What is called an agent capable of preventing or arresting epilepsy?

An agent capable of preventing or arresting epilepsy is called an "anticonvulsant" or "antiepileptic drug" (AED). These medications work by stabilizing electrical activity in the brain, thereby reducing the frequency and severity of seizures. Common examples include phenytoin, valproate, and lamotrigine. They are essential in the management of epilepsy for many patients.