How do antiepileptic medications work to control seizures?

Chemical way.: Anti epileptics work at molecular level by controlling ionic channel gate in cell membrane like na, k, ca, nmda. Etc thereby altering excitability of cell membrane. It is a very advanced detailed science.

Good question: They just do - sometimes. We can sound erudite with eloquent explanations. But no one really knows. Many years ago one lab had huge success with many agents as long as they were suspended in a certain solvent. It turned out the solvent was valproic acid. When they realized it was the actual active agent, it was refined and marketed as depakote.