Effects of zonisamide on dopaminergic system

Role of zonisamide in advanced Parkinson's disease: a randomized placebo-controlled study

BACKGROUND

Zonisamide (ZNS) has shown some efficacy in motor symptoms of PD; however, more evidence is lacking, and its effects on nonmotor symptoms (NMSs) and quality of life (QoL) remain to be investigated. This randomized double-blinded placebo-controlled crossover study investigated the effect of ZNS on motor and NMS symptoms and QoL in advanced PD.

METHODS

PD patients with Hoehn and Yahr stage ≥ 2 ("On" state) and at least 2 h off time daily were randomized to groups: ZNS 25 mg, ZNS 50 mg and placebo. Groups were assessed at baseline and at the 1- and 3-month follow-ups. The primary endpoint was the change in the total MDS-UPDRS III "On", while the secondary endpoint was the change in the total and parts I and IV MDS-UPDRS, Nonmotor Symptoms Scale and Parkinson's disease questionnaire-39 at the final assessment.

RESULTS

Sixty-nine patients were assessed for efficacy at the 1-month follow-up, and 58 patients were assessed at the 3-month follow-up. The primary endpoint showed significant improvement in the ZNS 25 mg group compared to the placebo group (p = 0.009). At the final assessment, the ZNS 25 mg group showed significant improvement of total and part VI MDS-UPDRS, bradykinesia, tremor and functional impact of fluctuations compared to placebo. There was no change in dyskinesia, NMSs, QoL or side effects except for sedation.

CONCLUSION

ZNS has a favourable effect on motor symptoms in patients with wearing off as adjunctive therapy with other dopaminergic drugs, with no exacerbation of dyskinesia and a limited impact on NMSs and QoL.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT04182399, in 24/11/2019.

Five-Membered Heterocyclic Sulfonamides as Carbonic Anhydrase Inhibitors

The development of heterocyclic derivatives has progressed considerably over the past decades, and many new carbonic anhydrase inhibitors (CAIs) fall into this field. In particular, five-membered heterocyclic sulfonamides have been generally shown to be more effective inhibitors compared to six-membered rings ones. Despite the importance of oxygen and nitrogen five-membered heterocyclic aromatic rings in medicinal chemistry, the installation of sulfonamide moiety on such heterocycles has not received much attention. On the other hand, 1,3,4-thiadiazole/thiadiazoline ring-bearing sulfonamides are the scaffolds which have been widely used in a variety of pharmaceutically important CAIs such as acetazolamide, metazolamide and their many derivatives obtained by using the tail approach. Here, we reviewed the field focusing on the diverse biological activities of these CAIs, such as antiglaucoma, antiepileptic, antitumor and antiinfective properties. This review highlights developments involving five-membered heterocyclic sulfonamides over the last years, with a focus on their pharmacological/clinical applications.

Comparative efficacy and safety of monoamine oxidase type B inhibitors plus channel blockers and monoamine oxidase type B inhibitors as adjuvant therapy to levodopa in the treatment of Parkinson's disease: a network meta-analysis of randomized controlled trials

BACKGROUND AND PURPOSE

The monoamine oxidase type B inhibitors plus channel blockers (MAO-BIs plus) are a new class of antiparkinsonian drug with additional mechanisms of action for their property as ion channel blockers. The present study aimed to compare the efficacy and safety of MAO-BIs plus and conventional MAO-BIs, as well as their corresponding doses, as adjuvant therapy to levodopa in the treatment of Parkinson's disease (PD).

METHOD

Randomized controlled trials enrolling PD patients treated with selegiline, rasagiline, safinamide or zonisamide as adjuvant therapy to levodopa were identified. Bayesian network meta-analysis was conducted.

RESULTS

Thirty-one randomized controlled trials comprising 7142 PD patients were included. Compared with levodopa monotherapy, the combination therapy of MAO-BIs and levodopa was significantly more effective, with a mean difference of 2.74 (1.26-4.18) on the Unified Parkinson's Disease Rating Scale (UPDRS) III score change for selegiline, 2.67 (1.45-3.87) for safinamide, 2.2 (0.98-3.64) for zonisamide and 2.04 (1.24-2.87) for rasagiline. No significant difference was detected amongst MAO-BIs. The surface under the cumulative ranking results showed that safinamide 100 mg and rasagiline 1 mg ranked first in improving UPDRS III and UPDRS II, respectively. Zonisamide 100 mg ranked first in reducing OFF time. For safety outcomes, rasagiline was associated with a higher incidence of adverse events than placebo and safinamide. MAO-BIs plus had a higher probability of being safer agents compared to conventional MAO-BIs.

CONCLUSIONS

Monoamine oxidase type B inhibitors plus, conventional MAO-BIs and the corresponding doses are similar in efficacy in PD treatment. MAO-BIs plus might be safer than conventional MAO-BIs. Head-to-head comparisons are needed for further investigation.

Zonisamide add-on in tremor-dominant Parkinson's disease- A randomized controlled clinical trial

INTRODUCTION

and objective: Tremor is a disabling symptom of PD that usually responds poorly to available standard pharmacological agents. This study aimed to assess the effect of Zonisamide 25 mg on tremor in tremor-dominant PD patients as compared to placebo.

METHODS

This was a randomized, placebo-controlled, double-blind study. Parkinson's disease patients were allocated either to the intervention group (standard treatment along with Zonisamide 25 mg add-on) or the placebo group (standard treatment along with placebo). Baseline Unified Parkinson's Disease Rating Scale (UPDRS) and Tremor Research Group Essential Tremor Rating Scale (TETRAS) scores, as well as accelerometric tremor analysis were done and follow-up assessments of the same were done after 12 weeks of intervention. Percentage change from baseline in the UPDRS tremor score was the primary outcome whereas percentage change from baseline of total UPDRS score, UPDRS rigidity and bradykinesia scores, TETRAS score, and accelerometric tremor analysis values were the secondary outcomes.

RESULTS

There was no significant difference in the percentage change from baseline UPDRS tremor scores between the two groups (placebo: 8.33 [-19.89-23.86] vs drug: 26.14 [-35.58 to -16.07], p-value: 0.164, CI: 0.157-0.171). Best-case analysis for missing values showed a significant improvement in the drug group, compared to the placebo group (p-value: < 0.001, CI: <0.001 - <0.001).

CONCLUSION

Zonisamide at a dose of 25 mg per day did not improve tremor in tremor-dominant PD patients, however, a positive trend was seen as compared to Placebo in the UPDRS tremor score. Larger studies are required to confirm this finding.

Zonisamide's Efficacy and Safety on Parkinson's Disease and Dementia with Lewy Bodies: A Meta-Analysis and Systematic Review

Objective

Clinical data has recently shown an association between Parkinson's disease (PD), Dementia with Lewy bodies (DLB), and zonisamide. The purpose of this study was to thoroughly evaluate the efficacy and safety of zonisamide in PD and DLB.

Methods

Pubmed, the Cochrane Library, Web of Science, and Embase databases were searched for all randomized clinical trials (RCTS) on the role of zonisamide in PD and DLB that were completed by April 18, 2022. UPDRS II (off) total score, UPDRS III total score, Daily "off" time, and UPDRS Part IV, Nos. 32, 33, and 34 were used as clinical efficacy endpoints. Adverse events reported in the RCTs will be considered in the final safety analysis. To better understand the effect of zonisamide on the efficacy and safety of PD and DLB, the UPDRS III total score and the six overlapping adverse events were examined in subgroups. Either a fixed effects model analysis (OR) or a random effects model analysis (MD) is used to figure out the mean difference (MD) and the relative risk.

Results

Seven articles involving 1749 patients (916 PD and 833 DLB) were included in this study. Compared to the control group, zonisamide could significantly reduce the UPDRS III total score in patients with PD and DLB (WMD-2.27 [95% CI: -3.06, -1.48], p < 0.0001). For patients with PD, compared to the control group, zonisamide could significantly reduce the UPDRS II (off) total score (WMD-0.81 [95% CI: -1.36, -0.26], p = 0.004), daily "off" time (WMD-0.67 [95% CI: -1.10, 0.24], p = 0.002), and UPDRS part IV, No. 32 worsen (OR-3.48 [95% CI: 1.20, 10.10], p = 0.02). In terms of safety, compared with the control group, for patients with DLB, zonisamide could significantly increase the incidence of contusion (OR-0.60 [95% CI: 0.38, 0.96], p = 0.03) and may increase the probability of reduced appetite (OR-3.13 [95% CI: 1.61, 6.08], p = 0.0008). And for patients with PD, zonisamide may increase the probability of somnolence (OR-2.17 [95% CI: 1.25, 3.76], p = 0.006).

