) have FDA approval in the U.S. for specific Pediatric epilepsy syndromes, which are discussed below. The Pediatrician or Neurologists decision on the use of a new AED is an evolutionary process largely dependent on the patient characteristics, personal/peer experiences and literature about efficacy and safety profiles of these medications. Evidence based guidelines are limited due to a lack of randomized controlled trials involving pediatric patients for many of these new AEDs.

Efficacy and safety of adjunctive zonisamide in adult patients with refractory partial-onset epilepsy: a randomized, double-blind, placebo-controlled trial

BACKGROUND AND OBJECTIVE

Clinical studies have reported that zonisamide is effective for a wide range of seizure types, including refractory partial-onset seizures. However, there have been no reported studies of the efficacy of zonisamide in the Chinese population to date. The aim of the present study was to evaluate the efficacy and safety of zonisamide in the treatment of adult Chinese patients with refractory partial-onset epilepsy.

METHODS

This was a randomized, double-blind, placebo-controlled trial conducted over a 16-week period. 104 patients with refractory partial-onset epilepsy were enrolled. Participants were randomly assigned to receive add-on zonisamide or placebo. Zonisamide was titrated to a target dosage of 300 or 400 mg/day. Seizure frequency and adverse effects were documented.

RESULTS

102 patients completed the trial. Zonisamide showed significantly greater efficacy compared with placebo (responder rate 55.8% vs 36.0%, p<0.05), including 55.2% (16 of 29 patients) in the zonisamide 300 mg/day arm and 56.5% (13 of 23 patients) in the zonisamide 400 mg/day arm. Zonisamide 300 and 400 mg/day showed similar efficacy (p>0.05). Moreover, similar efficacy of zonisamide was found in the control of complex partial seizures, simple partial seizures and secondary generalized seizures. There was no difference in the incidence of adverse effects between zonisamide and placebo. Reported adverse effects in the zonisamide group involved the digestive system (32.5% of total adverse effects in the group) [including transient increases in liver enzymes (27.8%)], weight changes (30.2%), the haematological system (15.1%), neurological/psychiatric effects (10.3%), the urinary system (7.9%) and the cardiovascular system (4.0%). Only digestive system adverse effects constituted a significantly higher proportion of adverse effects in the zonisamide group than in the placebo group (32.5% vs 30.2%, p<0.05).

CONCLUSION

Zonisamide 300-400 mg/day is effective and well tolerated as an adjunctive drug in adult Chinese patients with refractory partial-onset epilepsy.

A pilot open-label trial of zonisamide in Unverricht-Lundborg disease

Action myoclonus frequently remains the primary cause of disability in Unverricht-Lundborg disease (EPM1) patients. Pharmacological treatment of myoclonus in these patients continues to be challenging; indeed conventional AEDs may be poorly effective in monotherapy or even in combination. We carried out a pilot, open-label trial of add-on zonisamide (ZNS) in patients with EPM1. Twelve EPM1 patients with epilepsy and action myoclonus were included in the study. Oral ZNS was gradually titrated until the target dose of 6 mg/Kg/day. Unified Myoclonus Rating Scale was obtained in each subject before and after ZNS add-on. A significant reduction of myoclonus severity was reached after ZNS introduction. ZNS was generally well tolerated and only two patients withdrew due to mild adverse effects. Our trial suggests that ZNS may be a valuable therapeutic option in EPM1 patients.

