Safety and Efficacy of Zonisamide in Patients with Epilepsy: A Post-Marketing Surveillance Study

Long-term effects of zonisamide in adult patients with intellectual disability

OBJECTIVE

This study aimed to evaluate the tolerability and efficacy of zonisamide (ZNS) in adult patients with drug-resistant epilepsy and intellectual disability (ID) at our epilepsy centre.

PATIENTS AND METHODS

By conducting a monocentric, open-label observational study based on standardized seizure records we retrospectively assessed 87 patients (39 female, mean age 40.6 ± 13.6, range 18-75 years) with ID and drug-resistant epilepsy. Evaluation, including calculation of retention rate, was performed for the intervals 3-6, 9-12 and 21-24 months after ZNS initiation. The Clinical Global Impressions Scale-Improvement (CGI-I) was used to detect qualitative changes in seizure severity and clinical status. Via regression analysis and the generalized estimating equations approach, we examined changes in body weight and impact of patient age also considering associations with other patient characteristics.

RESULTS

The retention rate after 24 months was 60%. 28% discontinued ZNS therapy due to increasing seizure frequency, lack of efficacy or adverse events (AEs). Sedation (38%), language impairment (19%), challenging behaviour (10%), mild rash (10%) and dizziness (10%) were the commonest AEs. The responder rate was 40%, eight patients (9%) became seizure free. We found CGI-I to be dose-dependent. Regarding changes in body weight, we observed no difference between patients continuing or withdrawing ZNS therapy and responders or non-responders. Though, we identified older age as a significant risk factor for weight loss.

CONCLUSIONS

Zonisamide may provide a safe and efficient therapeutic option for patients with ID and drug-resistant epilepsy. However, weight status should be carefully monitored, especially in elderly patients.

Incidence rates of severe cutaneous adverse reactions due to antiseizure medication: A nationwide study using health claims data in Korea

OBJECTIVE

Antiseizure medications (ASMs) can rarely result in severe, sometimes fatal, cutaneous adverse reactions. To date, few studies have reported on the incidence rates (IRs) of severe cutaneous adverse reactions (SCARs) due to ASM use. This study aimed to determine the IRs of SCAR resulting from the use of seven commonly prescribed ASMs, carbamazepine (CBZ), phenytoin (PHT), oxcarbazepine (OXC), lamotrigine (LMT), zonisamide (ZNS), levetiracetam (LVT), and topiramate (TPM), and to compare the associated risks among the drugs.

METHODS

Using a nationwide health claims database, we selected all the patients prescribed with one of the target ASMs. We defined a SCAR case as the first hospitalization with one of three specific codes provided by the International Classification of Diseases, 10th revision (L511, L512, and L27). We then calculated the IR of SCARs according to each target ASM.

RESULTS

The IR of SCARs for each ASM was as follows: 870/1 000 000 person-years (PYs) for CBZ, 5750/1 000 000 PYs for PHT, 1490/1 000 000 PYs for OXC, 3860/1 000 000 PYs for LMT, 1540/1 000 000 PYs for ZNS, 830/1 000 000 PYs for LVT, and 400/1 000 000 PYs for TPM. Concomitant use of antibiotics and nonsteroidal anti-inflammatory drugs significantly increased the risk of SCARs with OXC, LVT, or TPM use. Comorbid skin disease was associated with a significantly higher IR of SCARs from CBZ, PHT, OXC, LMT, or LVT use.

SIGNIFICANCE

This is the first study in Asia to determine the IRs of SCARs for various ASMs and compare the rates across drugs using a large dataset. The results from this study should help clinicians select safer ASMs in practice.

Adverse Cutaneous Drug Reactions Associated with Old- and New- Generation Antiepileptic Drugs Using the Japanese Pharmacovigilance Database

BACKGROUND AND OBJECTIVE

Adverse cutaneous drug reactions associated with antiepileptic drugs (AEDs) are a serious problem in the clinical setting. New-generation AEDs have been reported to be better tolerated than old-generation forms; however, information about the risks of adverse cutaneous drug reactions to new-generation AEDs is limited.

OBJECTIVE

The purpose of this study was to clarify the association of AEDs with adverse cutaneous drug reactions using a spontaneous reporting database.

METHODS

We performed a retrospective pharmacovigilance disproportionality analysis using the Japanese Adverse Drug Event Report (JADER) database. Adverse event reports submitted to the Pharmaceuticals and Medical Devices Agency between April 2004 and January 2017 were analyzed. Based on reports of all adverse events, we obtained 4805 reports of adverse cutaneous drug reactions associated with AEDs, and calculated the reporting odds ratio (ROR) and 95% confidence interval (CI) for drug rash, Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN).

RESULTS

Individual AEDs had variable signals for drug rash, SJS, and TEN. The strongest signals were detected for drug rash caused by lamotrigine (ROR 9.18, 95% CI 8.65-9.74), SJS caused by zonisamide (ROR 9.85, 95% CI 8.23-11.78), and TEN caused by phenobarbital (ROR 14.08, 95% CI 11.28-17.57).

CONCLUSION

There are clear differences in the risk of cutaneous reactions among AEDs, and further studies are needed to confirm these findings.

[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.

Stevens-Johnson syndrome/toxic epidermal necrolysis associated with zonisamide

This report highlights zonisamide as a potential cause of serious cutaneous reactions as well as its cross-reactivity with other sulfonamides. Here, we present a case of SJS-TEN due to zonisamide, which was effectively treated with IVIg. Subsequently, the patient was transitioned to levetiracetam for seizure control.