Conclusions

For the analysis of the current study results, our results show that zonisamide could improve the motor function in patients with PD and DLB and improve the activities of daily living (off) and wearing off and decrease the duration of dyskinesia in patients with PD. In terms of safety, the use of zonisamide significantly increases the probability of contusion in patients with DLB and may increase the probability of reduced appetite in patients with DLB and somnolence in patients with PD. Zonisamide appears to be a new treatment option for patients with PD and DLB. However, the effectiveness and safety of zonisamide in the treatment of PD and DLB need to be further investigated.

Long-Term Efficacy and Safety of Zonisamide for Treatment of Parkinsonism in Patients With Dementia With Lewy Bodies: An Open-Label Extension of a Phase three Randomized Controlled Trial

OBJECTIVES

To evaluate the long-term efficacy and safety of zonisamide, an antiepileptic agent, in dementia with Lewy bodies (DLB).

DESIGN

Phase three clinical trial with 12 week, randomized, placebo-controlled, double-blind, and subsequent 40 week, open-label, extension periods.

SETTING

A total of 109 centers in Japan between April 2015 and November 2017.

PARTICIPANTS

Outpatients diagnosed with probable DLB.

INTERVENTION

Outpatients were randomly assigned to receive placebo (P) or zonisamide 25 or 50 mg/day for 12 weeks. In the subsequent open-label 40 week period, all patients initially received zonisamide 25 mg/day for at least 2 weeks followed by optional flexible dosing with zonisamide 25 or 50 mg/day for the remaining period.

MEASUREMENTS

The primary outcome was efficacy on motor symptoms, assessed using the Unified Parkinson's Disease Rating Scale part III (UPDRS-III) score, over the total 52 week trial period. Effects on behavioral and psychological symptoms of dementia and cognitive function, and safety were also evaluated.

RESULTS

In total, 335 patients were included in the long-term analysis: 106, 117, and 112 in the P-, 25mg-, and 50mg-Flex groups, respectively. UPDRS-III score continued to improve for an additional 12 to 16 weeks in the open-label period (mean [standard deviation] change from baseline at Week 28: -5.1 [7.3] and -6.3 [8.2] in the 25mg- and 50mg-Flex groups) and remained almost constant thereafter. No unexpected neurological or psychiatric adverse events occurred, and no adverse events increased in incidence in the open-label period.

CONCLUSIONS

Long-term treatment with zonisamide was well tolerated and yielded sustained improvement in motor symptoms.

TRIAL REGISTRATION

JapicCTI-152839 (Registered on 9 March 2015) https://www.clinicaltrials.jp/cti-user/trial/ShowDirect.jsp?japicId=JapicCTI-152839.

Zonisamide improves wearing off in Parkinson's disease without exacerbating dyskinesia: Post hoc analysis of phase 2 and phase 3 clinical trials

INTRODUCTION

Although phase 2 and 3 clinical trials in Japan showed that zonisamide improved wearing off in patients with Parkinson's disease (PD), no studies to date have evaluated whether zonisamide improves wearing off in patients with PD without exacerbating dyskinesia. Therefore, we examined this hypothesis in a post hoc analysis of pooled data from the previous phase 2 and 3 trials.

METHODS

Both trials evaluated zonisamide 25 mg and 50 mg versus placebo during a 12-week treatment period. In our analysis, primary efficacy variables were adjusted mean change in wearing off (evaluated as change in "off" time) and dyskinesia from baseline to 12 weeks. Dyskinesia was evaluated using Unified Parkinson's Disease Rating Scale (UPDRS) part 4 items 32 (4-32; duration of dyskinesia) and 33 (4-33; disability of dyskinesia) score. Criteria outcomes included rates of patients meeting specific criteria based on off time plus UPDRS part 4-32 or 4-33.

RESULTS

A total of 212 patients were included in this analysis. Zonisamide 50 mg significantly reduced off time and UPDRS part 4-33 score at week 12 versus placebo without increasing UPDRS part 4-32 score. The proportion of patients receiving zonisamide 50 mg who met the criterion "Off time decreased and UPDRS part 4-33 score did not increase" was significantly higher than that of patients receiving placebo.

CONCLUSION

Zonisamide improves wearing off without exacerbating dyskinesia in Japanese patients with PD. Moreover, zonisamide 50 mg may improve dyskinesia. Further studies are needed to prospectively determine the benefits and clinical relevance of zonisamide on dyskinesia.

Are ion channels potential therapeutic targets for Parkinson's disease?

Parkinson's disease (PD) is primarily associated with the progressive neurodegeneration of the dopaminergic neurons in the substantia nigra region of the brain. The resulting motor symptoms are managed with the help of dopamine replacement therapies. However, these therapeutics do not prevent the neurodegeneration underlying the disease and therefore lose their effectiveness in managing disease symptoms over time. Thus, there is an urgent need to develop newer therapeutics for the benefit of patients. The release of dopamine and the firing activity of substantia nigra neurons is regulated by several ion channels that act in concert. Dysregulations of these channels cause the aberrant movement of various ions in the intracellular milieu. This eventually leads to disruption of intracellular signalling cascades, alterations in cellular homeostasis, and bioenergetic deficits. Therefore, ion channels play a central role in driving the high vulnerability of dopaminergic neurons to degenerate during PD. Targeting ion channels offers an attractive mechanistic strategy to combat the process of neurodegeneration. In this review, we highlight the evidence pointing to the role of various ion channels in driving the PD processes. In addition, we also discuss the various drugs or compounds that target the ion channels and have shown neuroprotective potential in the in-vitro and in-vivo models of PD. We also discuss the current clinical status of various drugs targeting the ion channels in the context of PD.

Zonisamide attenuates the severity of levodopa-induced dyskinesia via modulation of the striatal serotonergic system in a rat model of Parkinson's disease

Glutamate, GABA, acetylcholine, dopamine, and serotonin interact with each other to regulate the flow of neural information in the striatum. Serotonin type 1A receptor (5HT1A) is primarily expressed on glutamatergic nerve terminals, and 5HT1B is expressed on GABAergic medium spiny neurons (MSNs). Zonisamide (ZNS) reportedly improves the off period without worsening levodopa-induced dyskinesia (LID) in patients with advanced Parkinson's disease. In this study, LID model rats were prepared by administrating levodopa to unilaterally 6-OHDA-lesioned rats. We analyzed changes in serotonergic neurotransmission of LID model rats to elucidate the relationship between LID and the serotonergic system and pathomechanism of the anti-dyskinetic effects of ZNS. Abnormal involuntary movements (AIMs) were most severe in intermittently levodopa-treated rats but milder in rats intermittently medicated with levodopa and ZNS. Continuously levodopa-infused rats or intermittently ZNS-injected rats did not develop AIMs, and no differences in the expression of brain-derived neurotrophic factor, 5-HT transporter, 5HT1A, and 5HT1B mRNA between the lesioned striatum and normal side were observed. Expression of 5HT1B mRNA was elevated in the lesioned striatum of intermittently levodopa-treated rats, but this elevation was normalized by concomitant use of ZNS. The severity of AIMs was correlated with the ratio of 5HT1B to 5HT1A mRNA expression in the lesioned striatum, indicating that the anti-LID effect of ZNS is based on inhibition via 5HT1B receptors to direct pathway MSNs sensitized by intermittent levodopa treatment. Selectively acting serotonergic drugs, especially those that lower the 5HT1B to 5HT1A ratio, are promising new therapeutic agents to attenuate LID development.

Efficacy and Safety of Zonisamide in Dementia with Lewy Bodies Patients with Parkinsonism: A Post Hoc Analysis of Two Randomized, Double-Blind, Placebo-Controlled Trials

Background:

Although previous phase II and III clinical trials conducted in Japan showed that zonisamide improved parkinsonism in patients with dementia with Lewy bodies (DLB), some differences in efficacy outcomes were observed between the trials.

Objective:

We aimed to further examine the efficacy and safety of zonisamide in DLB patients with parkinsonism in a post hoc analysis of pooled data from the previous phase II and III trials.

Methods:

Both trials featured a 4-week run-in period followed by a 12-week treatment period with a double-blind, placebo-controlled, parallel-group, randomized, multicenter trial design. In our pooled analysis, the primary outcome was the change in Unified Parkinson’s Disease Rating Scale (UPDRS) part III total score. Other outcomes included the changes in Mini-Mental State Examination (MMSE) and Neuropsychiatric Inventory-10 (NPI-10) scores, and the incidence of adverse events.