Zonisamide in managing impulse control disorders in Parkinson's disease

Impulse control disorders (ICDs) are a set of behaviours that take place in a subgroup of patients with Parkinson's disease (PD). Although reduction or switch of dopamine agonists or decrease of levodopa are the common treatment, this does not always improve the compulsive behaviour. Zonisamide (ZNS) has proved effective for motor symptoms in PD and it may be also useful in the field of ICDs. The aim of our study is to evaluate the safety and efficacy of ZNS in PD patients with ICDs who did not improve following a reduction of either levodopa or dopamine agonists. Fifteen patients were initiated on 25 mg/day ZNS dosage, which was titrated to 200 mg/day, as tolerated. Severity of the behaviours was assessed by means of the Clinical Global Impression and the Barratt Impulsiveness Scale, while motor impairment was assessed by means of the Unified Parkinson's Disease Rating Scale (UPDRS). Demographic data, medication dose, treatment duration and adverse events were also collected and analyzed. There was a marked reduction in the severity of impulsive behaviours and global impulsiveness (mean change from baseline -5.8 to -4.8, respectively). UPDRS changed only marginally. ZNS was generally well tolerated. Our study suggests that ZNS may be effective for ICDs in PD. The lack of studies with other medications to treat these behaviours in PD and the potential beneficial effects of ZNS for motor complications make this drug important in the treatment of the disease.

Efficacy and tolerability of adjunctive therapy with zonisamide in childhood intractable epilepsy

PURPOSE

This study investigated the efficacy and safety of zonisamide (ZNS) adjunctive therapy in children with intractable epilepsy to existing antiepileptic drugs (AEDs).

METHODS

A clinical retrospective study was performed from 2003 to 2005 at two tertiary epilepsy centers. We reviewed the data from 163 children (107 boys and 56 girls) who experienced more than four seizures per month, whose seizures were intractable to an initial 2 or more AEDs, and could be followed up for at least 6months after ZNS adjunctive therapy initiation. Efficacy was estimated by seizure reduction rate according to seizure types including infantile spasms, and adverse events were also measured.

RESULTS

Seventy-nine patients (48.5%) out of 163 patients experienced a reduction in seizure frequency of more than 50%, and 25 patients (15.3%) became seizure-free. The rate of seizure reduction greater than 50% in children with partial seizures was 40.5% (17/42) and in children with generalized seizures was 51.2% (62/121). Of 36 patients who manifested mainly myoclonic seizures, 20 patients (55.6%) showed a seizure reduction of more than 50% and 9 patients (25.0%) were seizure-free. Mean maintenance dosage of drug was 8.2mg/kg/day (range 5.0-16.0mg/kg/day). Adverse events were documented in 15 children (9.2%), including somnolence (8 patients), fatigue, and anorexia, but all were transient and successfully managed. One patient discontinued ZNS therapy due to acute pancreatitis.

CONCLUSION

ZNS adjunctive therapy is an effective and safe treatment in various childhood intractable epilepsy.

Seizures in patients with low-grade gliomas--incidence, pathogenesis, surgical management, and pharmacotherapy

Seizures complicate the clinical course of > 80% of patients with low-grade gliomas. Patients with some tumor variants almost always have epilepsy. Diffuse low-grade gliomas (LGG) are believed to cause epilepsy through partial deafferentiation of nearby brain cortex (denervation hypersensitivity). Glioneural tumors may interfere with local neurotransmitter levels and are sometimes associated with structural abnormalities of the brain which may produce seizures. The severity of tumor associated epilepsy varies considerably between patients. Some cases may present with a first seizure. Others suffer from long-standing pharmacoresistant epilepsy. Seizure control rates of > 70-80% can be expected after complete tumor resections. Patients with drug-resistant epilepsy require a comprehensive preoperative epileptological work-up which may include the placement of subdural (and intraparenchymal) electrodes or intraoperative electrocorticography (ECoG) for the delineation of extratumoral seizure foci. Partial and subtotal tumor resections are helpful in selected cases, i.e. for gliomas involving the insula. In one series, 40% of patients presented for surgery with uncontrolled seizures, i.e. medical therapy alone often fails to control tumor-related epilepsy. Use of the newer (second generation) non-enzyme inducing antiepileptic drugs (non-EIAED) is encouraged since they seem to have lesser interactions with other medications (e.g. chemotherapy). Chemotherapy and irradiation may have some minor beneficial effects on the patients' seizure disorder. Overall 60-70% of patients may experience recurrent epilepsy during long-term follow-up. Recurrent seizures (not infrequently heralding tumor recurrence) after surgery continue to pose significant clinical problems.

