Zonisamide for the treatment of epilepsy

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.

Effect of zonisamide on refractory epilepsy during pregnancy in lamotrigine resistant kindled rats

Drug-resistant epilepsy with uncontrolled severe seizures despite state-of-the-art medical treatment continues to be a major clinical problem. Pregnancy is a state where drug pharmacokinetic changes are more pronounced and more rapid than any other period of life. The current study investigated the effect of zonisamide (ZNS) on refractory epilepsy during pregnancy in lamotrigine-resistant kindled rats. Fifty-six lamotrigine (LTG)-resistant kindled Wistar rats were divided into five experimental (four pregnant and one non-pregnant) and 2 positive controls (pregnant and non-pregnant) groups and eight intact Wistar rats were put in the negative pregnant control group. Experimental groups received daily ZNS 50mg/kg by oral gavage and 30min later, pentylenetetrazol (PTZ) (30mg/kg) was injected intraperitoneal (i.p) on Gestational Days 10-15 (in rats with or without ZNS or methanol and ethyl acetate as a ZNS solvent challenge in days -5 to 0) or Days 15-20 and for six days in the non-pregnant group. The positive control groups received the ZNS solvent for the same number of days, but the negative pregnant control group did not receive any treatment. Epilepsy was significantly controlled by ZNS in the experimental groups compared to the positive control groups. It was concluded that ZNS can control refractory epilepsy during pregnancy and increase pregnancy survival in refractory epileptic rats.

Retention rate of zonisamide in intractable epilepsy

OBJECTIVES

To assess the effect and tolerability of zonisamide (ZNS) as adjunctive treatment for difficult-to-treat epilepsy in adult Scandinavian patients.

MATERIAL AND METHODS

151 outpatients (mean age: 42.5 years) from 18 centres in Denmark, Sweden and Norway were recruited to the study. 81.5% had focal epilepsy, and the mean number of previously tried AEDs was 4.5. The patients were given ZNS as add-on treatment, and the ZNS dosing and the visit frequency were governed by the treating physician. The primary efficacy endpoint was the retention rate after 12-month treatment. Assessments included also responder rate, type and frequency of adverse events, healthcare resource utilization (HCRU) and quality of life (QOLIE-31).

RESULTS

90 patients (59.6%) completed the study. Mean daily ZNS dose was 300.8 mg. After 12 months, 81 patients were still on ZNS, that is a retention rate of 53.6%. The mean reduction of seizure frequency at 12 months was 27%. Best effect was seen in those with focal and those with secondary generalized seizures. In the QOLIE-31, there was a mean increase from baseline of 4.8 points. The tolerability was generally good. The majority of side effects were CNS-related, dizziness, fatigue, seizure aggravation, and headache being most prevalent. 21.2% had adverse events leading to withdrawal of ZNS.

CONCLUSIONS

A retention rate of 53.6% after 1 year of treatment with ZNS is roughly in accordance with the retention rates found for lamotrigine, oxcarbazepine, levetiracetam and topiramate in drug-resistant patients.

Rapid and sensitive high performance liquid chromatographic determination of zonisamide in human serum application to a pharmacokinetic study

An accurate and very rapid method for determination of zonisamide an antiepileptic drug, in human serum is described. The analytical procedure involves liquid-liquid extraction of the analyte and an internal standard (vanillin) from human serum by ethyl acetate as extracting solvent. Chromatographic separation was achieved using a monolithic C18 analytical column and a mixture of 0.05 M phosphate buffer containing triethylamine (1 ml/l; pH 2.7) and methanol (83:17 v/v) was used as the mobile phase. The detection wavelength was set at 240 nm. The calibration curve was linear over a concentration range of 0.015-6.4 μg/ml of zonisamide in human serum. The total run time of analysis was 3.5 min and the lower limits of detection and quantification were 0.005 and 0.015 μg/ml, respectively. The method validation was carried out in terms of specificity, sensitivity, linearity, precision, accuracy and stability. The validated method was applied in a randomised crossover bioequivalence study of two different zonisamide preparations in 24 healthy volunteers, and the assay was sensitive enough to measure drug levels up to 8 days following a single dose administration of zonisamide.

A review of the use of zonisamide in Parkinson's disease

Although zonisamide was previously only used to treat epilepsy, recently more applications have been forthcoming. Due to a good side effect profile, a lower frequency of interactions and a more comfortable posology, there are several studies regarding its uses in other pathologies such as migraine, neuropathic pain, essential tremor and various psychiatric diseases. A multicentered, randomized, double-blind, placebo-controlled study conducted in Japan suggested that zonisamide, as an add-on treatment, has efficacy in treating motor symptoms in patients with Parkinson's disease. In addition, other studies support the utility of zonisamide in other symptoms of this disease. The therapeutic doses of zonisamide for the treatment of Parkinson's disease are considerably lower than those for the treatment of epilepsy. This antiepileptic drug has been used in Japan for more than 15 years and so it is expected that it will be safe and well tolerated in patients with Parkinson's disease. However, the pharmacological mechanisms of the antiparkinsonian actions of zonisamide remain unclear and more basic investigation is warranted. The aim of this paper is to review the structure, mechanisms of action, pharmacokinetics and antiparkinsonian action of zonisamide.

Long-term use of zonisamide in refractory childhood-onset epilepsy

This open label study examined the long-term efficacy and safety of zonisamide as adjunctive therapy in mentally retarded and multiple-handicapped patients with severe childhood-onset epilepsy. The study included 24 patients (mean age 12.5 years, range 2-40 years) which had different severe epilepsy syndromes (75% focal, 12.5% generalized, 12.5% refractory status epilepticus) refractory to at least 6 (median 10) anti-epileptic drugs. All patients were followed for at least 18 months after beginning of zonisamide treatment. Mean duration of zonisamide therapy was 55 weeks (range 5-168 weeks) and mean maintenance dosage was 7.7 mg/kg/day (range: 4-16 mg/kg/day). The patients received an average of 1.9 (range 1-3) concomitant antiepileptic drugs. The initial response rate defined as a > or =50% reduction of seizure frequency after 8 weeks was 58.3% (14 of 24 patients). Four of 14 initial responders developed loss of efficacy during long-term treatment. The retention rate after 18 months was 41.7% (10 of 24 patients). One patient (4.2%) became completely seizure-free after initiation of zonisamide treatment and remained seizure-free for the entire observation period of 18 months. Overall, zonisamide was well tolerated. Side effects were observed in 46% of patients and were mild to moderate. They mostly occurred during titration and subsided in maintenance dosing. Only in two patients (8.3%) zonisamide therapy was discontinued due to side effects (loss of appetite). No serious side effects were observed. These results are similar to the findings of Japanese studies suggesting that long-term use of adjunctive zonisamide therapy may be beneficial for treating mentally retarded, multiple handicapped patients with highly refractory childhood-onset epilepsy.

Zonisamide for the treatment of Parkinson's disease

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