Results:

Zonisamide significantly decreased the UPDRS part III total and individual motor symptom scores but did not affect the MMSE or NPI-10 scores at week 12. There was no difference in the incidence of adverse events between the zonisamide and placebo groups except for decreased appetite, which had an increased frequency in the zonisamide 50 mg group compared with placebo.

Conclusion:

Our findings indicate that zonisamide improved parkinsonism with DLB without deterioration of cognitive function and or worsening behavioral and psychological symptoms of dementia.

[Effects of switching from dopamine agonists to zonisamide on psychiatric and motor symptoms in patients with Parkinson's disease]

In 11 patients with Parkinson's disease (PD) who were using levodopa and had hallucinations and/or delusions considered to be attributed to use of dopamine agonists (DAs), we reduced or discontinued DAs and added zonisamide, and we then evaluated the effects of this treatment on psychiatric and motor symptoms. As a result, changes in the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale Part 1.2 (Hallucinations and Psychosis) and Part 3 (Motor Examination) scores 12 weeks from baseline were -2.4 ± 0.2 and -5.1 ± 0.9 (least-squares mean ± standard error), respectively, with the score reductions being statistically significant. These results indicated that zonisamide switching therapy is a useful strategy for managing psychiatric and motor symptoms in patients with PD when DAs are reduced or discontinued to avoid the onset or exacerbation of hallucinations and delusions.

The Application of Zonisamide to Patients Suffering from Dementia with Lewy Bodies: Emerging Clinical Data

Zonisamide is an anti-epileptic medication with multiple mechanisms of action and a favorable safety profile. Zonisamide may interact with Lewy body dementia pathophysiology through a mechanism unrelated to its original indication. Zonisamide has shown efficacy as adjunct therapy for the management of motor symptoms in patients with Parkinson's disease (PD). Given that dementia with Lewy bodies (DLB) and PD are considered subtypes of a Lewy body disease spectrum, zonisamide was investigated for the treatment of parkinsonism in DLB. Phase II and phase III clinical trials were conducted in patients with DLB in Japan. In both studies, participants were randomized to receive 12 weeks of zonisamide 25 or 50 mg/day or placebo. Zonisamide significantly improved the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) without affecting the Mini-Mental State Examination (MMSE) or Neuropsychiatry Inventory-10 (NPI-10) scores at week 12. In 2018, zonisamide received Japanese regulatory approval for the additional indication of parkinsonism in DLB. This review discusses the emerging clinical data on zonisamide in the field of DLB.

Zonisamide for the Treatment of Parkinson Disease: A Current Update

Zonisamide has been used as an add-on treatment in order to overcome the deficiencies of the general therapies currently used to resolve the motor complications and non-motor symptoms of Parkinson disease. Various trials have been designed to investigate the mechanism of action and treatment effects of zonisamide in this condition. Most clinical trials of zonisamide in Parkinson disease were from Japan. The vast majority of studies used changes in the Unified Parkinson’s Disease Rating Scale (UPDRS) scores and daily “OFF” time as primary endpoints. Based on adequate randomized controlled trials, zonisamide is considered a safe and efficacious add-on treatment in Parkinson disease. The most convincing proof is available for a dosage of 25–50 mg, which was shown to lead to a significant reduction in the UPDRS III score and daily “OFF” time, without increasing disabling dyskinesia. Furthermore, zonisamide may play a beneficial role in improving non-motor symptoms in PD, including impulsive–compulsive disorder, rapid eye movement sleep behavior disorder, and dementia. Among the various mechanisms reported, inhibition of monoamine oxidase-B, blocking of T-type calcium channels, modulation of the levodopa–dopamine metabolism, modulation of receptor expression, and neuroprotection are the most often cited. The mechanisms underlying neuroprotection, including modulation of dopamine turnover, induction of neurotrophic factor expression, inhibition of oxidative stress and apoptosis, inhibition of neuroinflammation, modulation of synaptic transmission, and modulation of gene expression, have been most extensively studied. This review focuses on structure, pharmacokinetics, mechanisms, therapeutic effectiveness, and safety and tolerability of zonisamide in patients with Parkinson disease.

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.

Zonisamide Therapy for Patients With Paroxysmal Kinesigenic Dyskinesia

BACKGROUND

We evaluated zonisamide therapy in patients with paroxysmal kinesigenic dyskinesia (PKD).

METHODS

We analyzed zonisamide therapy in 17 patients with PKD at Saitama Children's Medical Center between November 1994 and April 2020. We collected information regarding family history, previous history, age at onset, age at zonisamide commencement, dyskinesia characteristics, brain magnetic resonance imaging, interictal electroencephalography, treatment lag, zonisamide efficacy, zonisamide dose, serum zonisamide concentration, and adverse effects. We evaluated PKD frequency at six months after zonisamide therapy commencement.

RESULTS

Fourteen patients met the inclusion criteria. The median age at zonisamide therapy commencement was 12.8 (9.4 to 16.3) years. Zonisamide therapy was effective in 13 of 14 (92.9%) patients: complete remission for more than three months after zonisamide therapy (n = 7), decreased dyskinesia frequency by more than 90% (n = 4), dyskinesia frequency by 75% to 90% (n = 2), and no change of dyskinesia frequency (n = 1). The initial and maintenance zonisamide doses were 2.0 (1.4 to 3.8) and 2.0 (1.5 to 5.9) mg/kg/day, respectively. The median duration between zonisamide therapy commencement and dyskinesia decrease or cessation was 4 (1 to 60) days: 10 of 14 (71.4%) patients responded to zonisamide within one week after zonisamide therapy commencement. Regarding adverse effects, two patients experienced somnolence and one developed reduced perspiration.

CONCLUSIONS

We suggest that zonisamide monotherapy is effective for patients with PKD as a first-line treatment. We can evaluate the efficacy of zonisamide therapy within one week. Because zonisamide lacks the enzyme-inducing effects of carbamazepine and phenytoin, it may be useful for PKD treatment.

Effects of Carbamazepine, Lacosamide and Zonisamide on Gliotransmitter Release Associated with Activated Astroglial Hemichannels

Recent studies using the genetic partial epilepsy model have demonstrated that hyperfunction of astroglial hemichannels contributes to pathomechanism of epileptic seizure. Therefore, to explore the novel anticonvulsive mechanisms, the present study determined the effects of voltage-dependent Na⁺ channel (VDSC)-inhibiting anticonvulsants, carbamazepine (CBZ), lacosamide (LCM), and zonisamide (ZNS) on the astroglial release of l-glutamate and adenosine triphosphate (ATP). The effects of subchronic administration of therapeutic-relevant dose of three anticonvulsants on the release of l-glutamate and ATP in the orbitofrontal cortex (OFC) were determined using microdialysis. The concentration-dependent effects of acute and subchronic administrations of anticonvulsants on astroglial gliotransmitter release were determined using primary cultured astrocytes. The concentration-dependent effects of subchronic administrations of anticonvulsants on connexin43 (Cx43) expression in the plasma membrane of primary cultured astrocytes were determined using the Simple Western system. An increase in the levels of extracellular K⁺ resulted in a concentration-dependent increase in the astroglial release of l-glutamate and ATP. The depleted levels of extracellular Ca²⁺ alone did not affect astroglial gliotransmitter release but did accelerate K⁺-evoked gliotransmitter release via activation of astroglial hemichannels. Both non-selective hemichannel inhibitor carbenoxolone (CBX) and selective Cx43 inhibitor GAP19 prevented both gliotransmitter release through activated astroglial hemichannels and the hemichannel-activating process induced by elevation of the levels of extracellular K⁺ with depletion of the levels of extracellular Ca²⁺. ZNS subchronically decreased Cx43 expression and acutely/subchronically inhibited Cx43 hemichannel activity. LCM acutely inhibited hemichannel activity but did not subchronically affect Cx43 expression. Therapeutic-relevant concentration of CBZ did not affect hemichannel activity or Cx43 expression, but supratherapeutic concentration of CBZ decreased Cx43 expression and hemichannel activity. Therefore, the present study demonstrated the distinct effects of CBZ, LCM, and ZNS on gliotransmitter release via modulation of astroglial hemichannel function. The different features of the effects of three VDSC-inhibiting anticonvulsants on astroglial transmission associated with hemichannels, at least partially, possibly contributing to the formation of the properties of these three anticonvulsants, including the antiepileptic spectrum and adverse effects regarding mood and cognitive disturbance.