Efficacy and tolerability of zonisamide as add-on in brain tumor-related epilepsy: preliminary report

BACKGROUND

Zonisamide (ZNS) is an antiepileptic drug (AED) with broad spectrum action that demonstrated a good efficacy in controlling seizures as add-on in adult and pediatric epilepsy. To date there have been no studies on ZNS in patients with brain tumor-related epilepsy (BTRE).

AIM OF THE STUDY

To evaluate efficacy and tolerability of ZNS as add-on in BTRE.

METHODS

We followed six patients suffering from BTRE who had already been treated with other AEDs and who had had not experienced adequate seizure control. Three patients underwent chemotherapy while being treated with ZNS. Mean duration of follow-up was 8 months.

RESULTS

Mean seizure number in the last month prior to the introduction of ZNS had been 27.7/month. ZNS mean dosage was of 283.3 mg/day. At last follow-up, the mean seizure number was reduced to 8.8/month. Responder rate was 83.3%.Two patients discontinued the drug because of side effects. There were no other reported side effects.

CONCLUSIONS

Preliminary data on the use of ZNS in add-on in patients with BTRE indicate that this drug may represent a valid alternative as add-on in this particular patient population. However, larger samples are necessary to draw definitive conclusions.

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.

Zonisamide prevents olanzapine-associated hyperphagia, weight gain, and elevated blood glucose in rats

Olanzapine (OLZ), one of the second-generation atypical antipsychotics (SGAs), has shown relative advantages in patient adherence and outcomes. However, OLZ has also been associated with a higher incidence of weight gain than most other SGAs. Excessive weight gain may in turn contribute to long-term health concerns for some individuals. Zonisamide (ZNS), a medication approved in the United States as an adjunct in the management of epilepsy, has a diverse pharmacological profile, including sodium channel blockade, monoamine enhancement, and inhibition of carbonic anhydrase. ZNS has also been reported to cause weight loss in both humans and rodents. We hypothesized that this profile might be beneficial when co-administered with OLZ. To test this hypothesis, we evaluated the effects of OLZ on body weight, as well as the pathways known to regulate feeding behavior and arousal in the Sprague-Dawley rat. As indicated via c-Fos expression, we found an OLZ-induced activation in the nucleus accumbens and orexin neurons in the lateral hypothalamus. An OLZ-associated development of hyperphagia, weight gain and elevated blood glucose in the rat was also found. These outcomes were attenuated and reversed in the presence of concomitant ZNS. These results suggest the hypothesis that ZNS may effectively treat or prevent weight gain or metabolic changes associated with the SGAs. Future studies of this combination in patients through appropriately designed human clinical studies are encouraged.

Zonisamide Concentrations During Pregnancy

Objective:

TO describe a series of serum concentrations of zonisamide in a pregnant woman.

Case Summary:

A 30-year-old woman with primary generalized tonic–clonic seizures and myoclonic jerks was taking zonisamide 200 mg daily as her sole antiepileptic agent when she conceived. She continued on zonisamide throughout her pregnancy. The zonisamide concentrations ranged between 7.5 μg/mL and 17 μg/mL during pregnancy, with the exception of a 4.4-μg/mL concentration at 27 weeks postconception. Following this lower concentration, the zonisamide dose was increased to 300 mg/day at week 29. She had an uneventful pregnancy, with only occasional myoclonic jerks, and delivered at 41 weeks. At 42 weeks, white taking zonisamide 300 mg/day, her concentration was 20.8 μg/mL

Discussion:

A single report from Japan reviewed 26 cases of prenatal exposure to zonisamide. Twenty-two offspring were exposed to zonisamide monotherapy; 4 were exposed to polytherapy. During the first trimester, 2 pregnant women on zonisamide and at least one other antiepileptic medication had serum concentrations of 6.1 μg/mL and 6.2 μg/mL; 2 of the Infants had teratogenic effects. Teratogenicity has also been reported in animals. There are no other published data regarding zonisamide concentrations during pregnancy.

Conclusions:

The change in zonisamide serum concentrations in a pregnant woman suggests an increase in clearance at the end of the second trimester.