Zonegran (zonisamide) is an oral anticonvulsant used to treat seizures that may be of benefit to Dravet syndrome patients whose seizures are treatment-resistant. It is marketed by the pharmaceutical company Eisai.

How Zonegran works

The brain functions by sending billions of electrical signals every day. Its electrical activity is maintained by channels that allow the movement of substances like calcium, potassium, and sodium in and out of nerve cells.

Exposure to triggers, such as light or sound, can sometimes provoke the brain to fire off electrical signals at a much higher rate than usual in patients with epilepsy and epilepsy syndromes such as Dravet syndrome. When this happens, a person experiences a seizure.

Dravet syndrome patients often experience multiple and prolonged seizures, which may occur frequently throughout the day.

Zonegran is approved by the U.S. Food and Drug Administration (FDA) as an adjunctive therapy to treat partial seizures in adults with epilepsy. How this medication prevents seizures is not yet fully understood. But it is thought to exert its anticonvulsant effects by acting on sodium and calcium channels, and by enhancing factors that suppress the excitability of nerve cells.

Research has also shown that Zonegran may be beneficial in patients with treatment-resistant epilepsy syndromes, such as Dravet. It has the advantage of being able to be taken in combination with a number of different anticonvulsants, as it is relatively well-tolerated.

Studies on Zonegran

Zonegran has not been tested in controlled clinical trials in Dravet syndrome specifically; its supposed anticonvulsant benefits for Dravet patients are based on experience.

A North American Consensus Panel of experts in pediatric epilepsy syndromes recommended Zonegran as an add-on therapy for Dravet syndrome in patients who do not respond optimally to one or two other anticonvulsant medications. The report was published in 2017.

A study in 57 children with poorly controlled epilepsy — they failed to respond to at least three different anticonvulsant medications — found that an average of 5 mg/kg of  Zonegran given them daily for one year resulted in reducing seizures by more than half in some 25 percent of these children. Six others saw their number of seizures fall less than half with treatment. Twenty-four children had no change in the number of their seizures and eight experienced a higher number of seizures.

Overall, the researchers concluded that Zonegran was reasonably effective and well-tolerated in children with treatment-resistant seizures. This study was carried out in the U.K. and its results were published in the journal Seizure in 2010.

Further details

The most common side effects of Zonegran use are mood changes — such as depression, irritability, apathy, and anxiety — dizziness, double vision, headache, nausea, shakiness or unsteady walking, lack of appetite, and trouble concentrating and sleeping. Suicidal thoughts are also connected to its use.

It is important for Zonegran to be taken regularly, without interruption. Stopping or tapering this medication is strongly advised to be done under a doctor’s supervision.

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