Upregulated Connexin 43 Induced by Loss-of-Functional S284L-Mutant α4 Subunit of Nicotinic ACh Receptor Contributes to Pathomechanisms of Autosomal Dominant Sleep-Related Hypermotor Epilepsy

To study the pathomechanism and pathophysiology of autosomal dominant sleep-related hypermotor epilepsy (ADSHE), this study determined functional abnormalities of glutamatergic transmission in the thalamocortical motor pathway, from the reticular thalamic nucleus (RTN), motor thalamic nuclei (MoTN) tosecondary motor cortex (M2C) associated with the S286L-mutant α4β2-nicotinic acetylcholine receptor (nAChR) and the connexin43 (Cx43) hemichannel of transgenic rats bearing the rat S286L-mutant Chrna4 gene (S286L-TG), which corresponds to the human S284L-mutant CHRNA4 gene using multiprobe microdialysis, primary cultured astrocytes and a Simple Western system. Expression of Cx43 in the M2C plasma membrane fraction of S286L-TG was upregulated compared with wild-type rats. Subchronic nicotine administration decreased Cx43 expression of wild-type, but did not affect that of S286L-TG; however, zonisamide (ZNS) decreased Cx43 in both wild-type and S286L-TG. Primary cultured astrocytes of wild-type were not affected by subchronic administration of nicotine but was decreased by ZNS. Upregulated Cx43 enhanced glutamatergic transmission during both resting and hyperexcitable stages in S286L-TG. Furthermore, activation of glutamatergic transmission associated with upregulated Cx43 reinforced the prolonged Cx43 hemichannel activation. Subchronic administration of therapeutic-relevant doses of ZNS compensated the upregulation of Cx43 and prolonged reinforced activation of Cx43 hemichannel induced by physiological hyperexcitability during the non-rapid eye movement phase of sleep. The present results support the primary pathomechanisms and secondary pathophysiology of ADSHE seizures of patients with S284L-mutation.

Pathomechanism of nocturnal paroxysmal dystonia in autosomal dominant sleep-related hypermotor epilepsy with S284L-mutant α4 subunit of nicotinic ACh receptor

To study the pathomechanism and pathophysiology of nocturnal paroxysmal dystonia of autosomal dominant sleep-related hypermotor epilepsy (ADSHE), this study determined functional abnormalities in thalamic hyperdirect pathway from reticular thalamic nucleus (RTN), motor thalamic nuclei (MoTN), subthalamic nucleus (STN) to substantia nigra pars reticulata (SNr) of transgenic rats (S286L-TG) bearing S286 L missense mutation of rat Chrna4 gene, which corresponds to the S284 L mutation in the human CHRNA4 gene. The activation of α4β2-nAChR in the RTN increased GABA release in MoTN resulting in reduced glutamatergic transmission in thalamic hyperdirect pathway of wild-type. Contrary to wild-type, activation of S286L-mutant α4β2-nAChR (loss-of-function) in the RTN relatively enhanced glutamatergic transmission in thalamic hyperdirect pathway of S286L-TG via impaired GABAergic inhibition in intra-thalamic (RTN-MoTN) pathway. These functional abnormalities in glutamatergic transmission in hyperdirect pathway contribute to the pathomechanism of electrophysiologically negative nocturnal paroxysmal dystonia of S286L-TG. Therapeutic-relevant concentration of zonisamide (ZNS) inhibited the glutamatergic transmission in the hyperdirect pathway via activation of group II metabotropic glutamate receptor (II-mGluR) in MoTN and STN. The present results suggest that S286L-mutant α4β2-nAChR induces GABAergic disinhibition in intra-thalamic (RTN-MoTN) pathway and hyperactivation of glutamatergic transmission in thalamic hyperdirect pathway (MoTN-STN-SNr), possibly contributing to the pathomechanism of nocturnal paroxysmal dystonia of ADSHE patients with S284L mutant CHRNA4. Inhibition of glutamatergic transmission in thalamic hyperdirect pathway induced by ZNS via activation of II-mGluR may be involved, at least partially, in ZNS-sensitive nocturnal paroxysmal dystonia of ADSHE patients with S284L mutation.

Effect of zonisamide on parkinsonism in patients with dementia with Lewy bodies: A phase 3 randomized clinical trial

INTRODUCTION

Zonisamide is approved in Japan for treating motor dysfunction in Parkinson's disease, and might also be effective for parkinsonism in patients with dementia with Lewy bodies (DLB). Our study evaluated the safety and efficacy of zonisamide for treating parkinsonism in patients with DLB.

METHODS

This multicenter, randomized, double-blind, phase 3 trial was conducted in Japan between April 2015 and November 2017. Following a 4-week run-in period, outpatients diagnosed with probable DLB who had developed parkinsonism were randomized to receive oral zonisamide (25 or 50 mg/day) or placebo for 12 weeks, followed by a 40-week open-label extension. The primary endpoint was the change in Unified Parkinson's Disease Rating Scale (UPDRS) part III total score at Week 12.

RESULTS

Of 351 patients randomized, 346 (mean age, 77.2 years; 188 males) were included in the modified intention-to-treat population. At Week 12, the group difference (least squares mean ± SEM) for changes from baseline (vs placebo) in UPDRS part III total score was -2.7 ± 0.9 (95% confidence interval [CI]: -4.4, -0.9, P = 0.005) in the zonisamide 25-mg group and -2.6 ± 0.9 (95% CI: -4.4, -0.8, P = 0.005) in the zonisamide 50-mg group. Adverse events were reported in 47.1%, 48.7%, and 54.5% of patients in the placebo and zonisamide 25- and 50-mg groups, and led to treatment discontinuation in 5.0%, 4.3%, and 9.8% of patients, respectively.

CONCLUSION

Daily administration of 25- or 50-mg zonisamide significantly improved motor function compared with placebo; both doses were safe and well tolerated in patients with DLB.

The effects of zonisamide on L-DOPA-induced dyskinesia in Parkinson's disease model mice

Parkinson's disease (PD) is a neurodegenerative disorder caused by the loss of dopaminergic neurons in the midbrain and shows motor dysfunctions. Zonisamide (ZNS, 1,2-benzisoxazole-3-methanesulfonamide), which was originally developed as an antiepileptic drug, was also found to have beneficial effects on motor symptoms in PD. In the current study, we have investigated the behavioral and physiological effects of ZNS on L-DOPA-induced dyskinesia (LID) in PD model mice. Chronic administration of L-DOPA plus ZNS in PD model mice was shown to increase the duration and severity of LID compared with PD model mice that were treated with L-DOPA alone. To elucidate the neural mechanism of the effects of ZNS on LID, we examined neuronal activity in the output nuclei of the basal ganglia, i.e., the substantia nigra pars reticulata (SNr). Chronic administration of L-DOPA plus ZNS in PD mice decreased the firing rate in the SNr while they showed apparent LID. In addition, chronic treatment of L-DOPA plus ZNS in PD mice changed cortically evoked responses in the SNr during LID. In the control state, motor cortical stimulation induces the triphasic response composed of early excitation, inhibition, and late excitation. In contrast, L-DOPA plus ZNS-treated PD mice showed longer inhibition and reduced late excitation. Previous studies proposed that inhibition in the SNr is derived from the direct pathway and releases movements, and that late excitation is derived from the indirect pathway and stops movements. These changes of the direct and indirect pathways possibly underlie the effects of ZNS on LID.

Zonisamide Enhances Motor Effects of Levodopa, Not of Apomorphine, in a Rat Model of Parkinson's Disease

Zonisamide is a relatively recent drug for Parkinson's disease. Multiple hypotheses have been proposed to explain the antiparkinsonian effects of zonisamide. However, it is still unclear whether the effect of zonisamide is mainly due to dopaminergic modification in the striatum, or if zonisamide works through nondopaminergic pathways. We conducted the present study to determine the mechanism that is mainly responsible for zonisamide's effects in Parkinson's disease. We examined the effects of zonisamide on motor symptoms in a hemiparkinsonian rat model when administered singly, coadministered with levodopa, a dopamine precursor, or apomorphine, a D1 and D2 dopamine receptor agonist. We used 6-hydroxydopamine-lesioned hemiparkinsonian rats, which were allocated to one of five groups: 14 rats received levodopa only (6 mg/kg), 12 rats received levodopa (6 mg/kg) plus zonisamide (50 mg/kg), six rats received apomorphine only (0.05 mg/kg), six rats received apomorphine (0.05 mg/kg) plus zonisamide (50 mg/kg), and six rats received zonisamide only (50 mg/kg). The drugs were administered once daily for 15 days. We evaluated abnormal involuntary movement every 20 min during a 3 h period following the injection of drugs on treatment Days 1, 8, and 15. Western blot analyses for dopamine decarboxylase and vesicular monoamine transferase-2 were performed using striatal tissues in the lesioned side of rats in the levodopa only group (n = 6) and levodopa plus zonisamide group (n = 4). Levodopa-induced abnormal involuntary movement was significantly enhanced by coadministration of zonisamide. In contrast, zonisamide had no effect on apomorphine-induced abnormal involuntary movement. Zonisamide monotherapy did not induce abnormal involuntary movement. Zonisamide did not affect striatal expression of dopamine decarboxylase or vesicular monoamine transferase-2. In conclusion, zonisamide appears to generate its antiparkinsonian effects by modulating levodopa-dopamine metabolism in the parkinsonian striatum.

Advances in the pharmacotherapeutic management of dementia with Lewy bodies

INTRODUCTION

Dementia with Lewy bodies (DLB) is the second most common type of dementia in people over 65 years of age. Given the complex clinical phenotype, the management of DLB may be challenging, especially considering that there is limited evidence about specific interventions, and there are currently no Food and Drug Administration (FDA)/European Medicines Agency (EMA)-approved medications.

AREAS COVERED

This article provides an overview of the current pharmacotherapy in DLB and gives review to the most recent drug candidates in clinical trials.

EXPERT OPINION

Commonly prescribed drugs are primarily aimed at treating the most troublesome clinical features of DLB. Although these medications provide some benefit to symptoms, there is, unfortunately, a lack of DLB-specific evidence on effective treatments and their off-label use. Indeed, most treatments used come from clinical trials on patients with Alzheimer's disease or Parkinson's disease. Thus, there is an urgent need for randomized clinical trials in DLB patients. Despite several challenges, potential new drugs are in ongoing clinical trials; furthermore, as our understanding of molecular and cellular mechanisms underlying DLB broaden, it is likely that we will identify novel drug targets for the development of better and more effective symptomatic products and disease-modifying therapies.

Pharmacological characterization of nicotine-induced tremor: Responses to anti-tremor and anti-epileptic agents

We previously showed that nicotine evoked kinetic tremor by activating the inferior olive, which is implicated in the pathogenesis of essential tremor, via α7 nicotinic acetylcholine receptors. Here, we evaluated the effects of various anti-tremor and anti-epileptic agents on nicotine-induced tremor in mice to clarify the pharmacological characteristics of nicotine tremor. Drugs effective for essential tremor, propranolol, diazepam and phenobarbital, all significantly inhibited kinetic tremor induced by an intraperitoneal (i.p.) injection of nicotine (1 mg/kg). In contrast, none of the medications for Parkinson's disease, l-DOPA, bromocriptine or trihexyphenidyl, affected the nicotine tremor. Among the anti-epileptic agents examined, valproate, carbamazepine and ethosuximide, significantly inhibited nicotine-induced tremor. In addition, a selective T-type Ca²⁺ channel blocker, TTA-A2, also suppressed the nicotine tremor. However, neither gabapentin, topiramate, zonisamide nor levetiracetam significantly affected nicotine-induced tremor. The present results show that nicotine-induced tremor resembles essential tremor not only on the neural basis, but also in terms of the pharmacological responses to anti-tremor agents, implying that nicotine-induced tremor can serve as a model for essential tremor. In addition, it is suggested that anti-epileptic agents, which have stimulant actions on the GABAergic system or blocking actions on voltage-gated Na⁺ channels and T-type Ca²⁺ channels, can alleviate essential tremor.

Pharmacometabolomics applied to zonisamide pharmacokinetic parameter prediction

INTRODUCTION

Zonisamide is a new-generation anticonvulsant antiepileptic drug metabolized primarily in the liver, with subsequent elimination via the renal route.

OBJECTIVES

Our objective was to evaluate the utility of pharmacometabolomics in the detection of zonisamide metabolites that could be related to its disposition and therefore, to its efficacy and toxicity.

METHODS

This study was nested to a bioequivalence clinical trial with 28 healthy volunteers. Each participant received a single dose of zonisamide on two separate occasions (period 1 and period 2), with a washout period between them. Blood samples of zonisamide were obtained from all patients at baseline for each period, before volunteers were administered any medication, for metabolomics analysis.

RESULTS

After a Lasso regression was applied, age, height, branched-chain amino acids, steroids, triacylglycerols, diacyl glycerophosphoethanolamine, glycerophospholipids susceptible to methylation, phosphatidylcholines with 20:4 FA (arachidonic acid) and cholesterol ester and lysophosphatidylcholine were obtained in both periods.

CONCLUSION

To our knowledge, this is the only research study to date that has attempted to link basal metabolomic status with pharmacokinetic parameters of zonisamide.

Combination Therapy with Zonisamide and Antiparkinson Drugs for Parkinson's Disease: A Meta-Analysis

BACKGROUND

There is uncertainty about the efficacy and tolerability of zonisamide for Parkinson's disease (PD).

OBJECTIVE

We performed a meta-analysis of zonisamide treatment in PD patients who received antiparkinson drugs such as levodopa.

METHODS

The primary outcome measures were the Unified Parkinson's Disease Rating Scale (UPDRS) Part III scores, wearing-off time, and discontinuation rate due to all causes. Secondary outcome measures were UPDRS total and subscale scores; discontinuation rates due to adverse events, inefficacy, and death; and individual adverse events.

RESULTS

Four randomized placebo-controlled trials including 1,068 PD patients were analyzed. All studies were conducted in Japan. UPDRS Part III scores were significantly lower with zonisamide than with placebo (weighted mean difference [WMD], -2.56; 95% confidence interval [CI]; -4.20 to -0.92; p = 0.002). Further, zonisamide significantly decreased the wearing-off time compared with placebo (standardized mean difference, -0.24; 95% CI, -0.39 to -0.09; p = 0.001). Discontinuation rates due to all causes were similar between the zonisamide and placebo groups (risk ratio, 1.29; 95% CI, 0.90 to 1.84; p = 0.16). While zonisamide also decreased both UPDRS Part II (off-time) and UPDRS total scores compared to placebo (UPDRS Part II [off-time] scores: WMD, -0.79; UPDRS total scores: WMD, -2.51), there were no significant differences in other secondary outcomes between the two groups.

CONCLUSIONS

Our results suggested that zonisamide combination therapy was beneficial in treating motor symptoms in PD patients receiving antiparkinson drugs and was well tolerated in Japanese patients. Future studies in populations other than the Japanese are needed.

Adjunct zonisamide to levodopa for DLB parkinsonism: A randomized double-blind phase 2 study

Objective

To investigate the efficacy and safety of zonisamide as an adjunct to levodopa therapy for parkinsonism in patients with dementia with Lewy bodies (DLB).

Methods

This phase 2, placebo-controlled, randomized, double-blind study consisted of run-in (placebo, 4 weeks) and treatment (placebo or zonisamide 25 or 50 mg once daily, 12 weeks) periods. Outpatients diagnosed with probable DLB were eligible for inclusion. The primary endpoint was the change from baseline in Unified Parkinson's Disease Rating Scale (UPDRS) part 3 total score at week 12. Cognitive function, behavioral and psychological symptoms of dementia (BPSD), caregiver burden, other UPDRS parts as secondary endpoints, and safety were also assessed.

Results

Overall, 158 patients with DLB received the study drug; 21 discontinued during treatment and 137 completed treatment. Improvement in UPDRS part 3 total score at week 12 was significantly greater in the zonisamide 50 mg group compared with placebo (between-group difference −4.1; 95% confidence interval −6.8 to −1.4; p = 0.003). Zonisamide did not worsen cognitive function, BPSD, or caregiver burden. The overall incidence of adverse events was higher in the zonisamide 50 mg than the 25 mg and placebo groups (65.3%, 43.1%, and 50.0%, respectively); similar rates of serious adverse events were observed among all groups.

Conclusion

Zonisamide (adjunctive to levodopa) improved parkinsonism accompanying DLB without worsening cognitive function or psychiatric symptoms.

Clinical trial registration

JapicCTI-122040.

Classification of evidence

This study provides Class I evidence that zonisamide (adjunctive to levodopa) improves parkinsonism and is well-tolerated in patients with DLB.

Efficacy, tolerability, and retention rates of zonisamide in older adult patients with focal-onset epilepsy: Experiences from two tertiary epilepsy centers

OBJECTIVE

The objective of this study was to evaluate the efficacy, tolerability, and retention rates for zonisamide (ZNS) in older adult patients with focal-onset epilepsy.

PATIENTS AND METHODS

Chart reviews of patients aged 60years and older with focal-onset epilepsy treated with ZNS in two tertiary epilepsy centers were analyzed retrospectively.

RESULTS

Eighty-five patients (41 males, 44 females) aged over 60years (range: 60-81) with focal-onset epilepsy treated with ZNS were identified; 55.3% of the patients (n=47) were on monotherapy. The median and average doses of ZNS doses were 200mg/day (range: 100-400) and 212.9±84.2mg/day, respectively. With ZNS treatment, 67.1% of the patients (n=57) were seizure-free for a median of 28months (range: 10-56) whereas 20% (n=17) of the patients had seizures that were unresponsive to ZNS treatment. Best seizure control was achieved in patients with poststroke epilepsy; seizure freedom was 80% in this subgroup. Overall retention rate was found to be 83.5%. There was no significant relation between receiving poly- or monotherapy and discontinuation of ZNS (p=0.18). Thirty-two of the patients (37.6%) lost weight. Median weight loss was 8kg (range: 2-16). There was no significant correlation between weight loss and the administered doses of ZNS (r=0.34; p=0.12).

CONCLUSION

Despite limitations due to the retrospective design of the study, the results show that ZNS is a well-retained drug with high efficacy in older adult patients with epilepsy.

Prevention of the adverse effects of olanzapine on lipid metabolism with the antiepileptic zonisamide

BACKGROUND

Atypical antipsychotic drugs, particularly olanzapine, represent a mainstay in the treatment of psychoses; however, their use is commonly associated with weight gain and diabetes. The aim of this study was to determine whether combined administration of olanzapine and zonisamide can be used to prevent olanzapine-induced metabolic disturbances.

METHODS AND RESULTS

These experiments involved female Sprague Dawley rats (n = 6-8/group) that were administered olanzapine, either acutely (6 mg/kg, s. c) or via continuous osmotic minipump infusion (6 mg/kg/day for 6 or 14 days), in combination with zonisamide (26 mg/kg/day,i.p.). Continuous infusion of olanzapine induced accumulation of adipose tissue and an associated reduction in stimulated lipolysis and reduced protein expression of CGI-58, a critical co-activator of ATGL. Olanzapine treatment caused a preferential shift toward carbohydrate oxidation (or reduced fat oxidation), elevated blood triglycerides and a reduction in locomotor activity. Olanzapine had a direct effect on glucose regulation, causing rapid hyperglycemia, and a reduction in glucose tolerance and insulin sensitivity. Continuous administration of olanzapine caused significant hyperinsulinemia and a significant reduction in insulin sensitivity. Zonisamide did not affect the impact of olanzapine on glucose homeostasis. On the other hand, co-administration of olanzapine with zonisamide completely ameliorated olanzapine-mediated shifts in lipid metabolism resulting in a normalization of olanzapine-induced weight gain.

CONCLUSION

These data collectively show an impact of olanzapine on body weight and lipid metabolism, which is ameliorated by co-administration with zonisamide. These findings suggest that a combined olanzapine and zonisamide approach might reduce weight gain, but will not provide protection against olanzapine-induced glucose intolerance.

Zonisamide attenuates lactacystin-induced parkinsonism in mice without affecting system xc<sup/>

Zonisamide (ZNS), an anticonvulsant drug exhibiting symptomatic effects in Parkinson's disease (PD), was recently reported to exert neuroprotection in rodent models. One of the proposed neuroprotective mechanisms involves increased protein expression of xCT, the specific subunit of the cystine/glutamate antiporter system x_c^-, inducing glutathione (GSH) synthesis. Here, we investigated the outcome of ZNS treatment in a mouse model of PD based on intranigral proteasome inhibition, and whether the observed effects would be mediated by system x_c^-. The proteasome inhibitor lactacystin (LAC) was administered intranigrally to male C57BL/6J mice receiving repeated intraperitoneal injections of either ZNS 30mgkg^-1 or vehicle. Drug administration was initiated three days prior to stereotaxic LAC injection and was maintained until six days post-surgery. One week after lesion, mice were behaviorally assessed and investigated in terms of nigrostriatal neurodegeneration and molecular changes at the level of the basal ganglia, including expression levels of xCT. ZNS reduced the loss of nigral dopaminergic neurons following LAC injection and the degree of sensorimotor impairment. ZNS failed, however, to modulate xCT expression in basal ganglia of lesioned mice. In a separate set of experiments, the impact of ZNS treatment on system x_c^- was investigated in control conditions in vivo as well as in vitro. Similarly, ZNS did not influence xCT or glutathione levels in naive male C57BL/6J mice, nor did it alter system x_c^- activity or glutathione content in vitro. Taken together, these results demonstrate that ZNS treatment provides neuroprotection and behavioral improvement in a PD mouse model based on proteasome inhibition via system x_c^- independent mechanisms.

Zonisamide Reduces Withdrawal Symptoms But Does Not Enhance Varenicline-Induced Smoking Cessation

INTRODUCTION

Varenicline (Chantix) is a first-line treatment for smoking cessation but does not produce cessation in many individuals. It may be possible to improve abstinence by co-administering varenicline with other medications. Zonisamide (Zonegran) has a similar pharmacologic profile to topiramate, which has been shown to reduce smoking, but is better tolerated. This study evaluated whether combined zonisamide and varenicline reduced tobacco withdrawal and increased abstinence among smokers trying to quit, relative to varenicline and placebo.

METHODS

This was a double-blind, randomized, placebo-controlled pilot trial of zonisamide + varenicline versus placebo + varenicline for smoking cessation. Smokers received brief counseling and study medications, and completed weekly assessments for 10 consecutive weeks. The primary outcome was continuous abstinence rates (biochemically verified) during the final 4 weeks of treatment.

RESULTS

Results are presented as intent-to-treat and completer analyses. Seventy-four individuals were enrolled; 45 completed the study. Overall, 14.9% (intent-to-treat) and 25.0% (completer) of participants maintained sustained abstinence during the final 4 weeks of treatment. There were no differences between groups for biochemically-verified smoking, but zonisamide + varenicline reduced self-reported smoking, nicotine withdrawal, and craving compared to placebo + varenicline.

CONCLUSIONS

Zonisamide decreased nicotine withdrawal and craving, though not of sufficient magnitude to modify smoking behavior. The sample size was small and low rates of abstinence across groups suggest the study population was difficult to treat. Additional evaluation of zonisamide or other medications that increase GABA or decrease glutamate in larger or more diverse populations may yield positive clinical benefit for nicotine/tobacco cessation.

IMPLICATIONS

This study provides support for layering novel medications with varenicline for smoking cessation, for investigating medications that target the GABA and glutamate system, and for assessing the contribution that reductions in nicotine withdrawal have on ultimate cessation outcomes.

Inhibition of hyperactivity and impulsivity by carbonic anhydrase inhibitors in spontaneously hypertensive rats, an animal model of ADHD

RATIONALE

Dysregulation of noradrenergic and dopaminergic systems is involved in the pathology of attention deficit hyperactivity disorder (ADHD). Carbonic anhydrase (CA) has been reported to affect monoamine transmission in the central nervous system.

OBJECTIVES

The aim of this study is to investigate the effect of CA inhibitors on the hyperactivity and impulsivity of the spontaneously hypertensive rat (SHR), which is currently the best-validated animal model of ADHD.

METHODS

SHRs and Wistar Kyoto rats at 6 to 8 weeks of age were pretreated with intraperitoneal injections of acetazolamide and methazolamide, both carbonic anhydrase inhibitors, before the behavior tests. The open-field locomotion test and the electro-foot shock aversive water drinking test were then applied to quantify their hyperactivity and impulsivity, respectively. The Morris water maze test, on the other hand, monitored their spatial learning.

RESULTS

Acetazolamide and methazolamide significantly inhibited the hyperactivity of SHRs but had no effects in Wistar Kyoto rats. Acetazolamide also inhibited the impulsivity of SHRs. Low doses of acetazolamide had the greater inhibitory effects on the hyperactivity and impulsivity, but did not impair the spatial learning of SHRs.

CONCLUSIONS

This is the first study to show that carbonic anhydrase inhibitors can strain-specifically antagonize the hyperactivity and impulsivity of SHRs. Under a low dose of acetazolamide, there was no cognition impairment in SHRs. Carbonic anhydrase inhibitors may be the novel drugs for treatment for patients with ADHD.

The safety and long-term efficacy of zonisamide as adjunctive therapy for focal epilepsy

Epilepsy is a chronic disease which affects 1% of the population worldwide. As treatment is required for many years or decades, the long-term efficacy and tolerability of antiepileptic drugs are particularly important. Zonisamide (ZNS) is a second-generation antiepileptic drug with a unique structure and multiple mechanisms of action. Here, recently published long-term outcomes of patient cohorts with focal epilepsy undergoing ZNS treatment are discussed. Whereas ZNS monotherapy maintains similar seizure control efficacy to carbamazepine after 2 years of treatment, seizure-free rates are low in pharmacoresistant patients undergoing late adjunctive therapy. In preselected patient populations derived from double-blind studies, long-term seizure reduction and responder rates support sustained ZNS efficacy, good adherence and long-term retention. Adverse effects include somnolence and weight decrease, but data suggest that long-term treatment with ZNS is safe with only rare newly occurring adverse effects, and good long-term tolerability also regarding mood, behavior, cognition and bone maturation.

Zonisamide improves wearing-off in Parkinson's disease: A randomized, double-blind study

BACKGROUND

Previously, we reported 50 mg/d zonisamide improved wearing-off without increasing dyskinesia in patients with Parkinson's disease (PD).

METHODS

To determine the efficacy of zonisamide for treatment of "off" time in PD patients, we conducted a multicenter, randomized, double-blind, parallel-group, placebo-controlled study in Japan. Patients with PD and wearing-off received placebo for 4 weeks and then were treated for 12 weeks with zonisamide 25 or 50 mg/d or placebo, in addition to their previous therapy. The primary endpoint was the change from baseline in daily "off" time as determined by patients' diaries at the final assessment. Secondary endpoints included changes from baseline in the total scores of the Unified Parkinson's Disease Rating Scale Parts I, II, III, and IV, the dyskinesia duration, and PDQ-39 score.

RESULTS

Of 422 patients enrolled, 389 (131 for placebo, 130 for zonisamide 25 mg, and 128 for zonisamide 50 mg) were randomized, and 354 (120, 119, and 115, respectively) completed the study. The "off" time significantly reduced by 0.719 ± 0.179 h for zonisamide, 50 mg compared with placebo (0.011 ± 0.173 h, P = 0.005). Although the incidence of somnolence was higher for zonisamide (3.1% for zonisamide 25 mg, 6.3% for zonisamide 50 mg) than for placebo (2.3%), the incidences of the other adverse events, including dyskinesia or hallucination, for both zonisamide treatments were comparable to those for placebo.

CONCLUSION

The study provides evidence that confirms the efficacy of zonisamide 50 mg/d for reduction in "off" time in PD patients with wearing-off phenomena.

Zonisamide in the management of epilepsy in the elderly

Zonisamide (ZNS), a second-generation antiepileptic drug, indicated as add-on treatment of focal epilepsy, has been recently approved as monotherapy for the treatment of partial seizures in adults affected by newly diagnosed epilepsy in Europe. Evidence on the efficacy and tolerability of antiepileptic drugs in the elderly is still lacking as these patients are frequently excluded from clinical trials. Here, a comprehensive overview of available data regarding the use of ZNS in the treatment of epilepsy in elderly people is provided. In a pooled analysis conducted in patients aged ≥65 years, no new/unexpected safety findings have emerged. Few data from uncontrolled investigations suggest that ZNS may be effective and well tolerated when administered as monotherapy or adjunctive antiepileptic treatment in the elderly. However, evidence from these observational studies is less than satisfactory, and randomized controlled trials focused on these patients are still needed.

Anticonvulsants for the treatment of alcohol withdrawal syndrome and alcohol use disorders

Alcoholic patients suffer from harmful allostatic neuroplastic changes in the brain causing an acute withdrawal syndrome upon cessation of drinking followed by a protracted abstinence syndrome and an increased risk of relapse to heavy drinking. Benzodiazepines have long been the treatment of choice for detoxifying patients and managing alcohol withdrawal syndrome (AWS). Non-benzodiazepine anticonvulsants (NBACs) are increasingly being used both for alcohol withdrawal management and for ongoing outpatient treatment of alcohol dependence, with the goal of either abstinence or harm reduction. This expert narrative review summarizes the scientific basis and clinical evidence supporting the use of NBACs in treating AWS and for reducing harmful drinking patterns. There is less evidence in support of NBAC therapy for AWS, with few placebo-controlled trials. Carbamazepine and gabapentin appear to be the most promising adjunctive treatments for AWS, and they may be useful as monotherapy in select cases, especially in outpatient settings and for the treatment of mild-to-moderate low-risk patients with the AWS. The body of evidence supporting the use of the NBACs for reducing harmful drinking in the outpatient setting is stronger. Topiramate appears to have a robust effect on reducing harmful drinking in alcoholics. Gabapentin is a potentially efficacious treatment for reducing the risk of relapse to harmful drinking patterns in outpatient management of alcoholism. Gabapentin's ease of use, rapid titration, good tolerability, and efficacy in both the withdrawal and chronic phases of treatment make it particularly appealing. In summary, several NBACs appear to be beneficial in treating AWS and alcohol use disorders.

Zonisamide attenuates α-synuclein neurotoxicity by an aggregation-independent mechanism in a rat model of familial Parkinson's disease

The anti-epileptic agent zonisamide (ZNS) has been shown to exert protective effects in neurotoxin-based mouse models of Parkinson disease. However, it is unknown whether ZNS can attenuate toxicity of familial Parkinson's disease-causing gene products. In this study, we investigated the effects of ZNS on neurodegeneration induced by expression of A53T α-synuclein in the rat substantia nigra using a recombinant adeno-associated virus vector. Expression of A53T α-synuclein yielded severe loss of nigral dopamine neurons and striatal dopamine nerve terminals from 2 weeks to 4 weeks after viral injection. Oral administration of ZNS (40 mg/kg/day) significantly delayed the pace of degeneration at 4 weeks after viral injection as compared with the vehicle group. This effect lasted until 8 weeks after viral injection, the final point of observation. ZNS treatment had no impact on the survival of nigrostriatal dopamine neurons in rats expressing green fluorescent protein. Quantification of striatal Ser129-phosphorylated α-synuclein-positive aggregates showed that these aggregates rapidly formed from 2 weeks to 4 weeks after viral injection. This increase was closely correlated with loss of nigrostriatal dopamine neurons. However, ZNS treatment failed to alter the number of all striatal Ser129-phosphorylated α-synuclein-positive aggregates, including small dot-like and large round structures. The number of these aggregates was almost constant at 4 weeks and 8 weeks after viral injection, although ZNS persistently prevented loss of nigrostriatal dopamine neurons during this period. Also, ZNS treatment did not affect the number of striatal aggregates larger than 10 µm in diameter. These data show that ZNS attenuates α-synuclein-induced toxicity in a manner that is independent of the formation and maturation of α-synuclein aggregates in an in vivo model of familial Parkinson's disease, suggesting that ZNS may protect nigrostriatal dopamine neurons by modulating cellular damage or a cell death pathway commonly caused by neurotoxins and α-synuclein.

Zonisamide: a review of the clinical and experimental evidence for its use in Parkinson's disease

The limitations of currently available therapies in addressing the non motor symptoms of Parkinson's disease (PD) have egged on the search for newer options. Zonisamide has been in use for epilepsy and it was serendipitously found to improve the symptoms of PD in a patient who had both epilepsy and PD. Thereafter, various trials were designed to assess the use of zonisamide in PD. The present article investigates the evidence for use of zonisamide in PD from the various clinical trials that were designed to address this issue. Furthermore, the article also summarizes the various mechanisms of its use in PD as described in various animal experiments. A search protocol was designed with predefined inclusion and exclusion criteria. The databases searched were Pubmed, Ovid medline, Cochrane and clinicaltrials.gov. The data thus generated, was fed into a predesigned format. Most of the clinical trials on zonisamide in PD have come from Japan. Most of these trials used the changes in the Unified Parkinson's Disease Rating Scale (UPDRS) score as the endpoints and the most conclusive evidence is for a dose of 25-50 mg, which caused a change in UPDRS part III (motor symptoms). These patients were on levodopa and other drugs used for PD during the trials. One of the clinical trials conducted in Spain investigates the use of zonisamide in impulse control disorders among 15 patients of PD. Among the many mechanisms postulated, a reduction in levodopa induced quinone formation, protection against mitochondrial impairment and an increase in astroglial cysteine transport, an inhibition of microglial activation, monoamine oxidase-B (MAO-B) inhibition, an increased dopamine release and blockade of calcium channels are the most cited. There is evidence for use of zonisamide in PD in addition to levodopa and other therapies for control of motor symptoms. For now, the evidence for its use in control of non motor symptoms in PD is not enough and needs to be investigated further.

Zonisamide regulates basal ganglia transmission via astroglial kynurenine pathway

To clarify the anti-parkinsonian mechanisms of action of zonisamide (ZNS), we determined the effects of ZNS on tripartite synaptic transmission associated with kynurenine (KYN) pathway (KP) in cultured astrocytes, and transmission in both direct and indirect pathways of basal ganglia using microdialysis. Interactions between cytokines [interferon-γ (IFNγ) and tumor-necrosis factor-α (TNFα)] and ZNS on astroglial releases of KP metabolites, KYN, kynurenic-acid (KYNA), xanthurenic-acid (XTRA), cinnabarinic-acid (CNBA) and quinolinic-acid (QUNA), were determined by extreme liquid-chromatography with mass-spectrometry. Interaction among metabotropic glutamate-receptor (mGluR), KP metabolites and ZNS on striato-nigral, striato-pallidal GABAergic and subthalamo-nigral glutamatergic transmission was examined by microdialysis with extreme liquid-chromatography fluorescence resonance-energy transfer detection. Acute and chronic ZNS administration increased astroglial release of KYN, KYNA, XTRA and CNBA, but not QUNA. Chronic IFNγ administration increased the release of KYN, KYNA, CNBA and QUNA, but had minimal inhibitory effect on XTRA release. Chronic TNFα administration increased CNBA and QUNA, but not KYN, KYNA or XTRA. ZNS inhibited IFNγ-induced elevation of KYN, KYNA and QUNA, but enhanced IFNγ-induced that of CNBA. TNFα-induced rises in CNBA and QUNA were inhibited by ZNS. ZNS inhibited striato-nigral GABAergic, striato-pallidal GABAergic and subthalamo-nigral glutamatergic transmission via activation of groups II and III mGluRs. ZNS enhanced astroglial release of endogenous agonists of group II mGluR, XTRA and group III mGluR, CNBA. Activated endogenous mGluR agonists inhibited transmission in direct and indirect pathways of basal ganglia. These mechanisms contribute to effectiveness and well tolerability of ZNS as an adjunct treatment for Parkinson's disease during l-DOPA monotherapy. This article is part of the Special Issue entitled 'The Synaptic Basis of Neurodegenerative Disorders'.

The effect of zonisamide on antipsychotic-associated weight gain in patients with schizophrenia: a randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Many patients with schizophrenia suffer from metabolic symptoms and weight gain in which predispose them to obesity, diabetes, and cardiovascular problems. This trial examines the efficacy and safety of zonisamide on weight and body mass index in patients with schizophrenia being administered with atypical antipsychotics.

METHOD

In this 10-week, double blind randomized placebo controlled clinical trial, forty one patients with schizophrenia diagnosed according to DSM-IV-TR criteria who were taking a stable dose of atypical antipsychotic are allocated into one of the two groups of zonisamide or placebo group. Weight, body mass index, waist circumference, and adverse effects were assessed.

RESULTS

The two groups were not statistically different regarding baseline characteristics on age, gender, education, diagnosis, weight, body mass index, daily cigarette smoking, and the duration of illness. After 10 weeks, the patients in the placebo group had significantly gained weight, while the patients in the zonisamide group lost weight (mean=1.9, SD=2.2 versus mean=-1.1 kg, SD=1.4). The changes of body mass index in the two groups were significantly different. Body mass index decreased in the zonisamide group (mean=-0.3, SD=0.4) while it increased in the placebo group (mean=2.2, SD=6.9). There was a significance difference between the two groups regarding waist circumference at the end of trial (P<0.0001), too. The waist increased in the placebo group while it decreased in the zonisamide group (mean=1.1, SD=1.7 versus mean=-0.7, SD=1.2, respectively), as well. The frequencies of adverse effects were not significantly different between the two groups and zonisamide was tolerated well.

CONCLUSION

Zonisamide as an adjuvant treatment is tolerated well and markedly affect on the weight loss of patients with schizophrenia being treated with atypical antipsychotics.

Antiepileptic drug effects on mood and behavior: molecular targets

With almost 100 years of clinical experience, antiepileptic drugs (AEDs) remain the mainstay of epilepsy treatment. They suppress epileptic seizures by acting on a variety of mechanisms and molecular targets involved in the regulation of neuronal excitability. These include inhibitory-GABAergic and excitatory-glutamatergic neurotransmission, as well as ion (sodium and calcium) conductance through voltage-gated channels. On the other hand, accruing evidence indicates that these mechanisms and targets are also implicated in the regulation of mood and behavior, which may explain why each AED is associated with specific psychotropic effects. These effects, however, cannot be explained solely on the basis of the known mode of action of each AED, and other mechanisms or targets are likely to be implicated. In this article, we review positive and negative effects of AEDs on mood and behavior, discuss putative underlying mechanisms, and highlight knowledge gaps which should be addressed in future studies.

Characteristics of selected second-generation antiepileptic drugs used in dogs

A significant number of cases of clinical canine epilepsy remain difficult to control in spite of the applied treatment. At the same time, the range of antiepileptic drugs is increasingly wide, which allows efficient treatment. In the present paper we describe the pharmacodynamics and pharmacokinetics of the newer antiepileptic drugs which were licensed after 1990 but are still not widely used in veterinary medicine. The pharmacokinetic profiles of six of these drugs were tested on dogs. The results of experimental studies suggest that second generation antiepileptic drugs may be applied in mono- as well as in poli- treatment of canine epilepsy because of the larger safety margin and more advantageous pharmacokinetic parameters. Knowledge of the drugs' pharmacokinetics allows its proper clinical appliance, which, in turn, gives the chance to improve the efficiency of pharmacotherapy of canine epilepsy.

Anticonvulsant action of indazole

Here we report that indazole is characterized as a potential anticonvulsant, inhibiting pentylenetetrazole-, electroshock- and strychnine-induced convulsions in mice (ED50's: 39.9, 43.2 and 82.4 mg/kg, respectively) but not bicuculline- and picrotoxin-induced convulsions. The median toxic dose (TD(50)) of indazole was 52.3 mg/kg by the minimal motor impairment test. Therefore, nontoxic doses produced anticonvulsant activity against pentylenetetrazole- and electroshock-induced seizures. Indazole (50 mg/kg) had no effect on spontaneous activity but induced hypothermia. It also inhibited the metabolism of dopamine and 5-hydroxytryptamine in the brain in vivo and the activities of monoamine oxidase A and B in vitro, with IC(50) values of 20.6 μM and 16.3 μM, respectively. However, these inhibitory effects do not account for the anticonvulsant activity because treatment with typical monoamine oxidase inhibitors such as pargyline or tranylcypromine did not completely reproduce the anticonvulsant activity of indazole. In the animal seizure models tested, the anticonvulsant profile of indazole most resembled that of gabapentin and somewhat resembled those of the AMPA/kainate antagonist NBQX and the sodium channel inhibitor phenytoin, but differed from that of benzodiazepine. The isobolographic analyses showed that the interactive mode of indazole with gabapentin, NBQX or phenytoin is additive. These results suggest that indazole has anticonvulsant activity and multiple mechanisms.

Zonisamide: its pharmacology, efficacy and safety in clinical trials

Zonisamide is a benzisoxazole derivative, chemically unrelated to other antiepileptic drugs, that appears to have multiple mechanisms of action, including inhibition of Na(+) channels and reduction of T-type Ca(2+) currents. It is currently licensed in Europe and the USA for adjunctive treatment of partial seizures in adults, and in Europe as monotherapy for treatment of partial seizures in adults with newly diagnosed epilepsy. Zonisamide displays predictable, dose-dependent pharmacokinetics and has a half-life of ~60 h, allowing once- or twice-daily administration. It has a low potential for interactions with other medications, including oral contraceptives. The clinical efficacy of adjunctive zonisamide therapy has been established in four pivotal, phase III, randomized, double-blind, placebo-controlled trials, which together included approximately 850 patients, aged 12-77 years, with refractory partial epilepsy. In all four trials, zonisamide 300-600 mg/day resulted in significant reductions in median total seizure rates vs placebo, and zonisamide was generally well tolerated; the most frequently reported adverse events being somnolence, dizziness and anorexia/weight loss. Subanalysis of the primary European trial indicated that zonisamide was effective when administered as first-line adjunctive treatment, and a long-term extension to the same trial demonstrated that the efficacy and safety/tolerability of adjunctive zonisamide was sustained for up to 36 months. Once-daily monotherapy with zonisamide (200-500 mg/day) has been shown to be non-inferior to, and as well tolerated as, twice-daily monotherapy with controlled-release carbamazepine (400-1200 mg/day) in adults with newly diagnosed partial epilepsy. Zonisamide has also been shown to have favourable long-term retention rates, an important indication of its overall effectiveness.